Effects of Intravenous Anesthetics on the Human Radial Artery Used as a Coronary Artery Bypass Graft

Objective: Intravenous anesthetics are often used for anesthesia, sedation, and analgesia in the intraoperative and postoperative periods of coronary artery bypass graft (CABG) surgery. This study was designed to investigate the direct effects of intravenous anesthetics on the human radial artery (RA).

Design: In vitro, prospective with repeated measures.

Setting: University research laboratory.

Participants: RA segments (n = 20) were obtained from CABG surgery patients and were divided into 3- to 4-mm vascular rings.

Interventions: Using the organ bath technique, the endothelium-independent vasodilatation function was tested in vitro by the addition of cumulative concentrations of thiopental, ketamine, etomidate, and propofol after vasocontraction by phenylephrine in the presence of N^G-nitro-L-arginine methyl ester (L-NAME) and indomethacin.

Measurements and Main Results: Thiopental (10⁻⁸ to 10⁻⁴ mol/L), ketamine(10⁻⁸ to 10⁻⁴ mol/L), propofol (10⁻⁸ to 3 × 10⁻⁴ mol/L), and etomidate (10⁻⁸ to 3 × 10⁻⁴ mol/L) caused concentration-dependent vasorelaxation in human RA rings precontracted with phenylephrine in the presence of L-NAME and indomethacin (n = 20, for each drug). The pEC₅₀ and maximum relaxant effect values of thiopental and ketamine were significantly higher than for etomidate and propofol (p < 0.05).

Conclusions: These findings indicate that thiopental, ketamine, etomidate, and propofol produce concentration-dependent relaxation on RA rings from humans. Thiopental and ketamine are more potent relaxant agents than etomidate and propofol. Intravenous anesthetics may be effective as alternative vasodilators for treatment of intraoperative and postoperative spasm of coronary artery grafts.

Key words: radial artery, intravenous anesthetics, vasorelaxation