Absorption of lidocaine following topical application in microvascular procedures on rabbits

Fifty rabbits were used to investigate the absorption of lidocaine following its topical application to blood vessels. The lidocaine level in the blood was determined by gas chromatography and the enzyme immunoassay. Animals were divided into five groups according to anatomic site (femoral vs iliac) and according to whether vessels were intact or anastomosed. In the last group (E), a water-tight sleeve was placed on the anastomosed femoral artery so that the lidocaine contacted only a small segment of the artery. In each group, 0.4 and 1 ml of 10% lidocaine were used. Our results revealed that absorption of lidocaine from topical usage was rapid. The absorption peak occurred within 5-15 min. The serum concentration of lidocaine was significantly higher in groups with intact vessels than in those with anastomosed ones. The peak level of lidocaine in the serum occurred sooner in the iliac area than in the femoral area. Absorption in group E was very low due to only a small segment of the artery being immersed with lidocaine. The main absorption site of lidocaine was not through the vessel but through the perivascular area. Toxicity may develop clinically if a high concentration of lidocaine is applied on a vessel during microsurgery.