Sympathetic influences during hemorrhagic hypotension

Abstract

Hemorrhagic hypotension was observed for several hours in open-chest dog preparations under pentobarbital anesthesia. Heart force, as recorded from a strain gage arch on the right ventricle, followed a pronounced upward trend above control levels in some cases while in others there were variable grades of cardiac depression. Plasma epinephrine levels progressively increased, reaching extreme values at terminal stages; norepinephrine levels were only moderately increased. Force and pressor responses to injected norepinephrine progressively decreased in association with progressive acidosis. Following interruption of sympathetic pathways with extradural procaine infusions or with ganglionic blocking agents, hemorrhage caused less pronounced increments in heart force and catechol amine levels while responsiveness to injected norepinephrine was better maintained.