Left ventricular volumes and contractility during hemorrhagic hypotension: dimensional analysis and biplane...

Biplane cinefluorography was used to study left ventricular volume and contractility in hemorrhagic hypotension in nine dogs. A blood loss of 42% of the total blood volume caused end-diastolic volume to fall 20% without any change in end-diastolic pressure. There were decreases in cardiac output (63%), end-systolic volume (23%), stroke volume (63%), ejected fraction (27%); and dP/dt DP 40 (47%) during hemorrhage. Without treatment of shock and dP/dt returned to the prehemorrhage level and the ejected fraction increased despite a decrease in end-diastolic volume, indicating a positive inotropic effect. Peripheral vascular resistance decreased after 2 h of hypotension at the same low cardiac output. These data suggest that in the spleen-intact dogs peripheral circulatory failure and not left ventricular dysfunction causes irreversibility in hemorrhagic hypotension.