Effect of Pentobarbital Anesthesia on the Blood Values of Rat Organs and Tissues

¹ From the Department of Anatomy, University of Washington School of Medicine, Seattle, Washington

Effect of pentobarbital anesthesia on the erythrocyte, plasma and true blood volumes of organs and tissues of male albino rats has been determined. The isotopic dilution method was applied utilizing Fe⁵⁹-labeled cells for the red cell determinations and I¹³¹ serum albumin for the plasma determinations. Animals were frozen in liquid nitrogen and organs were removed and assayed without blood loss. Redistribution of body blood occurred with anesthesia so that great increases in blood volume and hematocrit were found in splanchnic organs and in the kidney. These changes are discussed in relation to postanesthetic renal and intestinal dysfunction. Pentobarbital decreased significantly the blood volume of central nervous system tissue, of skeletal and cardiac muscle, and of bone. It increased the blood volume of skin and reproductive organs. Respective tissue hematocrit changes were noted and an interpretation of some of the changes is offered. The total body change produced by pentobarbital was an increase in both cellular and plasma constituents of blood in such a ratio that the total body hematocrit fell. The ratio of body hematocrit to venous hematocrit also declined. It is pointed out that these changes may result from an opening of many capillaries allowing low hematocrit blood to enter the general circulation. Passage of tissue fluid into the vascular system may also account for part of the increased total plasma volume.