EFFECT OF PREOPERATIVE IRRADIATION ON WOUND-HEALING AFTER BRONCHIAL ANASTOMOSIS IN MONGREL DOGS

To determine the endurable radiation dose before bronchial anastomosis , the bronchial circulation of mongrel dogs was assessed after broncho plastic surgery conducted after various single doses of radiation. Pla stic surgery of the right main bronchus was carried out 1 week after c obalt 60 irradiation to the right hilar region. Bronchial blood flow w as measured with laser Doppler velocimetry 7, 14, and 30 days after op eration. Animals were killed 30 days after operation and the region of the bronchial anastomosis was examined histologically. Tle animals we re divided into five groups: group A (control group without irradiatio n), group B (8 Gy irradiation), group C (16 Gy), group D (19 Gy), and group E (24 Gy). Wound healing of the anastomosed bronchus was excelle nt in groups A and B. In group A, bronchial blood flow did not drop be low 80 % of the preoperative level throughout the postoperative observ ation period. In group B, bronchial blood flow on day 7 after operatio n was only 65 % of the preoperative level, but blood flow had returned to the preoperative level by day 30. In groups C, D, and E, bronchial blood flow was less than 60 % of the preoperative level on day 30. Th ere was a high prevalence of radiation-induced morbidity in the region of anastomosis in groups C, D, and E. Postoperative recovery of bronc hial blood flow and wound healing of the anastomosed bronchus were thu s delayed in dogs that had received high doses of radiation before ope ration. We conclude that the safe dose of preoperative radiation in cl inically used fractionation is 36 Gy or less (corresponding to a singl e dose of 16 Gy or less in dogs).