To evaluate
etomidate as a
neuroprotective agent in the brain stem, 33 dogs were divided into seven groups and were exposed to isolated, reversible brainstem
ischemia in the presence or absence of
etomidate using a newly developed canine model of brainstem
ischemia. Brainstem auditory evoked potentials (BAEP) and regional cerebral blood flow were measured during
ischemia and for 5 hours after reperfusion. This model provides a potential physiological environment in which to test the efficacy of putative brainstem ischemic protective strategies. During
ischemia, BAEP were abolished in all animals. Without
etomidate 10 minutes of
ischemia was of short enough duration to allow complete recovery of BAEP.
Ischemia of 20 or 30 minutes' duration resulted in minimal recovery. The dose of
etomidate administered did not suppress BAEP or brainstem cardiovascular response to
ischemia. In animals receiving
etomidate and rendered ischemic for 20 minutes, a significant but only temporary recovery in BAEP was seen.
Etomidate failed to have a significant effect in animals rendered ischemic for 30 minutes. The minimal effect of
etomidate on the current measures of brainstem function is in contrast to
etomidate's known suppressive effect on cortical electroencephalogram and predicts that
etomidate does little to alter brainstem metabolism.
Etomidate's failure to provide for permanent recovery of BAEP suggests that the
drug does not give sufficient protection from
ischemia to the brainstem neurons in the auditory pathway. If these auditory neurons reflect brainstem function as a whole,
etomidate may not be the
protective agent of choice during temporary
arterial occlusion of posterior circulation.