Topical and systemic calcium channel blockers in the prevention and treatment of microvascular spasm in a rat epigastric island skin flap model

Vasospasm is a frustrating problem commonly encountered in microuascular su rgery, Extreme arterial vasoconstriction usually occurs intraoperatively, s hortly after release of the vascular clamps, but can he a problem for 48 to 72 hours postoperatively. Failure to alleviate vasospasm can have disastro us consequences in replanted and revascularized tissues, ultimately resulti ng in microsurgical failure. The authors investigated the efficacy of topic al and systemic administration of two commonly prescribed calcium channel b lockers-nifedipine and verapamil-in both the prevention and treatment of va sospasm in a rat epigastric island skin flap model. Superficial epigastric island skin flaps were elevated in 60 Sprague-Dawley rats. Femoral vessels were isolated from the inguinal ligament to a point 1 cm distal to the orig in of the epigastric vessels, and the feeding vessels were ligated. The fla p was returned to its natural anatomic bed and was. sutured into place, lea ving the femoral vessels exposed. The femoral artery and vein were transect ed, and anastomoses were. performed under the operating microscope. A block of ice was then applied directly to the anastomotic site for 1 minute to i nduce additional vasospasm. Groups I through III received topical applicati on of solutions of 0.5 ml of either 0.9% normal saline (control), verapamil (2.5 mg per milliliter), or nifedipine: (5 mg per milliliter) directly to the anastomotic site immediately prior to release of the Vascular clamps. G roups IV through VI received intraperitoneal injections of 1.0-ml solutions of either 0.9% normal saline (control), verapamil (2.5 mg per milliliter), or nifedipine (5 mg per milliliter) at 30 minutes prior to performing the anastomoses. Thermocouple temperature probes reflecting blood flow were pla ced at the center of the skin flap in a subcutaneous position, at the proxi mal femoral artery, and at the takeoff of the epigastric artery. Accurate, direct temperature measurements of the isolated skin flap and femoral vesse ls were recorded at 10, 20, and 30 minutes after release of the vascular cl amps. Topical and systemic administration of verapamil and nifedipine moder ated significantly the temperature declines observed at 10 minutes at the l evel of the femoral artery proximally and distalIy compared with controls. Following this decline, groups I through III (topical) demonstrated signifi cant recovery of: temperature toward baseline, with vetapamil and nifedipin e showing significantly better recovery of temperature than controls, Group s IV through VI (systemic) demonstrated a stabilization of temperature with out any significant additional recovery of temperature toward baseline. Ver apamil was more effective than nifedipine in its actions when administered topically or systemically. The authors' results suggest a potential role fo r topical and systemic administration of verapamil and nifedipine in preven ting, or at least minimizing, the deleterious effects of vasospasm on flap survival, as demonstrated by its temporizing effect on temperature change a cross the anastomosis in their model.