Intraperitoneal hypothermia during surgery enhances postoperative tumor growth

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Abstract
Recent work has shown that intraoperative hypothermia is a significant source of surgical trauma, with wide-ranging physiological and immunological sequelae. The aim of this study was to examine the effects of intraperitoneal hypothermia during laparoscopy on tumor growth in an animal model. Thirty WAG rats were randomized to undergo anesthesia alone (n = 10), insufflation with cold carbon dioxide (CO2) (n = 10), or insufflation with warm CO2 (n = 10). During insufflation, 1 x 105/ml CC531s colon cancer cells in suspension were injected into the peritoneal cavity. The control group was anesthetized and tumor cells were injected without insufflation. After 3 weeks, total tumor weight and the extent of tumor spread, as assessed by the modified Peritoneal Cancer Index (PCI), were compared at autopsy. Laparoscopy with cold CO2 resulted in a significant reduction in local and core body temperatures (p <0.05). Tumor growth in both groups that underwent CO2 pneumoperitoneum was significantly increased compared with the group that did not (p <0.0001, control vs warm CO2 and cold CO2). There was significantly more tumor growth in the rats insufflated with unwarmed CO2 than in the normothermic group (mean total tumor 0.01 g +/- 0.03 vs. 0.043 g +/- 0.07; p = 0.025 Mann-Whitney U test). Tumor spread as shown by the PCI scores was less in the warm gas group than it was in the animals insufflated with cold gas (151 vs 266). These data demonstrate that the peritoneal insufflation of CO2 enhances tumor growth and that the prevention of perioperative hypothermia during laparoscopy attenuates tumor growth. This effect may be partially mediated by the increased peritoneal trauma that results from insufflation with cold gas.