Abstract

This prospective study was designed to quantify the effect of epinephrine on end-tidal PCO₂ (PetCO₂) during prehospital cardiopulmonary resuscitation (CPR) in humans. It included 20 patients (age range, 26 to 90 years) who presented in ventricular asystole on arrival of the prehospital medical team. Protocol began 5 minutes after tracheal intubation and during chest compressions. Mechanical ventilation was applied at constant rate and tidal volume. PetCO₂ was measured before and 3 minutes after peripheral intravenous (IV) injection of 2 mg epinephrine. No other resuscitative drugs were administered during the study period. Mean PetCO₂ decreased from 16.7 ± 9.3 mm Hg before epinephrine to 12.6 ± 7.1 mm Hg after epinephrine. The mean change in PetCO₂ was 4.15 ± 3.5 mm Hg (P < .0001). Four patients exhibited return of spontaneous circulation (ROSC). The decrease in PetCO₂ was similar between the patients who exhibited ROSC and those who did not. There was a significant relationship between the epinephrine-induced change in PetCO₂ and the PetCO₂ value before epinephrine injection (r = .760; P < .0001). This study demonstrates a variable decrease in PetCO₂ after IV epinephrine injection during CPR. Isolated PetCO₂ readings may be misleading in assessing CPR efficacy or predicting outcome, and continuous measurement is recommended.