Comparison of sodium thiopental and methohexital for high-dose barbiturate anesthesia.

High-dose sodium thiopental is frequently used in neuroanesthesia. The authors performed a study to compare a shorter-acting barbiturate, methohexital, to sodium thiopental in producing high-dose barbiturate anesthesia. In two groups of five mongrel dogs each, regional cerebral blood flow (CBF) was determined using the radioactive-microsphere technique, and cardiovascular parameters were measured before, during, and 1 hour after a 1 1/2-hour period of deep barbiturate anesthesia with either sodium thiopental or methohexital. Doses of the barbiturates were adjusted to produce electroencephalogram burst suppression of greater than 30 seconds. Both agents produced a similar degree of cardiac depression, reduction in CBF, and decrease in cerebral metabolic rate of oxygen (CMRO2). Changes in cerebral and peripheral vascular resistance indicated that methohexital caused less vasoconstriction than sodium thiopental. When the barbiturate infusions were discontinued, CMRO2 and CBF returned more rapidly toward control values in the methohexital group than in the thiopental group. The more rapid recovery time and decrease in cerebral vascular resistance with methohexital suggest that it may have some advantage over sodium thiopental during certain neurosurgical procedures.