Estimation of Left Ventricular Residual Volume in the Dog by a Thermodilution Method

Thermodilution was used to estimate left ventricular volumes by the indicator-dilution principle. The results of multiple determinations in the same animal were in close agreement. Average values determined in 16 dogs anesthetized with a chloralose-urethane mixture were SV 18 ml., ESV 37 ml., EDV 56 ml., and CO 2.54 L./min. The ratio ESV/EDV averaged 66 per cent, which was significantly less than the ESV to EDV ratio of 79 per cent observed in 14 other dogs anesthetized with sodium pentobarbital and studied in a comparable fashion. This difference was attributed primarily to the myocardial depressant effects of the barbiturate anesthetic.The ability to perform multiple determinations without “indicator” accumulation, to record the time-temperature curve directly at the base of the aorta without sampling through a catheter system, to avoid introducing substances into the circulation which may produce significant circulatory effects, and to perform calibration quickly and easily suggests that the thermodilution technique offers a simple, rapid, and reproducible method for estimating ventricular volumes.