[A comparison of various ways of cardiac output measurement by thermodilution methods]

We compared cardiac output values obtained by the following 3 methods: 1. Iced bolus injectate method, using the injectate temperature actually measured for computation [bolus cardiac output with flow-through temperature probe: BCO (p)]. 2. Continuous cardiac output measurement, using Vigilance system (continuous cardiac output: CCO). 3. Iced bolus injectate method, assuming injectate temperature to be 0 degrees C (bolus cardiac output without flow-through temperature probe: BCO). Only the subject receiving cardiovascular surgeries using cardiopulmonary bypass (CPB), and requiring a thermodilution catheter for hemodynamic monitoring during anesthesia were selected for the study. The total cases consisted of 15 patients (10 males), in which 60 measurement were made. Following the anesthetic induction with fentanyl, midazolam, vecuronium bromide, and intubation, a Baxter Swan-Ganz CCO thermodilution catheter was inserted through the right internal jugular vein. Compared to BCO(p), CCO showed excellent precision and bias; (r2 = 0.935, P < 0.0001, bias = -0.19 l.min-1, SD = 0.36 l.min-1). Although BCO correlated well with BCO(p), the bias was much greater (r2 = 0.919, P < 0.0001, bias = -1.25 l.min-1, SD = 0.45 l.min-1) than BCO(p). In conclusion, the values obtained by BCO(p) and CCO methods were very accurate. On the other hand, a considerable overestimation was found with BCO since the compensation for actual injectate temperature was not performed