Whole body hyperthermia: effects upon canine immune and hemostatic functions

Abstract

In this study, the effects of induced whole body hyperthermia (WBH; 42.3°C for 90 min) on peripheral blood mononuclear cell (PBMC) phenotype distribution, in vitro blastogenic responsiveness and selected parameters of hemostasis were determined in dogs. Hyperthermia was induced by heating venous blood during extracorporeal circulation (EC); induction of WBH by peritoneal lavage (PL) and perfusion without heating (i.e. euthermic EC and euthermic PL) were used as controls. Whole body hyperthermia was associated with lymphopenia and thrombocytopenia that persisted throughout the eight-day post-treatment observation interval. The lymphopenia was selective in that CD5-positive T lymphocytes were more sensitive than were sIg-positive B cells and, within the T-cell compartment, suppressor (CD8-positive) cells were more sensitive to hyperthermic stress than helper (CD4 positive) lymphocytes. Lymphopenia was also observed in EC and PL euthermic controls, although that lymphopenia was transient and nonselective. Persistent suppression of T-cell phytomitogen-induced blastogenesis was induced by WBH in contrast to transient suppression in euthermic controls. For all treatment groups, lymphopenia and suppressed blastogenesis were correlated to elevated plasma cortisol levels. Induction of WBH by EC resulted in coagulopathy characterized by thrombocytopenia, increased plasma fibrin degradation products, prolonged clotting times, and evidence of spontaneous bleeding. These hemostatic alterations were correlated temporally to increased serum levels of liver enzymes. However, there was no evidence of hepatic injury when WBH was induced by PL, where transient thrombocytopenia was the only significant hemostatic alteration. These results indicate that 42.3°C whole body hyperthermia can be well-tolerated and, although associated with suppression of general indexes of immunocompetence, is not associated with opportunistic infections.