EPINEPHRINE-INDUCED CHANGES IN HUMAN COCHLEAR BLOOD-FLOW

Cochlear blood flow (CBF) was monitored over the basal turn stria vasc ularis using laser Doppler flowmetry in five human subjects during mid dle ear surgery. The effects of systemically administered epinephrine (0.3 mug/kg) and topically applied epinephrine (1:10,000) on the round window membrane (RWM) were examined. Topical epinephrine caused a mea n reduction of 60 percent in CBF (maximum peak reduction 65-85% across subjects), which slowly recovered (>10 min) toward baseline following epinephrine removal from the RWM. The changes in CBF are similar to t hose found in animal studies, but are much larger, indicating a relati vely more pronounced role of adrenergic agents in CBF control in human s. Systemic epinephine caused a 40 percent decrease in skin blood flow , a 90 percent increase in blood pressure (BP), above a resting hypote nsive mean level of 65 mm Hg, and a 50 percent increase in CBF. The CB F change followed the change in BP, but recovered toward baseline more slowly. The dramatic and somewhat prolonged decreases in CBF with RWM application of epinephrine may compromise sensor function and could a ccount for the occasional unexplained sensorineural hearing loss or ti nnitus associated with middle ear procedures that use topical epinephr ine. The semipermeability of the RWM may, on the other hand, offer a r oute for therapeutic increases in CBF with vasodilative agents and pro vide an appropriate treatment for some cases of sensorineural hearing loss.