What is the optimal dose of epinephrine?
Pharmacologic therapy has been changed significantly from the previous ACLS protocols. Epinephrine is still the therapy of choice, but vasopressin has emerged as an alter-native in the treatment of VF/VT. The vasoconstriction caused by the α-adrenergic effects of large doses of epi-nephrine that are administered during CPR increases arterial pressure and improves myocardial and cerebral blood flow. Studies have suggested that this is a dose-dependent phe-nomenon. Animal studies have shown better outcomes from cardiac arrest using 0.1–0.2 mg/kg of epinephrine rather than the present recommended dose of 0.01 mg/kg. Two recent large multicenter investigations, however, did not demonstrate survival differences in patients treated with larger doses of epinephrine. This lack of clinical efficacy may arise from the fact that the time elapsed prior to the initial dose of epinephrine was significantly longer than was the case in the animal studies.
The presence of coronary artery disease in many patients hinders coronary artery blood flow even in the pres-ence of higher aortic diastolic pressures. The β-adrenergic effects of epinephrine may actually worsen the outcome by increasing myocardial oxygen requirements. Until further studies clarify this issue, the 2000 ACLS protocol recom-mends a standard dose of 1 mg epinephrine (0.01 mg/kg intravenous (i.v.) push) every 3–5 minutes. Higher doses up to 0.2 mg/kg may be considered, but these doses are not recommended and may be harmful.