Influence of Plasma Oncotic Pressure on Lung Water Accumulation and Gas Exchange After Experimental Lung Injury in the Pig

Abstract

In 18 anaesthetized and artificially ventilated pigs, oleic acid was infused intravenously in order to induce a lung injury characterized by increased lung water content, decreased compliance and a ventilation/perfusion disturbance. After a stabilizing period, half of the animals (group P) underwent repeated plasmapheresis, which halved their plasma oncotic pressure (POP). The rest of the animals were bled and re-transfused with the shed blood, thus serving as a control group. In both groups, care was taken to keep the mean left atrial pressure as constant as possible. During plasmapheresis and "shamapheresis", there was no significant increase in venous admixture (F102 0.21 and 0.6) in either of the groups. At the end of the study, end-inspiratory pressure, dead space/tidal volume ratio and wet/dry lung weight ratio (WW/DW) were significantly higher in group P. Venous admixture and WW/DW correlated significantly with pulmonary arterial pressure and calculated pulmonary capillary pressure, but not with POP or POP minus pulmonary arterial occlusion pressure. It is concluded that reduction of plasma oncotic pressure may increase the lung water content in previously injured lungs, but this extra water accumulation does not necessarily impair oxygenation in the lungs.

A stable model of respiratory distress by small injections of oleic acid in pigs

“…An excessive amount of oleic acid could lead to severe pulmonary edema, circulatory shock and death of the animal. Some authors reported a mortality of 25-30% during application of oleic acid [3,7]. In another study in pigs in which oleic acid was given as a continuous infusion in 30 min [8], a dose similar to the one we applied caused an unacceptably high mortality.…”

“…Oleic acid has often been used to induce an experimental model of respiratory distress in animals [1-81. In these studies oleic acid was given either as a single bolus or as a continuous infusion, and the amount administered differed between studies. Mortality was up to 30% [3,7]. In most studies, respiratory distress criteria according to Petty [9] and Murray [10] were not fulfilled and interventions were studied without a proper description of the model.…”

Early detection of acute lung injury uncoupled to hypoxemia in pigs using ultrasound lung comets*

“…Samples were placed in a dish and weighed, dried in an oven at 60°C for 72 hrs, and weighed again. Lung water was expressed as a wet to dry weight ratio, a wellknown index of pulmonary edema (16).…”

Acute Pulmonary Edema Following Plasma Exchange in a Patient With Guillian Barre Syndrome

“…She also received 2 U of fresh frozen plasma to replace lost plasma volume. 3 To conclude, acute pulmonary edema can occur following plasmapheresis in patients with GBS. She was intubated and shifted to intensive care unit for acute care management and mechanical ventilation.…”