Respiratory quotients of human kidney in vivo

¹ Renal Section, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania

Renal respiratory quotient (RQ) has been calculated from data collected in unanesthetized human subjects. In contrast to RQ recently reported on anesthetized dogs, these data do not indicate a mean value greater than 1. Under control conditions in 24 subjects, renal RQ calculated without special corrections averaged 0.88. Correcting for differences in blood flow between renal artery and vein due to urine formation the mean was 0.73, with 95% confidence limits 0.49–0.97. With alkaline urines an additional correction for urinary excretion of CO₂ is advised. Excluding procedures known to alkalinize the urine, RQ values were similar in 46 observations after a variety of experimental procedures. Since both numerator and denominator of the ratio involve small differences between large values, small analytical errors can produce large changes indistinguishable from physiologic variation. Therefore mean values rather than individual observations are stressed. While such values in our data appear similar to RQ for other organs and the whole body, they do not preclude considerable anaerobic metabolism.