The effects of topical and intravenous ropivacaine on canine pial microcirculation

Bupivacaine Inhibits Thromboxane A2-Induced Vasoconstriction in Rat Thoracic Aorta

Plasma levels of thromboxane A2 (TXA2), an inflammatory mediator inducing platelet aggregation, bronchoconstriction, and vasoconstriction, are increased in the perioperative period. A major role in the pathogenesis of perioperative thromboembolic and ischemic syndromes is attributed to this prostanoid. Local anesthetics (LA) inhibit signaling of TXA2 receptors expressed in cell models. Therefore, we hypothesized that LA may inhibit vasoconstriction induced by the TXA2 analog U46619 in rat thoracic aorta. Rings (3-mm length) of the rat thoracic aorta were mounted in organ baths and isometric contractile force was measured. Rings, with or without endothelium, were incubated for 60 min in bupivacaine (10(-6) or 10(-5) M) or Krebs-Henseleit solution (control group) and subsequently exposed to cumulative concentrations of U46619 (10(-10) to 10(-6) M). The reversibility of the TXA2-induced vasoconstriction by bupivacaine was also studied. Pretreatment of rings with bupivacaine concentration-dependently diminished TXA2-induced contraction in rat aortic rings. We found no significant differences in relaxing effect of bupivacaine between rings with and without endothelium. Contraction in rings established with U46619 could not be reversed by cumulative concentrations of bupivacaine. Bupivacaine inhibited carbachol-induced vascular relaxation. This study provides experimental evidence that bupivacaine is an endothelium-independent inhibitor of TXA2-induced vasoconstriction of rat thoracic aorta.

Chirality in anaesthesia - ropivacaine, ketamine and thiopentone

Drug chirality (molecular handedness) is a source of pharmacological differences between otherwise chemically identical molecules. Specific applications to the pharmacology of ropivacaine (single enantiomer), ketamine and thiopentone (both racemates) are discussed. Ropivacaine is produced as a single S-enantiomer homologue of the more toxic bupivacaine to preclude the higher central nervous system and heart toxicity found in the R-enantiomer. S-ketamine is presently undergoing trials as a potential replacement for the racemate, on the grounds that it optimizes anaesthesia and minimizes psychotomimetic phenomena. Thiopentone, previously known to have quantitative differences in the pharmacology of its enantiomers, has recently also been shown to have pharmacokinetic differences. The evidence for these claims is discussed in this review.