Pharmacologic intervention in prehospital care: a critical appraisal

Barriers to EMS System Evaluation: Problems Associated with Field Data Collection

For more than two decades, emergency medical services (EMS) systems have proliferated primarily based upon governmental impetus and funding at the federal, state, and local levels. Although many of the foundations of patient care rendered in these systems have been based upon intuitive logic, the understanding of the impact on patient outcome is poor, at best. The reasons for the current status are varied, but five issues are preeminent:

1) The authority for the development of these medical systems has been based primarily in political and bureaucratic institutions which have little or no medical expertise;

2) Little attention has been paid to system evaluation, particularly in the area of cost-effectiveness;

3) Few academic medical institutions have become involved in EMS research;

4) Traditional approaches to medical research primarily are disease-specific and are not multidisciplinary. Thus these are not useful for evaluating and understanding the highly complex and uncontrolled environmental interactions that typify EMS systems; and

5) The process of efficiently and reliably collecting accurate data in the prehospital setting is extremely difficult.

Analgesia in the Field

Emergency Medical Services and the care of patients in the field have taken giant steps forward over the past decade. Born of the desire of physicians to influence the mortality rates of sudden cardiac death in the community, systems of advanced life support have taken root in the urban centers in the United Kingdom, Australia, the United States, and other countries (1-3). Although originally largely designed around the concept of “mobile coronary care,” these systems soon were deluged with calls for help from all sectors of the community, and faced a variety of medical problems. As trauma gradually became recognized for the killer and maimer of young lives that it is, regional programs of trauma care were developed in the United States and led gradually to the expansion of prehospital and interhospital transport systems in which critically injured patients were being moved about, often over long distances. The growth of emergency medicine as a specialty in its own right has encouraged the study and improvement of systems of disaster and mass casualty management.

Although the focus of these efforts has been largely the overall reduction of death and disability in critically ill or injured patients, controversy continues around not only the extent of field intervention but also the influence of our efforts on the outcome of these patients (4, 5). The importance of particular interventions such as intravenous line placement, administration of certain medications, the use of the pneumatic anti-shock garment, and other sacred cows of prehospital care, all have been questioned of late (6, 7).

Paramedic Skills And Medications: Practice Options Utilized By Local Advanced Life Support Medical Directors

Local advanced life support (ALS) medical directors in North Carolina choose the skills and medications they want utilized in their jurisdiction from a list of options authorized by the State Board of Medical Examiners. We surveyed all 35 medical directors of paramedic providers in the state to determine which optional skills and medications local medical directors allow to be used and, therefore, how they tailor their prehospital practices. Information concerning the urban or rural status of the paramedic service area, annual call volume, and the specialty classification of the medical director also were obtained.

All of the medical directors surveyed responded. Twenty-one (60%) of the paramedic service areas were rural and 14 (40%) urban. Twenty-three physicians (66%) listed emergency medicine as their primary specialty. Annual call volumes ranged from 580 to 33,500. Skills allowed by >80% of the medical directors include: drawing blood, insertion of esophageal and endotracheal airways, defibrillation, cardioversion, and initiation of intravenous fluids prior to hospital contact. The majority permit the administration of bretylium, dopamine, NaCl injection, sodium bicarbonate, furosemide, sublingual nitroglycerin, diazepam, diphenhydramine, and morphine. The majority do not allow the use of positive-pressure ventilators and do not allow administration of dobutamine, nifedipine, procainamide, propranolol, local procaine, isoetharine, metaproterenol, nitroglycerin paste, 10% dextrose solution, methylprednisolone, mannitol, phenytoin, meperidine, or nitrous oxide. Nitroglycerin paste and dexamethasone were significantly (p<.05) more likely to be allowed in rural than in urban areas. No differences in utilization by medical director specialty classification or call volume were detected. The results suggest that, when given a choice, local ALS medical directors select a limited prehospital practice. Further study is warranted to determine why available skill and medication options are not utilized.

A Survey of Advanced Life Support Practices in the United States

Study Objective:

A national survey was conducted to determine the sponsorship of emergency medical services (EMS) projects, composition of EMS advanced life support (ALS) teams, types of medications and equipment carried, and procedures approved for use by EMS systems in the United States.

Methods:

A mail survey was sent to 211 training supervisors of EMS services across the United States in 1989. The survey requested demographic and service-related information, including types of EMS sponsorship, composition of ALS teams, medications and equipment carried, and procedures which personnel have been trained to use. Medications carried were correlated with advanced cardiac life support (ACLS), the American College of Emergency Physicians (ACEP) recommended drug lists, and with the sponsoring agency.

Results:

One-hundred seventy (70%) survey forms were returned. The major providers of ALS in the United States are fire departments (36%), followed by private providers (26%), hospitals (22%), and local governments (16%). The most common ALS team composition was two paramedics followed by one paramedic and one emergency medical technician (EMT). Most ALS services carry all of the recommended ACLS medications; a much smaller percentage carry all of the drugs recommended by ACEP. Fire department based ALS units carried the least number of medications; hospital-based ALS units carried the highest number of medications. Combined, over 80 different medications were carried by the services responding to the survey.

Conclusion:

The use of ACLS drugs and procedures are well-established nation-wide; less accepted are the medications recommended by ACEP. While over 80 different medications are carried by the EMS systems that responded to this survey, only a small fraction have been investigated in the prehospital setting.

Study Design and Pre-Trial, Peer Review in EMS Research

In order to identify the study designs andthe type of pre-trial peer review in published EMS research, we reviewed three refereed emergency medicine journals during the period from 1985 through 1988. All original scientific manuscripts utilizing human subjects in prehospital care were analyzed. Ninety-six issues were examined, and 79 manuscripts met the criteria for analysis. The research design was cross-sectional in 7.5%, retrospective in 51%, and prospective in 41.5%. Pre-trial peer review had been sought in nine (11%). Each was performed by a hospital or university-based Institutional Review Board (IRB). Only four (5%) manuscripts contained statements about pre-trial peer review. All reviewed trials were prospective in design (9/33, 27%). A follow-up telephone survey of the authors of the non-reviewed prospective trials indicated that 96% were unaware of the potential need for pre-trial review, 16% anticipated difficulty obtaining approval from traditional IRB committees, and 11% feared that the protocol would be interfered with by the review committee.

We conclude that 92.5% of the current published EMS research is retrospective or prospective in design, and that pre-trial peer review is not obtained in the majority of prehospital EMS research. Guidelines should be developed to educate EMS researchers about the need for and the value of pre-trial peer review. Journal editors should clearly state and enforce policies about manuscripts lacking information about pre-trial peer review when human subjects are involved.

Management of prehospital seizure patients by paramedics

BACKGROUND

Seizure patients are frequently encountered in the prehospital environment and have the potential to need advanced interventions, though the utility of advanced life support (ALS) interventions in many of these patients has not been proven.

OBJECTIVE

Our goals were to assess the management of prehospital seizure patients by paramedics in an urban EMS system with an existing ALS-based prehospital seizure protocol and to assess characteristics and short-term outcomes that may aid in addressing the utility of specific ALS interventions.

METHODS

This was a retrospective study of 97 EMS cases with the chief complaint of seizure. Prehospital records were reviewed for patient and event characteristics, including past seizure history, seizure timing, level of consciousness, on-scene and transport times, and EMS interventions. Emergency department (ED) records were reviewed for recurrence of seizure activity, ED evaluation, and disposition. Data were analyzed using descriptive statistics and Student t-test.

RESULTS

Of 87 patients meeting the protocol inclusion criteria for all ALS interventions, 11 (12.6%) received cardiac monitoring, 55 (63.2%) had intravenous (IV) access attempted, and 56 (64.4%) had blood glucose determination. Average on-scene time was 5.9 minutes longer if IV access was attempted (p = 0.001), though transport times were not significantly different (11.6 versus 11.3 minutes, respectively; p = 0.851). Additional seizure activity occurred in the prehospital and/or ED settings in 28 patients (28.9% of all cases), including 17 in the prehospital setting and 15 in the ED. Diazepam was administered by EMS for half of the eight (8.2%) patients who had seizures lasting more than 1 minute, while the remainder had seizures that were focal or spontaneously resolved.

CONCLUSION

This study showed a lower-than-anticipated level of compliance with an ALS-based prehospital seizure protocol, though patient-specific care appeared appropriate. Prehospital seizure patients have the potential for seizure recurrence and may benefit from focused ALS interventions, but their heterogeneity makes uniform protocols difficult to develop and follow.

Initial cardiac rhythm correlated to emergency department survival

BACKGROUND

This study attempted to correlate the initial cardiac rhythm and survival from prehospital cardiac arrest, as a secondary end-point.

METHODS

Prospective, randomized, double-blinded clinical intervention trial where bicarbonate was administered to 874 prehospital cardiopulmonary arrest patients in prehospital urban, suburban, and rural emergency medical service environments.

RESULTS

This group's manifested an overall survival rate of 13.9% (110 of 793) of prehospital cardiac arrest patients. The most common presenting arrhythmia was ventricular fibrillation (VF) (45.0%), asystole (ASY) (34.4%), and pulseless electrical activity (PEA) (15.7%). Less commonly found were normal sinus rhythm (NSR) (1.8%), other (1.8%), ventricular tachycardia (VT) (0.6%), and atrioventricular block (AVB) (0.5%) as prearrest rhythms. The best survival was noted in those with a presenting rhythm of AVB (57.1%), VT (33.3%), VF (15.7%), NSR (14.3%), PEA (11.2%), and ASY (11.1%) (p = 0.02). However, there was no correlation between the final cardiac rhythm and outcome, other than an obvious end-of-life rhythm.

CONCLUSION

The most common presenting arrhythmia was VF (45%), while survival is greatest in those presenting with AVB (57.1%).

Sodium bicarbonate improves outcome in prolonged prehospital cardiac arrest

OBJECTIVE

This study evaluates the effect of early administration of an empirical (1 mEq/kg) sodium bicarbonate dose on survival from prehospital cardiac arrest within brief (<5 minutes), moderate (5-15 minutes), and prolonged (>15 minutes) down time.

METHODS

Prospective randomized, double-blinded clinical intervention trial that enrolled 874 prehospital cardiopulmonary arrest patients managed by prehospital, suburban, and rural regional emergency medical services. Over a 4-year period, the randomized experimental group received an empirical dose of bicarbonate (1 mEq/kg) after standard advanced cardiac life support interventions. Outcome was measured as survival to emergency department, as this was a prehospital study.

RESULTS

The overall survival rate was 13.9% (110/792) for prehospital arrest patients. There was no difference in the amount of sodium bicarbonate administered to nonsurvivors (0.859 +/- 0.284 mEq/kg) and survivors (0.8683 +/- 0.284 mEq/kg) (P = .199). Overall, there was no difference in survival in those who received bicarbonate (7.4% [58/420]), compared with those who received placebo (6.7% [52/372]) (P = .88; risk ratio, 1.0236; 0.142-0.1387). There was, however, a trend toward improved outcome with bicarbonate in prolonged (>15 minute) arrest with a 2-fold increase in survival (32.8% vs 15.4%; P = .007).

CONCLUSION

The empirical early administration of sodium bicarbonate (1 mEq/kg) has no effect on the overall outcome in prehospital cardiac arrest. However, a trend toward improvement in prolonged (>15 minutes) arrest outcome was noted.

Survival from prehospital cardiac arrest is critically dependent upon response time

STUDY OBJECTIVE

This study correlated the delay in initiation of bystander cardiopulmonary resuscitation (ByCPR), basic (BLS) or advanced cardiac (ACLS) life support, and transport time (TT) to survival from prehospital cardiac arrest. This was a secondary endpoint in a study primarily evaluating the effect of bicarbonate on survival.

DESIGN

Prospective multicenter trial.

SETTING

Patients treated by urban, suburban, and rural emergency medical services (EMS) services.

PATIENTS

Eight hundred and seventy-four prehospital cardiac arrest patients.

INTERVENTIONS

This group underwent conventional ACLS intervention followed by empiric early administration of sodium bicarbonate noting resuscitation times. Survival was measured as the presence of vital signs on emergency department (ED) arrival. Data analysis utilized Student's t-test and logistic regression (p<0.05).

RESULTS

Survival was improved with decreased time to BLS (5.52 min versus 6.81 min, p=0.047) and ACLS (7.29 min versus 9.49 min, p=0.002) intervention, as well as difference in time to return of spontaneous circulation (ROSC). The upper limit time interval after which no patient survived was 30 min for ACLS time, and 90 min for transport time. There was no overall difference in survival except at longer arrest times when considering the primary study intervention bicarbonate administration.

CONCLUSION

Delay to the initiation of BLS and ACLS intervention influenced outcome from prehospital cardiac arrest negatively. There were no survivors after prolonged delay in initiation of ACLS of 30 min or greater or total resuscitation and transport time of 90 min. This result was not influenced by giving bicarbonate, the primary study intervention, except at longer arrest times.

Evolution of statewide EMS drug formularies and regulations

OBJECTIVE

To characterize and follow the variability present in statewide emergency medical services (EMS) medication formularies across the United States over a ten-year period.

METHODS

Investigators contacted the lead EMS agencies in all 50 states during three years (1992, 1997, and 2002). Using a standardized form, the investigators collected information about each state's prehospital medication policies, including whether a statewide EMS medication formulary existed, the authority of local medical directors to modify it, and what medications it contained. The investigators then sorted states into categories based on the regulatory intent of their EMS medication policies and compared medication listings across years.

RESULTS

Responses were obtained from all 50 states (n = 50, 100%) during each of the survey periods. There appeared to be a trend toward stricter state control and toward less variation between statewide formularies. State regulations in seven states stopped allowing local medical directors to retain full control of their systems' formularies, and eight states implemented mandatory statewide formularies. There was a trend toward more consistency between states, with more "most commonly" listed medications (6.9% in 1992 versus 22.1% in 2002) and fewer "least commonly" listed medications (58.3% in 1992 versus 42.3% in 2002). Controversial medications such as neuromuscular blockers and thrombolytics appeared in a small but increasing number of statewide formularies.

CONCLUSIONS

Considerable variation was found among statewide EMS medication formularies, both in how they were established and in their contents. Although several states continued to rely solely on local medical direction, there seemed to be a trend toward more uniformity and stricter state control over prehospital medication formularies during the study period.

The influence of urban, suburban, or rural locale on survival from refractory prehospital cardiac arrest

There are many variables that can have an effect on survival in cardiopulmonary arrest. This study examined the effect of urban, suburban, or rural location on the outcome of prehospital cardiac arrest as a secondary end point in a study evaluating the effect of bicarbonate on survival. The proportion of survivors within a type of EMS provider system as well as response times were compared. This prospective, randomized, double-blind clinical intervention trial enrolled 874 prehospital cardiopulmonary arrest patients encountered by prehospital urban, suburban, and rural regional EMS area. Population density (patients per square mile) calculation allowed classification into urban (>2000/mi2), suburban (>400/mi2), and rural (0-399/mi2) systems. This group underwent standard advanced cardiac life support (ACLS) intervention with or without early empiric administration of bicarbonate in a 1-mEq/kg dose. A group of demographic, diagnostic, and therapeutic variables were analyzed for their effect on survival. Times were measured from collapse until onset of medical intervention and survival measured as the presence of ED vital signs on arrival. Data analysis used chi-squared with Pearson correlation for survivorship and Student t test comparisons for response times. The overall survival rate was approximately 13.9% (110 of 793), ranging from 9% rural, 14% for suburban, and 23% for urban sites for 372 patients (P=.007). Survival differences were associated with classification of arrest locale in this sample-best for urban, suburban, followed by rural sites. There was no difference in time to bystander cardiopulmonary resuscitation, but medical response time (basic life support) was decreased for suburban or urban sites, and intervention (ACLS) and transport times were decreased for suburban sites alone. Although response times were differentiated by location, they were not necessarily predictive of survival. Factors other than response time such as patient population or resuscitation skill could influence survival from cardiac arrest occurring in diverse prehospital service areas.

Options in prehospital analgesia

BACKGROUND

Prehospital analgesia options for paramedics have been limited due to the difficulty in achieving safe and effective pain relief without compromising transportation to hospital. The present paper identifies the analgesia methods currently available in the prehospital setting so as to evaluate the various options and highlight areas for future research.

METHODS

A literature review of Medline and Embase databases from 1966 until the present was undertaken. Further hand searching of all the references identified in these papers was also performed. All current literature was analysed and categorized according to one of four levels of evidence using National Health and Medical Research Council of Australia guidelines (1999).

RESULTS

There is a paucity of randomized control trials relating to prehospital analgesia. All published literature was level III or IV prospective or retrospective studies. Drug options used included nitrous oxide/oxygen mixtures, intravenous/intramuscular nalbuphine, intravenous tramadol and intravenous pure opiate agonists.

CONCLUSIONS

The evidence supporting analgesic options in the prehospital setting is limited. There are few published data in this area despite the inadequacy of pain relief being recognized as a weakness in prehospital care. Prehospital analgesia is an area worthy of innovative methods for the administration of safe and effective analgesics without significant impact on transport times. Such methods should be prospectively evaluated in well-constructed trials.

Paramedic decisions with placement of out-of-hospital intravenous lines

To determine the incidence of unused out-of-hospital intravenous line (IV) placements, we prospectively studied IV placement in emergency medical services (EMS) patients. Unused IV placement was defined as any patient having an EMS initiated IV that was not used for fluid bolus or medication administration in the field or in the emergency department (ED). Data were analyzed on placement and use of IV lines in the field and in the ED, transport time, years of paramedic practice, and paramedic student presence. Of 290 patients, 165 had an IV initiated (147) or attempted (18). Twenty-nine percent (84 of 290) of the patients received an unused EMS IV. One hundred twenty-five patients had no IV initiated by EMS. Seven subsequently had an IV started and used in the ED, for an undertreatment rate of 2.4% (7 of 290). The presence of a paramedic student increased the odds of an unused IV 1.4 (95% CI, 1.1 to 2.0). IVs are frequently started and not used.

Fatal intracranial bleeding associated with prehospital use of epinephrine

We present a case of paramedic misjudgment in the execution of a protocol for the treatment of allergic reaction in a case of pulmonary edema with wheezing. The sudden onset of respiratory distress, rash, and a history of a new medicine led the two paramedics on the scene to administer subcutaneous epinephrine. Subsequently, acute cardiac arrest and fatal subarachnoid hemorrhage occurred. Epinephrine has a proven role in cardiac arrest in prehospital care; however, use by paramedics in patients with suspected allergic reaction and severe hypertension should be viewed with caution.

Does the level of prehospital care influence the outcome of patients with altered levels of consciousness?

HYPOTHESIS

Significant differences exist in the outcome of patients with altered level of consciousness (ALOC) cared for by advanced life support (ALS) compared with basic life support (BLS) prehospital providers.

METHODS

Patients transported by ambulance to a community teaching hospital during an 11-month period were studied retrospectively. Study patients were those considered not alert by prehospital personnel. Exclusion criteria included; trauma, intoxication, drowning, shock, and cardiac arrest. Data were abstracted from the ambulance reports and hospital records.

RESULTS

Two hundred three patients with an ALOC were identified; 113 were transported by ALS providers (56%) and 90 (44%) by BLS providers. Prehospital levels of consciousness, according to the "alert, verbal, painful, unresponsive" scale (ALS vs BLS) were: "verbal" (40% vs 51%), "painful" (23% vs 23%), and "unresponsive" (37% vs 25%). The mean value for some time was 15 +/- 6 minutes for ALS versus 10 +/- 4 minutes for BLS (p < 0.001). On arrival in the emergency department, the LOC of 72 (64%) ALS patients and 58 (64%) BLS patients had improved to "alert." The level of consciousness in one ALS patient worsened. Fifty-two ALS (46%) and 38 (42%) BLS patients were admitted. Principal final diagnoses were seizure (27% ALS vs 38% BLS), hypoglycemia (23% ALS vs 23% BLS), and stroke (22% ALS vs 20% BLS). Remaining diagnoses each constituted less than 7% of total discharge diagnoses. No statistically significant differences in measures of outcome were noted between ALS or BLS patients. Diagnoses of seizure, stroke, and hypoglycemia were studied individually. No differences in admission rate, mortality rate, or disposition were identified. Hypoglycemic patients conveyed by ALS providers had significantly shorter emergency department treatment times than did those transported by BLS providers (160 +/- 62 minutes ALS vs 229 +/- 67 minutes BLS [p < 0.005]).

CONCLUSION

Advanced life support levels of care of patients with an ALOC does not significantly change outcome compared with those receiving BLS care with the exception of shorter emergency department treatment times for hypoglycemic patients.

Outcomes in severely ill patients transported without prehospital ALS

Because of the debate regarding the impact of advanced life support (ALS) care on the outcome of prehospital patients, we monitored the influence of lack of sophisticated prehospital treatment in cases of severe illness arriving by ambulance to the emergency department (ED). A prospective cohort study to examine and compare the outcome of trauma- and nontrauma-induced "ALS-eligible" cases in the setting of no prehospital care was carried out from August 1, 1993 through May 31, 1994. On arriving at the ED, patients meeting the criteria for ALS cases and sent by EMS public prehospital personnel were assessed for subjective and objective status and change in severity by triage nurses as well as being followed up for neurological status until discharged from the hospital. Chi-Square method was used to compare the data between two groups and P < .05 was considered statistically significant. Of 667 studied ALS cases (155 trauma and 512 nontrauma), < 20% had their condition change subjectively and < 10% had their condition change objectively; 68% of medical patients and 60% of trauma cases were discharged from the hospital (neurologically intact). However, subgroup analysis showed that objective measures worsened in transit in nearly 18% of trauma victims, a rate nearly 3 times greater than that of medical cases. Moreover, neurological outcome was particularly poor in trauma cases. These results suggest that ALS care may be valuable for severely ill trauma victims.

Use of on-line medical command to randomize patients in a prehospital research study

OBJECTIVE

To describe the efficiency of using on-line medical command (OLMC) to conduct a prospective, randomized clinical trial addressing safety and patient enrollment.

DESIGN, SETTING, AND PARTICIPANTS

Prospective design using OLMC to randomize adult asthmatics into one of three treatment groups. After verifying inclusion and exclusion criteria, OLMC physicians removed a covering label on study sheets and ordered the treatment specified underneath the label that had been assigned in a random sequence.

RESULTS

A total of 204 patients were seen with dyspnea and wheezing during the three-month study. Of these, 68 (33%) were excluded from the study. Of the 136 (67%) patients who were eligible for study, 87 were enrolled (enrollment efficiency 64%), with 79 fully evaluable (evaluable efficiency 91%). The study safety was 100% because no enrolled patients met any exclusion criteria.

CONCLUSIONS

The design was random and prospective, with patient entry blinded, using paramedics to enroll patients and OLMC physicians as gatekeepers, thus ensuring appropriate patient eligibility and study-arm assignment. Use of OLMC physicians to perform prospective randomized studies is safe and efficient, and results in a high yield of evaluable patients.

Terbutaline vs albuterol for out-of-hospital respiratory distress: randomized, double-blind trial

OBJECTIVE

To determine the efficacy and safety of single doses of subcutaneous terbutaline (TERB) or nebulized albuterol (ALB) during out-of-hospital treatment for respiratory distress from asthma or chronic obstructive pulmonary disease.

METHODS

Patients aged > 18 years who had respiratory distress were enrolled in a double-placebo, double-blind, randomized trial. Paramedics measured respiratory severity using an empiric score [respiratory rate, wheezing, speech, and peak expiratory flow rate (PEFR)], and the patients rated their own respiratory distress using a visual analog scale (VAS). The patients received O2 plus ALB (2.5 mg) and saline injection (n = 40) or TERB (0.25 mg) and saline aerosol (n = 43).

RESULTS

The groups were similar with respect to age, gender, initial empiric scores (median score 9 for both groups), PEFRs (89 +/- 84 L/min, mean +/- SD, for ALB vs 97 +/- 84 L/min for TERB), and respiratory distress VAS scores. Both groups showed significant improvement in their respiratory distress VAS scores by the time of ED arrival. The ALB group had a greater improvement in respiratory distress VAS score than did the TERB group (p < 0.05). Empiric scores, PEFR scores, and hospital admission frequencies were not significantly different. No complication was observed.

CONCLUSION

The out-of-hospital administration of either aerosolized ALB or subcutaneous TERB reduced respiratory severity. Albuterol provided greater subjective improvement in respiratory distress.

Effects of prehospital care on outcome in patients with cardiac illness

STUDY OBJECTIVE

To compare outcomes of patients with acute cardiac illness transported by ambulance for whom prehospital care was provided by emergency medical technician-paramedics (EMT-Ps) or EMTs trained in defibrillation (EMT-Ds).

DESIGN

A prospective chart review carried out over 3.5 years.

SETTING

The Hamilton-Wentworth region of Ontario, Canada, which covers 1,136 km2 and includes five receiving hospitals.

PARTICIPANTS

We prospectively identified 8,720 potentially eligible patients from approximately 30,000 who presented to the ambulance service. We reviewed hospital charts to confirm eligibility. The group of 8,720 patients yielded 3,066 patients with acute cardiac illness who met all other eligibility requirements. We excluded patients in cardiac arrest.

RESULTS

Incidence of myocardial infarction (MI), length of hospital stay, and mortality were evaluated. Analysis was performed with chi 2 tests for association, linear regression, and logistic regression. Of the eligible patients who received prehospital EMS care, 783 sustained MIs. The proportions of people discharged alive with the diagnosis of MI did not differ between crew types (P = .16). Average hospital stay was 13 days in both groups for patients with the discharge diagnosis of MI; hospital stay ranged from 9 (EMT-D) to 11 days (EMT-P) for any patient with a discharge diagnosis other than MI. These values were statistically similar. The odds ratio of having had an MI after treatment by an EMT-D crew was 1.02 (95% confidence interval, .86 to 1.21) compared with that for treatment by an EMT-P crew.

CONCLUSIONS

In an urban setting with short (less than 10 minutes) average transport times, the availability of prehospital paramedic care does not affect occurrence of MI, length of hospital stay, or mortality of patients presenting to the EMS system with cardiac illness.

Differential prehospital benefit from paramedic care

STUDY OBJECTIVES

To determine whether prehospital outcome of patients who receive care from emergency medical technicians-paramedic (EMT-Ps) differs from that of patients who receive care from emergency medical technicians-defibrillation (EMT-Ds), as rated by the treating EMTs using standardized scales, and to determine whether the patient's seriousness of illness is relevant to any differential benefit of one level of care over the other.

DESIGN

Historical (retrospective) cohort.

SETTING

An urban and semiurban region of southwest Ontario comprising an area of 1,136 square kilometers (438 square miles) with a population of more than 445,000.

TYPE OF PARTICIPANTS

Patients (10,291) who were transported by the Hamilton-Wentworth EMS system between January 1, 1991, and December 31, 1991.

METHODS AND MEASUREMENTS

EMTs rated the prehospital outcome of their own patients, using scales that had been tested in a previous study. Comparisons between EMT-P- and EMT-D-treated patients were made by chi 2, chi 2 by trend, and Fisher's exact test as appropriate.

RESULTS

More seriously ill or injured EMT-P-treated patients were rated as improved and fewer EMT-P-treated patients were rated as worsened compared with similar patients who were cared for and rated by EMT-Ds. The differential benefit from EMT-P to EMT-D care ranged from 8% to 25% for patients rated as "severe" and from 27% to 49% for patients rated as "life-threatened."

CONCLUSION

According to the ratings of prehospital care providers, patients classified as "severe" or "life-threatened" had their conditions "improve" by the time they arrived at the hospital more often when care was provided by an EMT-P team than when it was provided by an EMT-D team.

Safety of prehospital nitroglycerin

STUDY OBJECTIVE

To define changes in vital signs and cardiac rhythm in prehospital patients given sublingual nitroglycerin.

DESIGN

A five-month prospective observational study with nitroglycerin administration as the independent variable.

SETTING

Five independent advanced life support services.

TYPE OF PARTICIPANT

Three hundred prehospital patients who were given nitroglycerin by advanced life support personnel for presumed myocardial ischemia or congestive heart failure; excluded were those without repeat vital signs or ECG monitoring and those given additional medications.

INTERVENTION

Nitroglycerin was administered by regional emergency medical services protocols or by the order of an on-line medical command physician.

RESULTS

Four study patients (1.3%) had adverse effects: One became asystolic and apneic for two minutes, two experienced profound bradycardia with hypotension, and one became hypotensive while tachycardic. All recovered. The 95% confidence interval for adverse effects was 0.5% to 3.4%. Mean fall in systolic blood pressure for the other 296 patients was 14 mm Hg for one dose (confidence interval, 11 to 16 mm Hg) and 8 mm Hg (confidence interval, 2 to 13 mm Hg) for a second dose. Heart rate changed minimally with nitroglycerin administration. The blood pressure drop was linearly correlated with initial systolic pressure (r = -.44; P < .001) but not correlated with number of prior doses of nitroglycerin, initial heart rate, advanced life support time interval, age, or sex.

CONCLUSION

Nitroglycerin seems to be a relatively safe advanced life support drug; however, a few patients experience serious adverse effects. Most of the adverse effects we observed were bradycardic-hypotensive reactions, which appeared to be unpredictable by pretreatment characteristics. Emergency personnel should have an increased awareness of this danger when considering the use of prehospital nitroglycerin.

Prospective validation of a new model for evaluating emergency medical services systems by in-field observation of specific time intervals in prehospital care

STUDY OBJECTIVE

To develop and validate a new time interval model for evaluating operational and patient care issues in emergency medical service (EMS) systems. DESIGN/SETTING/TYPE OF PARTICIPANT: Prospective analysis of 300 EMS responses among 20 advanced life support agencies throughout an entire state by direct, in-field observation.

RESULTS

Mean times (minutes) were response, 6.8; patient access, 1.0; initial assessment, 3.3; scene treatment, 4.4; patient removal, 5.5; transport, 11.7; delivery, 3.5; and recovery, 22.9. The largest component of the on-scene interval was patient removal. Scene treatment accounted for only 31.0% of the on-scene interval, whereas accessing and removing patients took nearly half of the on-scene interval (45.8%). Operational problems (eg, communications, equipment, uncooperative patient) increased patient removal (6.4 versus 4.5; P = .004), recovery (25.4 versus 20.2; P = .03), and out-of-service (43.0 versus 30.1; P = .007) intervals. Rural agencies had longer response (9.9 versus 6.4; P = .014), transport (21.9 versus 10.3; P < .0005), and recovery (29.8 versus 22.1; P = .049) interval than nonrural. The total on-scene interval was longer if an IV line was attempted at the scene (17.2 versus 12.2; P < .0001). This reflected an increase in scene treatment (9.2 versus 2.8; P < .0001), while patient access and patient removal remained unchanged. However, the time spent attempting IV lines at the scene accounted for only a small part of scene treatment (1.3 minutes; 14.1%) and an even smaller portion of the overall on-scene interval (7.6%). Most of the increase in scene treatment was accounted for by other activities than the IV line attempts.

CONCLUSION

A new model reported and studied prospectively is useful as an evaluative research tool for EMS systems and is broadly applicable to many settings in a demographically diverse state. This model can provide accurate information to system researchers, medical directors, and administrators for altering and improving EMS systems.

Effects of prehospital medications on mortality and length of stay in congestive heart failure

HYPOTHESIS

Prehospital medications for congestive heart failure should affect hospital outcomes (survival and length of stay).

STUDY DESIGN

In a retrospective case series, hospital outcomes were compared for patients treated with prehospital nitroglycerin, furosemide, and/or morphine (252) versus those given no medications (241).

SETTING

A rural/suburban emergency medical services system (population 140,000) served by three paramedic units.

PARTICIPANTS

Four hundred ninety-three consecutive cases of congestive heart failure or pulmonary edema were identified by hospital discharge diagnosis from a data base of 8,315 paramedic transports with known outcome.

INTERVENTIONS

Oxygen was given by protocol to 489 patients. Other medications were given by order of on-line physician medical command.

RESULTS

Overall mortality was 10.9% (54 of 493). Treated and untreated patients were comparable in age, sex, cardiac rhythms, prior use of cardiac medications, and response and scene times; mortality was reduced in treated versus untreated patients (odds ratio for improved survival, 2.51; 95% confidence interval, 1.37 to 4.55; P less than .01). Positive treatment effect was greatest for 58 nonhypotensive, critical patients (odds ratio for survival, 10.25; P less than .01). No single drug combination was unique in terms of treatment benefit. Patients treated in the field received medications 36 minutes earlier than patients first treated in the emergency department. No survival benefit was evidence for noncritical, nonhypotensive patients, and patients with final diagnoses of asthma, chronic obstructive pulmonary disease, pneumonia, or bronchitis had a higher than expected mortality if erroneously treated for congestive heart failure. Differences in hospital length of stay were not significant for any group.

CONCLUSION

Prehospital medications improve survival in congestive heart failure, especially in critical patients. More than one combination of medications seems effective, and early treatment is associated with improved survival. However, these medications appear to increase mortality in patients misdiagnosed in the field. Factors used in paramedica and medical command assessments require further study.

Safety of pre-hospital therapy with morphine sulfate

The safety of prehospital pharmacologic therapy has not been well studied. The authors evaluated field use of morphine sulfate (MS) in San Francisco County over a 6-month period. Paramedics assessed patients for ischemic chest pain (ICP) and/or pulmonary edema (PE), made base hospital contact, and administered 2- to 4-mg doses of intravenous morphine according to treatment protocols. Clinical assessments and patient responses to therapy were recorded by both field paramedics and emergency department (ED) physicians. Safety was evaluated by determining the (1) accuracy of paramedic field assessment, (2) appropriateness of field administration of MS, and (3) therapeutic complications. During the study period, paramedics administered MS to 84 patients. In 69 cases paramedic assessment of either ICP and/or PE corresponded to ED physician diagnosis. In five cases paramedics correctly recognized ICP but missed physical findings of PE. In this group the paramedics' assessment was considered inaccurate but the judgement to give MS was considered appropriate. In the remaining 10 cases paramedics identified ICP or PE but the ED physician diagnosed a different condition. These assessments were considered inaccurate and the management inappropriate. Therefore, overall paramedic accuracy was 77% (true rate 73% to 82%, 95% confidence interval); appropriateness of therapy was 88% (true rate 85% to 92%, 95% confidence interval); and the overall complication rate was 6% (true rate 2% to 12%, 95% confidence interval). Complications of respiratory depression or hypotension occurred in only one of the cases in which MS was inappropriately administered.(ABSTRACT TRUNCATED AT 250 WORDS)

The prehospital use of albuterol inhalation treatments

The use of bronch odilators in the prehospital EMS setting is common. This study examined the safety of the administration of 2.5 mg albuterol using a hand-held nebulizer for the treatment of such patients. A total of 55 patients were included. Following treatment, peak expiratory flow rates (PEFR) increased a mean of 27 L/min, ventilatory rate decreased four breaths/min, heart rate decreased slightly, and systolic blood pressure increased 10 mmHg. Five of the 53 patients in whom cardiac rhythm was monitored, had premature ventricular complexes prior to treatment; only one did following therapy. Breath sounds improved in 61% and were unchanged in 39%. Breathing was reported by the patient as improved in 51 of the 53 (93%) and only one felt worse. Adverse reactions were reported in 15%, but none were severe. This study shows that albuterol (2.5 mg) administration by hand-held nebulizer is both safe and efficacious in the prehospital setting.

Prehospital care: the future of emergency medical services

Most prehospital interventions, both pharmacologic and procedural, have been accepted without clear demonstrations of their abilities to impact patient outcomes or without clear indications that withholding or delaying the intervention pending arrival at a definitive emergency department will adversely affect the patient. Interventions that have the benefit of supportive research have been applied equally to urban and nonurban emergency medical services environments. In selecting interventions, inadequate consideration has been given to the differences in emergency medical services personnel training, frequencies of their exposure to patients, frequencies of skill use, and availabilities of effective continuing education programs in the urban and nonurban environments. These issues are discussed, and the necessary focus of the future of emergency medical services in urban, suburban, and rural environments is predicted.

A controlled trial of nebulized isoetharine in the prehospital treatment of acute asthma

Acute asthma is a potentially life-threatening disorder, recognizable to the prehospital care provider. While therapies are available to the prehospital care provider for treating acute asthma, no previous controlled studies have been performed demonstrating the treatment in the field is efficacious and safe. The authors conducted a controlled trial of the prehospital use of nebulized isoetharine in an urban emergency medical services system. Fifty-two patients with acute asthma were studied. Patients were initially evaluated with a peak flow meter. Half of the patients received isoetharine, while the control group received basic life support only. There was no difference in baseline values. Peak expiratory flow increased from 138 L/min to 148 L/min in the control group, while it increased from 149 L/min to 218 L/min in the treatment group (P less than .001). The authors conclude that paramedic treatment of acute asthma with nebulized isoetharine is effective in improving pulmonary function and clinical status during transport.

Prehospital data entry compliance by paramedics after institution of a comprehensive EMS data collection tool

OBJECTIVE

To determine the completeness of data entry by paramedics after an extensive modification of the prehospital first-care form in an urban emergency medical services (EMS) system.

DESIGN

Comprehensive medical information was added to the EMS data collection tool used by a metropolitan fire department. We evaluated the frequency of failure to enter data pertaining to medical assessment and/or treatment of victims of cardiac arrest after implementation of the system.

RESULTS

Failure to enter data in the first month was compared with two subsequent two-month blocks. A high rate of noncompliance existed in the first month (all medical data were missing in 24.6%). However, the subsequent two months revealed a marked decline in noncompliance (4.4%, P less than .001). This decline was maintained after a three-month interim (5.0%, P less than .001).

CONCLUSION

Data entry noncompliance can be a significant problem after implementation of a new prehospital data collection system. However, compliance can be markedly improved over a relatively short period. Because EMS system evaluation is based on data collected in the field. EMS researchers and administrators must be aware of the data entry compliance rate in their system when attempting to make conclusions from such information.

Success rates for initiation of intravenous therapy en route by prehospital care providers

The optimal extent of prehospital care, including intravenous (IV) therapy for critically ill patients, remains unclear. The authors evaluated the success rate for IV cannulation in a moving ambulance by trained emergency medical technicians and paramedics in 641 adult medical- and trauma-related cases. At least one IV line was started in 80% of medical patients and 92% of trauma patients, regardless of blood pressure. In hypotensive patients, the success rates for at least one IV in medical and trauma patients were 80% and 95%, respectively. These data suggest that IV lines can be secured with a high degree of success en route to the hospital by trained personnel, and that prompt transport of unstable patients should not be delayed solely to obtain IV access.

Characteristics of midsized urban EMS systems

Emergency medical services (EMS) systems in 25 midsized cities (population, 400,000 to 900,000) are described. Information describing EMS system configuration and performance was collected by written and telephone surveys with follow-ups. Responding cities provide either one- or two-tier systems. In a one-tier system, an advanced life support (ALS) unit responds to and transports all patients who use 911 to activate the system. Three types of two-tier systems are identified. In system A, ALS units respond to all calls. Once on scene, an ALS unit can turn a patient over to a basic life support (BLS) unit for transport. In system B, ALS units do not respond to all calls; BLS units may be sent for noncritical calls. In system C, a nontransport ALS unit is dispatched with a transporting BLS unit. For ALS calls, ALS personnel join BLS personnel for transport. Overall, cities staff an average of one ambulance per 51,223 population. One-tier systems average one ambulance per 53,291 compared with two-tier systems, which average one ambulance per 47,546. In the two-tiered system B, the average ALS unit serves 118,956 population. In the 60% of cities that use a one-tier system, one ALS unit serves 58,336 (P less than .0005). Overall, the code 3 response time for all cities is an average of 6.6 minutes. The average response time of two-tier systems is 5.9 minutes versus 7.0 minutes for one-tier systems (.05 less than P less than .1). These data suggest that the two-tiered system B allows for a given number of ALS units to serve a much larger population while maintaining a rapid code 3 response time.