The current guidelines of cardiopulmonary resuscitation (CPR) recommend that defibrillation may be attempted with up to three sequential shocks when ventricular fibrillation is identified. However, we hypothesized that the additional time required for repetitive rhythm analyses and recharging of the capacitor of 20 seconds or more prior to the delivery of the second and then the third shock in each sequence and the consequences of more prolonged interruptions of chest compression may compromise the success of defibrillation.
In 101 pigs ventricular fibrillation (VF) was electrically induced and untreated for between 4 and 7 minutes. After one minute of CPR, including precordial compression and ventilation, up to three sequential shocks were delivered. All animals were successfully resuscitated. For purposes of the present study we analyzed the success of the first, second, or third shock of the sequence.
After the first shock 71% of the animals were restored to spontaneous circulation, 18% after the second shock, and only 11% after the third shock. Importantly, successful defibrillation was closely related to a threshold level of 15 mmHg of coronary perfusion pressure (CPP) and 16 mmHg of end-tidal CO2 (TableTableSequentialResuscitated AnimalsCPPPETCO21st7219±7**†16±6*†2nd1815±612±23rd1110±6†11±2†
p< .05 vs 2nd;**
p< .01 vs 3rd;*
p<.05 vs 3rd.). The present study therefore indicates that it is the first shock in each sequence that is associated with the highest CPP and the greatest likelihood of successful defibrillation. The data support the earlier reports of Falk et al. (1988) and Paradis et al. (1990).
The present study supports the use of a single electrical shock, especially when threshold levels of CPP or ETCO2 are achieved during precordial compression, rather than a sequence of three shocks.
In ventricular defibrillation settings, deliver only one shock in lieu of three between chest compression increase the likelihood of successful defibrillation.
G.A. Cammarata, None.