Intraoperative validation of a new system for invasive continuous cardiac output measurement.

OBJECTIVE: Although bolus thermodilution technique for cardiac output (CO) measurement has widespread acceptance, new systems are currently available. We evaluated a continuous CO system (TruCCOMS, Aortech International Inc.) that operates on the thermal conservation principle and we compared it with the reference standard transit time flow measurement (TTFM).
MATERIALS AND METHODS: Nine consecutive cardiac surgery patients were evaluated. After general anesthesia and intubation, a TruCCOMS catheter was percutaneously placed in the pulmonary artery (PA). After median sternotomy and pericardiotomy, a TTFM probe was placed around the main PA. Right ventricular (RV) CO measurements were recorded with both TruCCOMS and TTFM at different times: before cardiopulmonary bypass (CPB) (T0), during weaning from CPB (T1), and prior to sternal closure (T2). Data analysis included paired student t test, Pearson correlation test, and Bland-Altman plotting.
RESULTS: TruCCOMS CO values were significantly lower at T0 (TruCCOMS 4.0 +/- 1.0 vs. TTFM 4.5 +/- 1.0 L/min; P < 0.0001) and T1 (TruCCOMS 3.6 +/- 0.5 vs. TTFM 4.2 +/- 0.7 L/min; P < 0.0001), and comparable at T2 (TruCCOMS 4.5 +/- 0.7 vs. TTFM 4.6 +/- 0.8 L/min; P = 0.4). Pearson test showed a significant correlation between TruCCOMS and TTFM CO measurements (RT0 = 0.9, RT1 = 0.8, RT2 = 0.6; P < 0.0001). Bland-Altmann plotting showed a bias of -0.53 +/- 0.43 L (-12%) at T0, -0.64 +/- 0.43 L (-14.5%) at T1, and -0.1 +/- 0.66 L (-0.8%) at T2.
CONCLUSION: Although TruCCOMS may significantly underestimate CO, measurement trends correlate with TTFM. For this reason, a negative trend in RV output should trigger more specific diagnostic procedures.