Noninvasive assessment of cardiac output by impedance cardiography in the newborn canine

Currently, critical care monitoring of cardiac function in the newborn human consists mainly of measuring heart rate and BP. A noninvasive technique for assessing cardiac output routinely in the critically ill neonate would facilitate clinical management. Impedance cardiography (IC) is a noninvasive technique which measures stroke volume on a beat-by-beat basis. This study compared cardiac output as measured by thermodilution (TD) to that measured by IC in seven canine pups 6 to 7 days old weighing 0.66 to 0.86 kg. Cardiac output was altered by the withdrawal and reinfusion of blood. There were no significant differences between the two methods for either the absolute value of cardiac output (r = .96) or the percent change in cardiac output (r = .97). Coefficients of variation were 3.0% for TD and 3.6% for IC. These results indicate that IC can be used to assess serially cardiac function in the newborn.