Effect of elevated intra-abdominal pressure and 100% oxygen on superior mesenteric artery blood flow and enterocyte turnover in a rat

Purpose Elevated intra-abdominal pressure (IAP) has been shown to reduce mesenteric blood flow and cause intestinal damage. The purpose of the present study was to evaluate the effects of IAP and hyperoxia on superior mesenteric artery (SMA) blood flow, enterocyte proliferation and apoptosis in a rat model of abdominal compartment syndrome (ACS). Methods Male rats underwent midline laparotomy. SMA was isolated and ultrasonic blood flow probes were placed on the vessel for continuous measurement of regional blood flow. Two catheters were introduced into the peritoneal cavity for inflation of air and for measurement of IAP. Rats were divided into three experimental groups: (1) Sham rats were subjected to IAP of 0 mmHg, (2) ACS-air rats were subjected to IAP of 6 mmHg for 2 h and were ventilated with air, and (3) ACS-O-2 rats were subjected to IAP of 6 mmHg and were ventilated with 100% oxygen (O-2) during the operation and for 6 h after the operation. Intestinal structural changes, enterocyte proliferation and enterocyte apoptosis were evaluated at 24 h after operation. A paired Student's t test and the non-parametric Kruskal Wallis ANOVA test were used as indicated. P < 0.05 was considered statistically significant. Results IAP at 6 mmHg caused a moderate decrease in SMA blood flow. Inhalation of 100% oxygen resulted in a trend toward an increase in SMA flow when compared to air-ventilated animals. ACS rats demonstrated a significantly lower index of proliferation in jejunum and ileum as well as a significantly greater apoptotic index in jejunum compared to sham animals. Exposure to 100% oxygen resulted in a significant increase in cell proliferation in jejunum and ileum as well as in a significant decrease in cell apoptosis in jejunum compared to air-breathing animals. Conclusions In a rat model of ACS, elevated IAP decreases SMA blood flow and inhibits enterocyte turnover. Hyperoxia results in a trend toward an increase in SMA blood flow, increases enterocyte proliferation and inhibits cell death via apoptosis. These findings may have significant implications for ventilation strategies during laparoscopy.