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Microsurgery: Transplantation and Replantation by Harry J. Buncke, MD, et al. | ||
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| We believe that general anesthesia, whether or not combined with a continuous regional technique, is indicated for microvascular surgery. The duration of the surgery is usually long: 6 to 12 hours for a transplant; for digital replants, 4 hours for the first digit and then 2 to 3 hours for each subsequent digit. It is not unusual to have 12- to 16-hour cases. General anesthesia provides for patient comfort and stability, and allows control of the airway, oxygen delivery, and ventilation. We believe that a volatile anesthetic, particularly isoflurane vaporized in nitrous oxide or air with oxygen and supplemented with narcotics, provides increased peripheral perfusion and blunting of autonomic responses. Recent evidence indicates that long exposure to nitrous oxide can lead to bone marrow suppression, leukopenia, and aplastic anemia and that inhibition of methionine synthetase leads to impairment of DNA synthesis.1
We have had no known clinical problems related to the use of nitrous oxide. Coughing and bucking on an endotracheal tube at the end of surgery can lead to catechole-induced vasospasm. Because many of these patients must be extubated when awake, we believe it is best to have an adequate level of parenteral analgesia to prevent vasospasm, even if regional techniques are used and even if prolonged endotracheal intubation is necessary, because one cannot risk aspiration pneumonitis from premature extubation. Although we perform long surgical procedures, we have not had problems with patients regaining consciousness too slowly. We decrease the concentration of the volatile agent during the final hour while the surgeons are closing, and supplement the nitrous oxide with narcotics. This technique allows the patient to emerge more rapidly with an adequate level of analgesia. |
We do not routinely use the combined techniques of continuous regional anesthesia and general anesthesia. If, for example, we wish to attempt to promote inflow to digital replant, we provide a neural blockade by means of a wrist block with a long-acting agent, such as hupivicaine. We believe that a wrist block is as effective as a brachial plexus block, but with fewer complications, and it can be repeated every 8 to 12 hours as necessary. Maintenance of Blood Flow Through the Flap Our hemodynamic goals are to promote peripheral blood flow and to prevent intraoperative and postoperative vascular spasm. Intraoperatively, decreased cardiac output secondary to anesthesia or hypovolemia, or vasospasm secondary to hypothermia, hypocarbia, surgical manipulation, or catecholamines (exogenous as well as endogenous) can contribute to decreased peripheral circulation. Postoperatively, edema, venous occlusion and vasospasm secondary to hypothermia, pain and anxiety, and emergent shivering can all contribute to decreased perfusion of the flap or replanted part. Temperature regulation, blood/fluid replacement, vasodilating agents, anesthetic techniques, and choice of anesthetic agents can influence peripheral blood flow and tissue perfusion. |
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