Comparison of cardiac outputs during major surgery using the Deltex CardioQ oesophageal Doppler monitor and the Novametrix-Respironics NICO: a prospective observational study.

INTRODUCTION: Recent studies have emphasised the importance of optimisation of intraoperative fluid administration in patients undergoing major abdominal surgery. A variety of non-invasive devices capable of measuring cardiac output are available for this purpose. Most studies have used the Deltex CardioQ Oesophageal Doppler monitor (DCQ ODM, Deltex, Chichester, Sussex, UK). A relatively new, totally non-invasive cardiac monitor is now available, the Novametrix-Respironics NICO machine (Novametrix-Respironics, USA).

AIMS: This pilot study compared cardiac output values obtained during major abdominal surgery from the simultaneous use of these two devices.

OBJECTIVES: To assess the reproducibility and consistency of the readings obtained to determine whether these monitors can be used interchangeably for optimising perioperative fluid administration.

METHODS: 182 simultaneous paired cardiac output readings were obtained from 12 consecutive patients undergoing prolonged major abdominal surgery. These were analysed using correlation coefficients, scattergrams and Bland Altman plots.

RESULTS: Although the r value obtained for correlation was 0.3639 (p<0.0001), the Bland Altman plot showed significant differences of between -4.1 and +5.1 lpm between the readings means with a bias of 0.5 lpm for the NICO over the DCQ ODM. In addition, a sequential plot of simultaneous cardiac outputs showed great disparity between the two devices in some patients.

CONCLUSION: Caution should be exercised before using these monitors to optimise intraoperative fluid administration as potentially very large volumes of fluid may be administered to achieve surrogate endpoints. These devices need to be compared side by side with a gold standard method of determining cardiac output before they can be used interchangeably for optimising intraoperative fluid administration in abdominal surgery.