Tolerance of small bowel anastomoses in rabbits to photodynamic therapy with dihematoporphyrin ethers and 630 nm red light.

Photodynamic therapy (PDT) is being evaluated in experimental clinical trials in patients with peritoneal malignancies. Some patients require partial small bowel resection with re-anastomosis prior to PDT because of bulky tumor or focal involvement of the small bowel by tumor. To assess the safety of PDT in this setting, the tolerance of small bowel anastomoses in New Zealand white rabbits to PDT with dihematoporphyrin ethers (DHE) and 630 nm light was studied. With conventional DHE doses of 1.5-2.5 mg/kg given 24 hours prior to surgery and light doses of 0-20 J/cm2 of 630 nm light, no adverse effects were seen on the healing of small bowel anastomoses. Higher photosensitizer doses of 10 mg/kg and 20 mg/kg in conjunction with 20 J/cm2, however, induced failure and breakdown of fresh anastomoses in 2/3 and 4/4 animals, respectively.