To the Editor
In the review article by Reuter et al.1 describing technical principles and features of each application of indicator dilution technique to measure cardiac output, the authors conclude that continuous pulmonary artery thermodilution cardiac output (CPATD-CO) versus intermittent bolus pulmonary artery thermodilution cardiac output (IBPATD-CO) are well correlated under a wide range of cardiac outputs (Table 1 in Reuter et al.).1
However, the patients studied by Bottiger et al.2 (reference 75 in Table 1) were undergoing cardiac surgery with cardiopulmonary bypass and not liver transplantation. Second, in more recent studies published by our group3 and Zollner et al.,4 the conclusions are quite different from those in studies referenced in Table 1.1 Even if the authors acknowledged that extreme temperature variations could cause poor correlation between CPATD-CO and IBPATD-CO,1 this is not the main problem.5 Indeed, in these studies performed in cardiac surgical patients,3,4 an important mean bias (Bland-Altman analysis comparing CPATD-CO and IBPATD-CO measurements) was established with 34% and 50% of all values obtained being outside the predefined clinical tolerable range, respectively.3,4 These results highlight that CPATD-CO should not be used as a monitoring tool to measure cardiac output in hypothermic patients because of the thermal instability and noise caused by the decrease in blood temperature. This is very important because conventional cooling methods to induce mild therapeutic hypothermia seem to improve survival and neurologic outcome after cardiac arrest and the 2 noncited studies3,4 do not support the use of CPATD-CO monitoring in this setting.
Karim Bendjelid, MD, PhD
Intensive Care Service
Department of Anaesthesiology, Pharmacology and
Geneva University Hospitals
Dr. Reuter does not wish to respond.
1. Reuter DA, Huang C, Edrich T, Shernan SK, Eltzschig HK. Cardiac output monitoring using indicator-dilution techniques: basics, limits, and perspectives. Anesth Analg 2010;110:799–811
2. Bottiger BW, Rauch H, Bohrer H, Motsch J, Soder M, Fleischer F, Martin E. Continuous versus intermittent cardiac output measurement in cardiac surgical patients undergoing hypothermic cardiopulmonary bypass. J Cardiothorac Vasc Anesth 1995;9:405–11
3. Bendjelid K, Schütz N, Suter PM, Romand JA. Continuous cardiac output monitoring after cardiopulmonary bypass: a comparison with bolus thermodilution measurement. Intensive Care Med 2006;32:919–22
4. Zollner C, Goetz AE, Weis M, Morstedt K, Pichler B, Lamm P, Kilger E, Haller M. Continuous cardiac output measurements do not agree with conventional bolus thermodilution cardiac output determination. Can J Anaesth 2001;48:1143–7
5. LaMantia KR, O'Connor T, Barash PG. Comparing methods of measurement: an alternative approach. Anesthesiology 1990;72:781–3