Postoperative peridural analgesia increases the strength of colonic contractions without impairing anastomotic healing in rats

Abstract

Background and aims. Peridural analgesia (PDA) is a common treatment in postoperative management after abdominal surgery to shorten postoperative ileus and to permit early postoperative nutrition. There are conflicting opinions on the effect of early peristalsis on healing of colonic anastomoses.

Patients and methods. A short segment of the distal colon was resected in 32 Wistar rats. Two strain gauge transducers were placed on the serosa proximal to the anastomosis to measure the strength and periodicity of bowel contractions. A peridural catheter was placed between lumbar vertebra 7 and the sacral crest. The animals received 4, 16, 20, and 24 h after operation an injection of either 0.03 ml ropivacaine 0.75%/kg body weight or the same amount of sodium chloride (controls). After 3 and 10 days the colonic anastomoses were resected to measure the bursting pressure. The anastomoses were prepared for histopathological examination and determination of relative collagen content.

Results. Postoperative PDA led to an increasing amplitude of phasic and tonic contractions while the frequency of contractions was not significantly affected. None of the groups presented with any anastomotic complications. The bursting pressure after 3 and 10 days was similar in the two groups. The relative amount of collagen I in the anastomotic area was significantly higher after treatment with peridural ropivacaine.

Conclusion. Postoperative PDA with ropivacaine increases the strength of colonic contractions. The increase in phasic contractions suggests a better propulsive bowel function. The significantly higher amount of collagen I in the anastomosis of animals in the PDA group supports the idea that healing of colonic anastomoses is improved rather than diminished by PDA.