INTRODUCTION
1This chapter is a revision of the chapter by Charles E. Saunders, MD, FACEP, & Thomas Hearne, PhD, from the 4th edition.
The delivery of effective, organized, prehospital emergency medical services (EMS) is a development that dates to the 1960s in the United States. Although there were ambulance providers and even some local systems, there was no national approach to prehospital care until publication of the 1966 White Paper entitled "Accidental Death and Disability—The Neglected Disease of Modern Society" (National Academy of Sciences, National Research Council).
When medical emergencies are reported, trained medical personnel arrive on the scene to provide emergency care within 6-10 minutes. The skills of these personnel range from basic first aid techniques and cardiopulmonary resuscitation (CPR) to advanced life support (ALS) techniques, including defibrillation, endotracheal intubation, and the use of emergency medications. Radio communications permit ongoing discussion of patient status and treatment between emergency medical personnel at the scene and the supervising physician at the base hospital. Air ambulances (fixed-wing aircraft or helicopters staffed with medically trained flight crews) can rapidly evacuate and transport patients from a remote emergency scene to a regional medical center.
COMPONENTS OF THE EMERGENCY MEDICAL SERVICES SYSTEM
Modern EMS systems consist of several major components: (1) professional field personnel trained to provide specific levels or types of care, (2) a comprehensive emergency communications network, (3) hospital emergency department physicians and nurses who supervise the treatment provided by EMS field personnel, (4) hospitals categorized according to their relationship with EMS field personnel and according to the level of care they can provide, and (5) EMS administrative officials who manage and coordinate the elements of the system.
Professional EMS Field Personnel
The health professionals and first responders who provide prehospital care are trained to carry out specific levels of care, ranging from basic first aid and CPR provided by first responders, through basic life support (BLS) given by emergency medical technicians (EMTs), to the ALS provided by advanced EMTs (paramedics). These personnel provide care only as extensions or agents of physicians and are not independently licensed to provide medical care. The care they deliver is authorized by standing orders (written authorization to administer certain treatments without prior attempt at base contact by radio) or protocols from physician directors or by orders transmitted by radio from supervisory physicians at the base hospital to EMS personnel at the scene. A critical element in the development of EMS since 1970 has been the recognition that personnel without prior medical training can be prepared through relatively short courses to provide effective prehospital care. The designations, levels of training, and skills of EMS personnel are now largely standardized according to United States Department of Transportation (DOT) curriculum and formal categories established in 1983 by the National Registry of Emergency Medical Technicians. The curriculum is regularly reviewed and updated to reflect changes in medicine and in the prehospital environment. The latest iteration released by the DOT was in 1998, with some modifications in 2000. Types of EMS field personnel and their training are described below and summarized in Table 2-1.
A. First Responders
First responders may include law enforcement officers, rescue squad members, firefighters, or volunteer EMS personnel. First-responder courses usually consist of about 40 hours of classroom instruction and clinical training in basic first aid and CPR. First responders are equipped with basic emergency care equipment (eg, bandages, dressings, tape, blanket and pillow, upper and lower extremity splint sets). Oxygen equipment and a self-refilling bag-valve-mask combination (eg, Ambu bag) are optional. First responders also carry basic tools to help them reach and extricate trapped individuals. Increasingly, first responders are being trained and equipped to perform defibrillation using automated external defibrillators (AEDs).
B. Emergency Medical Technicians (EMTs)
The National Registry of Emergency Medical Technicians currently recognizes 3 formal grades of EMTs according to the typical number of hours of training given, the breadth of skills covered, and the range of procedures authorized: EMT-A (basic), EMT-I (intermediate), and EMT-P (advanced, paramedic). Designations and levels of training may vary from state to state. Emergency physicians should be familiar with regional variations and deviations from the National Registry guidelines.
1. EMT-A—Basic EMTs constitute the essential workforce of EMS systems throughout the United States. Most state laws require at least one certified EMT on board ambulance vehicles that transport patients.
The basic EMT course requires at least 81 hours of training standardized by the DOT. Basic classes frequently exceed this minimum by up to 140 hours. Students learn basic principles of patient care, how to identify signs and symptoms central to patient assessment and diagnosis, and how to provide treatment in specific emergencies. The use of AEDs is now standard curriculum for EMTs in most regions. Optional modules for EMTs include advanced airway management, intravenous access, and assisting patients with self-administration of medications. Additionally, some states allow administration of medications, including epinephrine in anaphylaxis and aspirin in suspected cardiac chest pain.
2. EMT-I—The intermediate EMT is trained to provide a level of advanced care in areas that are underserved by paramedics. The scope of practice has evolved since 1990 to incorporate many advanced cardiac life support procedures, including cardiac monitoring, treatment of arrhythmias, defibrillation, and advanced airway management with either endotracheal intubation or an alternative airway.
3. EMT-P—Advanced EMTs (paramedics) receive over 1000 hours of training in ALS techniques. Their skills include the basic EMT procedures as well as intravenous cannulation, invasive airway management (including endotracheal intubation), recognition of cardiac dysrhythmias, defibrillation, and the use of specific emergency medications. In addition to extensive classroom training, EMT-P personnel also complete clinical training and a field internship with experienced paramedic teams.
Paramedics operate under standing orders and treatment protocols developed by a physician medical director that are usually broader and more advanced than those guiding basic EMTs. These protocols determine the type and level of care administered at the emergency site. Physicians who provide on-line medical supervision of paramedics (by radio and telemetry) from base hospitals may permit paramedics to deviate from established protocols or to provide treatment not specifically covered in standing orders.
Special Qualifications
Additional training is available at all levels of providers for specific care settings. At the first responder level, a Winter Emergency Care course has been developed for the National Ski Patrol to address special situations that occur in ski areas. Similarly there are Wilderness modules at all levels of training that provide additional training for care provided in a remote setting with anticipated long evacuations and transportation. EMT-Tactical courses train EMTs and paramedics to function in a tactical law enforcement situation in which they may support or be part of a police special tactics teams. Finally, Paramedic-Critical Care training enables the advanced provider to provide care to critically injured or ill patients who are being transferred from one facility to another.
Types of EMS Systems
EMS systems can be delivered in various ways. There are 2 basic forms of EMS response: a single-response system and a layered-response (or tiered-response) system. In a single-response system, there is only one grade of EMS unit, and the closest available unit is dispatched to any nearby emergency. In a layered-response system, 2 or more grades of EMS personnel respond hierarchically (eg, first responder, then EMT-A, then EMT-P) as needed. Layered-response systems usually provide for an EMT-A response for all less severe reported medical emergencies, reserving an EMT-P response for severe or life-threatening incidents (Table 2-2).
Communications Network
The communications network is important in tying together the components of an EMS system. A dispatcher at a communications center receives a telephone request from a caller at the site of the emergency and dispatches mobile EMS personnel via the radio network. Dispatchers may use a call triaging system (eg, Priority Medical Dispatching) to assign resources to a call. In many areas of the United States, an easily remembered emergency telephone number (9-1-1) provides the public with rapid access to the communications center. Many systems offer an "enhanced 9-1-1" service that provides immediate callback and location information to the dispatcher.
Communications between the EMS unit and medical facilities varies from region to region. For many BLS transports, contact with the base station or receiving facility is not required. In the event of an ALS transport, contact must be made with a medical facility. In some areas, the facility is called a base station hospital, which provides on-line direction and supervision for an entire EMS region. Information called into the base station hospital is then relayed to the receiving facility. In other areas, the receiving facility is called directly.
Hospital Facilities & Staffing
EMS systems typically include hospitals with a variety of treatment capabilities, ranging from local community hospitals with a limited emergency department staffing to large teaching hospitals in urban areas with emergency physicians, surgeons, anesthesiologists, and surgical teams available 24 hours a day. Hospital facilities are frequently classified according to their relationship to EMS mobile units and their ability to provide definitive care.
A. Base Station Hospitals
Physicians or specially trained nurses with physician backup in the emergency department of the base station hospital provide EMS units with on-line medical supervision during treatment. EMS units may be housed at the base station hospital, but this may not be necessary or feasible because the units are usually strategically deployed in the hospital's service area. In many EMS systems, the base station hospital may also be the one most capable of providing definitive follow-up care.
B. Receiving Hospitals
Receiving hospitals are facilities to which patients may be transported. For each patient, the receiving hospital is selected according to its proximity; its capability to provide definitive care; and the preference of the patient, family members, or family physician, as long as transport to the hospital does not draw the EMS unit away from its primary service area.
C. Hospitals Categorized by Capability
Hospitals may be categorized by their ability to provide acute care as determined by the availability of physicians, nurse, allied health personnel, and other hospital resources (eg, operating rooms, laboratory, blood bank). Many categorization schemes exist. The Joint Commission on Accreditation of Healthcare Organizations has established 4 levels of emergency service:
1. Level I—This service offers emergency care 24 hours a day with at least one physician experienced in emergency care on duty in the emergency care area. In addition, there must be in-house physician coverage by residents at the senior level or higher for the medical, surgical, orthopedic, obstetric-gynecologic, pediatric, and anesthesiologic services.
2. Level II—This service offers emergency care 24 hours a day with at least one physician experienced in emergency care on duty in the emergency care area. Specialty consultation should be available within 30 minutes.
3. Level III—This service offers emergency care 24 hours a day with at least one physician on duty in the emergency care area available within 30 minutes through a medical staff call roster.
4. Level IV—This service is capable of performing a triage function and can administer life-saving first aid until transportation to the nearest appropriate facility is available.
D. Hospitals Categorized by Areas of Care
Hospitals can also be categorized by special areas of care (eg, trauma, burns, neonatal intensive care), especially where regionalization of services in these areas is practiced. The American College of Surgeons, for example, has established the following categorization of trauma facilities:
1. Level I—This designates a full-service trauma center that can provide optimal care of the trauma patient. One or more experienced emergency physicians, a general surgeon, anesthesiology services, laboratory, blood bank, and an operating room team must be available in-house 24 hours a day. All surgical subspecialty services should be immediately available on call. A commitment to education and research in trauma must also be demonstrated.
2. Level II—This trauma center is similar to a level I center but does not necessarily include a commitment to education or research. Occasionally patients with the most severe injuries or those needing highly specialized care may be transferred from a level II center to a level I center.
3. Level III—This trauma center does not have all of the resources available at a level I or level II center but may represent the highest level available in a given community. Usually, initial stabilization and life-saving procedures are performed and the patient is then transferred to a level I or level II center.
EMS Administration
EMS systems may be administered through a variety of organizations, including local health departments, public safety agencies such as police or fire departments, hospitals, or privately owned provider agencies. Often several of these agencies operate EMS systems in the same area, and these agencies are coordinated through an EMS regional council, which interacts with hospitals, public safety agencies, and physician medical directors; sets operational standards; and monitors performance (quality assurance).
Operation of the EMS System
One way to visualize the interplay between various components of the EMS system is to review the sequence of events surrounding a typical emergency medical incident. There are 4 major phases: (1) report of the emergency and activation of the EMS system, (2) dispatch of appropriate prehospital units, (3) medical evaluation and field treatment by EMS personnel, and (4) transport of the patient to the appropriate hospital.
A. Report of the Emergency
In many areas of the United States, a single, easily remembered telephone number (9-1-1) can now be used to request emergency help from the police and fire departments and to activate the EMS system.
B. Dispatch
Dispatchers receive the emergency call, interview the caller to determine the type and severity of the emergency, and dispatch the appropriate type of emergency medical response. In systems with heavy call volumes, calls may be priority ranked and then dispatched in order of urgency of need and resource availability. In some systems, dispatchers offer advice to callers to assist patients pending the arrival of emergency units (prearrival instructions). Algorithms may be employed to guide the dispatcher in decision making (Figure 2-1). Dispatchers in layered-response emergency medical systems frequently follow specific protocols in determining which type of EMS unit to dispatch (ie, ALS, BLS, first responder; see Table 2-2). Dispatchers may also be trained to provide CPR instructions by telephone to callers. Dispatch centers may also monitor hospital availability, manage the status and geographic deployment of EMS vehicles, and through computer-aided dispatch perform EMS management information and quality assurance functions.
C. Medical Evaluation and Treatment
Most EMS systems in urban and suburban areas are capable of responding within a few minutes of receiving an emergency call. First responders can frequently arrive at the scene within 3-6 minutes, and paramedics within 5-10 minutes of receiving the call. Survival following time-sensitive medical emergencies such as cardiac arrest is closely correlated with unit response time, especially when basic EMTs have been trained in defibrillation. In layered-response systems, paramedics are held in reserve for such critical or life-threatening incidents, where their advanced skills may provide definitive or stabilizing care to patients. Many systems have advanced-level first responders, such as engine companies manned with paramedics. These responders can provide the same interventions as ambulance-based paramedics but lack the means to transport patients. These assets can be additional resources in the single complex patient or in the multiple-patient incident.
Upon arrival at the emergency scene, EMS personnel undertake patient assessment and examination. EMT-paramedics in most cases are authorized by standing orders to proceed with patient care. Following patient evaluation and treatment, the EMS unit contacts the supervising emergency medical physician (or, in some states, a nurse) at the base station hospital by radio or telephone to describe the patient's condition and any treatment undertaken. The physician may give specific instructions for further treatment at the scene or request transport to the hospital for care.
D. Transport
The mode of transport (ground or air, with or without sirens or lights) depends on availability, stability of the patient's condition, transport time and distance, risks, and the like. Hospital destination decisions are often guided by local protocols, with critically ill patients directed to the closest, most appropriate facility. For example, a community hospital may be bypassed in favor of the nearest designated trauma center in the case of a severely injured patient. Noncritical cases may be transported to the hospital of the patient's choice.
1. Ground transport—Most patients are transported in surface ambulances. These vehicles vary slightly from state to state in their configuration and on-board equipment, but all follow guidelines set by the DOT. Emergency vehicle operators usually are allowed by local and state laws to violate certain traffic laws while responding to an emergency or carrying a patient in a life-threatening emergency. In the vast majority of cases, however, the patient's life is not in danger and posted speeds and traffic laws should be obeyed. The time gained in using red lights and sirens to get to the hospital is often outweighed by the additional risk of death and disability associated with rapid transport.
In most EMS systems, the responding unit is also the transporting unit. In others, especially layered-response systems, the responding unit may primarily evaluate and stabilize the patient and may summon a lower-level unit to provide transport.
2. Air transport—Some EMS systems and regional trauma hospitals, particularly those serving large outlying rural areas, use helicopters or fixed-wing aircraft with trained medical teams on board as additional resources for prehospital care and transportation. The majority of these aircraft are hospital based, but some are operated by municipal or state governmental agencies. Where these services are unavailable, or when search-and-rescue missions are required, aircraft equipped for medical evacuation may be sent from local military bases, operating within the Military Assistance to Safety and Traffic program.
Air ambulances are usually integrated into the EMS system and are activated according to certain locally established criteria. The decision to transport a patient by air requires careful consideration of the risks and benefits of air versus ground transport (see below).
Medical Supervision
A. On-Line Medical Direction
On-line medical direction is the direction given by radio to EMS personnel at the scene while care is being provided. It is usually given by emergency physicians or nurses at the base station hospital or receiving hospital. In most systems, the use of standing orders is allowed (Figure 2-2). This approach allows treatment to begin as soon as possible. Systems that have changed over from on-line medical control to standing orders have not shown a decrement in medical care but have shown an increase in EMS provider morale.
Even in systems that operate nearly exclusively by standing orders, some exceptions may require on-line direction. These may include cessation of CPR in a nonviable patient or the administration of restricted medications such as narcotics or paralytics. Systems that employ standing orders require effective monitoring, training, and quality assurance mechanisms.
B. Off-Line Medical Direction
Off-line medical direction is the overall direction of the activities of EMS personnel. It includes establishing protocols and standing orders, ensuring adequate training and skills, reviewing patient care records and voice tapes retrospectively, and reviewing performance and outcome data. Off-line medical direction is usually provided by a physician experienced in emergency services or by an agency in which physicians play an active role.
Performance Evaluation
System performance evaluation has many aspects, including the evaluation of input resources and operating guidelines (eg, protocol validation, personnel review, training assessment), evaluation of the process of delivering care in the field (eg, response times, service volume, treatment audits for adherence to protocols), and evaluation of the outcome of prehospital care (eg, complications, complaints, success in the performance of procedures, and patient survival). Outcome data are the most difficult to obtain.
PREHOSPITAL SKILLS & TECHNIQUES
Field Assessment
EMTs responding to a call usually have certain dispatch information, including the location, the nature of the complaint, and the number of patients. Upon arrival, they must quickly determine the presence of hazards to themselves and the patient, ascertain the probable mechanism of injury, and identify other patients, if any. Support can be summoned for hazard suppression or additional medical assistance. Patients who are conscious and in minimal distress may be able to provide historical information. Information may also be obtained from witnesses or family members.
Patients who are very ill may require that interventions be performed simultaneously with assessment. Interventions aimed at stabilizing airway, breathing, or circulation (the ABCs) will take precedence over secondary assessment. The receiving physician should expect that, if the patient is seriously ill or injured, only life-saving measures may be performed prior to arrival. In the more stable patient, a more thorough primary and secondary survey should be performed.
Field Treatment
A. Airway Control
Methods of airway control depend on the EMT's level of skill and certification. Initial steps to provide an airway include positioning the jaw and suctioning secretions (taking care in the trauma victim not to hyperextend the neck). Should this fail to achieve and maintain airway patency, the basic EMT can insert an oral or nasal airway. Ventilation may be assisted by a bag-valve-mask.
EMTs and paramedics may establish alternative airways, depending on local protocol. The Combitube, a dual lumen tube designed to be placed blindly, can be used to ventilate the patient regardless of whether the tube is placed in the esophagus or the trachea. The laryngeal mask airway (LMA) is designed to be placed without laryngoscopy. It has an inflatable cuff that sits over the glottis. This allows for ventilation while minimizing gastric insufflation and aspiration. It is not as secure an airway as the endotracheal tube. An improvement on the original LMA is the LMA-Fastrach, which allows for an endotracheal tube to be passed through the LMA. Both the Combitube and the LMA have been implemented successfully in the prehospital setting.
Endotracheal intubation is the preferred method of airway control in patients with inadequate ventilation. Typically the success rate for prehospital intubation is greater than 90%. However, two recent papers have questioned the value of intubation in the field. A randomized trial involving pediatric intubation found that patients did as well with bag-valve-mask ventilation as they did with intubation. Another study found that over 25% of adult intubations in the prehospital setting were misplaced. When intubation is performed in the field it is suggested that end-tidal CO2 detection and an esophageal detector device be used in addition to more conventional means of confirming location. After the tube is confirmed in the correct location, the risk of dislodgement should be minimized by using a commercial endotracheal tube holder and by securing the patient in a cervical collar and to a long spinal board.
B. Emergency Cardiac Care
1. Cardiopulmonary resuscitation—The probability of survival for victims of sudden cardiac arrest is inversely related to the elapsed time before an effective cardiac rhythm is reestablished. CPR is a temporizing measure that, when initiated within 4-6 minutes, increases the chances of survival. In most systems, a paramedic unit cannot routinely reach the scene within this period. Many systems provide first responders with AEDs. AEDs have been successfully deployed with police and fire first responders. In addition, public access defibrillators provide AEDs to the public at busy venues such as sporting arenas and airports.
2. Defibrillation—Ventricular fibrillation is the initial rhythm encountered in many victims of sudden death. The sooner defibrillation is performed, the higher the survival rate. AEDs (Laerdal Heartstart 2000, others) can recognize ventricular fibrillation (or tachycardia) and deliver a countershock. The rescuer need not be able to recognize dysrhythmias but must be able to recognize cardiac arrest and operate the device. AEDs have enabled nonparamedic first responders to provide rapid defibrillation and have consequently improved survival rates.
3. Electrocardiography—In the treatment of acute coronary syndromes, the prehospital 12-lead electrocardiogram (ECG) significantly shortens the time from arrival in the emergency department to administration of thrombolytic therapy ("door to drug time"). Prehospital fibrinolytic therapy has had mixed results. In European trials, where prehospital care is typically provided by physician-staffed ambulances, 6-month and 1-year survival rates have increased. However, trials in the United States with paramedic-staffed units has not shown a significant improvement over 12-lead ECG in the field with hospital-administered fibrinolytics.
C. Invasive Procedures
1. Venous catheterization—(See Chapter 6.) The use of intravenous techniques by EMS field personnel is usually limited to cannulation of peripheral veins of the upper extremities. In most EMS systems, the procedure can be initiated under standing order by intermediate or paramedic EMTs. Basic EMTs who have had special training in intravenous techniques and fluid therapy may also initiate intravenous lines. Studies have demonstrated that skilled paramedics in the field are able to start an intravenous line in approximately 3 minutes and achieve a success rate greater than 90%. However, when transport times are short (ie, 10 minutes or less), venous catheterization is usually unnecessary because the volume of fluid infused or the medications administered during such a short period are unlikely to be life saving. Further, in penetrating trauma to the thorax, fluid boluses may be detrimental by disrupting the clotting process. In addition, field placement of intravenous lines may increase the chances of infection. Needlestick injuries, which may occur during venous cannulation under adverse circumstances, such as in the back of a moving ambulance, are an increasing concern. Intraosseous needles may be placed by paramedics in the event that vascular access cannot be obtained in the pediatric patient.
2. Needle thoracostomy—Chest decompression for suspected tension pneumothorax may occasionally be life saving and is performed by paramedics in some systems. A 14- or 16-gauge catheter-clad needle is inserted into the second intercostal space along the midclavicular line immediately above the subjacent rib using sterile technique. The catheter is sealed with a Heimlich valve or a latex glove with the fingertip removed. (The open fingertip of the glove is secured around the catheter, allowing air to escape but preventing its reentry.)
3. Cricothyrotomy—(See Chapter 6.) Emergency entry to the airway may be life saving in cases of supraglottic airway obstruction or laryngeal trauma. Cricothyrotomy may be performed by paramedics in some EMS systems, usually after approval by the base physician via radio. Cricothyrotomy may be performed using a surgical, needle, or Seldinger technique. Because the procedure can be unexpectedly difficult, it should be performed as a last resort and only by properly trained personnel.
D. Medications
Medications are a contentious area in the prehospital realm. Because of the lack of clinical trials, it is difficult to state what interventions are of benefit. The emergency physician should know what medications are available to their EMS providers and under what indications they may be used.
1. Advanced cardiac life support—Most drugs for advanced cardiac life support are stocked on most ALS ambulances. Consistently, epinephrine, atropine, lidocaine, sodium bicarbonate, and adenosine are stocked. In addition, nitroglycerin, aspirin, and morphine are available for treatment of acute coronary syndromes. Amiodarone often is not used because of the ongoing debate about its effectiveness and because of cost issues. Some systems do not stock diltiazem because patients with a tachydysrhythmia that requires rate control are relatively stable. Fibrinolytics are rarely used because of their cost, the staffing needed to administer and monitor them, and the minimal benefit shown in prehospital use. Other medications such as labetalol, magnesium, procainamide, and calcium chloride are typically stocked at the discretion of the agency's medical director.
2. Pulmonary—Albuterol should be available to all ALS EMS agencies. Ipratropium has been shown to be beneficial to patients with moderate to severe asthma and to those with chronic obstructive pulmonary disease. In addition to sublingual nitroglycerin, furosemide is typically stocked for treatment of pulmonary edema.
3. Other drugs—Benzodiazepines are typically stocked for treatment of seizures, anxiolysis, and sedation. The use of prehospital benzodiazepines is beneficial to patients presenting with recurrent seizures. Agents stocked include diazepam, lorazepam, and midazolam.
Glucose, in the form of 50% dextrose in water (D50W) and oral glucose solution (occasionally D25W or D10W for pediatric patients), is stocked for treating hypoglycemia.
E. Extrication
Extrication is the process of removing a patient from a condition of entrapment, usually from a motor vehicle. It requires considerable skill and experience. Often, special tools are necessary, such as heavy bolt and metal cutters or large, powered spreading devices (eg, Jaws of Life, Hurst Tool). In most EMS systems, when there is a report of a trapped victim, a fire rescue team is dispatched in addition to the EMS unit to clear fire hazards, wash away spilled gasoline, and provide additional heavy equipment and personnel.
As soon as the patient is accessible with minimal risk to emergency workers, the primary survey should be initiated while further efforts to free the patient continue. Once the patient is immobilized in place, emergency resuscitation can begin.
F. Immobilization and Splinting
1. Immobilization—Victims of trauma may have injuries to the spine or extremities, which, if manipulated, can lead to spinal cord or limb damage. Upon reaching a trauma victim, the rescue team must stabilize the patient's cervical spine. Manual stabilization is maintained throughout extrication. A cervical collar is applied as soon as practicable. Spine boards are sometimes difficult to maneuver in closed spaces, but alternative devices are available, such as the Kendrick Extrication Device (KED). In a hemodynamically unstable patient, rapid extrication onto a long spine board can be accomplished by multiple rescuers manually supporting the spine without the aid of a KED. Immobilization is not considered complete until the patient is secured to the spine board with straps, the patient's head is secured to the spine board with tape across the forehead and beneath the chin, and a cervical collar and lateral neck rolls or head immobilization device are in place.
If endotracheal control intubation is necessary, the cervical spine should remain immobilized while the procedure is performed. Should vomiting occur, the patient may be logrolled to face sideways while one rescuer maintains cervical spine traction.
2. Splinting—(See Chapters 28 and 29.) In general, extremities should be placed in an anatomic position, especially if pulses cannot be felt below a suspected fracture. If the patient protests or if resistance is felt, extremities should remain in a position of comfort. Reduction of fracture dislocations at a joint should be attempted only if vascular compromise is impending, the duration of transport is long, and the rescuer is experienced in the technique. This usually requires the base physician's approval.
A pillow, rolled-up blanket, or other material may often serve as a simple splint. Specific splinting devices include cardboard splints, inflatable air splints, the MAST (military antishock trousers) garment, and traction splints. If inflatable devices are used, care must be taken to monitor distal perfusion, because a compartment syndrome may occur with swelling of the extremity or changes in atmospheric pressure (eg, during air transport). Traction splints are used primarily with fractures of the femur.
G. Protocols and Standing Orders
Protocols are guidelines designed to assist the EMT in performing tasks in a complete and orderly fashion (Figure 2-3). Because situations vary widely and protocols cannot anticipate every variable, they are not meant to be absolute and must be accompanied by training, judgment, and experience. Each EMS system tailors its protocol to the training and skill of its EMTs and the needs of the local medical community.
Standing orders are express authorizations for the performance of a specific task or procedure. Under the standing order, an EMT may be authorized to perform a task or procedure without first obtaining verbal authorization by radio. Standing orders are useful when radio contact is impractical or would delay life-saving intervention (eg, CPR, defibrillation). Standing orders usually contain a clear list of circumstances under which the authorization applies (indications) and detailed instructions on the manner in which the procedure should be performed. They are signed by the physician medical director, who shares legal responsibility for the outcome.
H. Communications
1. Equipment and frequencies—EMS units communicate with receiving hospitals by various methods. Three main radio systems exist: the HEAR network (in the 150-MHz range), the COR system (400 MHz), and the 800-MHz truncated system. The HEAR system is the oldest and has largely been replaced in urban areas by 800-MHz systems, which provide multiple frequencies for providers. In addition, cellular phones and landline telephones are used frequently for communications. Communication is simplex. Signals pass in only one direction at a time, and neither party can simultaneously speak and be heard. In rural areas, communication may be direct, via radio, without a relay station or ground lines.
2. Communication technique—Radio communication must provide information in a concise, precise, and easily understood manner. To facilitate speed and understanding, a common format is followed, with slight variations depending on the community. However, no one should hesitate to ask for clarification, because misunderstandings may prove fatal.
a. The initial contact—The caller always names the party being called first, followed by the caller's own identification:
"Central Hospital, this is medic 19, how do you copy?"
b. The initial response—The initial response confirms the contact in the same manner:
"Medic 19, Central Hospital, receiving you loud and clear, over."
c. The report—The caller gives a concise, orderly report containing pertinent history, physical findings, destination, estimated time of arrival (ETA), and any necessary request for instructions. It should be as brief as possible:
"Central Hospital, medic 19 en route to your location, ETA 8 minutes, with a 20-year old male victim of multiple, small-caliber gunshot wounds to the left chest, right flank, and right thigh. Patient is lethargic; blood pressure 80, pulse 140, respirations 46. Breath sounds absent over the left chest, abdomen soft. We have an ET tube in place, 2 IVs with lactated Ringer's wide open, and MAST garment inflated. Requesting permission for needle decompression of the left chest."
d. The report acknowledgment—This acknowledgment is kept brief; only essential queries should be made:
"Medic 19, have you checked ET tube position?"
"That's affirmative. Withdrawn 2 centimeters without improvement."
"Okay, medic 19; needle thoracostomy, left chest, is approved. Will stand by for update."
e. The sign-off—After receiving an order, the field personnel should repeat it to demonstrate that it was received accurately before signing off:
"Central Hospital, understand needle thoracostomy, left chest, is approved. Stand by."
3. 10-Codes—"Ten codes" are phrases represented by 2 numbers, the first being 10. In many areas, these are used to ensure precise communication and to add some measure of privacy to the conversation. Unfortunately, few EMS personnel have all of the possible 120 codes memorized. The result is often more confusion rather than less. Because mistakes may be dangerous, the codes should not be used unless thoroughly understood by all parties.
4. Telemetry—Receiving hospitals and ambulances may have equipment designed for the transmission of electrocardiographic traces (telemetry). This equipment is seldom used, however, because well-trained paramedics have shown the ability to interpret unstable rhythms (eg, ventricular fibrillation, ventricular tachycardia, bradycardia, and asystole) with acceptable precision, and more complex rhythms (eg, supraventricular tachycardia) rarely require treatment that cannot be postponed until arrival at the hospital. As indicated above, the prehospital 12-lead ECG has shortened the door to drug time in patients with acute coronary syndromes.
I. Air Transport
1. Indications—As noted above, the benefits to the patient must outweigh the risks inherent in this mode of transport. Aeromedical transport is most advantageous when great distances must be covered rapidly, when ground transport is unavailable or impeded by geographic obstacles or dense traffic, or when specialized care (eg, trauma resuscitation) is needed at the scene or en route. Emergency medical helicopters serving rural areas often provide a higher level of care and more skilled procedures (eg, intubation, needle thoracostomy, cricothyrotomy) than are provided by localized services using basic EMTs. However, air transport is hazardous, and helicopters operating at night and in inclement weather have crashed.
2. Requesting service—Helicopters equipped for medical evacuation can be requested, through the EMS communications network, from an area hospital that offers such services or from a local military base that participates in the Military Assistance to Safety and Traffic program.
3. Patient preparation—Before departure, stabilize the patient on a spine board and immobilize the patient as clinically indicated. Secure airway tubes and intravenous catheters.
4. Anticipated physiologic consequences of air transport—
a. Hypoxia—Atmospheric pressure decreases with increasing altitude, as does the partial pressure of oxygen. Patients with existing heart or lung disease may suffer adverse consequences. Supplemental oxygen is required.
b. Expansion of trapped gas—The volume of trapped gas increases with decreasing barometric pressure. Thus, as altitude increases, air may expand in endotracheal tube cuffs, air splints, MAST garments, the bowel lumen, the stomach, pneumothorax, abscess cavities, and the bottles and tubing of intravenous infusion apparatus. These compartments must be monitored frequently and vented as necessary. Intravenous flow rates should be adjusted accordingly.
c. Motion, noise, and vibration—These may cause patient discomfort. Forward acceleration with the patient's head forward may cause transient hypotension. This may be prevented by positioning the patient with feet forward.
5. Helicopter safety—
a. Site selection and lighting—A helicopter landing site should be level, approximately 100 feet square, and free of obstacles (eg, trees, wires) to approach and departure. It should also be clear of loose debris. The site should be secure from bystanders. At night, the site should be well lighted (eg, with vehicle headlights), but lights should never be directed upward toward the approaching helicopter, because they might interfere with the pilot's vision.
b. Approaching a helicopter—While the rotor blades are turning, approach the aircraft only from the front and only after prompting by the pilot. Avoid the tail rotor. Approach in a crouched position. Do not run. Never approach from uphill.
Lower tall objects such as poles associated with intravenous infusion apparatus. Secure sheets, hats, and loose clothing. Extinguish all smoking material.
1This chapter is a revision of the chapter by Charles E. Saunders, MD, FACEP, & Thomas Hearne, PhD, from the 4th edition.
The delivery of effective, organized, prehospital emergency medical services (EMS) is a development that dates to the 1960s in the United States. Although there were ambulance providers and even some local systems, there was no national approach to prehospital care until publication of the 1966 White Paper entitled "Accidental Death and Disability—The Neglected Disease of Modern Society" (National Academy of Sciences, National Research Council).
When medical emergencies are reported, trained medical personnel arrive on the scene to provide emergency care within 6-10 minutes. The skills of these personnel range from basic first aid techniques and cardiopulmonary resuscitation (CPR) to advanced life support (ALS) techniques, including defibrillation, endotracheal intubation, and the use of emergency medications. Radio communications permit ongoing discussion of patient status and treatment between emergency medical personnel at the scene and the supervising physician at the base hospital. Air ambulances (fixed-wing aircraft or helicopters staffed with medically trained flight crews) can rapidly evacuate and transport patients from a remote emergency scene to a regional medical center.
COMPONENTS OF THE EMERGENCY MEDICAL SERVICES SYSTEM
Modern EMS systems consist of several major components: (1) professional field personnel trained to provide specific levels or types of care, (2) a comprehensive emergency communications network, (3) hospital emergency department physicians and nurses who supervise the treatment provided by EMS field personnel, (4) hospitals categorized according to their relationship with EMS field personnel and according to the level of care they can provide, and (5) EMS administrative officials who manage and coordinate the elements of the system.
Professional EMS Field Personnel
The health professionals and first responders who provide prehospital care are trained to carry out specific levels of care, ranging from basic first aid and CPR provided by first responders, through basic life support (BLS) given by emergency medical technicians (EMTs), to the ALS provided by advanced EMTs (paramedics). These personnel provide care only as extensions or agents of physicians and are not independently licensed to provide medical care. The care they deliver is authorized by standing orders (written authorization to administer certain treatments without prior attempt at base contact by radio) or protocols from physician directors or by orders transmitted by radio from supervisory physicians at the base hospital to EMS personnel at the scene. A critical element in the development of EMS since 1970 has been the recognition that personnel without prior medical training can be prepared through relatively short courses to provide effective prehospital care. The designations, levels of training, and skills of EMS personnel are now largely standardized according to United States Department of Transportation (DOT) curriculum and formal categories established in 1983 by the National Registry of Emergency Medical Technicians. The curriculum is regularly reviewed and updated to reflect changes in medicine and in the prehospital environment. The latest iteration released by the DOT was in 1998, with some modifications in 2000. Types of EMS field personnel and their training are described below and summarized in Table 2-1.
A. First Responders
First responders may include law enforcement officers, rescue squad members, firefighters, or volunteer EMS personnel. First-responder courses usually consist of about 40 hours of classroom instruction and clinical training in basic first aid and CPR. First responders are equipped with basic emergency care equipment (eg, bandages, dressings, tape, blanket and pillow, upper and lower extremity splint sets). Oxygen equipment and a self-refilling bag-valve-mask combination (eg, Ambu bag) are optional. First responders also carry basic tools to help them reach and extricate trapped individuals. Increasingly, first responders are being trained and equipped to perform defibrillation using automated external defibrillators (AEDs).
B. Emergency Medical Technicians (EMTs)
The National Registry of Emergency Medical Technicians currently recognizes 3 formal grades of EMTs according to the typical number of hours of training given, the breadth of skills covered, and the range of procedures authorized: EMT-A (basic), EMT-I (intermediate), and EMT-P (advanced, paramedic). Designations and levels of training may vary from state to state. Emergency physicians should be familiar with regional variations and deviations from the National Registry guidelines.
1. EMT-A—Basic EMTs constitute the essential workforce of EMS systems throughout the United States. Most state laws require at least one certified EMT on board ambulance vehicles that transport patients.
The basic EMT course requires at least 81 hours of training standardized by the DOT. Basic classes frequently exceed this minimum by up to 140 hours. Students learn basic principles of patient care, how to identify signs and symptoms central to patient assessment and diagnosis, and how to provide treatment in specific emergencies. The use of AEDs is now standard curriculum for EMTs in most regions. Optional modules for EMTs include advanced airway management, intravenous access, and assisting patients with self-administration of medications. Additionally, some states allow administration of medications, including epinephrine in anaphylaxis and aspirin in suspected cardiac chest pain.
2. EMT-I—The intermediate EMT is trained to provide a level of advanced care in areas that are underserved by paramedics. The scope of practice has evolved since 1990 to incorporate many advanced cardiac life support procedures, including cardiac monitoring, treatment of arrhythmias, defibrillation, and advanced airway management with either endotracheal intubation or an alternative airway.
3. EMT-P—Advanced EMTs (paramedics) receive over 1000 hours of training in ALS techniques. Their skills include the basic EMT procedures as well as intravenous cannulation, invasive airway management (including endotracheal intubation), recognition of cardiac dysrhythmias, defibrillation, and the use of specific emergency medications. In addition to extensive classroom training, EMT-P personnel also complete clinical training and a field internship with experienced paramedic teams.
Paramedics operate under standing orders and treatment protocols developed by a physician medical director that are usually broader and more advanced than those guiding basic EMTs. These protocols determine the type and level of care administered at the emergency site. Physicians who provide on-line medical supervision of paramedics (by radio and telemetry) from base hospitals may permit paramedics to deviate from established protocols or to provide treatment not specifically covered in standing orders.
Special Qualifications
Additional training is available at all levels of providers for specific care settings. At the first responder level, a Winter Emergency Care course has been developed for the National Ski Patrol to address special situations that occur in ski areas. Similarly there are Wilderness modules at all levels of training that provide additional training for care provided in a remote setting with anticipated long evacuations and transportation. EMT-Tactical courses train EMTs and paramedics to function in a tactical law enforcement situation in which they may support or be part of a police special tactics teams. Finally, Paramedic-Critical Care training enables the advanced provider to provide care to critically injured or ill patients who are being transferred from one facility to another.
Types of EMS Systems
EMS systems can be delivered in various ways. There are 2 basic forms of EMS response: a single-response system and a layered-response (or tiered-response) system. In a single-response system, there is only one grade of EMS unit, and the closest available unit is dispatched to any nearby emergency. In a layered-response system, 2 or more grades of EMS personnel respond hierarchically (eg, first responder, then EMT-A, then EMT-P) as needed. Layered-response systems usually provide for an EMT-A response for all less severe reported medical emergencies, reserving an EMT-P response for severe or life-threatening incidents (Table 2-2).
Communications Network
The communications network is important in tying together the components of an EMS system. A dispatcher at a communications center receives a telephone request from a caller at the site of the emergency and dispatches mobile EMS personnel via the radio network. Dispatchers may use a call triaging system (eg, Priority Medical Dispatching) to assign resources to a call. In many areas of the United States, an easily remembered emergency telephone number (9-1-1) provides the public with rapid access to the communications center. Many systems offer an "enhanced 9-1-1" service that provides immediate callback and location information to the dispatcher.
Communications between the EMS unit and medical facilities varies from region to region. For many BLS transports, contact with the base station or receiving facility is not required. In the event of an ALS transport, contact must be made with a medical facility. In some areas, the facility is called a base station hospital, which provides on-line direction and supervision for an entire EMS region. Information called into the base station hospital is then relayed to the receiving facility. In other areas, the receiving facility is called directly.
Hospital Facilities & Staffing
EMS systems typically include hospitals with a variety of treatment capabilities, ranging from local community hospitals with a limited emergency department staffing to large teaching hospitals in urban areas with emergency physicians, surgeons, anesthesiologists, and surgical teams available 24 hours a day. Hospital facilities are frequently classified according to their relationship to EMS mobile units and their ability to provide definitive care.
A. Base Station Hospitals
Physicians or specially trained nurses with physician backup in the emergency department of the base station hospital provide EMS units with on-line medical supervision during treatment. EMS units may be housed at the base station hospital, but this may not be necessary or feasible because the units are usually strategically deployed in the hospital's service area. In many EMS systems, the base station hospital may also be the one most capable of providing definitive follow-up care.
B. Receiving Hospitals
Receiving hospitals are facilities to which patients may be transported. For each patient, the receiving hospital is selected according to its proximity; its capability to provide definitive care; and the preference of the patient, family members, or family physician, as long as transport to the hospital does not draw the EMS unit away from its primary service area.
C. Hospitals Categorized by Capability
Hospitals may be categorized by their ability to provide acute care as determined by the availability of physicians, nurse, allied health personnel, and other hospital resources (eg, operating rooms, laboratory, blood bank). Many categorization schemes exist. The Joint Commission on Accreditation of Healthcare Organizations has established 4 levels of emergency service:
1. Level I—This service offers emergency care 24 hours a day with at least one physician experienced in emergency care on duty in the emergency care area. In addition, there must be in-house physician coverage by residents at the senior level or higher for the medical, surgical, orthopedic, obstetric-gynecologic, pediatric, and anesthesiologic services.
2. Level II—This service offers emergency care 24 hours a day with at least one physician experienced in emergency care on duty in the emergency care area. Specialty consultation should be available within 30 minutes.
3. Level III—This service offers emergency care 24 hours a day with at least one physician on duty in the emergency care area available within 30 minutes through a medical staff call roster.
4. Level IV—This service is capable of performing a triage function and can administer life-saving first aid until transportation to the nearest appropriate facility is available.
D. Hospitals Categorized by Areas of Care
Hospitals can also be categorized by special areas of care (eg, trauma, burns, neonatal intensive care), especially where regionalization of services in these areas is practiced. The American College of Surgeons, for example, has established the following categorization of trauma facilities:
1. Level I—This designates a full-service trauma center that can provide optimal care of the trauma patient. One or more experienced emergency physicians, a general surgeon, anesthesiology services, laboratory, blood bank, and an operating room team must be available in-house 24 hours a day. All surgical subspecialty services should be immediately available on call. A commitment to education and research in trauma must also be demonstrated.
2. Level II—This trauma center is similar to a level I center but does not necessarily include a commitment to education or research. Occasionally patients with the most severe injuries or those needing highly specialized care may be transferred from a level II center to a level I center.
3. Level III—This trauma center does not have all of the resources available at a level I or level II center but may represent the highest level available in a given community. Usually, initial stabilization and life-saving procedures are performed and the patient is then transferred to a level I or level II center.
EMS Administration
EMS systems may be administered through a variety of organizations, including local health departments, public safety agencies such as police or fire departments, hospitals, or privately owned provider agencies. Often several of these agencies operate EMS systems in the same area, and these agencies are coordinated through an EMS regional council, which interacts with hospitals, public safety agencies, and physician medical directors; sets operational standards; and monitors performance (quality assurance).
Operation of the EMS System
One way to visualize the interplay between various components of the EMS system is to review the sequence of events surrounding a typical emergency medical incident. There are 4 major phases: (1) report of the emergency and activation of the EMS system, (2) dispatch of appropriate prehospital units, (3) medical evaluation and field treatment by EMS personnel, and (4) transport of the patient to the appropriate hospital.
A. Report of the Emergency
In many areas of the United States, a single, easily remembered telephone number (9-1-1) can now be used to request emergency help from the police and fire departments and to activate the EMS system.
B. Dispatch
Dispatchers receive the emergency call, interview the caller to determine the type and severity of the emergency, and dispatch the appropriate type of emergency medical response. In systems with heavy call volumes, calls may be priority ranked and then dispatched in order of urgency of need and resource availability. In some systems, dispatchers offer advice to callers to assist patients pending the arrival of emergency units (prearrival instructions). Algorithms may be employed to guide the dispatcher in decision making (Figure 2-1). Dispatchers in layered-response emergency medical systems frequently follow specific protocols in determining which type of EMS unit to dispatch (ie, ALS, BLS, first responder; see Table 2-2). Dispatchers may also be trained to provide CPR instructions by telephone to callers. Dispatch centers may also monitor hospital availability, manage the status and geographic deployment of EMS vehicles, and through computer-aided dispatch perform EMS management information and quality assurance functions.
C. Medical Evaluation and Treatment
Most EMS systems in urban and suburban areas are capable of responding within a few minutes of receiving an emergency call. First responders can frequently arrive at the scene within 3-6 minutes, and paramedics within 5-10 minutes of receiving the call. Survival following time-sensitive medical emergencies such as cardiac arrest is closely correlated with unit response time, especially when basic EMTs have been trained in defibrillation. In layered-response systems, paramedics are held in reserve for such critical or life-threatening incidents, where their advanced skills may provide definitive or stabilizing care to patients. Many systems have advanced-level first responders, such as engine companies manned with paramedics. These responders can provide the same interventions as ambulance-based paramedics but lack the means to transport patients. These assets can be additional resources in the single complex patient or in the multiple-patient incident.
Upon arrival at the emergency scene, EMS personnel undertake patient assessment and examination. EMT-paramedics in most cases are authorized by standing orders to proceed with patient care. Following patient evaluation and treatment, the EMS unit contacts the supervising emergency medical physician (or, in some states, a nurse) at the base station hospital by radio or telephone to describe the patient's condition and any treatment undertaken. The physician may give specific instructions for further treatment at the scene or request transport to the hospital for care.
D. Transport
The mode of transport (ground or air, with or without sirens or lights) depends on availability, stability of the patient's condition, transport time and distance, risks, and the like. Hospital destination decisions are often guided by local protocols, with critically ill patients directed to the closest, most appropriate facility. For example, a community hospital may be bypassed in favor of the nearest designated trauma center in the case of a severely injured patient. Noncritical cases may be transported to the hospital of the patient's choice.
1. Ground transport—Most patients are transported in surface ambulances. These vehicles vary slightly from state to state in their configuration and on-board equipment, but all follow guidelines set by the DOT. Emergency vehicle operators usually are allowed by local and state laws to violate certain traffic laws while responding to an emergency or carrying a patient in a life-threatening emergency. In the vast majority of cases, however, the patient's life is not in danger and posted speeds and traffic laws should be obeyed. The time gained in using red lights and sirens to get to the hospital is often outweighed by the additional risk of death and disability associated with rapid transport.
In most EMS systems, the responding unit is also the transporting unit. In others, especially layered-response systems, the responding unit may primarily evaluate and stabilize the patient and may summon a lower-level unit to provide transport.
2. Air transport—Some EMS systems and regional trauma hospitals, particularly those serving large outlying rural areas, use helicopters or fixed-wing aircraft with trained medical teams on board as additional resources for prehospital care and transportation. The majority of these aircraft are hospital based, but some are operated by municipal or state governmental agencies. Where these services are unavailable, or when search-and-rescue missions are required, aircraft equipped for medical evacuation may be sent from local military bases, operating within the Military Assistance to Safety and Traffic program.
Air ambulances are usually integrated into the EMS system and are activated according to certain locally established criteria. The decision to transport a patient by air requires careful consideration of the risks and benefits of air versus ground transport (see below).
Medical Supervision
A. On-Line Medical Direction
On-line medical direction is the direction given by radio to EMS personnel at the scene while care is being provided. It is usually given by emergency physicians or nurses at the base station hospital or receiving hospital. In most systems, the use of standing orders is allowed (Figure 2-2). This approach allows treatment to begin as soon as possible. Systems that have changed over from on-line medical control to standing orders have not shown a decrement in medical care but have shown an increase in EMS provider morale.
Even in systems that operate nearly exclusively by standing orders, some exceptions may require on-line direction. These may include cessation of CPR in a nonviable patient or the administration of restricted medications such as narcotics or paralytics. Systems that employ standing orders require effective monitoring, training, and quality assurance mechanisms.
B. Off-Line Medical Direction
Off-line medical direction is the overall direction of the activities of EMS personnel. It includes establishing protocols and standing orders, ensuring adequate training and skills, reviewing patient care records and voice tapes retrospectively, and reviewing performance and outcome data. Off-line medical direction is usually provided by a physician experienced in emergency services or by an agency in which physicians play an active role.
Performance Evaluation
System performance evaluation has many aspects, including the evaluation of input resources and operating guidelines (eg, protocol validation, personnel review, training assessment), evaluation of the process of delivering care in the field (eg, response times, service volume, treatment audits for adherence to protocols), and evaluation of the outcome of prehospital care (eg, complications, complaints, success in the performance of procedures, and patient survival). Outcome data are the most difficult to obtain.
PREHOSPITAL SKILLS & TECHNIQUES
Field Assessment
EMTs responding to a call usually have certain dispatch information, including the location, the nature of the complaint, and the number of patients. Upon arrival, they must quickly determine the presence of hazards to themselves and the patient, ascertain the probable mechanism of injury, and identify other patients, if any. Support can be summoned for hazard suppression or additional medical assistance. Patients who are conscious and in minimal distress may be able to provide historical information. Information may also be obtained from witnesses or family members.
Patients who are very ill may require that interventions be performed simultaneously with assessment. Interventions aimed at stabilizing airway, breathing, or circulation (the ABCs) will take precedence over secondary assessment. The receiving physician should expect that, if the patient is seriously ill or injured, only life-saving measures may be performed prior to arrival. In the more stable patient, a more thorough primary and secondary survey should be performed.
Field Treatment
A. Airway Control
Methods of airway control depend on the EMT's level of skill and certification. Initial steps to provide an airway include positioning the jaw and suctioning secretions (taking care in the trauma victim not to hyperextend the neck). Should this fail to achieve and maintain airway patency, the basic EMT can insert an oral or nasal airway. Ventilation may be assisted by a bag-valve-mask.
EMTs and paramedics may establish alternative airways, depending on local protocol. The Combitube, a dual lumen tube designed to be placed blindly, can be used to ventilate the patient regardless of whether the tube is placed in the esophagus or the trachea. The laryngeal mask airway (LMA) is designed to be placed without laryngoscopy. It has an inflatable cuff that sits over the glottis. This allows for ventilation while minimizing gastric insufflation and aspiration. It is not as secure an airway as the endotracheal tube. An improvement on the original LMA is the LMA-Fastrach, which allows for an endotracheal tube to be passed through the LMA. Both the Combitube and the LMA have been implemented successfully in the prehospital setting.
Endotracheal intubation is the preferred method of airway control in patients with inadequate ventilation. Typically the success rate for prehospital intubation is greater than 90%. However, two recent papers have questioned the value of intubation in the field. A randomized trial involving pediatric intubation found that patients did as well with bag-valve-mask ventilation as they did with intubation. Another study found that over 25% of adult intubations in the prehospital setting were misplaced. When intubation is performed in the field it is suggested that end-tidal CO2 detection and an esophageal detector device be used in addition to more conventional means of confirming location. After the tube is confirmed in the correct location, the risk of dislodgement should be minimized by using a commercial endotracheal tube holder and by securing the patient in a cervical collar and to a long spinal board.
B. Emergency Cardiac Care
1. Cardiopulmonary resuscitation—The probability of survival for victims of sudden cardiac arrest is inversely related to the elapsed time before an effective cardiac rhythm is reestablished. CPR is a temporizing measure that, when initiated within 4-6 minutes, increases the chances of survival. In most systems, a paramedic unit cannot routinely reach the scene within this period. Many systems provide first responders with AEDs. AEDs have been successfully deployed with police and fire first responders. In addition, public access defibrillators provide AEDs to the public at busy venues such as sporting arenas and airports.
2. Defibrillation—Ventricular fibrillation is the initial rhythm encountered in many victims of sudden death. The sooner defibrillation is performed, the higher the survival rate. AEDs (Laerdal Heartstart 2000, others) can recognize ventricular fibrillation (or tachycardia) and deliver a countershock. The rescuer need not be able to recognize dysrhythmias but must be able to recognize cardiac arrest and operate the device. AEDs have enabled nonparamedic first responders to provide rapid defibrillation and have consequently improved survival rates.
3. Electrocardiography—In the treatment of acute coronary syndromes, the prehospital 12-lead electrocardiogram (ECG) significantly shortens the time from arrival in the emergency department to administration of thrombolytic therapy ("door to drug time"). Prehospital fibrinolytic therapy has had mixed results. In European trials, where prehospital care is typically provided by physician-staffed ambulances, 6-month and 1-year survival rates have increased. However, trials in the United States with paramedic-staffed units has not shown a significant improvement over 12-lead ECG in the field with hospital-administered fibrinolytics.
C. Invasive Procedures
1. Venous catheterization—(See Chapter 6.) The use of intravenous techniques by EMS field personnel is usually limited to cannulation of peripheral veins of the upper extremities. In most EMS systems, the procedure can be initiated under standing order by intermediate or paramedic EMTs. Basic EMTs who have had special training in intravenous techniques and fluid therapy may also initiate intravenous lines. Studies have demonstrated that skilled paramedics in the field are able to start an intravenous line in approximately 3 minutes and achieve a success rate greater than 90%. However, when transport times are short (ie, 10 minutes or less), venous catheterization is usually unnecessary because the volume of fluid infused or the medications administered during such a short period are unlikely to be life saving. Further, in penetrating trauma to the thorax, fluid boluses may be detrimental by disrupting the clotting process. In addition, field placement of intravenous lines may increase the chances of infection. Needlestick injuries, which may occur during venous cannulation under adverse circumstances, such as in the back of a moving ambulance, are an increasing concern. Intraosseous needles may be placed by paramedics in the event that vascular access cannot be obtained in the pediatric patient.
2. Needle thoracostomy—Chest decompression for suspected tension pneumothorax may occasionally be life saving and is performed by paramedics in some systems. A 14- or 16-gauge catheter-clad needle is inserted into the second intercostal space along the midclavicular line immediately above the subjacent rib using sterile technique. The catheter is sealed with a Heimlich valve or a latex glove with the fingertip removed. (The open fingertip of the glove is secured around the catheter, allowing air to escape but preventing its reentry.)
3. Cricothyrotomy—(See Chapter 6.) Emergency entry to the airway may be life saving in cases of supraglottic airway obstruction or laryngeal trauma. Cricothyrotomy may be performed by paramedics in some EMS systems, usually after approval by the base physician via radio. Cricothyrotomy may be performed using a surgical, needle, or Seldinger technique. Because the procedure can be unexpectedly difficult, it should be performed as a last resort and only by properly trained personnel.
D. Medications
Medications are a contentious area in the prehospital realm. Because of the lack of clinical trials, it is difficult to state what interventions are of benefit. The emergency physician should know what medications are available to their EMS providers and under what indications they may be used.
1. Advanced cardiac life support—Most drugs for advanced cardiac life support are stocked on most ALS ambulances. Consistently, epinephrine, atropine, lidocaine, sodium bicarbonate, and adenosine are stocked. In addition, nitroglycerin, aspirin, and morphine are available for treatment of acute coronary syndromes. Amiodarone often is not used because of the ongoing debate about its effectiveness and because of cost issues. Some systems do not stock diltiazem because patients with a tachydysrhythmia that requires rate control are relatively stable. Fibrinolytics are rarely used because of their cost, the staffing needed to administer and monitor them, and the minimal benefit shown in prehospital use. Other medications such as labetalol, magnesium, procainamide, and calcium chloride are typically stocked at the discretion of the agency's medical director.
2. Pulmonary—Albuterol should be available to all ALS EMS agencies. Ipratropium has been shown to be beneficial to patients with moderate to severe asthma and to those with chronic obstructive pulmonary disease. In addition to sublingual nitroglycerin, furosemide is typically stocked for treatment of pulmonary edema.
3. Other drugs—Benzodiazepines are typically stocked for treatment of seizures, anxiolysis, and sedation. The use of prehospital benzodiazepines is beneficial to patients presenting with recurrent seizures. Agents stocked include diazepam, lorazepam, and midazolam.
Glucose, in the form of 50% dextrose in water (D50W) and oral glucose solution (occasionally D25W or D10W for pediatric patients), is stocked for treating hypoglycemia.
E. Extrication
Extrication is the process of removing a patient from a condition of entrapment, usually from a motor vehicle. It requires considerable skill and experience. Often, special tools are necessary, such as heavy bolt and metal cutters or large, powered spreading devices (eg, Jaws of Life, Hurst Tool). In most EMS systems, when there is a report of a trapped victim, a fire rescue team is dispatched in addition to the EMS unit to clear fire hazards, wash away spilled gasoline, and provide additional heavy equipment and personnel.
As soon as the patient is accessible with minimal risk to emergency workers, the primary survey should be initiated while further efforts to free the patient continue. Once the patient is immobilized in place, emergency resuscitation can begin.
F. Immobilization and Splinting
1. Immobilization—Victims of trauma may have injuries to the spine or extremities, which, if manipulated, can lead to spinal cord or limb damage. Upon reaching a trauma victim, the rescue team must stabilize the patient's cervical spine. Manual stabilization is maintained throughout extrication. A cervical collar is applied as soon as practicable. Spine boards are sometimes difficult to maneuver in closed spaces, but alternative devices are available, such as the Kendrick Extrication Device (KED). In a hemodynamically unstable patient, rapid extrication onto a long spine board can be accomplished by multiple rescuers manually supporting the spine without the aid of a KED. Immobilization is not considered complete until the patient is secured to the spine board with straps, the patient's head is secured to the spine board with tape across the forehead and beneath the chin, and a cervical collar and lateral neck rolls or head immobilization device are in place.
If endotracheal control intubation is necessary, the cervical spine should remain immobilized while the procedure is performed. Should vomiting occur, the patient may be logrolled to face sideways while one rescuer maintains cervical spine traction.
2. Splinting—(See Chapters 28 and 29.) In general, extremities should be placed in an anatomic position, especially if pulses cannot be felt below a suspected fracture. If the patient protests or if resistance is felt, extremities should remain in a position of comfort. Reduction of fracture dislocations at a joint should be attempted only if vascular compromise is impending, the duration of transport is long, and the rescuer is experienced in the technique. This usually requires the base physician's approval.
A pillow, rolled-up blanket, or other material may often serve as a simple splint. Specific splinting devices include cardboard splints, inflatable air splints, the MAST (military antishock trousers) garment, and traction splints. If inflatable devices are used, care must be taken to monitor distal perfusion, because a compartment syndrome may occur with swelling of the extremity or changes in atmospheric pressure (eg, during air transport). Traction splints are used primarily with fractures of the femur.
G. Protocols and Standing Orders
Protocols are guidelines designed to assist the EMT in performing tasks in a complete and orderly fashion (Figure 2-3). Because situations vary widely and protocols cannot anticipate every variable, they are not meant to be absolute and must be accompanied by training, judgment, and experience. Each EMS system tailors its protocol to the training and skill of its EMTs and the needs of the local medical community.
Standing orders are express authorizations for the performance of a specific task or procedure. Under the standing order, an EMT may be authorized to perform a task or procedure without first obtaining verbal authorization by radio. Standing orders are useful when radio contact is impractical or would delay life-saving intervention (eg, CPR, defibrillation). Standing orders usually contain a clear list of circumstances under which the authorization applies (indications) and detailed instructions on the manner in which the procedure should be performed. They are signed by the physician medical director, who shares legal responsibility for the outcome.
H. Communications
1. Equipment and frequencies—EMS units communicate with receiving hospitals by various methods. Three main radio systems exist: the HEAR network (in the 150-MHz range), the COR system (400 MHz), and the 800-MHz truncated system. The HEAR system is the oldest and has largely been replaced in urban areas by 800-MHz systems, which provide multiple frequencies for providers. In addition, cellular phones and landline telephones are used frequently for communications. Communication is simplex. Signals pass in only one direction at a time, and neither party can simultaneously speak and be heard. In rural areas, communication may be direct, via radio, without a relay station or ground lines.
2. Communication technique—Radio communication must provide information in a concise, precise, and easily understood manner. To facilitate speed and understanding, a common format is followed, with slight variations depending on the community. However, no one should hesitate to ask for clarification, because misunderstandings may prove fatal.
a. The initial contact—The caller always names the party being called first, followed by the caller's own identification:
"Central Hospital, this is medic 19, how do you copy?"
b. The initial response—The initial response confirms the contact in the same manner:
"Medic 19, Central Hospital, receiving you loud and clear, over."
c. The report—The caller gives a concise, orderly report containing pertinent history, physical findings, destination, estimated time of arrival (ETA), and any necessary request for instructions. It should be as brief as possible:
"Central Hospital, medic 19 en route to your location, ETA 8 minutes, with a 20-year old male victim of multiple, small-caliber gunshot wounds to the left chest, right flank, and right thigh. Patient is lethargic; blood pressure 80, pulse 140, respirations 46. Breath sounds absent over the left chest, abdomen soft. We have an ET tube in place, 2 IVs with lactated Ringer's wide open, and MAST garment inflated. Requesting permission for needle decompression of the left chest."
d. The report acknowledgment—This acknowledgment is kept brief; only essential queries should be made:
"Medic 19, have you checked ET tube position?"
"That's affirmative. Withdrawn 2 centimeters without improvement."
"Okay, medic 19; needle thoracostomy, left chest, is approved. Will stand by for update."
e. The sign-off—After receiving an order, the field personnel should repeat it to demonstrate that it was received accurately before signing off:
"Central Hospital, understand needle thoracostomy, left chest, is approved. Stand by."
3. 10-Codes—"Ten codes" are phrases represented by 2 numbers, the first being 10. In many areas, these are used to ensure precise communication and to add some measure of privacy to the conversation. Unfortunately, few EMS personnel have all of the possible 120 codes memorized. The result is often more confusion rather than less. Because mistakes may be dangerous, the codes should not be used unless thoroughly understood by all parties.
4. Telemetry—Receiving hospitals and ambulances may have equipment designed for the transmission of electrocardiographic traces (telemetry). This equipment is seldom used, however, because well-trained paramedics have shown the ability to interpret unstable rhythms (eg, ventricular fibrillation, ventricular tachycardia, bradycardia, and asystole) with acceptable precision, and more complex rhythms (eg, supraventricular tachycardia) rarely require treatment that cannot be postponed until arrival at the hospital. As indicated above, the prehospital 12-lead ECG has shortened the door to drug time in patients with acute coronary syndromes.
I. Air Transport
1. Indications—As noted above, the benefits to the patient must outweigh the risks inherent in this mode of transport. Aeromedical transport is most advantageous when great distances must be covered rapidly, when ground transport is unavailable or impeded by geographic obstacles or dense traffic, or when specialized care (eg, trauma resuscitation) is needed at the scene or en route. Emergency medical helicopters serving rural areas often provide a higher level of care and more skilled procedures (eg, intubation, needle thoracostomy, cricothyrotomy) than are provided by localized services using basic EMTs. However, air transport is hazardous, and helicopters operating at night and in inclement weather have crashed.
2. Requesting service—Helicopters equipped for medical evacuation can be requested, through the EMS communications network, from an area hospital that offers such services or from a local military base that participates in the Military Assistance to Safety and Traffic program.
3. Patient preparation—Before departure, stabilize the patient on a spine board and immobilize the patient as clinically indicated. Secure airway tubes and intravenous catheters.
4. Anticipated physiologic consequences of air transport—
a. Hypoxia—Atmospheric pressure decreases with increasing altitude, as does the partial pressure of oxygen. Patients with existing heart or lung disease may suffer adverse consequences. Supplemental oxygen is required.
b. Expansion of trapped gas—The volume of trapped gas increases with decreasing barometric pressure. Thus, as altitude increases, air may expand in endotracheal tube cuffs, air splints, MAST garments, the bowel lumen, the stomach, pneumothorax, abscess cavities, and the bottles and tubing of intravenous infusion apparatus. These compartments must be monitored frequently and vented as necessary. Intravenous flow rates should be adjusted accordingly.
c. Motion, noise, and vibration—These may cause patient discomfort. Forward acceleration with the patient's head forward may cause transient hypotension. This may be prevented by positioning the patient with feet forward.
5. Helicopter safety—
a. Site selection and lighting—A helicopter landing site should be level, approximately 100 feet square, and free of obstacles (eg, trees, wires) to approach and departure. It should also be clear of loose debris. The site should be secure from bystanders. At night, the site should be well lighted (eg, with vehicle headlights), but lights should never be directed upward toward the approaching helicopter, because they might interfere with the pilot's vision.
b. Approaching a helicopter—While the rotor blades are turning, approach the aircraft only from the front and only after prompting by the pilot. Avoid the tail rotor. Approach in a crouched position. Do not run. Never approach from uphill.
Lower tall objects such as poles associated with intravenous infusion apparatus. Secure sheets, hats, and loose clothing. Extinguish all smoking material.
2 comments:
May 20, 2017 at 12:18 AM
May 20, 2017 at 12:25 AM
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