Comparison of the pulmonary lymphatic and hemodynamic changes of near-drowning in a sheep model.

The hemodynamic and lung lymph changes following near-drowning (ND) were studied in sheep. Experimental ND was by transtracheal aspiration of 10 ml/kg body weight of either seawater (SW) or freshwater (FW). Extravascular lung water and lung lymph protein flux were significantly increased, but cardiac index was depressed in both groups following ND. Systemic and pulmonary vascular resistances were markedly elevated with FW compared to only a slight rise with SW. Lung lymph oncotic pressure decreased with SW ND from baseline of 9.7 +/- 0.4 to 6.8 +/- 0.63 mm Hg (P < 0.05). In contrast, FW ND increased lung lymph oncotic pressure from 12.8 +/- 0.9 to 16.6 +/- 1.3 mm Hg (P < 0.05). These data suggest that the changes in lung lymph and hemodynamic response to SW and FW ND differ in sheep. The changes are immediate and profound with SW, but slower in onset and less severe with FW. FW ND is associated with hemolysis, which is absent in SW ND.