Determination of renal hypothermic temperature adequacy for renoprotection during ischemia using renal interstitial glycerol concentrations in a porcine model.

Objectives To determine the effect of renal cooling on interstitial glycerol concentration during renal ischemia. The rate of cellular release of glycerol into the interstitial fluid at various hypothermic temperatures during ischemia was used to assess adequacy for renoprotection at those temperatures. Methods Twenty-four renal units in 12 pigs underwent ischemia during measurement of renal interstitial fluid glycerol concentration. Kidneys were categorized into a body temperature control group or various hypothermic temperature groups (n = 4): 5°, 10°, 15°, 20°, and 25°. Results The glycerol concentration of all kidneys increased directly with ischemic time. The rate of increase in glycerol concentrations over ischemic time decreased sequentially as renal temperature decreased. The glycerol concentration of the kidneys cooled to 25°C during ischemia was significantly less ( P = .03) relative to the glycerol levels obtained from the kidneys subjected to warm ischemia at 120 minutes. Conclusions Renal hypothermia decreases the rate of cellular release of glycerol into the interstitial fluid. Hypothermia at 25°C doubles the time required for renal interstitial glycerol to accumulate to levels associated with irreparable renal function damage. Therefore, relatively warmer hypothermic temperatures may be sufficient to extend a significant renoprotective effect during ischemia.