Research

Comparison of uncalibrated arterial waveform analysis in cardiac surgery patients with thermodilution cardiac output measurements

Michael Sander¹ , Claudia D Spies¹ , Herko Grubitzsch² , Achim Foer¹ , Marcus Müller¹ and Christian von Heymann¹

¹  Department of Anesthesiology and Intensive Care Medicine, Charité University Medicine Berlin, Charité Campus Mitte, Campus Virchow Klinikum, Charitéplatz 1, 10117 Berlin, Germany

²  Department of Cardiovascular Surgery, Charité University Medicine Berlin, Campus Charité Mitte, Charitéplatz 1, 10117 Berlin, Germany

author email corresponding author email

Critical Care 2006, 10:R164doi:10.1186/cc5103

Published:	21 November 2006

See related letter by Umgelter et al., http://ccforum.com/content/pdf/cc5154.pdf

Abstract

Introduction

Cardiac output (CO) monitoring is indicated only in selected patients. In cardiac surgical patients, perioperative haemodynamic management is often guided by CO measurement by pulmonary artery catheterisation (CO_PAC). Alternative strategies of CO determination have become increasingly accepted in clinical practice because the benefit of guiding therapy by data derived from the PAC remains to be proven and less invasive alternatives are available. Recently, a device offering uncalibrated CO measurement by arterial waveform analysis (CO_Wave) was introduced. As far as this approach is concerned, however, the validity of the CO measurements obtained is utterly unclear. Therefore, the aim of this study was to compare the bias and the limits of agreement (LOAs) (two standard deviations) of CO_Wave at four specified time points prior, during, and after coronary artery bypass graft (CABG) surgery with a simultaneous measurement of the gold standard CO_PAC and aortic transpulmonary thermodilution CO (CO_Transpulm).

Methods

Data from 30 patients were analysed during this prospective study. CO_PAC, CO_Transpulm, and CO_Wave were determined in all patients at four different time points prior, during, and after CABG surgery. The CO_PAC and the CO_Transpulm were measured by triple injection of 10 ml of iced isotone sodium chloride solution into the central venous line of the PAC. Measurements of CO_Wave were simultaneously taken at these time points.

Results

The overall correlation showed a Spearman correlation coefficient between CO_PAC and CO_Wave of 0.53 (p < 0.01) and 0.84 (p < 0.01) for CO_PAC and CO_Transpulm. Bland-Altman analysis showed a mean bias and LOAs of 0.6 litres per minute and -2.2 to +3.4 litres per minute for CO_PAC versus CO_Wave and -0.1 litres per minute and -1.8 to +1.6 litres per minute for CO_PAC versus CO_Transpulm.

Conclusion

Arterial waveform analysis with an uncalibrated algorithm CO_Wave underestimated CO_PAC to a clinically relevant extent. The wide range of LOAs requires further evaluation. Better results might be achieved with an improved new algorithm. In contrast to this, we observed a better correlation of thermodilution CO_Transpulm and thermodilution CO_PAC measurements prior, during, and after CABG surgery.