Effects of bupivacaine and ropivacaine on the isolated human umbilical artery

Perillyl Alcohol Promotes Relaxation in Human Umbilical Artery

BACKGROUND

Perillyl alcohol (POH) is a monoterpenoid found in plant essential oils and has been shown to relax murine vessels, but its effect on human vessels remains poorly studied.

OBJECTIVE

The study aimed to characterize the effect of POH on human umbilical arteries (HUA).

METHODS

Rings of HUA were obtained from uncomplicated patients and suspended in an organ bath for isometric recording. The vasorelaxant effect of POH in HUA was evaluated on basal tone and electromechanical or pharmacomechanical contractions, and possible mechanisms of action were also investigated.

RESULTS

POH (1-1000 μM) altered the basal tone of HUA and completely relaxed HUA rings precontracted with KCl (60 mM) or 5-HT (10 μM), obtaining greater potency in the pharmacomechanical pathway (EC50 110.1 μM), suggesting a complex interference in the mobilization of extra- and intracellular Ca2+. POH (1000 μM) inhibited contractions induced by BaCl2 (0.1-30 mM) in a similar way to nifedipine (10 μM), indicating a possible blockade of L-type VOCC. In the presence of potassium channel blockers, tetraethylammonium (1 mM), 4-aminopyridine (1 mM), or glibenclamide (10 μM), an increase in the EC50 value of the POH was observed, suggesting a modulation of the activity of BKCa, KV, and KATP channels.

CONCLUSION

The data from this study suggest that POH modulates Ca2+ and K+ ion channels to induce a relaxant response in HUA.

The Mechanisms Underlying Lipid Resuscitation Therapy

The experimental use of lipid emulsion for local anesthetic toxicity was originally identified in 1998. It was then translated to clinical practice in 2006 and expanded to drugs other than local anesthetics in 2008. Our understanding of lipid resuscitation therapy has progressed considerably since the previous update from the American Society of Regional Anesthesia and Pain Medicine, and the scientific evidence has coalesced around specific discrete mechanisms. Intravenous lipid emulsion therapy provides a multimodal resuscitation benefit that includes both scavenging (eg, the lipid shuttle) and nonscavenging components. The intravascular lipid compartment scavenges drug from organs susceptible to toxicity and accelerates redistribution to organs where drug (eg, bupivacaine) is stored, detoxified, and later excreted. In addition, lipid exerts nonscavenging effects that include postconditioning (via activation of prosurvival kinases) along with cardiotonic and vasoconstrictive benefits. These effects protect tissue from ischemic damage and increase tissue perfusion during recovery from toxicity. Other mechanisms have diminished in favor based on lack of evidence; these include direct effects on channel currents (eg, calcium) and mass-effect overpowering a block in mitochondrial metabolism. In this narrative review, we discuss these proposed mechanisms and address questions left to answer in the field. Further work is needed, but the field has made considerable strides towards understanding the mechanisms.

Effect of Local Ropivacaine on Hemodynamic Responses in Craniotomy Patients

BACKGROUND

Increased intracranial pressure (ICP) with hemodynamic is of major concern to anesthesiologists and surgeons in craniotomy surgery. Thus, the management of hemodynamic stability is essential in neuro-anesthesia. This study was performed to investigate the effect of local infiltration of 0.5% ropivacaine on hemodynamic responses in craniotomy patients.

MATERIAL AND METHODS

64 ASA class I -II patients, scheduled for elective craniotomies, were enrolled in this prospective randomized double blind placebo controlled study. These patients were randomly divided into the ropivacaine group, who were administered with 0.5% ropivacaine (n = 32), and the placebo group administered with 0.9% normal saline (NaCl) (n = 32). Anesthesia was induced with 3 µg/kg fentanyl, 5 mg/kg thiopental and 0.5 mg/kg atracurium, and was maintained with isoflurane (0.8-1 = MAC) in 50% N₂O, 1 mg/kg /30 minutes, 40% oxygen and 0.05 mg/kg /hour fentanyl. Five minutes prior to surgery, 10 mL of 0.5% ropivacaine was injected in the line of skin incision in the ropivacaine group, while 10 mL of normal saline was injected in placebo group. Thereafter, the systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressures (MABP), and heart rate (HR) were measured before infiltration into the incision area, 30 seconds, 3 minutes, 5, 10, and 30 minutes after infiltration into the scalp. For higher BP and HR, an adjunct 0.5 mcg/kg of fentanyl was prescribed and administered.

RESULTS

A significant difference was observed for SBP, DBP, MABP and HR, between the two groups at different times during craniotomy (p < 0.05). A significant decrease was observed for SBP, DBP, MABP and HR during craniotomy in 0.5% ropivacaine group as compared with placebo group (p < 0.05).

CONCLUSION

Local anesthetic of 0.05% ropivacaine scalp infiltration is effective in clinical usage of regional anesthesia for producing good quality anesthesia, it seems to be a significant choice for management of optimal hemodynamic profile, providing a better hemodynamic stability during craniotomy.

Differential effects of short- and long-term bupivacaine treatment on α1-adrenoceptor-mediated contraction of isolated rat aorta rings and the reversal effect of lipid emulsion

AIM

Arterial function is significantly influenced by bupivacaine at both clinically relevant concentrations and toxic concentrations, but the underlying mechanisms are not fully understood. In the present study we investigated the role of α1-adrenoceptors in bupivacaine effects on isolated rat aortas.

METHODS

Isolated aortic rings were prepared from rats and suspended in an organ bath. Phenylephrine (Phe)-induced vasoconstriction and acetylcholine (ACh)-induced vasodilation were recorded through an isometric force transducer connected to a data acquisition system.

RESULTS

Administration of bupivacaine (30-300 μmol/L) produced mild vasoconstriction, and this response declined with repeated administrations. Treatment of the aortic rings with bupivacaine (3-30 μmol/L) for 20 min enhanced Phe-induced vasoconstriction, while treatment for 40 min suppressed Phe-induced vasoconstriction. Both the short- and long-term bupivacaine treatment suppressed ACh-induced vasodilation. Incubation of the aortic rings with 0.2%-0.6% lipid emulsion (LE) for 100 min significantly increased the pD2 and Emax values of Phe-induced vasoconstriction, and incubation with 0.4% LE for 100 min reversed the inhibition of bupivacaine on vasoconstriction induced by Phe (30 μmol/L). In contrast, incubation with LE suppressed ACh-induced vasodilation, even at a lower concentration and with a 5-min incubation.

CONCLUSION

Bupivacaine exerts dual effects on α1-adrenoceptor-mediated vasoconstriction of isolated rat aortic rings: short-term treatment enhances the response, while long-term treatment inhibits it; the inhibition may be reversed via long-term incubation with LE.

Lipid emulsion for local anesthetic systemic toxicity

The accidental overdose of local anesthetics may prove fatal. The commonly used amide local anesthetics have varying adverse effects on the myocardium, and beyond a certain dose all are capable of causing death. Local anesthetics are the most frequently used drugs amongst anesthetists and although uncommon, local anaesthetic systemic toxicity accounts for a high proportion of mortality, with local anaesthetic-induced cardiac arrest particularly resistant to standard resuscitation methods. Over the last decade, there has been convincing evidence of intravenous lipid emulsions as a rescue in local anesthetic-cardiotoxicity, and anesthetic organisations, over the globe have developed guidelines on the use of this drug. Despite this, awareness amongst practitioners appears to be lacking. All who use local anesthetics in their practice should have an appreciation of patients at high risk of toxicity, early symptoms and signs of toxicity, preventative measures when using local anesthetics, and the initial management of systemic toxicity with intravenous lipid emulsion. In this paper we intend to discuss the pharmacology and pathophysiology of local anesthetics and toxicity, and the rationale for lipid emulsion therapy.

Direct vasocontractile activities of bupivacaine enantiomers on the isolated rat thoracic aorta

Background. In vitro studies with isolated arteries have shown direct vasoactivity of racemic bupivacaine. However, there is little information on the direct vasoactivities of bupivacaine enantiomers, S(−)- and R(+)-bupivacaine. Methods. We performed functional examinations using isolated intact thoracic aortic rings from male Wistar rats. Changes in ring tension produced by S(−)-, R(+)-, or racemic bupivacaine were measured in Krebs solution. Results. S(−)-bupivacaine produced the strongest contraction of the three agents. R(+)-bupivacaine showed limited vasoconstriction. The effects of racemic bupivacaine were located between these two. Conclusion. Each bupivacaine enantiomer showed specific vasocontractile activity, which affects the activity of racemic bupivacaine.

A review of local anesthetic cardiotoxicity and treatment with lipid emulsion

Cardiovascular collapse from accidental local anesthetic toxicity is a rare but catastrophic complication of regional anesthesia. The long-acting amide local anesthetics bupivacaine, levobupivacaine and ropivacaine have differential cardiac toxicity, but all are capable of causing death with accidental overdose. In recent times, the chance discovery that lipid emulsion may improve the chance of successful resuscitation has lead to recommendations that it should be available in every location where regional anesthesia is performed. This review will outline the mechanisms of local anesthetic toxicity and the rationale for lipid emulsion therapy.

Effect of ropivacaine on endothelium-dependent phenylephrine-induced contraction in guinea pig aorta

BACKGROUND

Previous studies have shown that ropivacaine has biphasic vascular effects, causing vasoconstriction at low concentrations and vasorelaxation at high concentrations. This study was designed to examine the role of the endothelium during accidental intravascular absorption of ropivacaine, and to elucidate the mechanisms responsible.

METHODS

Isolated guinea pig aortic rings were suspended for isometric tension recording. The effects of ropivacaine on endothelium-intact and endothelium-denuded aortic rings were assessed. Endothelium-intact aortic rings were pre-contracted with phenylephrine before being exposed to ropivacaine and acetylcholine, in order to generate and compare concentration-response curves. In the absence and presence of yohimbine, propranolol, atropine, indometacin, N(G)-nitro-l-arginine methyl ester (l-NAME), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) or methylene blue, the contractile response induced by ropivacaine was assessed on endothelium-intact aortic rings pre-contracted with phenylephrine.

RESULTS

Ropivacaine (3 x 10(-4) to 10(-2) mol/l) produced vasoconstriction in endothelium-denuded aortic rings, whereas no such response was observed in aortic rings with intact endothelium. In phenylephrine pre-contracted intact aortic rings, ropivacaine induced a greater degree of vasorelaxation than did acetylcholine. Yohimbine, propranolol and atropine all failed to affect the relaxation responses induced by ropivacaine. However, pre-treatment with indometacin (cyclo-oxygenase inhibitor), l-NAME (nitric oxide synthase inhibitor), methylene blue (soluble guanylyl cyclase inhibitor) or ODQ (soluble guanylyl cyclase inhibitor), significantly decreased the ropivacaine-induced relaxation of endothelium-intact aortic rings (3 x 10(-4) to 10(-2) mol/l).

CONCLUSIONS

Ropivacaine elicits an endothelium-dependent vasorelaxation in phenylephrine pre-contracted aortic rings via the nitric oxide-cyclic guanosine 3',5'-monophosphate pathway and the prostaglandin system.

Effects of the Local Anaesthetic Ropivacaine on Vascular Reactivity in the Mouse Perfused Mesenteric Arteries

Previous clinical and experimental studies have indicated that ropivacaine, a local anaesthetic agent, exerts vasoconstrictor effects. In this study, the contractile effects of ropivacaine were investigated in vitro on mesenteric arteriolar beds obtained from 22 adult male C57BL/6J mice. The mesenteric arteriolar bed was perfused at constant rate (2 ml/min.) with oxygenated physiological salt solution using a roller pump. First we studied the effects of ropivacaine (3.2x10(-4) to 2.2x10(-2) mol/l) on the perfusion pressure and observed a dose-dependent pressor response, reaching a maximal increase of 26.0+/-3.7 mmHg. In a second study, we observed that after the mechanical removal of the endothelium ropivacaine-induced contractile responses were significantly reduced to a maximal of 13.5+/-0.7 mmHg. In a third set of experiments, we observed that under the effect of the cyclooxygenase inhibitor indomethacin (0.01 micromol/l) the ropivacaine-induced pressor response was significantly reduced to a maximal increase of 17.5+/-0.4 mmHg. This is the first evidence that this long-acting local anesthetic causes vasoconstriction in the perfused mesenteric arteriolar bed and that, at least in part, this effect is mediated by the endothelium since the cyclooxygenase inhibitor indomethacin reduced the ropivacaine-induced vasoconstriction to approximately 50%.