Comparison of continuous with intermittent bolus thermodilution cardiac output measurements

BACKGROUND: Few complete studies have been published to validate the agreement between continuous cardiac output and intermittent thermodilution cardiac output. OBJECTIVE: To analyze the agreement between cardiac output measurements by the continuous thermodilution method and the intermittent bolus thermodilution method, using a continuous cardiac output catheter in postoperative cardiothoracic surgery patients. METHODS: A convenience sample of 14 adult cardiothoracic surgical patients with thermodilution pulmonary artery catheters placed preoperatively was used. A total of 214 comparison measurements of cardiac output by both the continuous and intermittent thermodilution methods were taken on patient admission to the critical care unit, every 4 hours, and with any change greater than 10% from baseline readings. RESULTS: The intraclass correlation between continuous cardiac output and intermittent cardiac output was .89. The limits of agreement were -1.34 to 1.18 L/min, indicating that in 95% of readings the difference between continuous cardiac output and intermittent cardiac output were within this range. CONCLUSIONS: The continuous cardiac output monitoring method shows clinically acceptable agreement with the intermittent cardiac output method.