Pulmonary artery vs. transpulmonary thermodilution for the assessment of cardiac output in mitral regurgitation: a prospective observational study.

Context: With increasing prevalence of mitral regurgitation, even noncardiac anaesthesiologists will be confronted by this disorder and will need to be familiar with the extended haemodynamic monitoring required. The assessment of cardiac output (CO) measured by transpulmonary thermodilution (COTP) has become an accepted alternative to the CO measured by thermodilution via pulmonary artery catheter (COPAC). However, the integrity of COTP in severe mitral regurgitation requires systematic evaluation.

Objective: This study was designed to test the hypothesis that transpulmonary thermodilution is compromised by severe mitral regurgitation.

Design: Prospective method comparison study.

Setting: Single university-affiliated hospital.

Participants: Thirty patients with mitral regurgitation undergoing elective mitral valve repair.

Main Outcome Measure: COTP and COPAC were determined in triplicate after induction of anaesthesia, and at the end of surgery after closure of the chest. The methods were compared using bias and precision statistics.

Results: Echocardiography revealed severe mitral regurgitation in most patients (n  =  27) after induction of anaesthesia. The least significant change in COTP (the minimum change in COTP required to detect a real change with a probability of 95%) was increased under the condition of mitral regurgitation (15.4  ±  10.2% after anaesthesia induction vs. 9.3  ±  5.9% after valve repair, P = 0.008), whereas it remained constant in COPAC (9.6  ±  5.4 vs. 8.5  ±  7.2%, P = 0.55). There was no significant bias between COTP and COPAC after anaesthesia induction [mean CO, 4.03 ± 0.92 l  min; bias 0.12 l  min (95% confidence interval, CI, -0.073 to 0.311)], and after valve repair [mean CO 7.47  ±  1.44 l  min; bias 0.045 l  min (95% CI, -0.147 to 0.237)]. The percentage error was 28.4 and 13.6%, respectively.

Conclusion: The results suggest that even severe mitral regurgitation has no significant impact on the accuracy of COTP. The precision of COTP was reduced under the condition of mitral regurgitation.