In vitro effects of lidocaine hydrochloride on coronary artery bypass grafts

Abstract

Aim. Coronary artery bypass grafting (CABG) is one of the most common procedures performed to improve blood supply to myocardium. The characteristics of grafts, mechanical stress and pharmacological agents have substantial influence on the short and long term graft patency. Lidocaine is among the most frequently used antiarrhytlunic agents perioperatively. The aim of this study was to evaluate the in vitro effects of lidocaine on internal mammarian artery (IMA), radial artery (RA) and saphenous vein (SV) grafts. Methods. Using standard tissue bath techniques, responses to increasing concentrations of lidocaine hydrochloride were obtained, in segments of IMA, RA and SV grafts. Twenty patients were enrolled in the study with a total number of 48 grafts (16 for IMA, RA and SV grafts each). In vitro lidocaine concentrations between 10(-9)M and 10(-3.5)M were studied to represent therapeutic plasma concentration of 1.5-5 mcg/mL. Results. In IMA and RA grafts, lidocaine hydrochloride caused vasodilatation (40.5 +/- 1.9% and 39.1 +/- 2.6 % respectively) at concentrations between 10(-9) to 10(-7.5) M while causing a dose dependent vasoconstriction response at concentrations above 10(-7.5)M. In SV graft samples, lidocain hydrochloride caused vasodilatation (24.4 +/- 1.9 %) at concentrations between 10(-9) to 10(-7.5) M while causing dose dependent vasoconstriction at concentrations above 10(-7) M. For vasoconstriction effect, mean +/- SD values for E-max were calculated as: 120.1 +/- 6.6% in IMA, 83.35 +/- 5.06% in RA, and 154.0 +/- 13.8% in SV. The vasoconstriction in the SV samples was higher than in the RA and IMA. The mean SD LogEC(50) values were -5.15 +/- 0.27, -5.76 +/- 0.11 and -5.56 +/- 0.19 for SV, IMA and RA grafts respectively.) There was a statiscally significant differences in the Log EC50 values between SV, IMA and RA (P<0.005) Conclusion. Based on the results of our study, we conclude that, increasing doses of lidocaine in the perioperative period may cause vasospasm in IMA, RA and SV grafts. Thus, avoiding high doses may have a role in improving perioperative and long term mortality.