Effect of xenon anaesthesia on accuracy of cardiac output measurement using partial CO2 rebreathing

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Abstract
Cardiac output (CO) determination based on partial CO2 rebreathing has recently been introduced into clinical practice. The determination of flow is crucial for exact CO readings and the physical properties of xenon, i.e. high density and viscosity, may influence flow readings. This study compared echocardiography‐derived CO measurements with the partial rebreathing method during total intravenous (TIVA) vs. xenon‐based anaesthesia. Thirty‐nine patients ASA physical status III undergoing aortic reconstruction were randomly assigned to receive either xenon (Xe, n = 20) or TIVA (T, n = 19) based general anaesthetic. Paired measurements were taken before xenon administration, after xenon administration, before and after clamping of the abdominal aorta and after declamping and at corresponding time points in the TIVA group. Data were analysed with a Bland‐Altmann plot. Bias and precision were acceptable and comparable before xenon administration (T 0.54 ± 0.92 l.min−1 vs. Xe 0.11 ± 1.1 l.min−1), but after xenon administration CO was largely overestimated by partial CO2 rebreathing (T 0.04 ± 0.91 l.min−1 vs. Xe −4.0 ± 2.1 l.min−1). In the TIVA group, bias and precision after declamping increased significantly (P < 0.01) compared to all time points except baseline. In its current application, the NICO cardiac output monitor appears to be inappropriate for determination of CO during xenon based anaesthesia.