Plasma Volume Expansion in Canine Pneumococcal Pneumonia

Patients with pneumococcal pneumonia are often given fluids intravenously for hydration and maintenance of circulating blood volume. We studied the effects of plasma volume expansion on respiratory gas exchange and pneumonia size in a canine model of lobar pneumonia. Seven ventilated anesthetized dogs (Group T) with left lower lobe pneumococcal pneumonia were infused with dextran 75 in 0.9% saline solution to increase the pulmonary capillary wedge pressure to 10 mmHg for 3 h. These were compared with 7 control dogs (Group C) with left lower lobe pneumonia. Measurements of cardiac output, intrapulmonary shunt , and lobar distribution of perfusion were taken at baseline (B), immediately after volume infusion (V), and 3 h later (F); similar intervals were used in control animals. In Group T, increased significantly from 24% at B to 34% at F. Part of this increase in occurred immediately after volume infusion (29% at V) and was associated with the concomitant increase in cardiac output (4.7 L/min at B to 10.6...