The American journal of emergency medicine
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Studies have shown that over 50% of cardiovascular deaths occur before hospitalization. A major factor associated with survival in cases of out-of-hospital cardiac arrest is the time from cardiovascular collapse to the initiation of cardiopulmonary resuscitation (CPR) or "downtime." The purpose of this study was to determine whether blood lactate levels could be used to predict downtime in the canine cardiac arrest model. Femoral arterial and Swan-Ganz catheters were placed in 22 mongrel dogs, and ventricular fibrillation was electrically induced. ⋯ Linear regression analysis revealed that 84% of the variability in serum lactate levels could be explained by downtime differences. In this model, blood lactate level is a reliable and objective measure of downtime and may be a useful indicator of the adequacy of CPR if levels decrease or remain stable. The clinical implications of this study lie with the use of blood lactate levels in the emergency department to guide the aggressiveness of resuscitative efforts.
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Comparative Study
Survival of out-of-hospital cardiac arrest with early initiation of cardiopulmonary resuscitation.
Records on 1,297 people with witnessed out-of-hospital cardiac arrest, caused by heart disease and treated by both emergency medical technicians (EMTs) and paramedics, were examined to determine whether or not early cardiopulmonary resuscitation (CPR) initiated by bystanders independently improved survival. Bystanders initiated CPR for 579 patients (bystander CPR); for the remaining 718 patients, CPR was delayed until the arrival of EMTs (delayed CPR). Survival was significantly better (P less than 0.05) in the bystander-CPR group (32%) than in the delayed-CPR group (22%). ⋯ The authors conclude that early initiation of CPR by bystanders significantly improves survival from out-of-hospital cardiac arrest, and they suggest that it may do so by prolonging the duration of VF after collapse and by increasing cardiac susceptibility to defibrillation. The benefit of this early CPR, however, appears to exist within a rather narrow window of effectiveness. It must be started within 4-6 minutes from the time of collapse and must be followed within 10-12 minutes of the collapse by advanced life support in order to be effective.
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Previous studies have shown that pulmonary edema occurs in half of all pre-hospital cardiac arrest victims who cannot be successfully resuscitated and is a major cause of hypoxemia and poor lung compliance during resuscitation. Pulmonary vascular hypertension and elevation of pulmonary capillary wedge pressure have been observed during cardiac resuscitation in humans. To further define the time course of the pulmonary hemodynamic changes, pulmonary artery diastolic pressure (PAd) was measured on a computerized trend recorder prior to, during, and immediately after arrest in three adult patients. ⋯ In both patients who were resuscitated successfully, the PADP returned to baseline within 5 minutes of effective spontaneous circulation. The finding that such hemodynamic changes occur rapidly during resuscitation and can reverse quickly with resumption of effective spontaneous circulation is consistent with the time course for the early development of pulmonary edema. Development of pulmonary edema many hours following successful resuscitation likely involves other mechanisms.
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Cardiac pacing has been used successfully in patients with asystole or bradycardia compromising hemodynamics when it was applied soon after the onset of the event. An external cardiac pacemaker was used as part of initial resuscitative efforts for patients in primary, out-of-hospital, cardiac arrest who arrived in the emergency department in asystole, agonal rhythm, pulseless idioventricular rhythm, or bradycardia with hemodynamic compromise. A pulse was successfully generated in only one of twelve patients. ⋯ The interval between arrest and application of the pacemaker was prolonged because of long periods for ambulance response, field resuscitation, and transport. It is concluded that the external cardiac pacemaker is a useful instrument for the treatment of bradyarrhythmias. While it may also be useful in the first few minutes after development of asystole, pulseless idioventricular rhythm, or agonal rhythm, it is of no benefit if applied long after the event.