Renal blood flow in dogs during diffusion respiration

¹ Department of Pharmacology, University of Colorado Medical Center, Denver, Colorado

Two series of experiments were performed with appropriate controls on dogs in which respiratory arrest was produced and maintained by the injection of an overdose of thiopental or by administration of decamethonium, respectively. Renal blood flow was measured by a modification of the method of Selkurt (Methods in Medical Research, vol. 1). A marked fall in renal blood flow coincident with apnea and anuria was found to occur consistently with diffusion respiration under thiopental. Both the renal ischemia and the anuria were preventable by renal denervation (pharmacological block). During diffusion respiration experiments in which decamethonium was used to cause and maintain apnea, a marked decline in renal blood flow or urine secretion did not occur during the first 15 minutes of apnea. It is concluded that the prompt onset of anuria in diffusion respiration under thiopental is due to a central synergism between thiopental and endogenous carbon dioxide. Further, it is reasoned that the delayed fall in renal blood flow and attendant anuria which occurred under decamethonium represent the central effects of increasing concentrations of carbon dioxide in the absence of thiopental.