Intra-Operative Tissue Oxygen Tension Is Increased by Local Insufflation of Humidified-Warm CO2 during Open Abdominal Surgery in a Rat Model

Introduction

Maintenance of high tissue oxygenation (PtO₂) is recommended during surgery because PtO₂ is highly predictive of surgical site infection and colonic anastomotic leakage. However, surgical site perfusion is often sub-optimal, creating an obstructive hurdle for traditional, systemically applied therapies to maintain or increase surgical site PtO_2. This research tested the hypothesis that insufflation of humidified-warm CO₂ into the abdominal cavity would increase sub-peritoneal PtO₂ during open abdominal surgery.

Materials and Methods

15 Wistar rats underwent laparotomy under general anesthesia. Three sets of randomized cross-over experiments were conducted in which the abdominal cavity was subjected to alternating exposure to 1) humidified-warm CO₂ & ambient air; 2) humidified-warm CO₂ & dry-cold CO₂; and 3) dry-cold CO₂ & ambient air. Sub-peritoneal PtO₂ and tissue temperature were measured with a polarographic oxygen probe.

Results

Upon insufflation of humidified-warm CO₂, PtO₂ increased by 29.8 mmHg (SD 13.3; p<0.001), or 96.6% (SD 51.9), and tissue temperature by 3.0°C (SD 1.7 p<0.001), in comparison with exposure to ambient air. Smaller, but significant, increases in PtO₂ were seen in experiments 2 and 3. Tissue temperature decreased upon exposure to dry-cold CO₂ compared with ambient air (-1.4°C, SD 0.5, p = 0.001).

Conclusions

In a rat model, insufflation of humidified-warm CO₂ into the abdominal cavity during open abdominal surgery causes an immediate and potentially clinically significant increase in PtO₂. The effect is an additive result of the delivery of CO₂ and avoidance of evaporative cooling via the delivery of the CO₂ gas humidified at body temperature.