Reduction of oxygenation and blood flow in pedicled bowel segments in the rat and its consequences for anastomotic healing.

PURPOSE: Experimental studies indicate that perioperative hypoperfusion impairs anastomotic healing. In bowel surgery, the part of bowel that will be anastomosed is often pedicled, leaving the blood supply dependent on the marginal artery only. Little is known about the blood supply in such a segment, and whether anastomotic strength is affected when flow would be reduced. This study describes oxygenation and blood flow in pedicled bowel segments in the rat and investigates whether early anastomotic strength changes with variations in blood flow. METHODS: In rats, pedicled segments were created in ileum and colon by successive ligation of the feeding arteries. Oxygenation and blood flow were measured in the distal part of this segment by use of near-infrared spectroscopy with indocyanine green as an intravascular tracer. In a second experiment, a short pedicled colonic segment was created and, after flow measurements, an anastomosis was constructed. Wound strength and hydroxyproline content were analyzed 2 and 5 days after operation. RESULTS: After creation of a pedicled segment, the concentration of oxygenated hemoglobin decreased significantly. Blood flow also significantly decreased to even less than 10% of baseline. A very large variation was observed between animals, in particular, after ligation of the first arteries. The strength of colonic anastomoses was not significantly correlated with the blood flow in the pedicled segment before anastomotic construction. CONCLUSIONS: The creation of a pedicled bowel segment greatly reduces tissue oxygenation and blood flow to its distal part. Such impaired perioperative flow does not significantly affect early wound strength after anastomotic construction