Direct effects of ropivacaine and bupivacaine on spinal pial vessels in canine. Assessment with closed spinal window technique

Topical lyophilized thrombin application improves wound healing for posterior spinal surgery

Background

The erector spinae plane block (ESPB) was proposed as a part of the postoperative multimodal analgesic regimen to improve pain management after posterior spinal surgery. However, ESPB might cause more surgical incisional wound exudate and poor wound healing, which might be improved after topical lyophilized thrombin application.

Materials and methods

We performed a retrospective study on patients who received posterior spinal surgery between January 2018 and December 2021. These patients were assigned into three groups: group A (general anesthesia), group B (general anesthesia with ESPB), and group C (general anesthesia with ESPB and topical 1000-unit thrombin application). Postoperative outcomes, including times of dressing changes, duration of suture removal, and incisional wound healing, were compared among these groups.

Results

Our study included 89 patients, with 48, 20, and 21 patients in groups A, B, and C, respectively. Baseline demographics, height, weight, comorbidities, and operation duration were comparable among the three groups. Group B required statistically significantly more dressing changes and had a prolonged duration of suture removal than group A (9.4 ± 4.7 versus 6.5 ± 2.0 times, 16.2 ± 3.7 versus 14.2 ± 1.4 days, respectively), which could be statistically significantly improved after the thrombin application in group C. Group B also had more frequent poor wound healing (25.0 %), which could also be improved after the thrombin application (0.0 %).

Conclusions

ESPB could cause more dressing changes and poor surgical wound healing after posterior spinal surgery, which could be improved by topical lyophilized thrombin powder application.

Efficacy of bupivacaine infiltration for controlling post-tonsillectomy pain, duration of surgery and post-operative morbidities: A systematic review and meta-analysis

The objective of the present review and meta-analysis was to evaluate the efficacy of bupivacaine during tonsillectomy in terms of reducing the mean operative procedure duration, post-operative pain and the onset of post-operative morbidities. The Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines were followed to perform a systematic literature search using the MEDLINE, Scopus, EMBASE and CENTRAL databases. The present meta-analysis sought to evaluate the efficacy of bupivacaine administered during tonsillectomy as compared to the administration of normal saline. The efficacy of the intervention was evaluated based on pain scores using the visual analogue scale, the duration of the operation and the occurrence of post-operative morbidities. Out of 1,427 records, 15 articles with 729 participants (mean age, 10.2±6.7 years) were included in the study. The present systematic review supported the use of bupivacaine during tonsillectomy at a level of evidence of 1b and confirmed beneficial effects of bupivacaine intervention by demonstrating small to large effect reductions in the visual analog scale score (Hedge's g, -1.48), the mean duration of the operative procedure (Hedge's g, -1.35) and the incidence of post-operative morbidity (Hedge's g, -0.23) in comparison to the placebo groups treated with normal saline. Based on these results, the administration of bupivacaine is recommended during tonsillectomies to reduce the perceived level of pain, the duration of the operation and the post-operative morbidity.

Local Anesthetic Wound Infiltration after Osteosynthesis of Extracapsular Hip Fracture Does Not Reduce Pain or Opioid Requirements: A Randomized, Placebo-Controlled, Double-Blind Clinical Trial in 49 Patients

Background and purpose

Local infiltration analgesia (LIA) supports early mobilization after hip and knee arthroplasty. Inspired by this, we studied the effectiveness of wound infiltration with the long acting local anesthetic ropivacaine in an effort to decrease the need for postoperative opioids after osteosynthesis of extracapsular hip fracture.

Methods

Forty-nine patients undergoing osteosynthesis with a sliding hip screw were randomized into two groups in a double-blind study (ClinicalTrials.gov:NCT01119209). The patients received intraoperative infiltration followed by 6 postoperative injections through a wound catheter in eight-hour intervals. 23 patients received ropivacaine and 26 received saline. The intervention period was 2 days, and the observation period was 5 days. In both groups, there were no restrictions on the total daily dose of opioids. Pain was assessed at specific postoperative time points, and the daily opioid usage was registered.

Results

Intraoperative infiltration with 200 mg ropivacaine and postoperative repeated infiltration with 100 mg ropivacaine did not result in statistically significant difference between the groups regarding postoperative opioid consumption or pain.

Interpretation

Ropivacaine as single component in postoperative treatment of pain after hip fracture is not effective. In our setup, wound infiltration with ropivacaine is not statistically significantly better than placebo.

Local anaesthetic wound infiltration after internal fixation of femoral neck fractures: a randomized, double-blind clinical trial in 33 patients

Pain control may assist early mobilisation after internal fixation of femoral neck fractures. Systemic opioids have significant side effects in elderly patients. We present an evaluation of the effect of local anaesthetic infiltration in such cases , the objective being to decrease the need for postoperative opioids and to improve pain control for patients after surgery. 33 patients undergoing internal fixation with 2 parallel hook pins were randomized into 2 groups in a double blind study (ClinicalTrials.gov: NCT00529425). 33 patients received intraoperative infiltration followed by 6 postoperative injections through an intraarticular catheter in eight-hour intervals. 19 patients received ropivacaine and 14 received saline. The intervention period was 48 hours and the observation period was 5 days. In both groups there were no restrictions on the total daily dose of rescue analgesics. Pain was assessed at specific postoperative time-points and the daily consumption of opioid drugs needed for analgesia was registered. There was no significantly reduced consumption of standardized opioid rescue analgesics or pain in the study group receiving ropivacaine injections. Apart from a reduction in nausea in the study group on the second postoperative day, there were no significant differences in the occurrence of side effects between the groups. On day 2 the placebo group had less pain than the study group. Local anaesthetic infiltration after fixation of femoral neck fractures does not reduce opioid consumption or pain'.

PRESSÃO INTRAOCULAR, PRESSÃO ARTERIAL MÉDIA E DIÂMETRO PUPILAR EM COELHOS ( (Oryctolagus cuniculus) ) SUBMETIDOS AO BLOQUEIO RETROBULBAR COM DIFERENTES PROTOCOLOS ANESTÉSICOS

Resumo O objetivo deste estudo foi buscar novos protocolos de anestesia loco regional para procedimentos oftálmicos que proporcionem segurança e manutenção das funções vitais, além de manter a pressão intraocular estável, com centralização do bulbo do olho e acinesia palpebral. Foram utilizados 20 coelhos da raça Nova Zelândia para a realização de quatro protocolos de anestesia local através do bloqueio retrobulbar com lidocaína 2% com vasoconstritor, lidocaína 2% sem vasoconstritor associada ao tramadol, ropivacaína 1% e bupivacaína 0,5%, cada animal recebeu o volume anestésico de 1,0 mL. Todos os protocolos anestésicos utilizados promoveram acinesia palpebral e centralização do bulbo do olho durante todo o período de avaliação. A realização do bloqueio retrobulbar com os protocolos anestésicos demonstrou ser factível e segura quanto à manutenção da pressão intraocular, pressão arterial invasiva e diâmetro pupilar e pode ser utilizada para realização de cirurgias intraoculares. Os anestésicos proporcionaram bom bloqueio retrobulbar, entretanto a bupivacaína foi o anestésico que ocasionou o maior diâmetro pupilar comparativamente aos demais fármacos testados.

Systemic ropivacaine diminishes pain sensitization processes: a randomized, double-blinded, placebo-controlled, crossover study in healthy volunteers

Introduction

Ropivacaine is a local anesthetic widely used for regional anesthesia. One of its advantages is low toxicity at plasma concentrations reached systemically during continuous peripheral or central nervous block. The objective of this study was to test the effect of systemic ropivacaine on pain, hyperalgesia, dynamic allodynia, and flare response.

Methods

This randomized, double-blinded, placebo-controlled, crossover study was carried out in at the Clinical Trials Centre, University of Zurich, Switzerland. Twenty healthy male volunteers were included in the study. Exclusion criteria were contraindications or hypersensitivity to local anesthetics, vulnerable subjects (intellectually or mental impaired), drug, alcohol or nicotine abuse, known peripheral neuropathies, diabetes mellitus and/or congestive heart disease. Ropivacaine and saline were infused intravenously during a subcutaneous electrical stimulation. The stimulation software adjusted the stimulus strength according to the rating on a numeric rating scale (NRS; 0–10) maintaining a NRS of 5. Areas of punctate hyperalgesia, dynamic allodynia, and flare response were measured before and after the infusion.

Results

The area of hyperalgesia increased significantly with saline (303 ± 380%, P < 0.05) and ropivacaine (186 ± 137%, P < 0.05). The area of allodynia (253 ± 299%, P < 0.05) and flare response (112 ± 24%, P < 0.05) increased only during the placebo infusion.

Conclusion

The results of this study imply that systemic ropivacaine may diminish pain sensitization processes.

Electronic supplementary material

The online version of this article (doi:10.1007/s40122-013-0021-z) contains supplementary material, which is available to authorized users.

Postoperative analgesia in children when using clonidine or fentanyl with ropivacaine given caudally

Background:

The aim of the study was to compare the efficacy of clonidine and fentanyl as an additive to ropivacaine given via single shot caudal epidural in pediatric patients for postoperative pain relief.

Materials and Methods:

In the present double blind study, 90 children of ASA-I-II aged 3-8 years scheduled for infraumblical surgical procedures were randomly allocated to two groups to receive either ropivacaine 0.25% 1 ml/kg + clonidine 2 μg/kg (group I) or ropivacaine 0.25% 1 μl/kg + fentanyl 1 μg/kg (group II). Caudal block was performed after the induction of general anesthesia. Postoperatively patients were observed for analgesia, sedation, hemodynamics, and side effects/complications.

Results:

Both the groups were similar with respect to patient and various block characteristics. The analgesic properties and hemodynamics were also comparable in both groups (P > 0.05). Side effects such as respiratory depression, vomiting bradycardia were significantly less in group I than group II (P < 0.05) ensuing more patient comfort.

Conclusions:

The analgesic properties of clonidine and fentanyl as additives to ropivacaine in single shot caudal epidural in children are comparable but clonidine offers a more favorable side effect profile. The use of clonidine as additive to ropivacaine in caudal epidural is superior choice to fentanyl because of lack of unwanted side effects and increased patient comfort.

Extended release formulations for local anaesthetic agents

Systemic toxicity through overdose of local anaesthetic agents is a real concern. By encapsulating local anaesthetics in biodegradable carriers to produce a system for prolonged release, their duration of action can be extended. This encapsulation should also improve the safety profile of the local anaesthetic as it is released at a slower rate. Work with naturally occurring local anaestheticss has also shown promise in the area of reducing systemic and neurotoxicity. Extended duration local anaesthetic formulations in current development or clinical use include liposomes, hydrophobic based polymer particles such as Poly(lactic-co-glycolic acid) microspheres, pasty injectable and solid polymers like Poly(sebacic-co-ricinoleic acid) P(SA:RA) and their combination with synthetic and natural local anaesthetic. Their duration of action, rationale and limitations are reviewed. Direct comparison of the different agents is limited by their chemical properties, the drug doses encapsulated and the details of in vivo models described.

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.

Ropivacaine in peribulbar anesthesia - vasoconstrictive properties

BACKGROUND AND OBJECTIVES

Peribulbar anesthesia can reduce ocular blood flow (OBF) by increasing intraocular pressure (IOP) or due to the action of drugs. Ropivacaine has low toxicity and intrinsic vasoconstrictive properties, yet to be proven on the ocular vasculature. Measurements of ocular pulse amplitude (OPA) allow the indirect evaluation of the OBF. The objective of the present study was to evaluate through the OBF the vasoconstrictive properties of ropivacaine in peribulbar anesthesia.

METHODS

Forty eyes undergoing peribulbar anesthesia with 7 mL of anesthetic solution without vasoconstrictor were randomly divided into two groups: ropivacaine (n = 20) and bupivacaine (n = 20). The IOP, ocular perfusion pressure (OPP), OPA, hemodynamic parameters, and the degree of akinesia before and 5 and 10 minutes after the blockade were evaluated. A dynamic contour tonometer was used to evaluate ocular parameters. Sedation was similar in both groups.

RESULTS

A significant variation in hemodynamic parameters and intensity of the motor blockade was not observed between groups. Differences in IOP, OPP, and OPA (p < 0.05) were observed between both groups at 5 and 10 minutes. The variation of IOP at 5 and 10 minutes was -0.88% and -4.54%, respectively with ropivacaine, and 17.61% and 16.56% with bupivacaine. The change in OPP after 5 and 10 minutes was 1.5% and 4.2% with ropivacaine, and -7% and -6% with bupivacaine. Ocular pulse amplitude varied -55.59% and -59.67% with ropivacaine at 5 and 10 minutes, and -34.71% and -28.82% with bupivacaine.

CONCLUSIONS

Ropivacaine reduced more intensely the ocular pulse amplitude despite little changes in IOP and OPP. The reduction in ocular blood flow caused by ropivacaine can be attributed to its vasoconstrictive effect.

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.

Review of prolonged local anesthetic action

IMPORTANCE OF THE FIELD

Pain following surgery is often treated by local anesthetic agents. Duration of the analgesia can be extended safely following administration of encapsulated large doses of local anesthetic agents.

AREAS COVERED IN THIS REVIEW

This review considers formulations used for encapsulation of local anesthetic agents for prolonged anesthesia effect. All studies describing encapsulation of a commercial local anesthetic agent for providing prolonged analgesia were considered using the NCBI Medline site. of local anesthetic, prolonged anesthesia, polymers and liposomes were entered in order to retrieve appropriate articles and reviews from 1966 to 2010, with emphasis on the last 10 years. Reference pages were searched manually for other relevant articles. The topics covered include an overview of local anesthetic agents and a review of local anesthetic carrier agents, with emphasis on liposomes and polymer carriers. Articles were limited to the English language.

WHAT THE READER WILL GAIN

The current research areas for prolongation of local anesthetic effect are evaluated, along with their limitations. Each topic has been summarized, and the review has attempted to cover all current laboratory and clinical studies in a simple manner that should also be useful for readers without a pharmacology background. The direction of research is promising and exciting, and this review should be a useful up-to-date reference.

TAKE HOME MESSAGE

Many formulations including polymer and liposome carriers have facilitated prolonged local anesthetic action for several days, although few clinical studies have been performed. This field promises a safe way to deliver local anesthetics for effect far beyond that of commercially available agents, with potential cost and health benefits for patients suffering chronic or postoperative pain.

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.

Injectable corticosteroid and local anesthetic preparations: a review for radiologists

Corticosteroids and local anesthetics are some of the most commonly administered medications in radiology departments. These medications have marked variability in their formulations, which may increase their adverse event profile for specific procedures. In particular, certain corticosteroid preparations are associated with adverse central nervous system (CNS) sequelae. This is most likely due to distal embolization by particulate formulations. Nonparticulate steroid formulations are not associated with such events. Local anesthetics have severe CNS and cardiac adverse effects if injected intravascularly and have recently been associated with intraarticular chondrolysis if used in large doses. This review discusses these medications with particular emphasis on their established and postulated adverse effects. The administering radiologist should be aware of these potential effects and how best to reduce their occurrence.

Mechanisms influencing the vasoactive effects of lidocaine in human skin

The vasodilator properties of lidocaine are believed to be due mainly to the inhibition of action potentials via sodium channel blocking in vasoconstrictor sympathetic nerves. However, mechanisms involving the vascular endothelium may also play a role, and in this study we investigated the potential influences of nitric oxide release, the cyclo-oxygenase pathway and the beta-adrenoceptors of vascular smooth muscle. Laser Doppler imaging was used to measure microvascular blood flow responses to intradermal injection of lidocaine 2%, with or without the addition of preservatives, in eight healthy, male volunteers. Co-injection of the nitric-oxide-synthase inhibitor Nomega-nitro-L-arginine methyl ester caused a 60% reduction in the response after about 20 min, and this reduction was enhanced with the lidocaine solution containing the preservatives methylhydroxybenzoate and propylhydroxybenzoate. No reduction in response was seen after blocking the cyclo-oxygenase or beta-adrenoceptor pathways. Nitric oxide release contributes to the vasoactivity of lidocaine in human skin.

Pharmacokinetic/pharmacodynamic modeling of anesthetics in children: therapeutic implications

Modeling the pharmacokinetics and pharmacodynamics of anesthetics in children is performed as a response to the clinical need for safe and efficacious administration of drugs with a low therapeutic index. Rates and concentrations of these drugs, which are the primary parameters used by anesthesiologists, depend on physiologic parameters that are markedly affected by development. Volatile anesthetics have been used for >50 years in pediatric patients. The pharmacokinetics of inhalation agents are context sensitive, but little difference between age groups has been described. These agents are not only eliminated unchanged by the lung but they are also metabolized by the liver. Halothane has Michaelis-Menten kinetics, with up to 40% of the administered dose metabolized by the liver. For volatile anesthetics, the effect measured is the minimum alveolar concentration (MAC) that leads to movement of the limb in response to skin incision in 50% of the patients studied. The MAC is higher in infants than in children and adults. Infants aged 6 months have a MAC 1.5-1.8 times the MAC observed in adults aged 40 years. Children have a greater clearance and volume of distribution of propofol than adults. In order to achieve similar plasma concentrations, children require three times the initial dose used in adults. In adults, an increased sensitivity to propofol has been demonstrated with aging, but nothing is known about the effects in children. However, it is clear that equipotent doses of propofol induce marked deleterious hemodynamic effects in infants compared with children. Regional anesthesia is used in pediatrics, both in combination with general anesthesia during surgery or alone for postoperative analgesia. A marked decrease in protein binding has been described in infants. In the postoperative period, a rapid increase in binding because of inflammation decreases the free fraction, but the free drug concentration remains constant because of the resulting decrease in total clearance. A low clearance because of liver function immaturity has been observed during the first year(s) of life for bupivacaine and ropivacaine. Pharmacodynamic interactions between general anesthesia and regional anesthesia need to be modeled. This is one of the future tasks for pharmacokineticists. Methods such as the Dixon up-and-down allocation and the isobolographic technique are promising in this field.

A prospective, double-blind, randomized trial of caudal block using ropivacaine 0.2% with or without fentanyl 1 microg kg-1 in children

BACKGROUND

It has been reported that ropivacaine produces vasoconstriction in contrast to vasodilation produced by bupivacaine. It is possible that additives to ropivacaine can provide further analgesic advantages compared with bupivacaine. We thus evaluated whether the addition of fentanyl to ropivacaine prolonged the duration of analgesia after a single shot caudal block.

METHODS

A total of 36 children undergoing surgical procedures below the umbilicus were randomly allocated to one of two groups: Group F received ropivacaine 0.2%, 1 ml kg(-1) with fentanyl 1 microg kg(-1) and Group S received ropivacaine 0.2%, 1 ml kg(-1) with saline. The analgesic effect of the caudal block was evaluated using the Children's Hospital of Eastern Ontario Pain Scale (CHEOPS) and sedation was assessed using the Steward score at 30 min after extubation and at 1, 2, 4, 6, 12 and 24 h. The first analgesic requirement time and side-effects in a 24 h period were also recorded.

RESULTS

There were no differences in characteristics between the groups. The end-tidal concentration of sevoflurane at extubation in Group F was significantly lower than in Group S. However, there was no significant difference in time from discontinuation of the volatile anaesthetics to tracheal extubation. No statistical differences were found in the CHEOPS and Steward score, and the time to first analgesia. The incidence of postoperative vomiting was not significantly different.

CONCLUSION

We found that the addition of fentanyl 1 mug kg(-1) to ropivacaine 0.2% for caudal analgesia provides no further analgesic advantages over ropivacaine 0.2% alone.

Effects of regional anesthesia with ropivacaine on arterial pressure and heart rate in healthy subjects

The anesthetic, ropivacaine, has been used extensively in clinical practice, but few studies have evaluated this long-acting local anesthetic in dentistry. In this study we evaluated the effects of ropivacaine alone and ropivacaine + vasoconstrictor on the cardiovascular system when used as a dental anesthetic in volunteers. Thirty-two healthy subjects received two consecutive infiltrations of 1.8 ml of either 0.75% ropivacaine or ropivacaine + epinephrine into the pterygomandibular region. Pain sensation, numbness of the lip, arterial pressure, heart rate, and electrocardiogram changes were monitored for 2 h. The onset of anesthesia was 10 min after the injection and lasted for more than 2 h, and numbness of the lip lasted for approximately 8 h. Ropivacaine alone did not cause significant changes in the cardiovascular parameters, but ropivacaine + epinephrine caused a transient increase in arterial pressure and heart rate 2 min postinjection. We conclude that ropivacaine alone injected into the pterygomandibular region does not affect the cardiovascular system and that the addition of epinephrine has no beneficial effect. This finding may be relevant to dentists endeavoring to find an anesthetic of minimal cardiovascular risk to produce regional anesthesia for long-lasting procedures without the need of a vasoconstrictor.

The Effect of Age on the Systemic Absorption and Systemic Disposition of Ropivacaine after Epidural Administration

Knowledge about the systemic absorption and disposition of ropivacaine after epidural administration is important in regard to its clinical profile and the risk of systemic toxicity. We investigated the influence of age on the pharmacokinetics of ropivacaine 1.0% after epidural administration, using a stable-isotope method. Twenty-four patients were enrolled in 1 of 3 groups according to age (group 1: 18-40 yr; group 2: 41-60 yr; group 3: > or =61 yr). Patients received 150 mg ropivacaine hydrochloride epidurally. After 25 min, patients received 50 mL 0.44 mg/mL deuterium-labeled ropivacaine (D3-ropivacaine) IV. Arterial blood samples were collected up to 24 h after epidural administration. Total plasma concentrations of ropivacaine and D3-ropivacaine were determined using liquid chromatography mass spectrometry. In the oldest patients, elimination half-life was significantly longer (ratio of the geometric means 0.60; 95% confidence interval, 0.37-0.99) and clearance was significantly decreased (mean difference, 194 mL/min; 95% confidence interval, 18-370 mL/min) compared with the youngest patients. The systemic absorption was biphasic. Absorption kinetics for ropivacaine (fractions absorbed: (F1, F2) and half-lives: (t(1/2),a1), t(1/2),a2) during the fast and slow absorption process: 0.27 +/- 0.08 and 0.77 +/- 0.12, respectively; 10.7 +/- 5.2 min and 248 +/- 64 min, respectively) were in the same range as for other long-acting local anesthetics. F1 was on average 0.11 (95% confidence interval, 0.002-0.22) higher in the youngest compared with the middle age group. Observed age-dependent pharmacokinetic differences do not likely influence the risk of systemic toxicity in the elderly after a single epidural dose of ropivacaine.

The effects of bupivacaine, ropivacaine and mepivacaine on the contractility of rat myometrium

Local anesthetic agents are commonly used for obstetric anesthesia and analgesia. We determined the effects of bupivacaine, ropivacaine and mepivacaine on the contractility of isolated pregnant rat uterine muscle strips. Uterine specimens were obtained from 18- to 21-day pregnant Wistar rats (n = 28). Myometrial strips were obtained from the uterine horns after removing the fetuses and non-uterine tissue, incubated in organ baths and contractions stimulated with oxytocin. When contractions became regular, strips were exposed to increasing concentrations of the study drugs. Mepivacaine (n = 8), ropivacaine (n = 10) and bupivacaine (n = 10) were used at cumulative doses from 10(-8) to 10(-4) mol/L. Two of the local anesthetics, bupivacaine most, ropivacaine least, caused a dose-dependent inhibition of uterine contractility. In contrast, mepivacaine significantly increased uterine contractility. Bupivacaine, ropivacaine and mepivacaine were found to have no effect on frequency of uterine contractions. These results demonstrate that bupivacaine and ropivacaine may inhibit myometrium contractility.

Pharmacokinetics of Local Anaesthetics in Infants and Children

Amide local anaesthetics used for regional anaesthesia in paediatric patients are potent sodium channel blockers with marked stereospecificity, which consistently influences their action, especially their toxic action on the heart. At toxic concentrations, they induce severe arrhythmias with the potential for cardiac arrest. These agents are all bound to serum proteins, mainly to alpha(1)-acid glycoprotein (AAG), but also to human serum albumin. Protein binding ranges from 65% (lidocaine) to more than 95% (bupivacaine, ropivacaine). Because AAG is a major acute phase protein, its concentration rapidly increases when inflammatory processes develop, particularly during the postoperative period. Neonates and infants have a lower AAG concentration in serum as compared with adults; therefore, their free fraction of local anaesthetics is increased accordingly. This has important clinical implications since, at least at steady state, the toxic effects of local anaesthetics are directly related to the free (unbound) drug concentration. After injection into the epidural space, absorption into the bloodstream follows a biphasic process. The buffering properties of the epidural space are important and prevent a rapid rise in concentration. In infants and children, the epidural space seems to protect patients in a similar manner. Moreover, it has been observed that the peak plasma concentration (C(max)) of ropivacaine is delayed in infants and children when compared with adults. The time to C(max) decreases from 90-120 minutes in infants aged less than 6 months to 30 minutes in children aged more than 8 years. This delay in C(max) may also be related to the lower clearance observed in younger patients. Local anaesthetics are metabolised by cytochrome P450 (CYP). The main CYP isoforms involved are CYP3A4 for lidocaine and bupivacaine and CYP1A2 for ropivacaine. CYP3A4 is not mature at birth but is partly replaced by CYP3A7. The intrinsic clearance of bupivacaine is only one-third of that in adults at 1 month of age, and two-thirds at 6 months. CYP1A2 is not fully mature before the age of 3 years. Indeed, the clearance of ropivacaine does not reach its maximum before the age of 5 years. However, at birth this clearance is not as low as expected, and ropivacaine may be used even in younger patients.

Effects of bupivacaine and ropivacaine on the isolated human umbilical artery

In this in vitro study on the human umbilical artery, the effects of N(omega)-nitro-L-arginine methyl ester (L-NAME), indomethacin, prazosin, yohimbine and propranolol on the responses induced by bupivacaine and ropivacaine were investigated. Arteries isolated from umbilical cords from women who did not exhibit systemic diseases, who were not on medication and who had normal full-term deliveries, were cut into spiral strips 12 x 3 mm. Strips were mounted in organ baths at 37 degrees C continuously gassed with 5% CO(2) in oxygen. The responses to the drugs were recorded isometrically on a polygraph. In the bupivacaine study, when we administered cumulative concentrations of bupivacaine (10(-9) - 10(-4) M; n = 6) on basal tonus, there was no relaxation or contraction response on the tissue. Strips were precontracted with serotonin (10(-6)M 5-HT) then bupivacaine (10(-9) - 10(-4) M) was directly administered cumulatively. In the ropivacaine group, when cumulative concentrations of ropivacaine (10(-9) - 10(-4) M; n = 6) were administered on the tissue, preconstricted with 5-HT, ropivacaine did not alter the contraction response. Ropivacaine (10(-9) - 10(-4) M) was directly administered to the bath. Though bupivacaine produced relaxation, ropivacaine produced contraction (P < 0.05). Indomethacin, prazosin, yohimbine and propranolol did not significantly alter these responses. In addition, it was demonstrated that L-NAME did not affect the relaxation responses induced by bupivacaine. Thus adrenergic receptors, nitric oxide syntenaze and prostaglandins do not appear to affect the responses induced by these two local anesthetics.

Analgesic, behavioral, and hemodynamic and respiratory effects of midsacral subarachnoidally administered ropivacaine hydrochloride in mares

OBJECTIVE

To determine the analgesic, behavioral, hemodynamic and respiratory effects of midsacral subarachnoid administration of ropivacaine hydrochloride solution in mares.

STUDY DESIGN

Randomized, blinded study.

ANIMALS

Ten healthy mares, weighing from 470 to 560 kg.

METHODS

Intravascular and subarachnoid catheters were placed after infiltration of the skin and subcutaneous tissues with 2% lidocaine. Ropivacaine (0.2%, 5 mL) or 0.9% NaCl was then administered subarachnoidally at the midsacral (S2-S3) vertebrae. Analgesia was determined by lack of sensory perception to electrical stimulation (>40 mA) and absence of response to needle pricks extending from coccygeal to S1 dermatomes. Numerical scores of sedation, change in pelvic limb position, sweating in analgesic zones, urination, behavior, response to noise, and compliance with restraint were determined. Two-way ANOVA with repeated measures and Dunnett's t-tests were used to evaluate differences between the listed numerical scores, and cardiovascular and respiratory variables before and during a 5-hour testing period.

RESULTS

Subarachnoidally administered ropivacaine-induced variable analgesia extending bilaterally from the coccyx to S1, with minimal sedation and change in pelvic limb position in standing mares. Perineal analgesia was attained at 7.5 +/- 2.6 minutes and lasted for 218 +/- 44 minutes (mean +/- SD). Subarachnoid ropivacaine significantly reduced respiratory rates and did not change heart rate, rectal temperature, arterial blood pressure, PCV, arterial gas tensions (PaO2 and PaCO2), pH, and arterial standard bicarbonate and base excess from baseline.

CONCLUSION AND CLINICAL RELEVANCE

Ropivacaine (0.2% solution, 5 mL 500 kg(-1)) can be administered subarachnoidally at midsacral (S2-S3) vertebrae to produce prolonged (>3 hours) bilateral perineal analgesia with minimal changes of behavior, and circulatory and respiratory disturbances in standing mares.

A Comparison of the Dynamics and Pharmacokinetics of Ropivacaine 7.5??mg/mL with and without Epinephrine Used for Epidural Anaesthesia in Urological Surgery

OBJECTIVE

To investigate the effects of adding a vasoconstrictor to ropivacaine for epidural anaesthesia.

PATIENTS AND METHODS

This randomised, double-blind study included 44 adults scheduled for urological surgery. Patients received either 20mL ropivacaine 7.5 mg/mL (group R, n = 22) or 20mL ropivacaine 7.5 mg/mL plus epinephrine 5 mug/mL (group R+E, n = 22) epidurally. Sensory and motor blocks were assessed and the pharmacokinetics of ropivacaine determined. Haemodynamic responses and adverse events were recorded. Patients were followed up for a maximum of 14 days.

RESULTS

The groups were similar with respect to epidural block characteristics. Only one patient in each group experienced inadequate blocks. Median onset of sensory block at surgically relevant dermatomes ranged between 5 and 10 minutes in both groups. No significant difference in onset time was observed between groups. Median duration of sensory block at relevant dermatomes ranged from 3.6 to 5.7h in group R and from 3.3 to 5.9h in group R+E. Haemodynamic changes were moderate and were not considered clinically relevant. The incidence of adverse events was similar between groups. Plasma concentrations of ropivacaine peaked around 30 minutes in both groups; the mean maximum concentration was slightly higher in group R (1.4 mg/L) than in group R+E (1.1 mg/L).

CONCLUSIONS

Ropivacaine 7.5 mg/mL with and without epinephrine 5 mug/mL produced equally effective and well tolerated epidural anaesthesia in urological patients. The addition of epinephrine did not offer any pharmacodynamic or pharmacokinetic advantages over ropivacaine alone.

Mechanisms contributing to the vaso-active effects of prilocaine in human skin

We investigated the roles of the endothelial nitric oxide and cyclo-oxygenase pathways in mediating the vasoactivity of prilocaine in the skin. We injected prilocaine 1% intradermally into forearm skin of 10 healthy, male subjects. Nitric oxide synthesis was inhibited at a second site by co-injecting prilocaine with l-NAME 1%. We then repeated the injections while blocking the cyclo-oxygenase pathway with aspirin (4 x 600 mg). We measured blood flow responses to the injections using laser Doppler imaging. We found that, after the traumatic effects of injection had subsided, l-NAME reduced the vascular response to prilocaine by a third (p = 0.012), indicating an influence specifically on the drug response. Aspirin had no effect on the response (p = 0.588). We conclude that the vasoactive effects of prilocaine in human skin are mediated partly through the release of endothelial nitric oxide and, although other mechanisms might also be involved, the cyclo-oxygenase pathway does not appear to play a role.

The dose-sparing effect of clonidine added to ropivacaine for labor epidural analgesia

To determine the effects of clonidine with ropivacaine during epidural labor analgesia, we studied 66 nulliparous women in early active labor. Women were randomized to receive ropivacaine 0.1% 8 mL plus 75 microg of clonidine (Group 1), ropivacaine 0.2% 8 mL plus 0.5 mL of NaCl 0.9% (Group 2), or ropivacaine 0.2% 8 mL plus 75 microg of clonidine (Group 3) 5 min after a bupivacaine 7.5 mg with epinephrine 15 microg test dose. Upon request, additional analgesia with ropivacaine 0.1% 8 mL followed by ropivacaine 0.2% 8 mL/h was administered. With clonidine, duration of analgesia was increased (132 +/- 48 min [Group 1] and 154 +/- 42 min [Group 3] versus 91 +/- 44 min [Group 2]; P < 0.05), and total ropivacaine dose over the first 4 h was significantly reduced (40.5 +/- 15 mg [Group 1] and 47.0 +/- 16 mg [Group 3] versus 72.5 +/- 18 mg [Group 2]; P < 0.01). The incidence of more profound motor block was more frequent in Group 2 (P < 0.05). Although there was a trend for more women receiving clonidine to require ephedrine for treatment of hypotension, this did not seem to have an impact on fetal outcome or incidence of cesarean deliveries for nonreassuring fetal heart rate tracings. This study demonstrates the dose-sparing effect of clonidine when added to ropivacaine.

IMPLICATIONS

The effect of adding 75 microg of clonidine to ropivacaine for epidural labor analgesia was studied. Clonidine increased analgesia duration and produced dose sparing compared with ropivacaine alone. Despite a tendency for hypotension in women receiving clonidine, there was no apparent effect on delivery mode or neonatal outcome.

The differential effects of stereoisomers of ropivacaine and bupivacaine on cerebral pial arterioles in dogs

We investigated whether the stereoisomers of ropivacaine and bupivacaine exert differential effects on the cerebral microcirculation. Pentobarbital-anesthetized dogs (n = 16) were prepared for measurement of cerebral pial vessel diameters by using a closed cranial window preparation. We administered three different concentrations (10(-7), 10(-5), and 10(-3) M) of each of three drug solutions [R(+), racemic, and S(-) forms of ropivacaine (n = 8) or bupivacaine (n = 8)] under the window in a randomized manner and measured cerebral pial arteriolar diameters. Various physiologic data were obtained before and after topical application of each test solution. All three forms of ropivacaine constricted cerebral pial arterioles, each in a concentration-dependent manner. The rank order for degree of vasoconstriction was S(-) ropivacaine > racemic ropivacaine > R(+) ropivacaine. In contrast, R(+) and racemic bupivacaine dilated, but S(-) bupivacaine constricted, cerebral pial arterioles, each in a concentration-dependent manner. We could find no difference in vascular reactivity to these drugs between large (> or = microm) and small (<100 microm) arterioles. Topical application of these drugs induced no changes in mean blood pressure or heart rate. The observed differences in the microvascular alterations induced by the stereoisomers of ropivacaine and bupivacaine suggest that the vasoactive effects of these drugs on cerebral arterioles could, at least in part, depend on their chirality.

IMPLICATIONS

The differential effects of the stereoisomers of ropivacaine and bupivacaine on cerebral pial vessels could, at least in part, depend on their chirality.

Low dose intrathecal ropivacaine with or without sufentanil provides effective analgesia and does not impair motor strength during labour: a pilot study

PURPOSE

Although ropivacaine has been used to provide spinal anesthesia in the surgical population, its intrathecal administration for labour analgesia has only recently been described. We evaluated the effects of low dose intrathecal ropivacaine with or without sufentanil for labour analgesia.

METHODS

Thirty-six term parturients in active labour were randomly assigned to receive 3 mg of intrathecal ropivacaine (group R) or 3 mg ropivacaine with 10 microg of sufentanil (group RS). Patients were evaluated by a blinded observer for hypotension, linear analogue score (VAS 0-100) for labour pain, motor power in the lower limbs, onset of analgesia, sensation to cold and pin prick, duration of analgesia, and neonatal Apgar scores. The following day patients were assessed for satisfaction, headache and neurologic deficit.

RESULTS

The mean duration of analgesia in the R group was 41.4 +/- 4.9 min and 95.0 +/- 6.1 min in the RS group (mean +/- SEM, P=0.0001). All subjects had satisfactory analgesia at five minutes, although analgesia from the ropivacaine- sufentanil combination was superior to that provided by ropivacaine alone. Total duration of labour was no different between the groups (R- 306 +/- 34, RS- 384 +/- 44 min, P=0.17). No patient showed evidence of motor block. All patients were satisfied with the labour analgesia. No neurological complications were observed.

CONCLUSIONS

Low dose ropivacaine provides effective analgesia during labour via the intrathecal route. It can be mixed with sufentanil in the above-mentioned concentrations to improve both the quality and duration of analgesia. Fetal outcome remains favourable. It may provide minimal or no motor block, to facilitate ambulation.

Neurologic sequelae after caesarean section

BACKGROUND

Because pregnancy increases the sensitivity of nervous tissue to local anaesthetics, pregnant patients may be at higher risk of developing neurologic deficits after spinal block than non-pregnant patients. Therefore, we evaluated prospectively the incidence and type of neurologic symptoms after spinal anaesthesia with hyperbaric bupivacaine for caesarean section.

METHODS

In this prospective follow-up study we recorded neurologic complications during anaesthesia and postoperatively until discharge from the hospital of 219 patients, who underwent caesarean section under spinal anaesthesia with hyperbaric bupivacaine (5 mg/ml, mean 13 mg). The patients filled in a questionnaire on the first and fifth postoperative days. In the case of complaints typical of neurologic symptoms they were checked first by the anaesthesiologist and, in the case of persistent symptoms, afterwards additionally by a neurologist.

RESULTS

Twenty-six of 219 patients were not included in the further evaluation because of incomplete return of their questionnaires. Seventeen mothers (8.8%) complained of transient neurologic symptoms (TNSs), lasting mostly 1-2 days, in the buttocks and/or legs during the first three postoperative days. Eleven patients (5.7%) complained of postdural puncture headache. Two patients (emergency caesarean section because of protracted labour in one and elective caesarean section because of previous caesarean section in the other) complained of persisting pain or sensory abnormalities. Neither of them felt paraesthesia during lumbar puncture.

CONCLUSION

Women after caesarean section under a spinal block seem to suffer more often from TNSs than non-pregnant women. The conclusions are, however, uncertain since we had no control group operated on under other than spinal anaesthesia. The persisting neurologic symptoms in two patients might also be due to the obstetric procedure itself. To find out about the validity and possible underlying causes of our results, we need randomised studies with control groups receiving epidural or general anaesthesia.

The role of new anesthetic agents

The three anesthetic drugs introduced most recently to the market are sevoflurane, desflurane, and ropivacaine. Sevoflurane and desflurane are both inhalational anesthetic agents and ropivacaine is a local anesthetic agent. Sevoflurane provides a rapid onset and offset of action; it is well tolerated with little airway irritation. It is hemodynamically stable, with low potential for toxicity. Concerns about its interaction with soda lime during low-flow anesthesia with the production of Compound A have not proved to be a clinical problem. While desflurane also provides rapid onset and recovery from anesthesia, it is not as hemodynamically stable as sevoflurane, and also causes airway irritation. Ropivacaine is a unique local anesthetic in that it is supplied as the pure S-enantiomer. It is at least as effective as bupivacaine, with lower toxicity and less motor block for the same degree of sensory block.

Attenuated additional hypocapnic constriction, but not hypercapnic dilation, of spinal pial arterioles during spinal ropivacaine

Ropivacaine constricts spinal vessels. Because the CO2 response of spinal vessels is similar to that of cerebral vessels, we tested to see if hypocapnia would cause further spinal vasoconstriction during ropivacaine administration. In 12 pentobarbital-anesthetized dogs, spinal pial arteriolar diameter was measured using a closed spinal window preparation. Either ropivacaine solution (0.1%; n = 6) or artificial cerebrospinal fluid (n = 6) was infused continuously into the spinal window. After a period of hypocapnia (Paco2, 20-25 mm Hg) had been induced, inspired CO2 levels were adjusted to produce normocapnia (35-40 mm Hg) followed by hypercapnia (55-60 mm Hg). When the desired Paco2 was reached, measurements were made of the arteriolar diameter and physiological variables. During normocapnia, ropivacaine infusion produced a significant constriction of pial arterioles, whereas artificial cerebrospinal fluid caused no change. Hypocapnia induced a much smaller (almost nonexistent) additional vasoconstriction in the ropivacaine group than in the control group (P < 0.01). The final hypercapnic vasodilation was somewhat greater during ropivacaine (P < 0.05 versus control group). Topical ropivacaine induced no change in hemodynamic variables. We conclude that hypocapnia of the magnitude tested did not cause further constriction in spinal vessels during spinal ropivacaine.

IMPLICATIONS

During topical application of the local anesthetic ropivacaine in dogs, hypocapnia (Paco2, 20-25 mm Hg) induced almost no additional constriction of spinal arterioles, and the hypercapnic vasodilation was maintained. These data suggest that an additional constriction in spinal vessels is unlikely when hypocapnia occurs during spinal ropivacaine.

The neurotoxicity of drugs given intrathecally (spinal)

Overall, most spinal drugs in clinical use have been poorly studied for spinal cord and nerve root toxicity. Laboratory studies indicate that all local anesthetics are neurotoxic in high concentrations and that lidocaine and tetracaine have neurotoxic potential in clinically used concentrations. However, spinal anesthesia (including lidocaine and tetracaine) has a long and enviable history of safety. Spinal analgesics such as morphine, fentanyl, sufentanil, clonidine, and neostigmine seem to have a low potential for neurotoxicity based on laboratory and extensive clinical use. Most antioxidants, preservatives, and excipients used in commercial formulations seem to have a low potential for neurotoxicity. In addition to summarizing current information, we hope that this review stimulates future research on spinal drugs to follow a systematic approach to determining potential neurotoxicity. Such an approach would examine histologic, physiologic, and behavioral testing in several species, followed by cautious histologic, physiologic, and clinical testing in human volunteers and patients with terminal cancer refractory to conventional therapy.

Intrathecal ropivacaine for labor analgesia: a comparison with bupivacaine

Ropivacaine has less potential for central nervous system and cardiovascular toxicity than bupivacaine; in pregnant patients and volunteers, it produces less motor block in equianalgesic doses than bupivacaine. We compared two doses of intrathecal ropivacaine combined with sufentanil with a standard dose of intrathecal bupivacaine plus sufentanil for labor analgesia using a combined spinal-epidural (CSE) technique. In a prospective, randomized, double-blind fashion, 48 patients requesting labor analgesia received either 2.5 mg of intrathecal bupivacaine plus sufentanil 10 microg (B), 2 mg of intrathecal ropivacaine plus sufentanil 10 microg (R2), or 4 mg of intrathecal ropivacaine plus sufentanil 10 microg (R4). Duration of analgesia and side effects, such as motor block, pruritus, hypotension, ephedrine requirements and fetal bradycardia, were recorded. Duration of analgesia (mean +/- SD) was 79+/-30 min for R2, 98+/-19 min for R4, and 92+/-38 min for B (P = not significant). No differences in motor block or side effects were detected among the groups. We conclude that ropivacaine, when combined with sufentanil, is effective for providing CSE labor analgesia and offers no advantage over bupivacaine in the studied doses.

IMPLICATIONS

In this study, we compared a standard dose of intrathecal bupivacaine with sufentanil for combined spinal epidural analgesia with two doses of the new local anesthetic ropivacaine. Both local anesthetics provided similar labor analgesia duration with equivalent side effect profiles in the doses studied.

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.