Lung water and vascular permeability-surface area in newborn lambs delivered by Caesarean section compared with the 3-5 days old lamb and adult sheep

Extravascular lung water and vascular permeability-surface area products were measured with a multiple indicator dilution method in five unanaesthetized newborn lambs 2 to 7 h following delivery by Caesarean section at a gestational age of 135-142 days. The indicators used were ⁵¹Cr-labelled erythrocytes, [ ¹²⁵I]albumin, [ ³H]water and [ ¹⁴C]urea. Post-mortem determination of extravascular lung water and dry bloodless lung weight were also performed. The results were compared with previously obtained data in unanaesthetized 3-5 days-old lambs and adult sheep. Normalized to dry lung weight, extravascular lung water by both techniques was significantly higher in lambs after Caesarean section than in either the 3-5 days-old lambs or the adult sheep (P<0.05). (Indicator values = 3.9 ± 0.2 (SEM) ml/g for Caesarean section lambs, 3.1 ± 0.3 for 3-5 days-old lambs and 3.3 ± 0.5 for adult sheep; post-mortem values were 6.12 ± 0.28 g/g for after Caesarean section lambs, 4.07 ± 0.26 for 3-5 days old lambs and 4.03 ± 0.17 for sheep). Vascular permeability-surface area product for [ ¹⁴C]urea, computed by a mathematical model, was significantly higher (P<0.05) in lambs after Caesarean section than in adult sheep (0.18 ± 0.02 compared with 0.10 ± 0.03). In 3-5 days-old lambs the value was 0.16 ± 0.04. It is concluded that, when normalized to dry lung weight, lung water and vascular permeability-surface area products are high at birth following Caesarean section delivery near the end of gestation. Adult values for lung water have been reached by the age of 3-5 days.