Effect of volume loading and dopamine on hemodynamics and red-cell redistribution in canine endotoxin shock

We studied in 20 anesthetized dogs (11-15 kg) the effect of volume loading and dopamine in the period between 90 and 120 min after injection of E Coli endotoxin (1.5 mg/kg). Changes in red-cell distribution were estimated from changes in regional radioactivity emitted by autologous 99mTc tagged red cells. Four groups of five animals were formed by randomization, such that effects of dopamine (15 micrograms/kg/min) and isotonic gelation solution (40 ml/kg/30 min) could be analyzed separately and in combination. Ninety minutes after endotoxin a significant decrease in cardiac output, arterial, and pulmonary arterial wedge pressures were observed. Thoracic radioactivity decreased by 26% and an increase in abdominal (11%) and hindlimb (17%) activity was measured, while the changes in hepatic activity were variable. No interaction between dopamine and volume for any parameter was found. Dopamine resulted in an increase in heart rate, while the other hemodynamic parameters did not change significantly. Dopamine resulted only in a slight increase in abdominal radioactivity. Volume loading produced an increase in cardiac output to greater than 200% of the value before endotoxin. This increase was accompanied by a considerable decrease in systemic resistance. No major changes in red-cell distribution were observed. We concluded that volume loading and dopamine did not affect red-cell redistribution in a later phase of canine endotoxin shock. Furthermore, our results suggest that correction of the volume deficit in this model results in a high-cardiac-output-low-systemic-resistance hemodynamic pattern.