Mild preseptic hypothermia is detrimental in rats.

OBJECTIVE We evaluated the effects of mild hypothermia (32 degrees C), established before experimental intra-abdominal sepsis, on outcome, cytokine pattern, and muscle tissue oxygenation. DESIGN Clinic modeling randomized laboratory trial. SETTING University laboratory. SUBJECTS Ninety-six male rats. INTERVENTIONS In a group-sequential design, using 42 rats per group, we compared mild hypothermia with normothermia before peritonitis. Peritoneal inoculation with human stool bacteria was performed to simulate clinical trial conditions. Additionally, 12 rats underwent preoperative mild hypothermia without infection. MEASUREMENTS AND MAIN RESULTS Primary end point was mortality at 120 hrs. Secondary end points were systemic cytokine concentrations, granulocyte counts, and muscle oxygen partial pressure. Survival rate was 40% (16 of 42) after preseptic hypothermia and 62% (26 of 42) after preseptic normothermia (p =.048). All hypothermic rats without infection survived. Interleukin-10 concentrations were 1843 +/- 96 pg/mL after preseptic hypothermia, 945 +/- 225 pg/mL with preseptic normothermia, and 520 +/- 121 pg/mL after hypothermia without infection (p<.001). Macrophage inflammatory protein-2 was comparable in the treatment groups. Interleukin-6 concentrations were 106 +/- 24 pg/mL after preseptic hypothermia and 276 +/- 76 pg/mL with preseptic normothermia (p<.05). Postinfection granulocyte count was 1.7 x 10(9)/L after hypothermia and 2.4 x 10(9)/L after normothermia (p =.2). After infection, muscle oxygen partial pressure was 47 +/- 10 mm Hg with preseptic hypothermia, 85 +/- 12 mm Hg in preseptic normothermia, and 49 +/- 9 mm Hg after hypothermia without infection (p =.7). CONCLUSIONS In this rat model of intra-abdominal sepsis, mild preseptic hypothermia (32 degrees C) reduced survival, impaired granulocyte recruitment, and changed cytokine balance, suggesting immunosuppression.