Thermodilution cardiac output determination in hypothermic postcardiac surgery patients: room vs ice temperature injectate.

In normothermic patients, room temperature and ice temperature injectate have been shown to result in comparable thermodilution cardiac output measurements. However, room temperature injectate may give inaccurate results in hypothermic patients, particularly if the injectate volume is small, because of the lower injectate-to-blood temperature differential. We compared determinations of cardiac output using 10- and 5-ml volumes of room temperature (19-25 degrees C) injectate to those using 10-ml volumes of ice temperature (0-5 degrees C) injectate in 26 hypothermic (32.7 +/- 1.2 degrees C) postcardiac surgery patients. The cardiac outputs ranged from 1.8 to 5.3 L/min. Regression analysis demonstrated a close relationship between the cardiac outputs measured using room temperature injectate compared to those using ice temperature injectate (0.951 for the 10-ml volumes, 0.925 for the 5-ml volumes). We conclude that the room temperature injectate method is acceptable for determining thermodilution cardiac outputs in moderately hypothermic patients.