A comparison of paramedic versus basic emergency medical care of patients at high and low risk during acute myocardial infarction.

This prospective study compares the outcome of patients with acute myocardial infarction managed by mobile intensive care (paramedic phase) with that of similar patients managed by basic emergency medical care (control phase) in the same community before the introduction of paramedics. All paramedic-transported patients were managed according to a standard chest pain protocol with use of prophylactic lidocaine and, as needed, treatment for sinus bradycardia, hypotension and life-threatening ventricular arrhythmia. There were no specific interventions for supraventricular tachyarrhythmia or hypertension. All patients were treated under similar in-hospital protocols. Percent mortality in patients with hypotension, the highest risk subgroup in the control phase, was significantly lowered with paramedic-level care (69 versus 10%, p = 0.01). Patients with hypertension, a relatively low risk subgroup during the control phase (16% mortality), were also at lower risk during the paramedic phase (10% mortality). In fact, there was no mortality in either study phase for patients with an initial systolic blood pressure greater than 180 mm Hg. During the combined study phases, patients with normotension and tachycardia demonstrated a tendency toward higher percent mortality (33%) than either patients with normotension without tachycardia (10%) or those with hypertension and tachycardia (6%). Although the overall percent mortality was reduced by 24% (from 21 to 16%), this decrease was largely due to the improvement of patients with hypotension. Investigation into the feasibility of prehospital interventions for the high risk patient with acute myocardial infarction normotension and tachycardia appears warranted.

Basic emergency medical care of patients with acute myocardial infarction: initial prehospital characteristics and in-hospital complications.

This prospective study documents the natural history of the prehospital phase of 110 patients with acute myocardial infarction transported by a basic emergency medical system during a 22 month period. Ambulances in a mixed urban-rural county were staffed by basic emergency medical technicians certified in basic life support and the administration of intravenous fluids. Systolic blood pressure, pulse rate and cardiac rhythm were noted for all patients at the time of ambulance arrival and intermittently during transport. Analyses of patient data were performed to determine the relation between the occurrence of subsequent in-hospital urgent complications and death and 1) patient delay time, 2) initial pulse rate, 3) initial systolic blood pressure, and 4) initial cardiac rhythm. Twenty-three (21%) of the 110 patients died and 66 (60%) experienced at least one in-hospital urgent complication. When initial rhythm, pulse rate and blood pressure were considered, patients with hypotension had a higher mortality rate than did those who were either normotensive or hypertensive. The 10 patients with initial sinus bradycardia but no hypotension constituted a subgroup with zero mortality. These results identify high and low risk patient subgroups that may benefit from either providing or withholding interventions directed toward hemodynamic stabilization during the prehospital phase of acute myocardial infarction.

Out-of-hospital management of cardiac arrest by basic emergency medical technicians.

The outcome in 126 consecutive patients with nontraumatic out-of-hospital cardiac arrest was analyzed to determine the effectiveness of a standard ambulance system over 22 months. Therapy was limited to basic life support (that is, administration of oxygen by mask, i.v. fluids, closed-chest massage and artificial respiration) by emergency medical technicians in a community in which less than 1% of the population had been trained in cardiopulmonary resuscitation (CPR). Analyses of patient data were performed to determine the relations between survival to hospital admission or discharge and 6 variables; response time, prior CPR, initial rhythm, acute myocardial infarction, initial blood pressure and initial pulse. Of 126 patients, 28 (22%) survived to hospital admission and 11 (9%) to hospital discharge. Two patient subgroups had a higher discharge rate: those with an initial rhythm of ventricular tachycardia or fibrillation (7 of 50, 14%), and those with an initial blood pressure greater than or equal to 90 mm Hg and a pulse rate of greater than 50 beats/min (3 of 6, 50%). For patients in arrest before ambulance arrival, there was no difference in outcome between those who did or those who did not receive prior CPR. Results of this study can be used as a basis for evaluating and comparing interventions directed toward stabilization of patients during the prehospital phase of cardiac arrest.