Effect of burn shock on myocardial function in guinea pigs.

The effect of burn shock on myocardial function was studied using an isolated working heart preparation. Guinea pig hearts were studied 2-, 4-, and 8-hr following burn injury as well as in time-matched controls. The hearts were excised from both burned (35% body surface area) and unburned unresuscitated animals, and ventricular function curves were generated on each heart. The 4- and 8-hr postburn hearts, particularly the 4-hr group, exhibited depression in cardiac output, stroke volume, coronary flow, peak systolic pressure, mean aortic pressure, estimated myocardial work, stroke work, and oxygen consumption when compared to controls. The ventricular function curve for the 4-hr postburn hearts was shifted to the right indicating a decrease in contractility, which complements a decrease seen in compliance. These pronounced changes seen in the 4-hr postburn hearts were not observed 2 hr after burn injury. The data suggest that intrinsic myocardial function following burn injury is depressed and the degree of dysfunction is influenced by the time from thermal injury.