Changes in Renal Blood Flow in Dogs During the Inhalation of 30% Carbon Dioxide

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

Mongrel dogs lightly anesthetized with thiopental sodium were used as experimental animals. After suitable controls were taken the changes in renal blood flow, urine volume, venous blood pH, blood pressure and heart rate, respiratory rate and volume and relative blood cell volume were measured at intervals during inhalation of 30% carbon dioxide in oxygen for 30 minutes. No anesthetic was administered during the period when CO₂ was inhaled. No constant change in pH, hematocrit or heart rate was observed to result from the CO₂ inhalation. Respiratory rate increased throughout the experiments. The inhalation of 30% carbon dioxide in oxygen produced a marked reduction in renal blood flow, concomitant with a marked oliguria. The renal ischemia under these conditions was prevented by pharmacological block of the left renal nerves (by injection of 5 ml of .5% tetracaine into the peripelvic area of the kidney). The pharmacologically denervated kidney continued to secrete urine in somewhat diminished quantities while the undenervated kidney developed severe oliguria or anuria. It is postulated that the renal ischemia observed in these experiments is a component of a generalized centrally induced vasoconstrictor response to the inhalation of a high concentration of carbon dioxide.