B

Studies measuring the arrhythmogenic dose of epinephrine during volatile anesthetic use show that the myocardium becomes irritable at about 6-7 µg/kg with isoflurane. Johnston et al. reported an ED50 of 6.7 µg/kg for isoflurane (versus 2.1 µg/kg for halothane and 10.9 µg/kg for enflurane) [Johnston, 1976, PMID 987729]. Similarly, Moore et al. found no premature ventricular contractions with doses <7 µg/kg during isoflurane anesthesia [Moore, 1993, PMID 7694528]. Hence, the recommended maximum safe dose is about 6.7 µg/kg.