Pulmonary hemodynamics, extravascular lung water and residual gas bubbles following low dose venous gas embolism in dogs.

Pulmonary hemodynamic responses, extravascular lung water and bubble longevity times were studied in halothane anesthetized dogs receiving low dose venous gas infusions. Dogs in one group (23.3 +/- 4.3 kg, n = 6) were embolized with air (0.05 ml.kg-1.min -1) for 60 min followed by a recovery period lasting 70 min. During the recovery the ventilatory gases were intermittently switched from nitrogen (68-69%)/oxygen (30%) to nitrous oxide (68-69%)/oxygen (30%) to expand any residual pulmonary vascular bubbles. Subsequent changes in pulmonary artery pressure, pulmonary vascular resistance, end-tidal carbon dioxide and arterial carbon dioxide tensions were used to indicate the presence of remaining bubbles that would have expanded in volume with the nitrous oxide ventilation. This embolization sequence was repeated three times to simulate repetitive exposure of the pulmonary circulation to venous gas emboli. In a second group of dogs (20.2 +/- 2.7 kg, n = 8) the venous gas infusions (0.05 ml.kg-1.min-1) were continuous for 180 min, followed by recovery with intermittent nitrous oxide/oxygen challenges to determine bubble longevity. Pulmonary hemodynamic and carbon dioxide data were significantly changed from baseline following each embolization. These differences as well as the development of extravascular lung water (edema formulation) were not significant when comparisons were made between the Repetitive gas embolism group after 180 min. Residual pulmonary vascular bubbles were indicated (mean +/- S.E.M.) 26.9 +/- 2.3 min following the 180 min Continuous venous gas infusion and 39.5 +/- 5.3, 46.4 +/- 5.0 and 55.5 +/- 4.4 min, respectively, following the three 60 min Repetitive venous gas infusions.