Cardiac output can be reliably measured noninvasively after coronary artery bypass grafting operation

Objective: To evaluate the reliability of whole-body impedance cardiography in the measurement of cardiac output after coronary artery bypass grafting operation in comparison with the thermodilution method. Design:Prospective, consecutive sampling. Patients: A total of 82 patients undergoing coronary artery bypass surgery were investigated. In a group of 41 patients who were intubated, cardiac ou tput measurements were taken simultaneously with whole-body impedance cardi ography and the thermodilution method within the first 3 hrs after the oper ation (early intensive care unit [ICU] period). In another group of 41 pati ents, the measurements were taken before the operation and in the second 12 hrs after cardiac surgery (late ICU period). Interventions: None. Measurements and Main Results:The agreement between the thermodilution and whole-body impedance cardiography cardiac output measurements was good befo re the operation, bias 0.04 +/- 1.64 L/min (n = 41), and in the late ICU pe riod, bias 0.00 +/- 1.84 L/min (+/-2 so) (0 = 41). The results were within 20% in 81%-85% of the cases. The agreement was satisfactory in the early IC U period, bias 0.38 +/- 2.74 L/min (n = 41). It was presumed that thermal i nstability of the patients was one possible source of measurement errors in the thermodilution method, causing reduced agreement between the methods i n this period. The repeatability values (rv = 2.83 x SDs) for whole-body im pedance cardiography were 0.44 L/min before the operation, 0.30 L/min in th e early ICU period, and 0.65 L/min in the late ICU period, being significan tly better than for the thermodilution method (0.79, 0.51, and 1.11 L/min, respectively) in all phases of the investigation (p < .001). The agreement between the thermodilution method and whole-body impedance cardiography is similar to reported comparisons between invasive methods in analogous setti ngs. Conclusions: Whole-body impedance cardiography reliably measures cardiac ou tput in patients after coronary artery bypass grafting operation. The excel lent repeatability of whole-body impedance cardiography enhances the value of the method in continuous monitoring of patients after the operation.