MINIMAL PHYSIOLOGICAL TEMPERATURE-VARIATIONS DURING RENAL ISCHEMIA ALTER FUNCTIONAL AND MORPHOLOGICAL OUTCOME

Aortic and renal vascular reconstruction often involve significant renal ischemia. Profound hypothermia during renal ischemia preserves renal tissue. However, in the clinical setting of vascular reconstruction specific attempts at cooling the kidney are often impractical, and renal ischemia frequently occurs at physiologic temperatures. This study demonstrates that minimal temperature changes during renal ischemia alter the functional and morphologic outcome. Rats anesthetized with halothane underwent a right nephrectomy and placement of a snare around the left renal pedicle for 45 minutes to produce renal ischemia. Seventy-five adult male Sprague-Dawley rats, weighing 250 to 350 gm were divided into three groups based on the body temperature maintained during renal ischemia (35-degrees-C, 37-degrees-C, 39-degrees-C). Body temperature was continuously monitored with a rectal thermistor and maintained by adjustment of a heating pad and lamp. Two postischemic protocols were followed including a creatinine assessment protocol with blood samples collected at 24, 48, and 72 hours and a histologic assessment protocol with biopsy of the kidney at 30 hours. At 24 hours after ischemia plasma creatinine concentrations were increased in rats with elevated body temperatures (35-degrees-C vs 37-degrees-C; [p = 0.001], 37-degrees-C vs 39-degrees-C; [p = 0.150]). The 30-hour histologic assessment indicated a difference in morphologic outcome (35-degrees-C vs 37-degrees-C; [p = 0.063], 37-degrees-C vs 39-degrees-C; [p = 0.0161), with proximal tubular morphology being better maintained at lower temperatures. In addition, 3-day mortality rates indicated a worsened outcome with increased body temperature (35-degrees-C vs 37-degrees-C; [p = 0.001], 37-degrees- C vs 39-degrees-C; [p = 0.0821). As a result of these findings it is recommended that attempts should be made at even modest lowering of renal temperature when more radical methods are not practical. Elective surgery involving significant renal ischemia should be avoided in the febrile/septic patient.