CONTINUOUS THERMODILUTION CARDIAC-OUTPUT - AGREEMENT WITH FICK AND BOLUS THERMODILUTION METHODS

Objective: Cardiac outputs were determined with continuous thermodilut ion, bolus thermodilution, and the Fick method during pharmacologicall y varied hemodynamics. Design: Prospective comparison of techniques. S etting: University animal laboratory. Participants: Swine. Interventio ns: Swine were anesthetized, tracheally intubated, and instrumented to measure continuous (QTDC) and bolus (QTDB) thermodilution cardiac out puts and sample arterial and mixed venous blood, Continuous thermodilu tion of blood was facilitated by computer modulation of a thermal fila ment wrapped around the portion of the pulmonary artery catheter resid ing in the right atrium and ventricle. QTDC was computed from the ther modilution curve monitored by the thermistor, Bolus thermodilution was performed in triplicate by injecting 10 mt of 5% dextrose in water (0 to 4 degrees C), Oxygen consumption (VO2) was calculated as the avera ged minute rate of disappearance of spirometer oxygen over a 6-minute steady state. Cardiac output was determined with the direct Pick metho d (QF) by dividing ire, by the difference in arterial and mixed venous oxygen content. Basal QTDC was increased and decreased with an intrav enous infusion of dobutamine or labetalol, respectively. Data are summ arized as mean +/- SD or 95% confidence interval ICI 95%), Agreement b etween methods of determining cardiac output was assessed by calculati ng bias, percent bias, and percent coefficient of determination (100 r (2)). Measurements and Main Results: Eighteen swine (38.9 +/- 1.2 kg) exhibited a range of QTDC from 2.2 to 14.8 L/min. Mean measurement var iance of VO2, CaO2, C ($) over bar vO(2), and QTDB was 1.5%, 1.5%, 2.0 %, and 11.8%, respectively, Mean bias, percent bias, and 100 r(2) was 0.004 +/- 1.05 L/min (CI 95%: 0.18 to 0.19 L/min), -0.37 r 13.8% (CI 9 5%: -2.75 to 2.01), and 89% between QTDC and QF, respectively, Bias, p ercent bias, and 100 r(2) was 0.05 +/- 1.09 L/min (CI 95%: -0.14 to 0. 23 L/min, 1.21 +/- 13.06% (CI 95%: -1.03 to 3.46%), and 91% between QT DC and QTDB, respectively. Bias, percent bias, and 100 r(2) (Fig 6) wa s -0.04 a 0.69 L/min (CI 95%: -0.16 to -.08 L/min), -1.23 a 9.17% (CI 95%: -2.8 to 0.35%), and 94% between QTDB and QF, respectively. Conclu sion: Automatic cardiac output computed with continuous thermodilution appears accurate and reliable. Also, good agreement was confirmed bet ween cardiac output derived by continuous and bolus thermodilution met hods and bolus thermodilution and Pick methods. Copyright (C) 1995 by W.B, Saunders Company