Haemodynamic and respiratory changes accompanying haemorrhagic shock in thoracotomized dogs

Haemorrhagic shock was induced after thoracotomy by bleeding into a reservoir and the reduction of systemic blood pressure to 40 mm Hg. After two hours the blood was retransfused. The haemodynamic and respiratory changes due to the haemorrhage and retransfusion were noted during the two hour shock period and one hour after transfusion. The results were as follows: 1. Pulmonary mean and systemic mean pressure during haemorrhage and retransfusion do not change in parallel; 2. there is a rapid rise in pulmonary arterial [PA] and pulmonary capillary [PC] pressure during retransfusion; 3. cardiac output and its pulmonary fraction decrease during shock and cardiac output failed to normalise on retransfusion of the lost blood; 4. pulmonary vascular resistance, pulmonary total resistance increase significantly at the end of the shock period and after retransfusion; 5. shunt volume, alveolo-arterial O2 difference, the difference in arterio-alveolar co2 tension and dead space ventilation increase; while 6. o2 consumption and CO2 production decrease; 7. arterial blood gas values alone do not indicate those serious metabolic; circulatory and respiratory changes which develop in the lung during shock; 8. effective pulmonary compliance and the plasma oncotic pressure decrease, indicating interstitial oedema; 9. the primary mechanism responsible for the disorder during shock is not entirely clear but beside a number of other factors, the importance of the hypoperfusion of the bronchial circulation is stressed; 10. the conclusions permit a certain insight into the pathogenesis and therapeutic possibilities of the adult respiratory distress syndrome.