Lung water and urea indicator dilution studies in cardiac surgery patients. Comparisons of measurements in aortocoronary bypass and mitral valve replacement.

We measured transpulmonary indicator dilution curves of 51Cr-erythrocytes, 125I-albumin, 14C-urea, and 3H-water before and six and 24 hours after operation in seven patients undergoing aortocoronary bypass (ACB) and eight patients undergoing mitral valve replacement (MVR). We calculated cardiac output (CO), extravascular lung water (EVLW), the difference between 125I-albumin and 51Cr-erythrocyte distribution volumes (EV albumin), the difference between 14C-urea and 51Cr-erythrocyte distribution volumes (EV urea) and 14C-urea extraction (E) and permeability -surface ares (PS) products. Comparisons between 16 ACB studies and 17 MVR studies showed the MVR group to have a higher EVLW (P less than 0.01). Extravascular lung water decreased after operation. The ratio of EV urea to EV albumin averaged 1.35 in the MVR group and 0.91 in the ACB group (P less than 0.001). 14C-urea E was also higher in the MVR group (P less than 0.05), but PS was similar in the two groups. None of the differences was related to the time that studies were done. We showed that EVLW, calculated using both 125I-albumin and 51Cr-erythrocytes as intravascular indicators and measured blood water content, had a constant relationship to EVLW calculated using only 125-I-albumin as the intravascular indicator and neglecting blood water content, over a broad range of cardiac outputs, hematocrist, and lung water volumes. We conclude that patients with mitral valve disease have an increased distribution volume and E for urea, probably due to hemodynamic changes but possibly due to increased vascular permeability. Extravascular lung water decreases after cardiac surgery regardless of the type of operation. A single intravascular indicator is adequate for estimating extravascular lung water in humans.