Hemorrhagic shock in the dog

Oxygen consumption, hemodynamics, and regional blood flow (with the radioactive microspheres technique) were determined in 12 anesthetized dogs subjected to hemorrhagic shock. The animals were kept in hypotension at 40 mm Hg, until 15% of the maximum shed blood had been infused to keep arterial pressure stable, whereafter all the shed blood was retransfused. Cardiac output (CO) decreased to 33% and 25% of preshock values in survivors (S) and nonsurvivors (NS), respectively, and after retransfusion it was significantly higher in S. After retransfusion, NS showed a higher arterial pCO2 than S adding a respiratory component to the metabolic acidosis that occurred during and after hemorrhage. Blood flow to the brain was not impeded during shock, but as CO decreased the fraction delivered to the brain was increased 2.6–3.3-fold. Myocardial blood flow decreased to about 28% of preshock values immediately after hemorrhage, and increased to about 54% at the end of hemorrhage. After retransfusion S had a higher myocardial flow than NS. The flow to the gut paralleled the decrease in CO during hemorrhage and immediately after retransfusion NS exhibited an overperfusion in ileum and colon compared to the preshock values. Kidney blood flow fell progressively during the course of hypotension, similarly in S and NS. After retransfusion it was normalized in S but not in NS. The preshock flow to pancreas was significantly higher in S than in NS, but during and after shock the blood flow did not differ between S and NS.