Evaluation of heavy water for indicator dilution cardiac output measurement

We evaluated deuterium oxide (D₂O) as a tracer for cardiac output measurements. Cardiac output measurements made by thermodilution were compared with those made by indicator dilution with D₂O and indocyanine green as tracers. Five triplicate measurements for each method were made at intervals of 30 minutes in each of 9 anesthetized, mechanically ventilated goats. Cardiac output ranged between 0.68 and 3.79 L/min. The 45 data points yielded a correlation coefficient of 0.948 for the comparison of D₂O indicator dilution cardiac output measurements with thermodilution measurements and a linear regression slope of 1.046. D₂O indicator dilution measurements were biased by –0.11±0.22 L/min compared with thermodilution measurements and had a standard deviation of ±0.12 L/min for triplicate measurements. Hematocrits ranging between 20 and 50 vol% had no effect on optical density for D₂O. D₂O is more stable than indocyanine green and approximately one-tenth the price (40 cents per injection compared with $4). The basic instrumentation cost of approximately $9,000 is an additional initial expense, but provides the ability to perform pulmonary extravascular water measurements with a double-indicator dilution technique. D₂O has potential as a tracer for the clinical determination of indicator dilution cardiac output measurements and pulmonary extravascular water measurements.This study was supported by a U.S. Veterans Administration Merit Review Grant (103). Dr Schreiner is a recipient of an American Society of Anesthesiologists starter grant (1985–86). Dr Leksell is on leave from the Dept of Anesthesia, Karolinska Hospital, Stockholm, Sweden, and is supported by grants from the Swedish Medical Research Council, Karolinska Institute, Sandoz AB, and the Swedish Medical Association.