Abstract
Aminoamide local anesthetics induce vasoconstriction in vivo and in vitro. The goals of this in vitro study were to investigate the potency of local anesthetic-induced vasoconstriction and to identify the physicochemical property (octanol/buffer partition coefficient, pKa, molecular weight, or potency) of local anesthetics that determines their potency in inducing isolated rat aortic ring contraction. Cumulative concentration-response curves to local anesthetics (levobupivacaine, ropivacaine, lidocaine, and mepivacaine) were obtained from isolated rat aorta. Regression analyses were performed to determine the relationship between the reported physicochemical properties of local anesthetics and the local anesthetic concentration that produced 50% (ED50) of the local anesthetic-induced maximum vasoconstriction. We determined the order of potency (ED50) of vasoconstriction among local anesthetics to be levobupivacaine > ropivacaine > lidocaine > mepivacaine. The relative importance of the independent variables that affect the vasoconstriction potency is octanol/buffer partition coefficient > potency > pKa > molecular weight. The ED50 in endothelium-denuded aorta negatively correlated with the octanol/buffer partition coefficient of local anesthetics (r2 = 0.9563; P < 0.001). The potency of the vasoconstriction in the endothelium-denuded aorta induced by local anesthetics is determined primarily by lipid solubility and, in part, by other physicochemical properties including potency and pKa.
Highlights
Aminoamide local anesthetics induce vasoconstriction at low doses and vasodilation at high doses [1]
This is because the absolute value of Standardized regression coefficients (SRCs) (−0.4701) of octanol/buffer partition coefficient was the highest among the independent variables representing the physicochemical properties of local anesthetics
Transient receptor potential canonical channels are thought to be involved in determining entry through sodium or calcium channels, which are modulated by cell membrane lipids and anesthetics [25]
Summary
Aminoamide local anesthetics induce vasoconstriction at low doses and vasodilation at high doses [1]. Levobupivacaine, ropivacaine, and mepivacaine are aminoamide local anesthetics that belong to the n-alkyl-substituted pipecholyl xylidine family [2]. Addition of carbon to the basic structure of the n-alkyl-substituted pipecholyl xylidine increases lipid solubility and potency [2, 3]. Depending on the vascularity of the injection site, vasoconstriction induced by local anesthetic and the addition of epinephrine may contribute to decreased absorption of local anesthetics into systemic circulation [14]. This leads to prolonged nerve exposure to local anesthetics and reduced plasma levels, in addition to the potency of intrinsic vasoconstriction being
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