Background
A new method for determining cardiac output (CO, l/min) using dye dilution combined with pulse dye densitometry (PDD), based on the principle of pulse oximetry, has been developed. The aim of the study was to determine the accuracy and precision of PDD by comparing it with the thermodilution method.
Methods
A prospective study was performed in 22 patients having surgery who were monitored using a pulmonary arterial catheter. In addition to the catheter, a specially designed photodetector was placed on the nasal wing. Ten milliliters of ice-cold indocyanine green dissolved in a 5% glucose solution (0.5 mg/ml) was injected. The dye and thermal dilution curves were simultaneously measured to calculate CO. Three to six injections were performed before and after surgery. Paired data were assessed in absolute terms, and the percentage errors were calculated by the degree of agreement and compared at three levels of CO (low < or = 3.5 < medium < or = 6 < high) by analysis of variance.
Results
The mean and SDs of the differences between dye and thermodilution CO were 0.16 +/- 0.80 l/min or 4.5 +/- 19.6% for 191 paired data. Measurement after surgery failed in one patient. The percentage error with low CO (9.3 +/- 19.3%) was greater (P < 0.05) than those obtained with other CO.
Conclusions
Pulse dye densitometry could measure CO repeatedly in patients having major surgery with the same degree of accuracy as the thermodilution method; however, a considerable degree of error was observed in some patients.
The initial distribution volume of glucose and cardiac output in the critically ill