Ropivacaine: an update of its use in regional anaesthesia

Cardiac arrest after interscalene brachial plexus block with ropivacaine and lidocaine

Serious adverse reactions to ropivacaine and lidocaine are rare. In this report, we describe a case of sudden cardiac arrest after an interscalene brachial plexus block with a mixture of 150 mg of ropivacaine and 360 mg of lidocaine in a previously healthy, 34-year-old, 97-kg man. Severe hypotension occurred after successful resuscitation, necessitating an infusion of epinephrine. The patient developed pulmonary oedema, and was mechanically ventilated for 22 h. He eventually made a good recovery. We conclude that although ropivacaine and lidocaine are often considered relatively safe local anesthetics, serious cardiovascular complications can occur after the use of these drugs.

The central nervous system and cardiovascular effects of levobupivacaine and ropivacaine in healthy volunteers

We compared the central nervous system (CNS) and cardiovascular effects of levobupivacaine and ropivacaine when given IV to healthy male volunteers (n = 14) in a double-blinded, randomized, crossover trial. Subjects received levobupivacaine 0.5% or ropivacaine 0.5% after a test infusion with lidocaine to become familiar with the early signs of CNS effects (e.g., tinnitus, circumoral paresthesia, hypesthesia). The development of CNS symptoms was assessed at 1-min intervals and study drug administration was terminated when the first CNS symptoms were recognized. Thereafter, symptoms were recorded at 1-min intervals until symptom resolution. Hemodynamic variables were assessed by transthoracic electrical bioimpedance. Continuous 12-lead electrocardiogram monitoring was also performed. There was no significant difference between levobupivacaine and ropivacaine for: the mean time to the first onset of CNS symptoms (P = 0.870), mean total volume of study drug administered at the onset of the first CNS symptom (P = 0.595), stroke index (P = 0.678), cardiac index (P = 0.488), acceleration index (P = 0.697), PR interval (P = 0.213), QRS duration (P = 0.637), QT interval (P = 0.724), QTc interval (P = 0.737), and heart rate (P = 0.267). Overall, fewer CNS symptoms were reported for levobupivacaine than ropivacaine (218 versus 277). This study found that levobupivacaine and ropivacaine produce similar CNS and cardiovascular effects when infused IV at equal concentrations, milligram doses, and infusion rates.

IMPLICATIONS

This study compared directly, for the first time, the toxicity of levobupivacaine and ropivacaine in healthy volunteers. Levobupivacaine and ropivacaine produced similar central nervous system and cardiovascular effects when infused IV at equal concentrations, milligram doses, and infusion rates.

Concept for postoperative analgesia after pedicled TRAM flaps: continuous wound instillation with 0.2% ropivacaine via multilumen catheters. A report of two cases

Pedicled TRAM flap surgery is a complex procedure characterised by an extensive wound site. We present two patients with efficient postoperative pain relief by continuous wound instillation of ropivacaine 0.2% via two multilumen catheters. The catheters were placed subcutaneously before the wound closure through the umbilicus into the abdominal wound, and under the autologous flap into the breast. Each multilumen catheter provides even distribution for local anaesthetics over 12.5 cm. At the end of surgery, patients received a single shot dose of local anaesthetic via the pain catheters. After surgery the continuous infusion of ropivacaine 0.2% was commenced at a rate of 10 ml/h per catheter. Pain scores at rest and on coughing were low on the first postoperative day, and later zero. No medication for breakthrough pain was required throughout the recovery period, and the patients experienced no adverse events linked to the analgesia scene. Patient satisfaction was excellent, and quality of recovery score was superior.

Comparison of 0.2% ropivacaine and 0.25% bupivacaine for axillary brachial plexus blocks in paediatric hand surgery

BACKGROUND

The purpose of this study was to compare the use of ropivacaine 0.2% with bupivacaine 0.25% for axillary brachial plexus block in children undergoing hand surgery.

METHODS

In a double-blind, randomized study, 35 children undergoing hand surgery received axillary brachial plexus blocks with 0.5 ml.kg-1 of either 0.2% ropivacaine or 0.25% bupivacaine. Pain scores were noted at 0, 3, 6, 12 and 24 h after surgery. The time to first dose of codeine phosphate and the total doses of all analgesics given were recorded.

RESULTS

There was no significant difference between the two groups in pain scores, the time to first dose of codeine phosphate or in analgesic requirements in the first 24 h.

CONCLUSIONS

Ropivacaine 0.2% is as effective as bupivacaine 0.25% for axillary brachial plexus blocks in children undergoing hand surgery.

Comparison of intrathecal isobaric bupivacaine-morphine and ropivacaine-morphine for Caesarean delivery

BACKGROUND

This study was designed to evaluate the effects of intrathecal isobaric bupivacaine 0.5% plus morphine and isobaric ropivacaine 0.5% plus morphine combinations in women undergoing Caesarean deliveries.

METHOD

Twenty-five parturients received ropivacaine 15 mg and morphine 150 micro g (RM group) and twenty-five parturients received bupivacaine 15 mg and morphine 150 micro g (BM group) for spinal anaesthesia. Sensory and motor block, haemodynamics, postoperative analgesia, fetal outcomes, and side-effects were evaluated.

RESULTS

Intrathecal bupivacaine-morphine and ropivacaine-morphine provided effective sensory anaesthesia and motor block. Time to reach complete motor block was shorter and time to complete recovery from motor block was longer in the BM group than the RM group (P<0.05). The time to regression of two dermatomes and time for the block to recede to the S2 dermatome were similar in both groups (P>0.05). Time to first complaint of pain and the mean total consumption of tenoxicam were similar in both groups (P>0.05). APGAR scores at 1 and 5 min were similar in the two groups, as were mean umbilical blood pH values (P>0.05). Hypotension and pruritus were the most common side-effects in both groups during the operation.

CONCLUSION

Intrathecal isobaric ropivacaine 0.5% 15 mg plus morphine 150 micro g provides sufficient anaesthesia for Caesarean delivery. The ropivacaine-morphine combination resulted in shorter motor block, similar sensory and postoperative analgesia.

Toxicity of local anaesthetics

The complications of failure, neural injury and local anaesthetic toxicity are common to all regional anaesthetic techniques, and individual techniques are associated with specific complications. All potential candidates for regional anaesthesia should be thoroughly evaluated and informed of potential complications. Central neural blockades still account for more than 70% of regional anaesthesia procedures. Permanent neurological injury is 0.02-0.07%. Pain on injection and paraesthesias while performing regional anaesthesia are danger signals of potential injury and must not be ignored. The incidence of systemic toxicity to local anaesthetics has significantly decreased in the past 30 years, from 0.2 to 0.01%. Peripheral nerve blocks are associated with the highest incidence of systemic toxicity (7.5 per 10,000) and the lowest incidence of serious neural injury (1.9 per 10,000).

The importance of stereoselective determination of drugs in the clinical laboratory

About 56% of the drugs currently in use are chiral compounds, and 88% of these chiral synthetic drugs are used therapeutically as racemates. Only a few of these drugs qualify for a stereospecific determination in a clinical laboratory for therapeutic drug monitoring of patients. If the qualitative and quantitative pharmacokinetic and pharmacodynamic effects are similar, the enantiomers do not need to be separated. However, if the metabolism of the different stereoisomers is handled by different enzymes which are either polymorphic or can be induced or inhibited, and if their pharmacodynamic effects have differences either in strength or in quality, enantiospecific analysis is urgently needed. Unfortunately, there are many racemic drugs where the stereospecificity of the metabolism and/or the pharmacodynamic effects of the enantiomers is not known today. For these drugs, there is a great need for studies concentrating on these differences to improve treatment of the patients.

A randomized, double-blinded comparison of thoracic epidural ropivacaine, ropivacaine/fentanyl, or bupivacaine/fentanyl for postthoracotomy analgesia

Epidural ropivacaine has not been compared with bupivacaine for postthoracotomy analgesia. Eighty patients undergoing elective lung surgery were randomized in a double-blinded manner to receive one of three solutions for high thoracic epidural analgesia. A continuous epidural infusion of 0.1 mL. kg(-1). h(-1) of either 0.2% ropivacaine, 0.15% ropivacaine/fentanyl 5 micro g/mL, or 0.1% bupivacaine/fentanyl 5 micro g/mL was started at admission to the intensive care unit. We assessed pain scores (rest and spirometry), IV morphine consumption, spirometry, hand grip strength, PaCO(2), heart rate, blood pressure, respiratory rate, and side effects (sedation, nausea, vomiting, and pruritus) for 48 h. Thoracic epidural ropivacaine/fentanyl provided adequate pain relief similar to bupivacaine/fentanyl during the first 2 postoperative days after posterolateral thoracotomy. The use of plain 0.2% ropivacaine was associated with worse pain control during spirometry, larger consumption of IV morphine, and increased incidence of postoperative nausea and vomiting. Morphine requirements were larger in the ropivacaine group, with no differences between bupivacaine/fentanyl and ropivacaine/fentanyl groups. Patients in the ropivacaine group experienced more pain and performed worse in spirometry than patients who received epidural fentanyl. There was no significant difference in motor block. We conclude that epidural ropivacaine/fentanyl offers no clinical advantage compared with bupivacaine/fentanyl for postthoracotomy analgesia.

IMPLICATIONS

Thoracic epidural ropivacaine/fentanyl provided adequate pain relief and similar analgesia to bupivacaine/fentanyl during the first 2 postoperative days after posterolateral thoracotomy. Plain 0.2% ropivacaine was associated with worse pain control and an increased incidence of postoperative nausea and vomiting. We conclude that epidural ropivacaine/fentanyl offers no clinical advantage compared with bupivacaine/fentanyl for postthoracotomy analgesia.

The effects of age on neural blockade and hemodynamic changes after epidural anesthesia with ropivacaine

We studied the influence of age on the neural blockade and hemodynamic changes after the epidural administration of ropivacaine 1.0% in patients undergoing orthopedic, urological, gynecological, or lower abdominal surgery. Fifty-four patients were enrolled in one of three age groups (Group 1: 18-40 yr; Group 2: 41-60 yr; Group 3: > or=61 yr). After a test dose of 3 mL of prilocaine 1.0% with epinephrine 5 microg/mL, 15 mL of ropivacaine 1.0% was administered epidurally. The level of analgesia and degree of motor blockade were assessed, and hemodynamic variables were recorded at standardized intervals. The upper level of analgesia differed among all groups (medians: Group 1: T8; Group 2: T6; Group 3: T4). Motor blockade was more intense in the oldest compared with the youngest age group. The incidence of bradycardia and hypotension and the maximal decrease in mean arterial blood pressure during the first hour after the epidural injection (median of Group 1: 11 mm Hg; Group 2: 16 mm Hg; Group 3: 29 mm Hg) were more frequent in the oldest age group. We conclude that age influences the clinical profile of ropivacaine 1.0%. The hemodynamic effects in older patients may be caused by the high thoracic spread of analgesia, although a diminished hemodynamic homeostasis may contribute.

IMPLICATIONS

Analgesia levels after the epidural administration of 15 mL of ropivacaine 1.0% increase with increasing age. This is associated with an increased incidence of hypotension in the elderly, although an effect of age on the hemodynamic homeostasis may have contributed. It appears that epidural doses should be adjusted for elderly patients.

Epidural and spinal analgesia and labour

Epidural and spinal analgesia for pain relief in labour are now commonplace. Adverse effects such as hypotension and toxicity to anaesthetic agents are well described and easily managed. The effects on obstetric outcome, however, have been unclear to both obstetricians and anaesthetists, but are important due to the large number of pregnancies involved. Efforts to define implications for mother and child have been frustrated by a relative lack of evidence derived from good quality, large randomized trials. Ethical and methodological difficulties together with an abundance of confounding factors have conspired to cause considerable difficulties for researchers in this area. Nevertheless, recent evidence has significantly advanced knowledge in the field and has implications for future practice.

An introduction to enantiomers in psychopharmacology

There is growing scientific, clinical, commercial and regulatory recognition that enantiomers offer benefits over racemates in the management of psychiatric diseases as well as in clinical medicine generally. However, relatively few studies consider enantiomers' individual characteristics. This review considers some of the clinical benefits associated with using stereochemically pure drugs in psychiatric conditions other than depression.A review of the evidence shows that enantiomers offer four main benefits. Firstly, using a single enantiomer may allow a reduction in total dose, while maintaining or improving outcomes. For example, (+)-nefopam's antinociceptive activity is greater than that produced by both the racemate and (-)-nefopam, but with the same level of acute toxicity. Thus, a single enantiomer may offer greater efficacy, dose for dose, than the racemate. Secondly, assessing dose-response relationships is simpler. There is no reason to suppose that a racemate will necessarily contain the isomers' optimum therapeutic ratio, that one of the isomers will be inactive or that the enantiomers' dose-response curves will coincide. For example, the dose-response relationship for the induction of catalepsy in the rat by thioridazine suggested that the racemate was around 12 times more potent than (+)-thioridazine and three times more potent than (-)-thioridazine, when considering the actual concentrations in the striatum. Thirdly, using a single enantiomer may reduce pharmacokinetic and pharmacodynamic variability between patients. For example, the coefficients of variation for some of methadone's pharmacokinetic parameters may reach 70%, which might have clinical consequences. Finally, using a single enantiomer may reduce toxicity arising from the therapeutically inactive stereoisomer. For example, the single enantiomers of bupivacaine and ropivacaine are significantly less cardiotoxic than their respective racemates.This review illustrates why stereochemistry should be considered when assessing the toxicology, pharmacokinetics, metabolism and efficacy of a racemate. Indeed, the differences may be so marked that achiral analyses may be misleading, and clinicians should consider prescribing an enantiomer whenever possible. In many cases, prescribing a single enantiomer improves the benefit:risk ratio. Finally, there is no reason to suppose that a racemate's characteristics will apply to the constituent enantiomers. Copyright 2001 John Wiley & Sons, Ltd.

Update on ropivacaine

Long-acting local anaesthetics are primarily used in the practice of anaesthesia, particularly in regional anaesthesia and analgesia. Ropivacaine is a new long-acting local anaesthetic that has been the focus of interest because of its increased cardiovascular safety compared with bupivacaine. Other advantages of ropivacaine over bupivacaine include a greater sensorimotor differential block and shorter elimination half-life (t(1/2)), with a lower potential for accumulation. The most important attribute of ropivacaine, however, is its increased margin of safety compared with bupivacaine when given in equal doses. Many post-marketing studies have focused on the comparisons of efficacy in blocks and toxicity profiles of bupivacaine versus ropivacaine. Recent animal toxicity studies confirm the results of original studies showing that ropivacaine has less cardiovascular toxicity than bupivacaine with respect to direct myocardial depression, success of resuscitation and arrhythmogenic potential when given in equal doses. Reduced cardiotoxicity may be a distinct characteristic of ropivacaine. A review of current literature suggests that, at clinically relevant doses, ropivacaine provides the lowest potential risk of cardiotoxicity for inadvertent intravascular injection. Studies are currently under way comparing ropivacaine with levobupivacaine, the latest addition to the group of long-acting local anaesthetics.

A new posterior approach to the sciatic nerve block: a prospective, randomized comparison with the classic posterior approach

To evaluate the efficacy and acceptance of a new posterior subgluteus approach to the sciatic nerve, as compared with the classic posterior approach, 128 patients undergoing foot orthopedic procedures were randomly allocated to receive either the classic posterior sciatic nerve block (Group Labat, n = 64) or a modified subgluteus posterior approach (Group subgluteus, n = 64). All blocks were performed with the use of a nerve stimulator (stimulation frequency, 2 Hz; intensity, 1-0.5 mA). In Group subgluteus, a line was drawn from the greater trochanter to the ischial tuberosity; then, from the midpoint of this line, a second line was drawn perpendicularly and extended caudally for 4 cm. The end of this line represented the needle entry. In both groups, a proper sciatic stimulation was elicited at 0.5 mA; then 20 mL of 0.75% ropivacaine was injected. The time from needle insertion to successful sciatic nerve stimulation was 60 s (range, 10-180 s) with the Labat's approach and 32 s (range, 5-120 s) with the new subgluteus approach (P = 0.0005). The depth of appropriate sciatic stimulation was 45 +/- 13 mm (mean +/- SD) after 2 (range, 1-7) needle redirections in Group subgluteus and 67 +/- 12 mm after 4 (range, 1-10) needle redirections in Group Labat (P = 0.0001 and P = 0.00001, respectively). The failure rate was similar in both groups. Severe discomfort during the procedure was less frequent and acceptance better in Group subgluteus (5 patients [8%] and 60 patients [94%], respectively) than in Group Labat (20 patients [31%] and 49 patients [77%], respectively) (P = 0.0005 and P = 0.005, respectively). We conclude that this new subgluteus posterior approach to the sciatic nerve is an easy and reliable technique and can be considered an effective alternative to the more traditional Labat's approach.

IMPLICATIONS

Evaluating the efficacy and acceptance of a new approach to the sciatic nerve block, this prospective, randomized study demonstrated that the new subgluteus posterior approach is an easy and reliable technique and can be considered an useful alternative to the more traditional Labat's approach in patients undergoing foot surgery, facilitating the performance of the sciatic nerve blocks.

Pharmacological considerations during pregnancy

We present a brief overview of recent literature concerning some of the drugs used in pregnancy, labour and delivery. Obstetric anaesthesia continues to evolve through the reuse of old drugs such as magnesium sulphate or the manipulation of current drugs (e.g. propofol for emesis) in order to improve patient outcome. Pregnant women have traditionally been therapeutic orphans. The use of new agents such as levobupivacaine and ropivacaine in obstetric patients lags behind that of their non-pregnant counterparts. However, this gap is decreasing and these new drugs offer benefits to the parturient woman.