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THE EFFECTS OF VASCULAR FREEZING TIME ON ARTERIAL VASOSPASM IN RATS

The outcomes of microvascular surgery may be jeopardized by factors that reduce the blood flow across the freshly performed anastomosis. Arterial vasospasm is one of such factors causing the failure of an anastomosis. Vascular spasm has been treated by systemic or topical administration of pharmacologic agents. However, despite the extensive works done to prevent and to elucidate the causes of vasospasm, a spasmolytic agent capable of consistently protecting against it or reversing it has not been found. Vascular freezing as an powerful spasmolytic maneuver has recently been reported. The purpose of the present study was to determine the optimal vascular freezing time. The effect of vascular freezing time was examined on the relief of arterial vasospasm. The vascular freezing was performed on the femoral artery of rats with hand-held liquid nitrogen oxide spray. The artery was frozen for 5, 15, or 30 seconds. Vascular spasm and patency were evaluated immediately after and 1, 3, 7, 14, and 56 days after the freezing. Femoral arteries were harvested at 1, 3, 7, 14, and 56 days after freezing for histologic examination. The results obtained were as follows: 1. Immediately after the freezing-thawing, the vasospasm was relieved and not induced by spasmogenic induction manipulation in all groups. 2. Immediately after the freezing-thawing, the artery became dialated, the diameter of which was slightly more than the initial, ranging between 0-17% and the diameter of 5-second group was slightly smaller than those of 15- and 30-second groups (P＜0.05). 3. One to 56 days after the freezing, arterial diameter was still 1-22% larger than the initial and there was no significant difference among groups. 4. One to 56 days after the freezing, vasospasm was not induced by spasmogenic induction manipulation in all groups. 5. One day after the freezing, almost all the cells in the vessel wall died and the normal architecture of the layer was deranged in all groups. The shorter was the duration of freezing, the more early was the healing of artery occurred. 6. Fifty-six days after the freezing, cellularity was increased and the architecture was regenerated, There was no significant difference among groups. It was suggested that vascular freezing for 5 seconds is useful to relieve the vasospasm and to lessen the injury of artery.