Effect of increased intra-abdominal pressure on various circulatory parameters of the anesthetized dog

¹ Aeromedical and Physical Environment Laboratory, University of Illinois, Chicago, Illinois

Abdominal pressure of anesthetized dogs was elevated by the introduction of 18.5 mm Hg compressed air through a cannula tied securely into the peritoneal cavity. Significant decreases in circulating plasma volume (T-1824) were observed during the first 80 minutes of elevated pressure. Thereafter, plasma volume returned toward the control level except for a marked drop when the pressure was released. Hematocrit levels and plasma protein concentrations also indicated a loss of fluid. Mean vena cava pressure at the level of the heart did not markedly change, although the venous pressure below the diaphragm increased significantly. Arterial pressures decreased immediately upon elevation of the abdominal pressure, but returned to pre-experimental levels prior to release of elevated abdominal pressure. Concomitant with these circulatory alterations was a decrease in urine volume as well as a slight increase in serum potassium. Serum sodium remained essentially unaltered. These observations are compared to similar circulatory changes which occur during positive pressure breathing.