NONINVASIVE MEASUREMENT OF CARDIAC-OUTPUT DURING CORONARY-ARTERY BYPASS-GRAFTING

Objective: A new device, using whole body bioresistance measurements a nd a new equation for calculating stroke volume has been developed. Us ing this equation, an attempt was made to correlate whole body bioresi stance cardiac output with thermodilution cardiac output in patients u ndergoing coronary artery bypass grafting. Methods: Thirty-one adults undergoing elective coronary artery bypass grafting were studied prosp ectively. Simultaneous paired cardiac output measurements by whole bod y bioresistance and thermodilution were made at five time points durin g coronary artery bypass grafting: in anesthetized patients before inc ision (T-1), after sternotomy (T-2), after opening the pericardium (T- 3), ten min post bypass (T-4), and in the intensive care unit (T-5). T he patients had a mean of three thermodilution cardiac outputs compare d with a mean of three bioimpedance measurements at each time point. T he bias and precision between the methods were calculated. Results: Th ere was good correlation between bioresistance cardiac output (nCO) an d thermodilution cardiac output (ThCO) measurements in both groups for all recorded times. The patients' mean ThCO and nCO, as well as bias and precision between methods were calculated. Mean ThCO ranged betwee n 4.14 and 5.06 1/min; mean nCO ranged between 4.12 and 4.97 1/ min. B ias calculations ranged between -0.072 and 0.104 1/min. Precision (2 S D) calculations ranged between 0.873 and 1.228 1/min for 95% confidenc e intervals. Pearson's correlation ranged from 0.919 to 0.938. Conclus ions: Cardiac output measured with the new device correlates well with the thermodilution measurements of cardiac output during and immediat ely following coronary artery bypass grafting. The overall agreement b etween the two methods was good. The new device is an accurate non-inv asive method of measuring cardiac output during coronary artery bypass grafting. (C) 1998 Elsevier Science B.V, All rights reserved.