Effects of certain anesthetics on distribution of red cells in the dog

¹ Departments of Pharmacology and Physiology, Baylor University College of Medicine, and University of Texas Dental Branch, Houston, Texas

The animals were anesthetized with either sodium pentobarbital or morphine alone or in combination and the effects of these drugs were determined on the cell and plasma volumes and hematocrits on unsplenectomized and splenectomized groups. ‘Circulatory’ hematocrit is used to designate the distribution of cells and plasma throughout the circulatory system rather than ‘body’ hematocrit or over-all cell percentage; and BVR_cells is used in place of the term F_cells. In unsplenectomized dogs with pentobarbital alone the venous hematocrit is significantly lower than the morphinized or morphine-pentobarbitalized dogs, and the BVR_cells (circ. hemat/venous hemat.) is 1.02. The latter figure is significantly different from 0.89 with morphine alone or 0.90 with the combined drugs. Removal of the spleen affected neither the variability of individual dogs nor significantly changed the BVR_cells. The action of morphine when given alone, markedly increased the plasma volume and when combined with pentobarbital resulted in a redistribution of red cells; thus the BVR_cells was decreased for these groups compared to pentobarbital alone. These data imply that cell and plasma volume should be measured simultaneously and independently for determining the blood volume with the utmost accuracy.