Impedance cardiography: non-invasive cardiac output measurement after burn injury

The election of blood from the heart produces changes in transthoracic impedance. It has been proposed that the cardiac output may be determined from these changes. The cardiac output was measured by impedance cardiography and by the thermal dilution method before and after full thickness burn injury to the skin of the anaesthetized rat. The values obtained by the impedance method showed a good correlation with simultaneous thermal dilution cardiac output measurements (r=+0.67 pre-burn, and +0.76 post-burn). Impedance cardiography confirmed the early post-burn reduction in cardiac output reported by other workers using invasive techniques. Good agreement between the two methods was also obtained when the cardiac output of burn injured animals was altered by fluid infusion. This non-invasive technique of cardiac output monitoring may therefore have an important place in the investigation of cardiac function after trauma and burn injury.