Purpose: Measurement of cardiac output is an essential part of anaesthetic practice in patients undergoing major operative procedures. A thermodilution technique, using a pulmonary artery catheter is currently accepted as the gold standard in clinical practice. However its use is associated with several limitations.
Method: In this prospective randomised controlled study measurement of cardiac output, an oesophageal Doppler monitor (ODM) was compared with the thermodilution technique in 18 patients undergoing orthotopic liver transplantation. Measurements were taken during the three phases of liver transplantation, i) dissection phase (three measurements), ii) anhepatic phase (four) and iii) reperfusion phase (six).
Results: There were no differences observed between the two measurements at any of the times studied and a strong correlation was observed (r = 0.714; P < 0.00001). However, when the data was analysed using Bland and Altman analysis, while the mean difference was small (0.07 l.min-1) it was > 2 l.min-1 in one third of measurements recorded i.e., the bias was near zero but the precision was large. No consistent differences were seen using the two methods in individual patients.
Conclusion: The use of the ODM results in cardiac output measurements which are considerably different from those obtained using thermodilution and its use cannot be recommended in patients undergoing orthotopic liver transplantation.