Mild hypothermia does not increase bacterial proliferation on implanted vascular grafts

Background: Mild hypothermia may offer protection against spinal cord ischemia during aortic surgery. However, hypothermia also promotes postoperative infection via two mechanisms: peripheral vasoconstriction and impairment of various immune functions. If mild hypothermia aggravates graft infections, immune function impairment would presumably be the most important factor because thermoregulatory vasoconstriction does not appreciably reduce aortic blood flow. We therefore tested the hypothesis that resistance to vascular graft infection is not reduced by mild perioperative hypothermia in dogs. Methods: After colonization with a solution of Staphylococcus epidermidis, prostheses were used to replace the infrarenal aorta in 20 dogs. During surgery, the dogs were randomly assigned to maintain of normothermia or passive cooling. Seven days later, grafts were recovered for bacteriologic study. Results: Colony counts for the grafts removed from the normothermic and hypothermic dogs did not differ significantly. Conclusions: Mild perioperative hypothermia does not increase proliferation of S epidermidis on aortic vascular grafts.