Induction of whole body hyperthemia with venovenous perfusion

Whole body hyperthermia can be used for the treatment of metastatic cancer and human immunodeficiency virus infections. The therapeutic effects of hyperthermia are dependent upon the actual temperature of the target tissues. Therefore, homogeneous distribution of heat and precise control of temperature gradients is critical. To describe heat distribution during hyperthermia induced by venovenous perfusion, the authors used multiple channel temperature monitoring and a servo-regulated perfusion/heat exchange system. Young swine were randomly assigned to either a heated group (perfusion-induced hyperthermia, target core temperature at 43 degrees C, n = 6), or a control group (perfusion alone, target core temperature at 38 degrees C, n = 6). Blood was drained from the external jugular vein, heated with a computer assisted heat exchange system, and reinfused through the femoral vein at a flow of 10 ml/kg-1/min-1. Temperature probes in the esophagus, right and left tympanic canals, brain, pulmonary artery, arterial and venous blood, rectus spinae muscle, kidney, rectum, bone marrow, bladder, subcutaneous tissue, gluteus, and skin were simultaneously recorded. During the heat induction phase, the maximum water temperature was 54 degrees C, with a heating gradient of the blood (blood in-blood out) at 6 degrees C. The maximum temperature difference between tissues was 3.6 degrees C (kidney and esophagus) during heat induction, but decreased to 1.75 degrees C during maintenance. Bone marrow temperature was consistently 1-2 degrees C below the average core temperature of 43 degrees C throughout the experiment. The authors conclude that venovenous perfusion can predictably induce hyperthermia, but is associated with heterogenous temperature distribution among organs. Further studies are necessary to evaluate different perfusion and heating patterns to achieve homogenous hyperthermia.