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

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).

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.

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.

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.