Use Of Noninvasive Bioelectric Impedance To Predict Cardiac Output After Open Heart Surgery
Ten stable male non-ventilated coronary artery bypass patients (mean age 59 f 12 years) were comparatively studied with thermodilution (T.D.) and bioelectric impedance (Z) 24-48 hrs. post surgery, in the Open Heart Recovery (OHR) Unit. Cardiac outputs (CO) were compared, after blinded measurements were obtained in three sequential positions (supine, 45 degree head-up tilt and supine). (Z) cardiac outputs were compared to (T.D.) using the actual value for resistivity @) of blood (sampled at the time of the study) and assumed values of 135.5 ohm-an and 150 ohm-an. The results indicate high correlations (range = .W to 99) in the initial supine position for all resistivity conditions followed by a progressive dedine when body position is changed to 45 degrees and supine (range = .74 to 30). The highest overall correlations and closest mean CO values were obtained when (p) was measured. Signifcant (p<.02) mean differences between 2 and T.D. were observed when (p) was assumed to be 150 ohm-cm. In this spedic group of patients, impedance CO is highly correlated to T.D. CO with mean values not significantly different when (p) is measured or assumed to be 135.5 ohm-cm, yet absolute mean values are closest when (p) is not assumed.