Cardiopulmonary effects of volume loading of primates in endotoxin shock

Myocardial performance was evaluated in rhesus monkeys after endotoxin shock, and the responses to fluid loading with colloid were measured in both anesthetized control and experimental groups. Minute work and cardiac output (CO) were decreased in five monkeys after 6 hours endotoxin to levels significantly below control values. Infusing colloid to a mean left ventricular end-diastolic pressure (LVEDP) of 12 to 15 mm. Hg increased both CO and minute work significantly but they remained one half that of the control group of four primates after fluid loading. Improved cardiac performance persisted after infusion through a 30 minute recovery stage when LVEDP returned to normal. Simultaneous pulmonary arterial wedge (PAW) pressures showed some correlation with LVEDP reading up to 6 mm. Hg, but above that level the PAW underestimated the LVEDP by 3 to 6 mm. Hg. Microscopic study showed that fluid loading produced comparable pulmonary edema in both groups, but endotoxin produced ultrastructural capillary lesions. A normal PAW pressure after fluid administration can occur after transient overloading of the left ventricle. Since interstitial pulmonary edema is not readily reversible, persistent respiratory insufficiency may result and the cause be unsuspected unless ventricular filling pressures are monitored during fluid administration.