Objective: To determine the effect on thermodilution cardiac output (TDCO) measurements of continuous volume infusion through the right atrial venous infusion port of the pulmonary artery catheter.
Design: Prospective, blinded, randomly allocated crossover.
Setting: Surgical intensive care unit in a university hospital.
Participants: Forty-nine hemodynamically stable patients between the ages of 43 and 84 in the intensive care unit and with a pulmonary artery catheter in place.
Interventions: Each patient received two room-temperature infusions (250 or 500 mL/hr) of 5% dextrose. Consecutive TDCO measurements were taken during each infusion and during a control period (no infusion). The sequence of infusion rates and control period was randomly determined. At both infusion rates, most patients exhibited a decrease in TDCO measurement of between 0.1 and 3.0 L/min. Although some patients exhibited an increase in measured TDCO, this increase was primarily between 0.1 and 0.5 L/min.
Measurements and main results: The mean TDCO measurements at infusion rates of 0, 250, and 500 mL/hr were 6.77, 6.49, and 6.47 L/min, respectively. Measured TDCO decreased on volume infusion by 0.3 +/- 0.13 L/min (mean +/- SD, p < 0.02).
Conclusion: Rapid continuous infusion of fluid through the venous infusion port of the pulmonary artery catheter significantly limits the accuracy of simultaneous TDCO measurements. Optimally, TDCO measurements should be avoided during rapid volume infusion.