Comparison of bioimpedance versus thermodilution cardiac output during cardiac surgery: evaluation of a second-generation bioimpedance device

Abstract

Objective: To compare a second-generation thoracic electrical bioimpedance (TEB) hemodynamic monitoring system with the clinically used pulmonary artery catheter thermodilution (TD-PAC) system.

Design: Blinded, simultaneous measurements at specified key time points during surgery.

Setting: University teaching hospital cardiac surgical operating rooms.

Participants: Forty-seven patients undergoing primary elective coronary artery bypass surgery.

Interventions: Timed cardiac output measurements by thermodilution and continuous monitoring of bioimpedance were performed.

Measurements and main results: Cardiac index (TEB and TD-PAC) and other hemodynamic parameters were measured at 4 time points: (1) after anesthesia induction, (2) with the mediastinum open, (3) immediately after cardiopulmonary bypass, and (4) at the end of the case. Pearson's correlation and Bland-Altman analysis were carried out. Cardiac index by TEB and TD-PAC had an overall correlation of r = 0.71 (p < 0.0001). The Bland-Altman statistics showed a mean difference of -0.28 L/min/m2 and precision of 0.67 L/min/m2. The best correlation was at time 1, and the lowest correlation was at time 4. Mediastinal opening and cardiopulmonary bypass had little or no effect on the correlation between technologies.

Conclusion: TEB reporting of cardiac index during coronary artery surgery generally agreed with TD-PAC cardiac index except at the end of the case (time 4).