Evaluation of a New Closed-System Thermodilution Method

Cardiac output estimates by a new closed-system auto­ matic injection thermodilution method (COI-TD) were compared serially with the direct Fick technique (COFICK) and the standard open-system manual injec­ tion thermodilution method (COTD). Comparison with cardiac outputs determined simultaneously by the di­ rect Fick technique in 100 measurements involving ten patients showed close agreement with the new closed system method using both 25°C and 3°C injectates. The cardiac output range was between 1.9 to 11.6 L/min. The open-system manual injection thermodilution method under identical conditions produced a wide scatter of measurements when compared to the direct Fick technique. Reproducibility of simultaneous COI-TD and COTD measurements was examined in quad­ ruplicate. The reproducibility of measurements was within 1.9 percent with COI-TD and 5.9 percent with the COTD method using both 25°C and 3°C injectates. The COI-TD method eliminates the technical problems of recirculation, unstable indicator baseline changes, thermal continuity, and reproducibility encountered with the current COTD method. Analysis of cardiac output by the closed-system automatic injection thermodilution method provides a simple, rapid, reproducible, and highly accurate method for multiple cardiac output measurements suitable for use at the bedside. A ggressive hemodynamic monitoring for the optimal treatment of critically ill patients with ischemic or valvular cardiac disease requires accu­ rate and frequent assessment of myocardial perfor­ mance. The present study demonstrates the ease and accuracy with which cardiac function can be quantitated at the bedside in intensive care units using a closed system automatic injection thermodilution cardiac ouput method ( COI-TD ).