Minimal physiologic temperature variations during renal ischemia alter functional and morphologic outcome

Abstract

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 = 0.016]), with proximal tubular morphology being better maintained at lower temperatures.(ABSTRACT TRUNCATED AT 250 WORDS)

Unilateral Renal Ischemia-Reperfusion as a Robust Model for Acute to Chronic Kidney Injury in Mice

“…Ischemia time, on the other hand, is the main factor that determines the severity of the long-term fibrotic outcome. This is a finding that is also true for other variants of the IRI model (bilateral IRI and unilateral IRI with contralateral nephrectomy) [ 13 , 43 , 52 , 53 , 58 ]. Contrary to these other variants of the IRI model, where spontaneous recovery of the ischemic kidneys is seen despite similar ischemia-conditions [ 25 , 84 ], it should be noted that all ischemia conditions tested in our study, both severe and mild, induced renal fibrosis consistently.…”

“…The effect of body temperature on the severity of acute IRI is connected to the body metabolism, and relates to three different processes: 1) higher body temperature during ischemia results in a more severe decrease of intracellular energy stores, 2) the concentration of degradation products inosine and hypoxanthine increases with increasing body temperature during ischemia, which results in increased production of free radicals upon reperfusion, and 3) increasing the body temperature during ischemia produces an increased damage of cell membranes [ 13 , 52 , 58 ]. It is known that hypothermia during experimental IRI provides renal protection, as it delays degradation processes and extends cell tolerance to ischemic stress [ 58 ]. In addition, hypothermia reduces inflammatory processes and limits the increase in vascular permeability [ 59 ].…”

Ischaemic preconditioning protects the rat kidney from reperfusion injury

“…After satisfactory surgical anaesthesia had been achieved, the left kidney was exposed through a midline laparotomy, and its renal artery exposed and dissected free to facilitate subsequent arterial clamping (see below). The presence of more than one artery supplying the kidney, haemorrhage from either the artery or vein, or a body temperature outside the range 36–38°C led to the exclusion of an animal from the study [ 12].…”

No Protection of the Porcine Kidney by Ischaemic Preconditioning

“…Arterial blood gases were monitored frequently in the initial stages of the preparation until stable and then periodically throughout the study (Radiometer, Copenhagen, Denmark). Since hypothermia is known to reduce the amount of ischaemic renal damage significantly (Pelkey et al 1992), rectal temperature was monitored and body temperature was kept between 37 and 39°C by the use of a heated surgical table and drapes. Through the cervical incision, one carotid artery and the internal jugular veins were isolated.…”