[Reliability of cardiac output by thermodilution. Effect of marker temperature]

Classically, the cardiac output is measured by the thermodilution method, employing a standard volume of 5% D/W at 4 degrees C. Recently, however, a room-temperature (17-24 degrees C) measurements have been used, in such a way that a lower gradient between the injectate and the patient temperature is established. This lact could question the sensitivity and reliability of the technique evaluated. We have studied 20 patients undergoing different operations, in whom the cardiac output was measured by injecting a standard volume of 5 ml 5% D/W at room-temperature or at 5 degrees C, randomly assigned, in order to evaluate any difference between the two techniques. Over a total of 100 cardiac output determinations taken in normothermic conditions (19-24 degrees C) the mean was 4.24 +/- 1.13 l/min (means +/- SD). In hypothermic conditions the cardiac output was 4.28 +/- 1.14 l/min (means +/- SD). Results showed no statistical difference between both methods.