Steven A Meador

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.

A multicenter validation of the prehospital index

The prehospital index (PHI) is a triage-oriented trauma severity scoring system. This prospective multicenter validation of the PHI was undertaken in response to a favorable pilot study. We applied the PHI to 3,581 patients from 14 different institutions during the period from January 1985 to February 1986. The PHI was accurate in predicting the need for emergency life-saving surgery within four hours (P less than .0001) and mortality within 72 hours (P less than .0001) following traumatic injury. The curves were generated for PHI versus emergency surgery, mortality, surgery and mortality, injury severity score, and ICU admission rate. These data compare favorably with those from previously published, prospectively tested, triage-oriented trauma severity scoring systems.

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.

Medical command errors in an urban advanced life support system

STUDY OBJECTIVE The aim of this study was to assist in focusing educational efforts for command physicians by identifying the most common types of errors made by on-line medical command. DESIGN Retrospective survey of prehospital advanced life support (ALS) trip sheets. SETTING An urban ALS paramedic service with on-line physician medical command rotating on a monthly basis among three hospitals. PARTICIPANTS From September 1988 through December 1990, all ALS run sheets were reviewed as part of an ongoing quality assurance program. Cases were identified as deviating from regional emergency medical services protocols as judged by agreement of three physician reviewers. Cases were excluded if all three reviewers did not agree that the command rendered was inappropriate. INTERVENTIONS Command errors were identified from the prehospital ALS run sheets and categorized. RESULTS One hundred ninety-four command errors in 167 cases were identified from 3,839 runs (4.4% of all runs). Six types of errors accounted for 80% of the total errors, with the most common error (34%) being failure to address the possibility of hypoglycemia with altered level of consciousness. Error rate decreased from 7.9% to 2.6% of total runs during the study period. CONCLUSION To reduce the medical command error rate, physician education should be directed at the six problem areas identified. Ongoing quality assurance review of medical command may result in a decrease of the command error rate.

Comparison of Interventions in Prehospital Care by Standing Orders Versus Interventions Ordered by Direct [On-line] Medical Command

OBJECTIVE The aim of this study was to compare the patient care measures provided by paramedics according to standing orders versus measures ordered by direct [on-line] medical command in order to determine the types and frequency of medical command orders. DESIGN Prospective identification of patient care measures done as part of a prehospital quality assurance program. SETTING An urban paramedic service in the northeast United States with direct medical command from three local hospitals. PARTICIPANTS One thousand eight paramedic reports from October 1992 through March 1993. INTERVENTIONS All patient care interventions recorded as done by standing orders or by direct medical command orders. Errors in patient care were determined by the same criteria as in the prior two studies of the same system. RESULTS Direct medical command gave orders in 143/1,008 (14.2%) cases. Paramedics performed 2,453/2,624 (93.5%) of the total patient care interventions using standing orders. In 61 cases (6.1%), medical command ordered a potentially beneficial intervention not specified by standing orders or not done by the paramedic. 21/171 (12.3%) command orders were for additional doses of epinephrine or atropine in cardiac arrest cases (where the initial doses had been given under standing orders), and 59/171 (34.5%) were for interventions already mandated or permitted by standing orders. The paramedic error rate was 0.6%, and the medical command error rate was 1.8% (unchanged form the prior study of the same standing-orders system). CONCLUSION Direct medical command gave orders in 14% of cases in this standing-orders system, but 35% of command orders only reiterated the standing orders. More selective and reduced uses of on-line command could be done in this system with no change in the types or numbers of patient care interventions performed.

Opportunity for Seatbelt Usage by ALS Providers

Purpose: Prehospital care providers commonly indicate that they cannot wear seat belts owing to their need to be unrestrained while delivering care to the patient in the back of the ambulance. Each year, providers are injured in situations in which seat belts have been shown to be protective. Are ALS providers able to wear a seat belt and provide care in an ambulance? Methods: The ALS providers were asked to complete a form following calls during which they rode with a patient in the back of an ambulance. They indicated the amount of time which they felt they would have needed to have been unrestrained by seat belts and the reasons. There were no attempts to regulate or quantify seat belt usage. Additional information was gathered from the trip report. Results: The percentage of the time of each trip during which they felt they needed to be unrestrained was calculated for each trip. The mean was 41%. The mean transport time was 14.7 minutes. Sub-groupings by protocol type, showed that for cardiac arrest patients, providers felt they needed to be unrestrained for 82% of the duration of transport, for patients with “chest pain or cardiac dysrhythmia” 63%, for “shortness of breath” 38%, and for trauma patients 41%. Excluding cardiac arrest patients, the nine patients were assigned by the providers to have the most critical level of case severity required unrestrained time of 72%. Those nine patients with the lowest severity level requires that the provider by unrestrained only 18% of the time. Management of intravenous line and patient assessments most frequently were cited as reasons for needing to be unrestrained. Conclusion: Perceived need of ALS providers to be unrestrained varied with respect to the type of call, with cardiac arrest patient transports having the greatest need to be unrestrained. However, on the average, providers felt they needed to be unrestrained only 41% of the time; markedly less on some types of call, with cardiac arrest patient transports having the greatest need to be unrestrained. However, on the average, providers felt they needed to be unrestrained only 41% of the time; markedly less on some types of calls. The ALS providers should be able to wear seat belts for at least part of the time, on most ALS calls.

Prehospital administration of inhaled metaproterenol

STUDY OBJECTIVES We conducted a study of the prehospital use of inhaled metaproterenol. DESIGN, SETTING, TYPE OF PARTICIPANTS, AND INTERVENTIONS: Advanced life support (ALS) providers were trained with a standardized curriculum to identify patients likely to benefit from prehospital inhaled metaproterenol administration. Unit doses of metaproterenol were used in a small-volume nebulizer. We prospectively included 122 patients in an initial study (71 men; age, 63 +/- 19 years) to evaluate the safety and effectiveness of metaproterenol in the field, and 150 patients (including the original 122) in an additional study to evaluate patient selection criteria. MEASUREMENTS AND MAIN RESULTS The treatments resulted in an increase in peak flows, a decrease in respiratory rates, and no change in heart rates. In 62% of patients, the increase in peak flow exceeded 15%. Wheezing improved in 59% of the patients, worsened in 4%, and did not change in the remainder. Air entry by auscultation improved subjectively in 59% of patients. Mild tremor occurred in 8% of patients, moderate tremor occurred in 1%, and no tremor occurred in the remainder. Significant dysrhythmias did not occur. CONCLUSIONS ALS providers correctly identified patients for this therapy. No technical problems were encountered in the field with this treatment approach. We conclude that ALS providers can be taught to identify patients likely to benefit from inhaled metaproterenol, that inhaled metaproterenol can be administered in the field, and that metaproterenol is both safe and effective when used in the prehospital setting.

COMPUTER SIMULATION OF CARDIOPULMONARY RESUSCITATION: COMPUTER ANALYSIS OF A SIMPLE ELECTRICAL MODEL OF THE CIRCULATION

Extensive research is being conducted to study the mechanism of blood flow during cardiopulmonary resuscitation (CPR). Recently, work has been published using a simple electrical model of the circulation to simulate the hemodynamics of CPR. This analog was a hard-wired circuit consisting of the heart and great vessels modeled as a resistive-capacitive network, pressure as voltage, blood flow as current, blood inertia as inductance and vascular valves as diodes. Such a model is useful for examining the physiology of various methods and techniques of CPR administration. In this investigation, a general purpose circuit simulation program, SPICE Version 2G.6, was used to analyze previously published CPR models. With minor modifications, the program was fully able to simulate the hard-wired circuits. The program is very flexible, allowing for easy model modification and a wide range of parameter values. In addition, the program offers the advantages of increased accuracy and low cost. Suggested future applications are for rapid evaluation of new CPR concepts.

Theoretical effects of fluid infusions during cardiopulmonary resuscitation as demonstrated in a computer model of the circulation

Recent studies have shown the potential adverse effects of venous volume loading on blood flow during closed chest cardiopulmonary resuscitation (CPR). To examine the effect of arterial and venous infusions, we employed a published computer simulation of the circulation during CPR. This model uses computer simulated electrical networks to model the heart and great vessels. CPR was modeled with compressions at a rate of 80/min and a force of 80 mmHg. Fluid infusions, simulated as current pulses into the abdominal aorta and superior vena cava, were given to measure their effect on myocardial and cranial blood flow. With 600 ml/min infusions into the abdominal aorta, there was a 12% peak increase in myocardial flow and a 3.8% peak increase in cranial flow. Every 100 ml/min increase in infusion from 0 to 900 ml/min produced a 1.4 ml/min linear increase in myocardial flow and a 4.2 ml/min linear increase in cranial flow. In agreement with previous CPR model studies, simulated vasoconstriction of abdominal and lower extremity vessels resulted in increased myocardial and cranial flows. As resistance of these vessels was increased, abdominal aortic infusions resulted in greater flow augmentations. In contrast to arterial results, infusions at 600 ml/min into the vena cava resulted in a 2.2% decrease in myocardial flow and a 0.62% decrease in cranial flow. Rise and fall times for initiation and cessation of flow augmentations were equal to four compression cycles. We conclude that these findings demonstrate the theoretical benefits of rapid arterial infusions during CPR with increases in myocardial and cranial blood flow. This method may provide an early temporary adjunct to myocardial perfusion during CPR.

Evaluation of a Prehospital Chest Pain Protocol

STUDY OBJECTIVES To evaluate the diagnostic accuracy and outcomes for patients treated by use of a prehospital chest pain protocol (CPP). DESIGN Consecutive case series for 1 year (1993) of prehospital nontrauma advanced life support (ALS) cases including hospital outcomes. SETTING Nonurban two-tiered emergency medical services system. PARTICIPANTS Patients treated under the prehospital CPP or with hospital diagnoses of ischemic heart disease (IHD; ICD-9 between 410 and 414). Patients with cardiac arrest or dysrhythmias were excluded. INTERVENTIONS Patients were given, by standing orders, ECG monitoring, i.v. access, and sublingual nitroglycerin. Further therapy was guided by on-line medical direction. RESULTS Of 3,122 ALS nontrauma patients, 620 (20%) were treated with the CPP. All patients underwent ECG monitoring, i.v. access was started in 83%, and 61% received nitroglycerin. Only 55% of patients completed the entire CPP; patients who failed to complete the CPP had the same prevalence of IHD as those who completed it. When compared with hospital diagnosis of IHD, the CPP had a sensitivity of 69% (95% confidence interval [CI], 64% to 74%), a specificity of 87% (95% CI, 86% to 88%), and a positive predictive value of 42%. The positive likelihood ratio of CPP for IHD was 5.31, and the negative likelihood ratio was .36. The hospital mortality rate for all patients was 2.2%; for those with IHD, it was 1.6%. CONCLUSION This prehospital ALS CPP had good diagnostic accuracy, but only half of patients completed it, and the hospital mortality rate was low. These data challenge the efficacy of the CPP.