Lung water and vascular permeability in sheep. Newborns compared with adults.

Abstract

To compare vascular permeability and water content in the lungs of newborn lambs with those in adult sheep, we measured extravascular water and permeability surface area products (PS) for >4 C-urea and 14 Csucrose in nine 3-to 5-day-old lambs and 13 yearling sheep. In normal, unanesthetized animals, we injected a mixture of "Cr-erythrocytes, ""I-albumin, 3 H-water, and either "C-sucrose or "C-urea as a bolus into the right atrium and sampled blood from the thoracic aorta, calculating extravascular water and PS for urea and sucrose from the time-concentration curves of the tracers. We also measured extravascular lung water and dry bloodless lung weight postmortem. Normalized to dry lung weight, extravascular lung water by both techniques was similar in newborns and adults (indicator dilution values = 3.2 0.03 (SEM) ml/g for lambs and 3.2 0.03 for sheep; postmortem values = 4.07 0.26 g/g for lambs and 4.03 0.17 for sheep). In newborn lambs, PS calculated by integral extractor! was 0.28 0.04 (SEM) g/g dry lung for "C-urea and 0.18 0.04 for l4 C-sucrose. These values were not significantly different from those for adult sheep ("C-urea PS = 0.26 0.05; l4 C-sucrose PS = 0.08 0.03). We conclude that, when normalized to dry lung weight, newborn and adult sheep have similar lung water and vascular permeability to small hydrophilic molecules and that indicator methods for measuring PS and lung water are feasible in newborns.