Microsurgery: Transplantation and Replantation by Harry J. Buncke, MD, et al.
  Table of Contents / Chapter 36:
Pharmacology
 
  We administer perioperative aspirin, dextran, and chlorpromazine to replantation patients and patients undergoing free tissue transfer. Patients receive aspirin preoperatively (when possible) and postoperatively for 8 weeks at a dosage equivalent of 3.0 mg/kg per day. Three 80 mg pediatric tablets for a 70 kg adult every day is an acceptable approximation. This dose reportedly interferes with platelet aggregation and preserves some prostacyclin (PGI2) production by vessel endothelium. 29 Prostacyclin is a vasodilator and an inhibitor of platelet aggregation. Aspirin suppresses prostacyclin production by acetylating the same enzyme (cyclo-oxygenase), essential for both endothelial prostacyclin production and platelet release of aggregating factors. The search for an aspirin dose that will inhibit platelet aggregation while totally sparing prostacycline production is being pursued by several investigators,64 but this fine dosage distinction may not be clinically significant in microsurgery. Small amounts of prostacycline are reportedly still produced at aspirin doses as high as 10 mg/kg, and these small amounts of prostacyclin appear to effectively exert local anti-platelet effects.96

Low molecular weight dextran-40 is administered at a rate of 7 to 8 cc/kg per day as a continuous intravenous infusion, begun at the completion of the first microvascular anastomosis and continued for three to five days. Chlorpromazine, 10 mg administered orally or intramuscularly every 8 hours, is given to adults for the first 5 postoperative days as a systemic vasodilator.

 

Intraoperatively, vessel irrigation with heparin solution (100 units per cc of saline) is routinely performed before anastomosis. Lidocaine (1%), bupivacaine (2%), and papaverine (0.3%) are used empirically to treat intraoperative vascular spasm.

Therapeutic doses of heparin (a bolus injection followed by continuous intravenous infusion determined by clotting studies) are given in instances of extensive tissue trauma, anastomotic revision, or prolonged tissue ischemia. The heparin is begun intraoperatively and continued for 7 to 10 postoperative days. Patients with replanted digits known or suspected to have impaired digital venous circulation receive systemic heparin and topical heparin scrubs to the exposed nail beds of the replanted digit until venous return appears established. Dextran is usually not given simultaneously with heparin.

We have used regional block, intra-arterial papaverine, intra-arterial streptokinase, nitropaste, coumadin, and nifedipine in small numbers of patients without consistent results. In the past, we have routinely administered isoxuprine, dipyridimole, and magnesium sulfate, but we no longer use these agents.

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