Effects of hyperthermia on renal functions
Logawney-Malik, S.; Bhalla, S.; Thomas, S.
Indian Journal of Medical Research 69: 312-318
1979
ISSN/ISBN: 0019-5340 PMID: 429040 Document Number: 140308
The effect of hyperthermia on renal functions and its morphology and the correlation between these changes and other thermoregulatory responses observed during and after acute thermal stress were determined. Renal functions were assessed by measuring glomerular filtration rate (GFR), renal plasma flow (RPF), standard urea clearance (SUC), urine volume and blood urea. Induction of hyperthermia in well hydrated dogs produced a gradual and steady decrease in renal functions with increasing rectal temperature. At a rectal temperature of 39.degree. C, despite a rise or no change in blood pressure (BP) and no significant increase in arterial hematocrit a decrease in GFR, RPF, SUC, urine volume and filtration fraction was observed. On raising the rectal temperature to 41-42.degree. C, the above parameters of renal functions decreased further along with a decrease in BP and an increase in arterial hematocrit. On cooling the hyperthermic dogs to 37.degree. C rectal temperature, renal functions showed partial recovery (65-80% of normal) though BP and arterial hematocrit recovered to near normal values. Hyperthermic kidneys were pale, enlarged and firm and their histological sections showed marked cloudy swelling of glomerular endothelium and necrosis of tubular cells. These changes persisted even after cooling. During hyperthermia, besides involvement of the kidneys in generalized thermoregulatory responses there apparently occurs an increase in intraglomerular and intrarenal vascular resistance due to direct effect of heat on the cells of the kidneys, which contributes to the decrease in renal functions during hyperthermia and prevents its full recovery after cooling.