Dose-dependent vasopressor response to epinephrine during CPR in human beings

The optimal dose of epinephrine during CPR in human beings is unknown. We studied ten prehospital cardiac arrest patients (six men and four women; mean age, 54 ± 5 years) to determine the vasopressor response and change in the end-tidal carbon dioxide concentration (P etCO 2) after incremental (1-, 3-, and 5-mg) doses of IV epinephrine given five minutes apart during closed-chest CPR. All patients were in ventricular fibrillation on arrival of the paramedics and did not respond to standard advanced cardiac life support. CPR was performed with a computerized Thumper ®; all patients were intubated and ventilated at 12 times a minute at an F 1O 2 of 0.8. Radial artery pressure was measured with a 20 angiocath inserted by radial artery cutdown. Paramedic response time was 4.3 ± 0.5 minutes; elapsed time to emergency department arrival was 40.0 ± 9.5 minutes. Initial blood gases were p aO 2, 241 ± 50 mm Hg; pH, 7.23 ± 0.08; p aCO 2, 27 ± 5 mm Hg; and HCO 3, 11 ± 2 mEq/L. Baseline systolic and diastolic blood pressures were 47 ± 5 mm Hg and 18 ± 2 mm Hg, respectively. Systolic blood pressure was directly related to the dose of epinephrine ( P < .0001), rising to 69 ± 7 mm Hg, 74 ± 8 mm Hg, and 85 ± 8 mm Hg after 1-, 3-, and 5-mg doses of epinephrine, respectively. Diastolic blood pressure was also directly related to the dose of epinephrine ( P < .004) and rose to 27 ± 3 mm Hg, 25 ± 4 mm Hg, and 36 ± 6 mm Hg after 1-, 3-, and 5-mg doses of epinephrine, respectively. P etCO 2 was 1.9 ± 0.2% at baseline and decreased progressively with each dose of epinephrine ( P < .0001). We conclude that epinephrine produces a significant dose-dependent vasopressor response during CPR in human beings. This finding supports work in animal models and anecdotal reports in human beings, indicating that doses of epinephrine that are higher than those currently recommended may be needed during late CPR in human beings.