Physiologic Effects of Rapid Infusion of Ringer's Lactate Solution into Dogs

SUMMARY Mild dehydration was induced in 12 dogs by withholding food and water until 8% to 14% of body weight had been lost. The dogs were then divided into 3 groups (A, B, and C) of 4 dogs each for rapid infusion of Ringer's lactate solution (warmed to 37 C) while unanesthetized. During a 1-hour period, group A was given 90 ml/kg; group B, 225 ml/kg; and group C, 360 ml/kg. Clinical signs were absent or minimal in groups A and B and included increased serous nasal discharge, mild coughing, and slight chemosis. Dogs in group C showed a marked increase in serous nasal discharge, restlessness, coughing, and dyspnea within 20 minutes after beginning fluid administration. Thereafter, marked abdominal distention (ascites), polyuria, chemosis, protrusion of the ocular globe, and profuse diarrhea were observed. Most of these signs quickly resolved once fluid administration was stopped, and no deaths occurred. Body temperature, packed cell volume, plasma total solids, and serum potassium decreased significantly in 1 or more groups during the infusion. There were no changes in serum sodium. Pulse rate, respiratory rate, and systemic arterial pressure (systolic and diastolic) increased slightly, but these changes were quite variable. Pulmonary arterial pressure (systolic and diastolic), pulmonary wedge pressure, and central venous pressure all increased significantly in 1 or more groups during fluid infusion. Pulmonary arterial diastolic pressure and pulmonary wedge pressure increased earliest and at the slowest rate of fluid administration (group A, 90 ml/kg/hr). Increases in pulmonary arterial pressure, pulmonary wedge pressure, and central venous pressure were significantly higher in group C (360 ml/kg/hr) than in groups A or B. Among all groups, statistically significant correlation was found between pulmonary wedge pressure and central venous pressure. It was concluded that in mildly dehydrated dogs without cardiovascular disease that (1) Ringer's lactate solution infused at the rate of 90 ml/kg/hr is tolerated with a substantial margin of safety, and (2) although pulmonary wedge pressure may increase earlier and to a greater extent than central venous pressure during rapid intravenous Ringer's lactate solution administration, overall agreement between the 2 pressures is good.