Effect of cold on ischemia--reperfusion-induced microvascular permeability increase in cat skeletal muscle

The effects of reduced temperature during ischemia (I) upon microvascular permeability and resistance increases during reperfusion (R) were assessed in skeletal muscle. Protein solvent-drag reflection coefficients (sigma f) and changes in vascular resistance were measured during 37 degrees C reperfusion of isolated, whole-blood perfused cat hindlimbs after the limbs had been subjected to 3.5 h of ischemia at several temperatures. sigma f was determined from the disappearance rates of water and protein from the circulating perfusate during a period of induced microvascular fluid filtration. The I/R procedure at 37 degrees C caused sigma f to fall from approximately 0.85 to approximately 0.5, indicating a large increase in microvascular permeability. Hypothermic ischemia at 30, 22, 17, or 12 degrees C totally abolished this drop in sigma f. However, when the ischemia was at approximately 5 degrees C, there was a significant fall in sigma f to approximately 0.7, which was similar to the value we found previously with 5 h of continuous perfusion at this low temperature. The normothermic I/R procedure led to an increase in vascular resistance of approximately 250% above the value measured prior to I/R. Hypothermic ischemia totally abolished this resistance increase, except for the lowest temperature, for which the increase was 150%. Therefore, hypothermia can prevent the microvascular dysfunction caused by 3.5 h of ischemia at 37 degrees C in this preparation. However, when the temperature was reduced too far (approximately 5 degrees C), a cold injury to the microvascular resulted in permeability and resistance increases.