Effect of cardiac output on extravascular lung water

Extravascular lung water (EVLW) and cardiac output (CO) were determined in 21 mongrel dogs using the thermal-green dye double indicator dilution technique. In 12 of the animals the renal vessels were ligated bilaterally to increase peripheral resistance and reduce cardiac output without altering actual EVLW. Measurements before and after renal pedicle ligation revealed an average 47 per cent decrease in cardiac output with an 11 per cent increase in measured lung water. In the remaining nine animals an external arteriovenous fistula was constructed to reduce afterload and increase cardiac output. In the baseline state, opening the fistula caused a 63 per cent increase in cardiac output with a simultaneous five per cent decrease in measured EVLW. This second group of animals was then given intravenous acid sufficient to cause 30-50 per cent increases in EVLW. Measurements of EVLW and CO with the fistula open and closed were continued for three hours. The inverse relation between cardiac output and EVLW continued. The results of these experiments show that cardiac output does exert a small effect on the measurement of EVLW.