Ropivacaine: an update of its use in regional anaesthesia

Neurotoxicity of a novel local anesthetic agent, ropivacaine: the possible roles of bursts of potential and cytoplasmic second messenger

BACKGROUND/PURPOSE

Ropivacaine has been shown to induce convulsion following overdose or accidental intravenous injection, but the mechanisms are poorly understood. Using an identifiable central neuron from giant African snail, the authors studied the mechanism of ropivacaine-elicited bursts of potential and explored the possible mechanisms of ropivacaine-induced neurotoxicity.

METHODS

Ropivacaine action on a central neuron (RP4) of the giant African snail (Achatina fulica Ferussac) was recorded by conventional electrophysiologic technique. Interactions between ropivacaine and prazosin, propranolol, atropine, d-tubocurarine, calcium-free solution, H89, U73,122, neomycin, high-magnesium solution, and chelerythrine were also observed.

RESULTS

The RP4 neuron showed spontaneous firing of action potentials. Extracellular application of ropivacaine (900 microM) reversibly elicited bursts of potential in the RP4 neuron. The bursts of potential elicited by ropivacaine were not blocked after administration of: (1) prazosin, propranolol, atropine, d-tubocurarine; (2) calcium-free solution; and (3) pretreatment with H89 or chelerythrine. The bursts of potential elicited by ropivacaine were blocked by pretreatment with U73122 (30 microM) or by adding neomycin (3.5 mM) or high-magnesium solution (30 mM).

CONCLUSION

Ropivacaine reversibly elicited bursts of potential in the central snail neuron. The ropivacaine-elicited bursts of potential were associated with phospholipase C activity in the RP4 snail neuron. Our results suggest that ropivacaine-induced neurotoxicity is highly associated with phospholipase C activity and phospholipase C inhibitor may offer a novel therapeutic approach for managing local anesthetic-induced convulsion or other transient neurologic toxicity.

Comparison of a bupivacaine 0.5% and lidocaine 2% mixture with levobupivacaine 0.75% and ropivacaine 1% in peribulbar anaesthesia for cataract surgery with phacoemulsification

PURPOSE

To compare a bupivacaine and lidocaine mixture with levobupivacaine and ropivacaine in terms of safety, efficacy and blocking quality in peribulbar anaesthesia for phacoemulsification.

METHODS

A total of 105 patients scheduled for cataract surgery with peribulbar anaesthesia were randomly allocated into three groups of 35 patients each, to receive 5 ml of, respectively, a 1 : 1 mixture of bupivacaine 0.5% and lidocaine 2% (group 1), levobupivacaine 0.75% (group 2), or ropivacaine 1% (group 3). Ocular movement scores were evaluated at 2, 4, 6, 8 and 10 mins after injection. Intraoperative and postoperative analgesia were evaluated by verbal pain scores. Duration of surgery, need for supplementary anaesthesia, haemodynamic parameters and the incidence of perioperative complications were recorded.

RESULTS

The ocular movement score in min 2 was significantly lower in group 1. There was no significant difference between groups 2 and 3. Ocular movement scores at mins 4 and 6 were significantly decreased in group 1 and 2 compared with group 3. There was no significant difference among the groups in ocular movement scores at mins 8 and 10. Verbal pain scores in postoperative hour 4 were highest in group 3, but scores for the intraoperative period and postoperative hours 1 and 2 were similar among the groups. Duration of surgery and haemodynamic parameters did not differ among the groups.

CONCLUSIONS

All agents were considered to be convenient for clinical use in cataract surgery with peribulbar anaesthesia. Although the ocular movement scores in the ropivacaine group were higher than in the other groups at mins 4 and 6, this did not imply any clinical significance.

Pain relief and motor function during continuous interscalene analgesia after open shoulder surgery: a prospective, randomized, double-blind comparison between levobupivacaine 0.25%, and ropivacaine 0.25% or 0.4%

BACKGROUND AND OBJECTIVES

To compare pain relief and motor impairment of 0.25% levobupivacaine with either an equivalent (0.25%) or equipotent (0.4%) concentration of ropivacaine for continuous interscalene block after open shoulder surgery.

METHODS

Seventy-two adult patients scheduled for elective major shoulder surgery received an interscalene injection of mepivacaine 1.5% 30 mL followed by 24 h patient-controlled interscalene analgesia (basal infusion rate: 5 mL h-1; incremental bolus: 2 mL; lockout period: 10 min; maximum boluses per hour: 4) with either 0.25% levobupivacaine (n = 24), 0.25% ropivacaine (n = 24) or 0.4% ropivacaine (n = 24). A blinded observer recorded the evolution of pain relief and recovery of motor block during the first 24 h. Motor function was assessed as the maximum pressure developed while squeezing a sphygmomanometer cuff with the blocked hand. The reduction from preoperative values was considered as an index of motor impairment.

RESULTS

No differences were reported among the three groups in the quality of postoperative analgesia. The number of incremental patient-controlled interscalene analgesia doses, total volume of local anaesthetic infused during the 24-h patient-controlled interscalene analgesia, and number of rescue ketoprofen analgesia were higher in the ropivacaine 0.25% group than in the other two groups (P = 0.0005). The hand strength recovered to >or=90% of baseline values within the first 24 h of infusion in all groups, without differences among the three groups.

CONCLUSION

When providing patient-controlled interscalene analgesia after open shoulder surgery 0.25% levobupivacaine and 0.4% ropivacaine performed equally in terms of pain relief, motor block and number of patient-controlled boluses required, while patients receiving 0.25% ropivacaine needed significantly more boluses and rescue analgesia to control their pain.

Skin temperature during sympathetic block: a clinical comparison of bupivacaine 0.5% and ropivacaine 0.5% or 0.75%

Measurement of skin temperature can be used as an indicator of sympathetic blockade induced by neuraxial anaesthesia. The aim of the study was to test the skin temperature response to epidural administration of bupivacaine and different concentrations of ropivacaine. Forty-eight ASA class I-II patients undergoing herniorraphy were enrolled into a prospective, randomized, double-blind clinical trial. Patients were randomly allocated to receive epidural anaesthesia with a single dose of 18 ml of bupivacaine 0.5% (n=16); ropivacaine 0.5% (n=16), or ropivacaine 0.75% (n=16). A temperature probe was positioned on the skin of the thigh and skin temperature registered before epidural anaesthesia, every 10 minutes for the first hour after the epidural injection and every hour for the following four hours. Sensory blockade was assessed by pinprick and motor blockade using the Bromage scale. No significant difference was observed in sensory or motor blockade. A skin temperature rise of 1 to 1.8 degrees C compared with basal values was observed in all patients within the first hour. Temperature returned to basal values within four hours in the ropivacaine 0.5% group, within five hours in the ropivacaine 0.75% group, and remained 1 degrees C higher after five hours in the bupivacaine 0.5% group (P<0.01). The duration of sympathetic block is significantly shorter with ropivacaine than with bupivacaine.

Tramadol, but not its major metabolite (mono-O-demethyl tramadol) depresses compound action potentials in frog sciatic nerves

BACKGROUND AND PURPOSE

Although tramadol is known to exhibit a local anaesthetic effect, how tramadol exerts this effect is not understood fully.

EXPERIMENTAL APPROACH

The effects of tramadol and its metabolite mono-O-demethyl-tramadol (M1) on compound action potentials (CAPs) were examined by applying the air-gap method to frog sciatic nerves, and the results were compared with those of other local anaesthetics, lidocaine and ropivacaine.

KEY RESULTS

Tramadol reduced the peak amplitude of the CAP in a dose-dependent manner (IC50=2.3 mM). On the other hand, M1 (1-2 mM), which exhibits a higher affinity for mu-opioid receptors than tramadol, did not affect CAPs. These effects of tramadol were resistant to the non-selective opioid receptor antagonist naloxone and the mu-opioid receptor agonist, DAMGO, did not affect CAPs. This tramadol action was not affected by a combination of the noradrenaline uptake inhibitor, desipramine, and the 5-hydroxytryptamine uptake inhibitor, fluoxetine. Lidocaine and ropivacaine also concentration-dependently reduced CAP peak amplitudes with IC50 values of 0.74 and 0.34 mM, respectively.

CONCLUSIONS AND IMPLICATIONS

These results indicate that tramadol reduces the peak amplitude of CAP in peripheral nerve fibres with a potency which is less than those of lidocaine and ropivacaine, whereas M1 has much less effect on CAPs. This action of tramadol was not produced by activation of mu-opioid receptors nor by inhibition of noradrenaline and 5-hydroxytryptamine uptake. It is suggested that the methyl group present in tramadol but not in M1 may play an important role in producing nerve conduction block.

Herniorrafia inguinal com anestesia locorregional - (uso de ropivacaína)

OBJETIVO: O objetivo deste estudo é relatar a eficiência e a segurança da realização de herniorrafias inguinais com a utilização da anestesia locorregional com ropivacaina, destacando sua técnica, suas indicações e limitações. MÉTODO: Foram operados 50 pacientes, no período compreendido entre janeiro e dezembro de 2005, sendo submetidos à herniorrafia inguinal mediante anestesia locorregional utilizando-se o anestésico ropivacaina, associada a sedação intra-venosa, no Hospital Universitário Cruz Vermelha Brasileira - UnicenP, na cidade de Curitiba-PR, sendo utilizada técnica sem tensão, com o uso de prótese. Foram avaliadas as variáveis idade, gênero e tipo de hérnia através da classificação de Nyhus. RESULTADOS: Não foram observadas quaisquer alterações conseqüentes a reações adversas ao anestésico local, não sendo necessária nenhuma conversão do método anestésico ou mesmo complementação deste. As complicações pós-operatórias foram de pequena monta e de resolução adequada. CONCLUSÃO: A anestesia local por bloqueio de campo, com o uso de ropivacaína e associada a sedação intravenosa, para a realização de herniorrafias inguinais, constitui-se em procedimento plenamente viável, prático, menos oneroso e benéfico ao paciente.

Sensory blockade after thoracic paravertebral injection of ropivacaine or bupivacaine

BACKGROUND AND OBJECTIVE

No clinical trials comparing the characteristics of sensory blockade caused by various local anaesthetics in thoracic paravertebral blockade have been published. The aim of this prospective study was a clinical assessment of sensory blockade after paravertebral injection of ropivacaine or bupivacaine in patients undergoing modified radical mastectomy.

METHODS

Seventy ASA I-II patients were randomized to receive a single injection of ropivacaine 0.5% (n = 35) or bupivacaine 0.5% (n = 35) at the T4 level. General anaesthesia with propofol and fentanyl was provided during the procedure and patients were not intubated. The following parameters were analysed: duration and dynamics of the sensory blockade and the patient's and surgeon's assessment.

RESULTS

Both ropivacaine and bupivacaine provided a similar level of analgesia. Ropivacaine was characterized by more rapid onset - after only 5 min 53% of patients in this group had the extent of sensory blockade wide enough to perform modified radical mastectomy in comparison to only 20% after bupivacaine (P 9 segments blocked) was noted more often in the ropivacaine group (88% vs. 65%, P < 0.05), lasted longer and appeared to be wider than sensory blockade produced by bupivacaine. Regression of sensory blockade was initially similar, but after 24 h sensory blockade in the ropivacaine group still had a potential to provide analgesia for modified radical mastectomy in 81% of patients in comparison to only 50% of such patients in the bupivacaine group (P < 0.05). Degree of postoperative pain, performance of the cardiovascular system, consumption of medications and complications were all similar between the study groups.

CONCLUSIONS

Both agents provide satisfactory conditions for mastectomy, but ropivacaine seems to be superior to bupivacaine for thoracic paravertebral blockade during breast cancer surgery.

Combination of hyperbaric lidocaine and ropivacaine in spinal anaesthesia for day surgery

BACKGROUND AND OBJECTIVE

Motor function recovers rapidly but the extended duration of sensory block after spinal anaesthesia with hyperbaric ropivacaine may delay patients' ambulation after surgery. We tested whether compensating a reduction of the ropivacaine dose with a small dose of lidocaine would be adequate for surgery and shorten recovery from spinal anaesthesia.

METHODS

Fifty-six consecutive outpatients, who were scheduled for lower extremity surgery under spinal anaesthesia, were randomized into two groups to receive either a hyperbaric solution of lidocaine 20 mg and ropivacaine 5 mg (Group LR) or hyperbaric ropivacaine 10 mg (Group R). Sensory block was tested with pinprick and motor block on the Bromage scale at 5-min intervals until 30 min, then at 15-min intervals until 90 min, and thereafter at 30-min intervals until full bilateral recovery. Blinded interviews were performed on the first and seventh postoperative day.

RESULTS

The groups did not differ significantly regarding success of sensory block reaching T10 dermatome on the operative side, 24 (86%) in Group LR and 23 (82%) in Group R, median (range) onset time 5 (5-20) vs. 10 (5-25) min or median duration of T10 sensory block 68 (5-115) vs. 50 (20-115) min, respectively. Two patients in each group required general anaesthesia. Recovery did not differ between the groups, median time of full motor recovery was 75 min in both groups, sensory recovery of S2 2.5 h vs. 2.8 h, first voluntary micturition 4.2 (2.2-6.1) vs. 4.5 (2.4-6.6) h in the LR vs. R Group, respectively. Transient neurological symptoms did not appear.

CONCLUSION

It is concluded that spinal anaesthesia with hyperbaric lidocaine 20 mg+ropivacaine 5 mg and hyperbaric ropivacaine 10 mg was quite similar regarding frequency, onset, duration of T10 dermatome sensory block and recovery. The patients would have been ready for discharge after voluntary micturition, 4.2-4.5 h from the subarachnoid injection of local anaesthetics.

The Effects of Age on the Median Effective Concentration of Ropivacaine for Motor Blockade After Epidural Anesthesia with Ropivacaine

Minimal local analgesic concentrations have been defined as the median effective concentration (EC50). In this study, we sought to examine the effect of age on motor blockade and determine the motor block EC50 of elderly patients after epidural administration of ropivacaine in patients undergoing urological or minor lower limb surgery. ASA physical status I-II patients were enrolled in 1 of 2 age groups (Group 1: > or =70 yr; Group 2: <70 yr). Each received a 15-mL bolus of epidural ropivacaine without epinephrine. The first patient in each group received 0.425%. Up-down sequential allocation was used to determine subsequent concentrations at a testing interval of 0.025%. Effective motor blockade was defined as a modified Bromage score >0 within 30 min. The motor blockade EC50 of ropivacaine was 0.383% (95% confidence interval, 0.358%-0. 409%) in group 1 and 0.536% (95% confidence interval, 0.512%-0.556%) in group 2 (P < 0.01). We conclude that age is a determinant of motor blockade EC50 of ropivacaine with epidural administration.

Ropivacaine: a review of its use in regional anaesthesia and acute pain management

Ropivacaine (Naropin) is the pure S(-)-enantiomer of propivacaine, and is a long-acting amide local anaesthetic agent, eliciting nerve block via reversible inhibition of sodium ion influx in nerve fibres. Ropivacaine is a well tolerated regional anaesthetic effective for surgical anaesthesia as well as the relief of postoperative and labour pain. The efficacy of ropivacaine is similar to that of bupivacaine and levobupivacaine for peripheral nerve blocks and, although it may be slightly less potent than bupivacaine when administered epidurally or intrathecally, equi-effective doses have been established. Clinically adequate doses of ropivacaine appear to be associated with a lower incidence or grade of motor block than bupivacaine. Thus ropivacaine, with its efficacy, lower propensity for motor block and reduced potential for CNS toxicity and cardiotoxicity, appears to be an important option for regional anaesthesia and for the management of postoperative and labour pain.

Analgesia pós-operatória

JUSTIFICATIVAS E OBJETIVOS: A dor sempre foi uma das maiores preocupações do homem, entretanto, apesar dos progressos da ciência, ainda existem várias barreiras ao seu adequado tratamento, incluindo a falta de conhecimento por parte da equipe médica, sobre o mecanismo das diversas drogas e técnicas empregadas. O objetivo deste trabalho é abordar as principais drogas e técnicas empregadas no controle da dor pós-operatória, visando estimular o interesse sobre o assunto bem como aumentar a eficácia do tratamento dado aos pacientes. CONTEÚDO: Está ressaltada neste artigo, a importância da adequada analgesia pós-operatória, considerando as principais drogas e técnicas utilizadas no controle da dor, seus mecanismos de ação, posologias, vias de administração e efeitos colaterais, bem como a importância da integração de toda a equipe envolvida nos cuidados do paciente para o sucesso do tratamento. O tratamento inadequado da dor no pós-operatório não se justifica, pois há um arsenal considerável de drogas e técnicas analgésicas. O que se faz necessário, portanto, é que toda equipe, anestesistas, cirurgiões, e enfermeiros tenham conhecimento e estejam integrados na utilização deste arsenal.

Infiltration continue prépéritonéale d'anesthésiques locaux pour l'analgésie après laparotomie. Données préliminaires

INTRODUCTION

Continuous administration of local anesthetic through a catheter placed in the scar of a laparotomy is a postoperative analgesic technique, which seems effective but remains little developed and poorly codified.

METHODS

In this prospective evaluation, we present a series of 25 observations of adult patients scheduled for abdominal laparotomy, to which a multiperforate catheter was placed at the end of the intervention by the surgeon in pre-peritoneal position, allowing the continuous perfusion of ropivacaïne over the first 48 postoperative hours. Patients received intravenous paracetamol associated with ketoprophene or nefopam. Opiates were given as rescue analgesics, in case of failure in pain relief, defined on objective criteria measured on visual analogic scale (VAS).

RESULTS

The feasibility of the technique was excellent, except in one case of catheter obstruction. Pain was adequately relieved, with a majority of patients having VAS scores lower than 3/10 cm with the VAS, as well as rest as during mobilization. Only 9 patients needed morphine rescue analgesics. There was no sign of clinical overdose nor parietal complication related to the technique. Blood dosages of ropivacaine, carried out among 5 patients having received 600 mg daily, showed serum concentrations below the thresholds of toxicity.

CONCLUSIONS

These results reveal a good effectiveness of the method, with moderate pain intensity and a low analgesic consumption. The local and general tolerance was excellent.

Antipruritic and antiemetic effect of epidural droperidol

BACKGROUND AND OBJECTIVES

This study was designed to investigate whether single epidural droperidol or continuous epidural droperidol inhibit pruritus and postoperative nausea and vomiting induced by postoperative continuous epidural fentanyl administration, and to identify the optimal method of administering epidural droperidol.

METHODS

120 ASA I-II patients undergoing subtotal gastrectomy with general anaesthesia combined with epidural anaesthesia were randomly allocated into three groups: control (no droperidol), single injection (droperidol 2.5 mg) and continuous group (droperidol 2.5 mg 2 day(-1)). Postoperatively the frequency and severity of pruritus and postoperative nausea and vomiting in all groups were compared during 48 h.

RESULTS

The frequency and severity of pruritus was significantly lower in both single injection and continuous groups than control group after epidural fentanyl administration (P < 0.05). The frequency and severity of postoperative nausea and vomiting was significantly lower in single injection group than control group after epidural fentanyl administration (P < 0.05).

CONCLUSION

Epidural continuous droperidol is effective for reducing pruritus, and single epidural droperidol injection is effective for reducing pruritus and postoperative nausea and vomiting induced by postoperative continuous epidural fentanyl analgesia.

A multimodal analgesia protocol for total knee arthroplasty. A randomized, controlled study

BACKGROUND

Although numerous methods of postoperative analgesia have been investigated in an attempt to improve pain control after total knee arthroplasty, parenteral narcotics still play a major role in postoperative pain management. Local anesthetics have the advantage of blocking pain conduction at its origin and minimizing the systemic side effects associated with postoperative narcotic use. This study was performed to evaluate the benefits and safety of a multimodal analgesia protocol that included periarticular injection of large doses of local anesthetics in patients undergoing total knee arthroplasty.

METHODS

We compared morphine consumption during the first twenty-four hours after unilateral total knee arthroplasty in forty-two patients who had been randomized to receive either (1) a perioperative infiltration mixture, consisting principally of local anesthetic, and self-administered morphine or (2) self-administered morphine only. Narcotics consumption, pain control, medication-related side effects, plasma levels of the local anesthetic (ropivacaine), and postoperative rehabilitation were monitored.

RESULTS

Although there was high satisfaction and good pain control in both groups, morphine consumption was significantly lower in the local analgesia group than it was in the control group (28.8 +/- 17.4 mg compared with 50.3 +/- 25.4 mg twenty-four hours after surgery, and 46.7 +/- 19.4 mg compared with 68.6 +/- 38.6 mg forty hours after surgery). Both groups achieved a similar amount of knee flexion on the fifth postoperative day. Over the five-day period after the procedure, the patients in the local analgesia group reported a total of 2.6 +/- 3.9 hours of nausea compared with 7.1 +/- 12.2 hours in the control group. No complications related to the infiltration of the local anesthetic were observed, and all plasma concentrations of the local anesthetic were below the toxic range.

CONCLUSIONS

This multimodal perioperative analgesia protocol that included infiltration of a local anesthetic offered improved pain control and minimal side effects to patients undergoing total knee arthroplasty. Our study also confirmed the safety of the protocol.

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.

Pharmacokinetics and efficacy of ropivacaine for continuous epidural infusion in neonates and infants

INTRODUCTION

The primary objective of this noncomparative study was to evaluate the pharmacokinetics of ropivacaine during a 48-72-h continuous epidural infusion of ropivacaine in children under 1 year. The secondary objectives were to assess efficacy and safety.

METHODS

Neonates and infants (ASA I-III, gestational age > or =37 weeks, > or =2.5 kg, scheduled for major abdominal or thoracic surgery) were included and separated into age groups: 0-30 (neonate), 31-90, 91-180, and 181-365 days. Ethics committee approval and informed parental consent were obtained before inclusion. An epidural catheter was introduced under general anesthesia at the appropriate dermatomal level. An initial bolus dose (0.9-2.0 mg.kg(-1) of ropivacaine 0.2%) was followed by an epidural infusion (0.2 mg.kg(-1).h(-1) for infants <180 days or 0.4 mg.kg(-1).h(-1) for infants >180 days). Plasma samples were collected every 12 h from 24 h, and on termination of the epidural infusion. Postoperative pain was evaluated using both the Objective Pain Scale and a four-graded descriptive scale.

RESULTS

Forty-five infants, median age 116 (0-362) days, were included. Forty-three and 19 patients received an infusion for at least 48 and 72 h, respectively. Satisfactory analgesia was provided in the majority, only 20 patients were given supplementary medication during the infusion. In all age groups, plasma concentrations of unbound ropivacaine leveled at 24 h, without any further increase at 48 and 72 h. Because of lower clearance of unbound ropivacaine in neonates (mean 33 ml.min(-1).kg(-1)) than in infants above the age of 30 days (80, 124, and 163 ml.min(-1).kg(-1), respectively, in the age groups 31-90, 91-180, and 180-365 days), unbound ropivacaine concentrations at the end of infusion were higher in neonates [median 0.10 mg.l(-1) (0.04-0.21 mg.l(-1))] than in infants >30 days [median 0.03 mg.l(-1) (0.003-0.10 mg.l(-1))].

CONCLUSION

Epidural infusions (0.2-0.4 mg.kg(-1).h(-1) ropivacaine) provided satisfactory pain relief in neonates and infants under 1 year. As plasma concentrations of unbound ropivacaine were not influenced by the duration of the infusion, ropivacaine can be safely used for postoperative epidural infusion for 48-72 h. Levels of unbound ropivacaine were higher in the neonates than in the infants, but were below threshold concentrations for CNS toxicity in adults (> or =0.35 mg.l(-1)). This should not preclude the use of ropivacaine infusions in neonates but suggests a need for caution during the first weeks of life.

Caudal anesthesia for minor pediatric surgery: a prospective randomized comparison of ropivacaine 0.2% vs levobupivacaine 0.2%

BACKGROUND

Previous published data comparing ropivacaine 0.2% with levobupivacaine 0.25% have suggested that ropivacaine might be associated with less early postoperative motor blockade compared with levobupivacaine. The aim of the present study was to further investigate this issue comparing equal concentrations (0.2%) of ropivacaine and levobupivacaine in children undergoing minor subumbilical surgery.

METHODS

Following induction of a standardized anesthetic, patients (1-7 years) were randomized in a double-blind manner to receive a caudal block with either ropivacaine 0.2% (group R, n=30) or levobupivacaine 0.2% (group L, n=30), total volume 1 ml.kg-1. Motor blockade (modified Bromage scale; primary end-point) and analgesia [Children and Infants Postoperative Pain Scale (CHIPPS) score] were assessed at predetermined time points during the first 24-postoperative hours.

RESULTS

Motor blockade was only registered during the first postoperative hour with no significant differences between the groups (group R n=5, group L n=8). Postoperative CHIPPS scores were almost identical in both groups with only seven and six patients requiring supplemental analgesia (CHIPPS score>or=4) in the R and L groups, respectively.

CONCLUSIONS

A 0.2% concentrations of ropivacaine or levobupivacaine are clinically very similar with regard to postoperative analgesia and unwanted postoperative motor blockade in children undergoing minor subumbilical surgery.

Effects of hyperbaric spinal ropivacaine for caesarean section

BACKGROUND AND OBJECTIVE

Adding various opioids to the local anaesthetic solution administrated intrathecally improves the analgesic potency of spinal analgesia. The purpose of this study was to evaluate the efficacy and safety of intrathecal fentanyl 10 microg added to 15 mg hyperbaric ropivacaine in patients undergoing caesarean section under spinal anaesthesia.

METHODS

Thirty-seven healthy, full-term parturients were randomly assigned into two groups: Group S (saline group, n=17) received 15 mg hyperbaric ropivacaine in 2.5 mL + 0.5 mL saline; Group F (fentanyl group, n=20) received 15 mg hyperbaric ropivacaine in 2.5 mL + 10 microg fentanyl in 0.5 mL, intrathecally. Characteristics of spinal block, intraoperative quality of spinal anaesthesia, time to first feeling of pain (complete analgesia), time to first request of analgesics postoperatively (effective analgesia), side-effects and fetal outcomes were evaluated.

RESULTS

Regression of sensory block to L5 was significantly prolonged in the fentanyl group compared with the saline group (P = 0.001). Time to the first feeling of pain (130.6 +/- 15.8 min vs. 154.3 +/- 31.1 min; P = 0.008) and the first analgesic requirement (161.2 +/- 32.6 min vs. 213.0 +/- 29.3 min; P < 0.001) were significantly shorter in the saline group compared with the fentanyl group. Side-effects, umbilical arterial and venous blood gases did not differ between the groups. Apgar scores were similar in both groups and no infants had an Apgar score < or =7 at 5 min.

CONCLUSIONS

The addition of fentanyl 10 microg, to hyperbaric ropivacaine 15 mg, for spinal anaesthesia increased the duration of analgesia in the early postoperative period in patients undergoing caesarean delivery.

The pharmacokinetics of ropivacaine in hepatic and renal insufficiency

In patients with chronic end-stage liver disease, the peak plasma concentrations of ropivacaine after a single intravenous ropivacaine dose are similar to those in healthy subjects. However, patients with end-stage liver disease have about a 60% lower mean ropivacaine clearance than healthy subjects and are thus expected to have over two-fold higher steady-state ropivacaine plasma concentrations during a continuous ropivacaine infusion. The peak plasma concentrations of ropivacaine after an axillary plexus block in uraemic patients are considerably higher than those in non-uraemic patients. However, uraemic patients have significantly higher alpha-1-acid glycoprotein plasma concentrations than non-uraemic patients, and the peak plasma concentrations of free ropivacaine (related to toxicity) are similar in both groups. The pharmacokinetics of intravenously administered ropivacaine in patients with renal insufficiency and the possibility of clinically significant (S)-2',6'-pipecoloxylidide metabolite accumulation during continuous or repeated ropivacaine administration in these patients remain to be clarified.

Ropivacaine in neonates and infants: a population pharmacokinetic evaluation following single caudal block

BACKGROUND

The aims of this study were to evaluate pharmacokinetics, efficacy and safety of ropivacaine in infants aged 0-12 months following a single caudal injection.

METHODS

Term ASA I-III patients, scheduled for surgery, with a body weight of > or = 2500 g received a caudal block with ropivacaine 2 mg x ml(-1), 1.0 ml x kg(-1). Plasma samples were collected at different time intervals up to 30 h, for analysis of total and unbound ropivacaine and alpha-1-acid glycoprotein (AAG). Pharmacokinetic data were characterized by population analysis. Unbound and total concentrations from 35 patients, median (min-max) postnatal age of 66 (4-351) days, were included in the nonlinear mixed effects modeling to provide estimates of pharmacokinetic parameters and the exploration of covariate relationships. Simulations were made to test the predictive performance of the final model and to describe the effect of significant covariates on systemic exposure.

RESULTS

The mean (min-max) peak plasma concentration of total ropivacaine was 0.83 (0.05-1.57) mg x l(-1) at 0.5-5.7 h (median: 1.0 h) and the plasma concentration of unbound ropivacaine was 0.042 (0.012-0.081) mg x l(-1) within 0.5-1 h. The observed unbound fraction in plasma was 6% (1%-14%). A one-compartment open model with first-order absorption and elimination, incorporating a linear-binding model of ropivacaine to AAG best described the data. The only significant covariate relationship was that of age on Clu/F according to the following relationship Clu/F = 3.01 x e0.00474 x Age. This predicts a Clu/F of 3.5 l x h(-1) x kg(-1) at 30 days and 10.8 l x h(-1) x kg(-1) at 270 days with corresponding terminal half-lives of 6.7 and 2.2 h. The interindividual variability (coefficient of variation, CV) in Clu/F was 39%. The population estimate (CV) of ka was 1.65 h(-1) (30%), Vu/F was 33.6 (l x kg(-1)) (45%) and Ka was 1.78 l x mg(-1) (14%). Thirty-five infants received supplementary analgesics (mostly paracetamol). The median time to first supplementary analgesic (based on all 37 patients) was 3.9 h. No safety concerns or signs of systemic toxicity were observed.

CONCLUSIONS

Following a caudal block with ropivacaine 2 mg x kg(-1) plasma concentrations of unbound ropivacaine were well below threshold levels for toxicity in adults. Apparent volume of distribution is unchanged, apparent unbound clearance increases and the terminal half-life decreases with age in 0-12-month-old neonates and infants. The postoperative pain management provided adequate analgesia and was well tolerated.

A prospective, randomized, double-blind comparison of epidural levobupivacaine 0.5% with epidural ropivacaine 0.75% for lower limb procedures

BACKGROUND AND OBJECTIVE

This prospective, randomized, observer-blinded study compared onset time and duration of epidural anaesthesia produced by with levobupivacaine and ropivacaine for lower limb surgery.

METHODS

ASA I-III adult patients undergoing elective lower limb procedures were randomized to receive epidural levobupivacaine 0.5% 15 mL (n = 30) or epidural ropivacaine 0.75% 15 mL (n = 35). A blinded observer evaluated onset time and regression of motor and sensory block, and intraoperative needs for fentanyl supplementation (0.1 mg intravenously).

RESULTS

With levobupivacaine, onset time was 29 +/- 24 min, with ropivacaine it was 25 +/- 22 min (P = 0.41). Complete resolution of motor block required 105 +/- 63 min with levobupivacaine and 95 +/- 48 min with ropivacaine (P = 0.86). The time for regression of sensory block to T12 was 185 +/- 77 min with levobupivacaine and 201 +/- 75 min with ropivacaine (P = 0.46). Analgesic supplementation was required in one patient receiving levobupivacaine (3.5%) and in two patients receiving ropivacaine (5.7%) (P = 0.99).

CONCLUSIONS

In adults undergoing lower limb surgery, levobupivacaine 0.5% 15 mL produces an epidural block with the same clinical profile as ropivacaine 0.75% 15 mL.

Three-dimensional pharmacology, a subject ranging from ignorance to overstatements

Stereoselectivity has been known to play a role in drug action for 100 years or more. Nevertheless, chiral drugs have been developed and used as racemates, neglecting the fact that they comprise mixtures of two or more compounds which may have quite different pharmacological properties. A very limited access to pure enantiomers in the past has been responsible for this unsatisfactory state of affairs. During the last 20 years, significant achievements have made it possible to perform stereoselective synthesis and analysis. Today, novel chiral drugs are as a rule developed as single enantiomers. Yet, studies of old racaemic drugs are still designed, performed and published without mention of the fact that two or more compounds are involved. In recent years, a number of old racaemic drugs have been re-evaluated and re-introduced into the clinical area as the pure, active enantiomer (the eutomer). While in principle correct, the clinical benefit of this shift from a well established racaemate to a pure enantiomer often seems to be limited and sometimes exaggerated. Racaemic drugs with a deleterious enantiomer that does not contribute to the therapeutic effect (the distomer), may have been sorted out in the safety evaluation process. However, in the future any pharmacological study of racaemic drugs must include the pure enantiomers. This will generate new, valuable information on stereoselectivity in drug action and interaction.

Exercise-induced changes of motor excitability with and without sensory block

To explore interactions between the sensory and motor system, we investigated motor excitability changes following a motor exercise with and without an anesthetic block of cutaneous inputs overlying the target muscle. Transcranial magnetic stimulation (TMS) with a focal coil was applied to determine motor output maps, intracortical inhibition (ICI) and intracortical facilitation (ICF) of the first dorsal interosseous muscle (FDI) on both sides. Twelve subjects performed phasic right index finger adductions (frequency: 0.333 Hz) for 30 min. TMS measurements were performed before and after the motor task (Experiment 1). In Experiment 2, median and radial nerve were blocked with Ropivacaine injections at the right wrist prior to the motor exercise. TMS was applied before and after induction of anesthesia and after exercise. In Experiment 3, the same anesthetic block was applied and TMS was performed before and after induction of anesthesia and after additional 30 min of rest. In Experiment 1, right FDI motor output area was enlarged, its center of gravity moved posteriorly, and ICI was reduced after the exercise. In Experiment 2, anesthesia was associated with a shrinkage of right FDI motor output area. After exercise, right FDI motor output area enlarged again but was still significantly smaller than pre-anesthesia. In both experiments, TMS results of left FDI remained unchanged. In Experiment 3, the anesthesia-induced decrease of right FDI motor output area remained unchanged after the period of rest. We conclude that a simple motor task enhanced the cortical representation of the target muscle and reduced intracortical inhibition. An impairment of cutaneous afferents decreased the cortical representation of the target muscle. The decrease of motor excitability induced by the sensory deficit could only partially be reversed by the motor exercise.

Comparison of ropivacaine with a combination of ropivacaine and fentanyl for the caudal epidural anaesthesia of mares

Two groups of six mares aged from eight to 18 years were anaesthetised by caudal epidural injections of ropivacaine (0.5 per cent, 0.1 mg/kg) or a combination of ripovacaine (0.08 mg/kg) and fentanyl (100 microg) in a randomised study. The onset of anaesthesia was significantly more rapid (P<0.001) and it lasted significantly longer (P<0.001) in the group anaesthetised with the combination of drugs. The surgical comfort scores of the group anaesthetised with the combination were higher than those of the group anaesthetised with ropivacaine alone (P<0.001), and the quality of intraoperative analgesia, as assessed by the surgeon, was significantly improved. There were no differences between the groups in their average scores for the levels of ataxia and sedation, in their behaviour, or in the incidence of side effects.

Epidural Levobupivacaine 0.1% or Ropivacaine 0.1% Combined with Morphine Provides Comparable Analgesia After Abdominal Surgery

Ropivacaine appears attractive for epidural analgesia because it produces less motor block than racemic bupivacaine. The potential benefits of levobupivacaine with regard to motor blockade require further investigations. In this study, we compared the efficacy, dose requirements, side effects, and motor block observed with epidural levobupivacaine and ropivacaine when given in combination with small-dose morphine for 60 h after major abdominal surgery. Postoperatively, 50 patients were randomly allocated, in a double-blinded manner, to patient-controlled epidural analgesia with the same settings and without basal infusion, using 0.1% levobupivacaine or 0.1% ropivacaine. Both were combined with an epidural infusion of 0.1 mg/h morphine. Pain scores, side effects, motor block, and local anesthetic consumption were measured for 60 h. Pain scores measured on a 100-mm visual analog scale were approximately 20 mm at rest and 40 mm during mobilization in both groups. Bromage scores were 1 for all patients after the fourth postoperative hour. Consumption of levobupivacaine and ropivacaine were similar: 344 +/- 178 mg levobupivacaine versus 347 +/- 199 mg ropivacaine 48 h postoperatively. On postoperative day 2, 19 patients in the ropivacaine group versus 12 in the levobupivacaine group were able to ambulate (P < 0.05). No difference was noted concerning incidence of side effects. We conclude that when used as patient-controlled epidural analgesia and combined with small-dose epidural morphine, 0.1% levobupivacaine and 0.1% ropivacaine produce comparable postoperative analgesia with a similar incidence of side effects.

IMPLICATIONS

Small concentrations (0.1%) of epidural levobupivacaine and ropivacaine combined with morphine (0.1 mg/h) produce comparable analgesia and have similar side effects for similar dose requirements.

Benefit-Risk Assessment of Ropivacaine in the Management of Postoperative Pain

Ropivacaine is a long-acting amide-type local anaesthetic, released for clinical use in 1996. In comparison with bupivacaine, ropivacaine is equally effective for subcutaneous infiltration, epidural and peripheral nerve block for surgery, obstetric procedures and postoperative analgesia. Nevertheless, ropivacaine differs from bupivacaine in several aspects: firstly, it is marketed as a pure S(-)-enantiomer and not as a racemate, and secondly, its lipid solubility is markedly lower. These features have been suggested to significantly improve the safety profile of ropivacaine, and indeed, numerous studies have shown that ropivacaine has less cardiovascular and CNS toxicity than racemic bupivacaine in healthy volunteers. Extensive clinical data have demonstrated that epidural 0.2% ropivacaine is nearly identical to 0.2% bupivacaine with regard to onset, quality and duration of sensory blockade for initiation and maintenance of labour analgesia. Ropivacaine also provides effective pain relief after abdominal or orthopaedic surgery, especially when given in conjunction with opioids or other adjuvants. Nevertheless, epidurally administered ropivacaine causes significantly less motor blockade at low concentrations. Whether the greater degree of blockade of nerve fibres involved in pain transmission (Adelta- and C-fibres) than of those controlling motor function (Aalpha- and Abeta-fibres) is due to a lower relative potency compared with bupivacaine or whether other physicochemical properties or stereoselectivity are involved, is still a matter of intense debate. Recommended epidural doses for postoperative or labour pain are 20-40 mg as bolus with 20-30 mg as top-up dose, with an interval of >or=30 minutes. Alternatively, 0.2% ropivacaine can be given as continuous epidural infusion at a rate of 6-14 mL/h (lumbar route) or 4-10 mL/h (thoracic route). Preoperative or postoperative subcutaneous wound infiltration, during cholecystectomy or inguinal hernia repair, with ropivacaine 100-175 mg has been shown to be more effective than placebo and as effective as bupivacaine in reducing wound pain, whereby the vasoconstrictive potency of ropivacaine may be involved. Similar results were found in peripheral blockades on upper and lower limbs. Ropivacaine shows an identical efficacy and potency to that of bupivacaine, with similar analgesic duration over hours using single shot or continuous catheter techniques. In summary, ropivacaine, a newer long-acting local anaesthetic, has an efficacy generally similar to that of the same dose of bupivacaine with regard to postoperative pain relief, but causes less motor blockade and stronger vasoconstriction at low concentrations. Despite a significantly better safety profile of the pure S(-)-isomer of ropivacaine, the increased cost of ropivacaine may presently limit its clinical utility in postoperative pain therapy.

The acute myotoxic effects of bupivacaine and ropivacaine after continuous peripheral nerve blockades

Bupivacaine causes muscle damage. However, the myotoxic potency of ropivacaine is still unexplored. Therefore, we performed this study to compare the effects of bupivacaine and ropivacaine on skeletal muscle tissue in equipotent concentrations. Femoral nerve catheters were inserted into anesthetized minipigs, and 20 mL of either bupivacaine (5 mg/mL) or ropivacaine (7.5 mg/mL) was injected. Subsequently, bupivacaine (2.5 mg/mL) and ropivacaine (3.75 mg/mL) were continuously infused over 6 h. Control animals were treated with corresponding volumes of normal saline. Finally, muscle samples were dissected at injection sites. After processing and staining, histological patterns of muscle damage were blindly examined, scored (0 = no damage to 3 = myonecrosis), and statistically analyzed. After normal saline, only interstitial edema was found. Bupivacaine treatment caused severe tissue damage (score, 2.3 +/- 0.7), whereas ropivacaine induced fiber injury of a significantly smaller extent (score, 1.3 +/- 0.8). Furthermore, bupivacaine, but not ropivacaine, induced apoptosis in muscle fibers. In summary, both drugs induce muscle damage with similar histological patterns. Compared with bupivacaine, which induces both necrosis and apoptosis, the tissue damage caused by ropivacaine is significantly less severe. We conclude that ropivacaine's myotoxic potential is more moderate in comparison with that of bupivacaine.

IMPLICATIONS

After continuous peripheral nerve blockades, the long-acting local anesthetics bupivacaine and ropivacaine both induce fiber necrosis in porcine skeletal muscle tissue. In comparison with ropivacaine, bupivacaine causes tissue damage of a significantly larger extent and additionally induces apoptosis in skeletal muscle cells.

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.