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REGIONAL ANESTHESIA

A Double-Blinded, Randomized Comparison of Either 0.5% Levobupivacaine or 0.5% Ropivacaine for Sciatic Nerve Block

Andrea Casati^*, Battista Borghi, Guido Fanelli^*, Elisa Cerchierini^*, Roberta Santorsola^*, Valeria Sassoli, Crispino Grispigni, and Giorgio Torri^*

Departments of *Anesthesiology and Orthopedic Surgery, Vita-Salute University, IRCCS H. San Raffaele, Milan, Italy; Departments of Anesthesiology and Pharmacy, IRCCS Istituti Ortopedici Rizzoli, Bologna, Italy

Address correspondence and reprint requests to Andrea Casati, MD, Department of Anesthesiology, IRCCS H. San Raffaele, Via Olgettina 60, 20132 Milan, Italy. Address e-mail to casati.andrea{at}hsr.it

	Abstract

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To compare intraoperative and postoperative clinical properties of levobupivacaine and ropivacaine for sciatic nerve block, 50 ASA physical status I and II patients undergoing hallux valgus repair received a femoral nerve block with 15 mL of 2% mepivacaine. They were then randomly allocated in a double-blinded fashion to receive a sciatic nerve block with either 0.5% levobupivacaine (n = 25) or 0.5% ropivacaine (n = 25). An independent blinded observer evaluated the onset time of surgical anesthesia as well as the quality of the surgical block and postoperative analgesia. The median (range) onset time of surgical block at the sciatic nerve distribution was 30 min (5–60 min) with levobupivacaine and 15 min (5–60 min) with ropivacaine (P = 0.63). Four patients (two patients in each group) received a supplementary ankle block by the surgeon just before the beginning of surgery. All four patients also received IV fentanyl supplementation, but in three of them, propofol infusion was required to complete surgery (two in the Levobupivacaine group [8%] and one in the Ropivacaine group [4%]; P = 0.99). In six patients of the Levobupivacaine group (24%) and five patients of the Ropivacaine group (20%), IV fentanyl supplementation was required to complete surgery (P = 0.99). No differences in the time to recovery of sensory and motor function were observed between the two groups, whereas median (range) duration of postoperative analgesia was 16 h (8–24 h) with levobupivacaine and 16 h (8–24 h) with ropivacaine (P = 0.83). We conclude that 0.5% levobupivacaine and 0.5% ropivacaine provide comparable surgical anesthesia and postoperative analgesia.

IMPLICATIONS: No studies have compared the clinical properties of levobupivacaine with those of ropivacaine when providing sciatic nerve block for hallux valgus repair. Results from this prospective, randomized, double-blinded study demonstrate that 20 mL of either 0.5% levobupivacaine or 0.5% ropivacaine provide comparable surgical block with prolonged postoperative analgesia.

	Introduction

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Regional anesthesia is safe and effective for surgical procedures involving the foot and ankle and optimizes postoperative pain relief (1). In our orthopedic department, a combined block of the sciatic and femoral nerves with long-acting anesthetic solutions is routine for foot surgery. In recent years, as many other physicians did, we switched from bupivacaine to ropivacaine both for its favorable clinical profile (2,3) and to minimize the risk of local anesthetic toxicity (4).

Levobupivacaine is the last local anesthetic introduced in clinical practice. It is the S(-)-enantiomer of the local anesthetic bupivacaine. Whereas both the R- and S-enantiomers of bupivacaine have anesthetic activity, preclinical studies suggested that levobupivacaine may be less cardiotoxic than the racemic mixture (5,6). Levobupivacaine is safe and effective for epidural and spinal anesthesia (5,7) and supraclavicular brachial plexus block (8). However, it is well established that the efficacy and clinical profile of local anesthetics also depends on the type of block for which the drug is being used; thus, the data obtained with the use of levobupivacaine for supraclavicular brachial plexus block may not be applied to lower extremity blocks, especially to the sciatic nerve block. Furthermore, no information is actually available in the current literature comparing the clinical use of levobupivacaine with ropivacaine for peripheral nerve block. We therefore conducted a prospective, randomized, double-blinded study to compare intraoperative and postoperative clinical properties of sciatic nerve block performed with either 0.5% ropivacaine or 0.5% levobupivacaine for hallux valgus repair.

	Methods

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After the study protocol had been approved by the Hospital Ethical Committee, informed consent to participate in the study was obtained from 50 ASA physical status I and II inpatients undergoing elective hallux valgus repair with combined block of the sciatic and femoral nerves. Patients receiving chronic analgesic therapy, as well as those with diabetes or peripheral neuropathies, were excluded.

After an 18-gauge IV cannula had been inserted in the forearm, midazolam 0.05 mg/kg was given as premedication. Standard monitoring was used throughout the study, including noninvasive arterial blood pressure, heart rate, and pulse oximetry. Surgery was performed in all patients using a standard thigh tourniquet inflated 100 mm Hg more than systolic arterial blood pressure.

Nerve blocks were performed using Teflon-coated stimulating needles (Locoplex, Vygon, France) (needle length/diameter was 3.5 cm/25-gauge for femoral nerve block and 12 cm/22-gauge for sciatic nerve block) and a nerve stimulator (Plexival, Medival, Italy). The stimulation frequency was set at 2 Hz, and the duration of the stimulating pulse was set at 0.1 ms. The intensity of the stimulating current was initially set to deliver 1 mA and was gradually decreased to 0.5 mA after the proper motor response was observed. Paresthesia was never intentionally sought; a multiple injection technique was used that elicited specific twitches on nerve stimulation to confirm exact needle location (9,10).

In all patients, a femoral nerve block was performed with 15 mL of 2% mepivacaine. Then the sciatic nerve block was performed with 20 mL of either 0.5% ropivacaine (Ropivacaine group, n = 25) or 0.5% levobupivacaine (Levobupivacaine group, n = 25). Sterile syringes with the local anesthetic solution were prepared in a double-blinded fashion by one of the authors not involved in further management of the studied patients. The sciatic nerve block was performed according to the classic Labat approach modified by Alon Winnie using a double stimulation technique (9,10). After eliciting an appropriate stimulation of the tibial (plantar flexion/inversion of the foot) and the common peroneal nerves (dorsiflexion/eversion of the foot), 10 mL of the study solutions was injected (with a total final volume of 20 mL).

An independent blinded observer recorded the onset time of surgical anesthesia of the sciatic nerve block. The zero time for clinical assessments was the completion of the anesthetic injection at the sciatic nerve. Surgical anesthesia was defined as complete loss of pinprick sensation (22-gauge) both in the tibial and common peroneal nerves distribution at the level of the ankle and foot and concomitant inability to move the ankle and the toes of the operated foot. Sensory and motor blocks were evaluated every 5 min. If 60 min after injection the block was not complete, the protocol included the performance of an ankle block with 2% lidocaine immediately before the beginning of surgery.

The nerve block was scored as: (a) satisfactory, if the block alone allowed surgery, (b) unsatisfactory, if analgesic implementation (0.1 mg IV fentanyl) or supplementary ankle blocks were required to complete surgery, or (c) failed, if propofol sedation (3–4 mg · kg^-1 · h^-1) was required to complete surgery.

The patients were instructed to ask for postoperative analgesia as soon as they experienced any pain on the operated foot. Postoperative analgesia consisted of 100 mg IV of ketoprofen every 8 h, and the primary end point was defined as the time for the first administration of ketoprofen. The time of recovery of motor (ability to move the ankle) and sensory (recovery of normal pinprick sensation) functions on the operated foot was also recorded by the blinded observer, as well as the time for the first postoperative pain medication. Rescue analgesia with 100 mg IV of tramadol was also available if requested by the patient.

The acceptance of the anesthetic technique was assessed 24 h after surgery using a two-point score: 1 = good, if required, I will repeat it and 2 = bad, I will never repeat it again.

To calculate the required sample size, we took into account results of a previous study (2). Twenty-five patients per group were required to detect a 10-min difference in the onset time and a 4-h difference in postoperative analgesia between the two anesthetic solutions, accepting a two-tailed error of 5% and a ß error of 20% (11).

Statistical analysis was performed using the program Systat 7.0 (SPSS Inc, Chicago, IL). The Mann-Whitney U-test was used to compare continuous variables, whereas categorical data were analyzed using the contingency table analysis and the Fisher’s exact test. Results are presented as median (range) or as a number (percentage). A P value 0.05 was considered as statistically significant.

	Results

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No differences in demographic variables were reported between the two groups. Median (range) age was 47 (21–69) yr in the Levobupivacaine group and 53 (22–70) yr in the Ropivacaine group; weight was 67 (46–90) kg in the Levobupivacaine group and 65 (49–87) kg in the Ropivacaine group; height was 170 (152–183) cm in the Levobupivacaine group and 168 (150–182) cm in the Ropivacaine group. The male to female ratio was 9:16 in the Levobupivacaine group and 6:19 in the Ropivacaine group. The onset time of surgical block was 30 (5–60) min in the Levobupivacaine group and 15 (5–60) min in the Ropivacaine group (P = 0.53).

Four patients (two patients in each group) received supplementary ankle block immediately before the beginning of surgery. All four of these patients also received IV fentanyl supplementation, but in three of these patients, propofol infusion was required to complete surgery (two in the Levobupivacaine group [8%] and one in the Ropivacaine group [4%]; P = 0.99). Patients with failed intraoperative nerve block were then excluded from further data analysis. In six patients of the Levobupivacaine group (24%) and five patients of the Ropivacaine group (20%), IV fentanyl supplementation was required to complete surgery (P = 0.99). However, in seven of these patients, fentanyl supplementation was required during surgery because of pain at the thigh tourniquet, although no pain was reported on the operated foot (four in the Levobupivacaine group [16%] and three in the Ropivacaine group [12%]; P = 0.99).

No differences in the times for recovery of sensory and motor function, or the time for the first request of pain medication, were observed between the two groups (Fig. 1). Three Levobupivacaine patients (12%) and four Ropivacaine patients (16%) asked for rescue tramadol administration during the first 24 h after surgery (P = 0.99). Only one patient in the Levobupivacaine group would prefer a different anesthesia technique for the future if required (in this patient a failed nerve block was reported requiring ankle supplementation and propofol sedation during surgery), whereas all the other patients reported adequate satisfaction with the anesthesia technique.

View larger version (26K): [in this window] [in a new window]   Figure 1. Times for recovery of motor and sensory functions and first request for postoperative analgesic medication after sciatic nerve block performed with 20 mL of either 0.5% levobupivacaine (Levobupivacaine group, n = 25) or 0.5% ropivacaine (Ropivacaine group, n = 25).

	Discussion

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When comparing 0.4 mL/kg of two concentrations of levobupivacaine (0.25% and 0.5%) for supraclavicular brachial plexus block, Cox et al. (8) reported a mean onset time of six to eight minutes. In the present investigation, the onset time observed with sciatic nerve block was much longer than that reported by Cox et al. A possible explanation for this observation is reasonably related to the different types of nerve block because the large size of the sciatic nerve can make the onset of the block less predictable than for other peripheral nerves (12). In fact, Coventry and Todd (13) reported onset times of sciatic nerve block with 0.5% bupivacaine of about 30 min, and similar results have been demonstrated in other previous clinical studies (2,3,14).

In the present study, we used identical volumes and concentrations of levobupivacaine and ropivacaine. Whereas levobupivacaine seems to have the same potency of racemic bupivacaine (15), ropivacaine is nearly 40% less potent than bupivacaine in the first stage of labor (16,17). Further properly designed studies are required to better evaluate the anesthetic potency of levobupivacaine compared with that of ropivacaine. Further, we used the 0.5% concentration of ropivacaine, although it has been demonstrated that increasing its concentration provides some benefits in terms of onset of nerve block (3). Future studies should also be advocated comparing the 0.75% concentration of both ropivacaine and levobupivacaine with clinical profile of nerve block provided by the 0.5% concentration.

Hallux valgus repair is often associated with relevant postoperative pain that can be difficult to control with oral analgesics, whereas the use of long-acting local anesthetics has been advocated to improve the quality of postoperative analgesia (1). Ropivacaine has the advantage of a lower toxic potential as compared with bupivacaine not only at equivalent but also at equipotent doses (4), and for this reason, we switched from bupivacaine to ropivacaine. The reduced toxic potential of ropivacaine is particularly important for lower-limb nerve blocks where a combination of different blocks is usually required and has an increased risk for local anesthetic overdosing. In animal studies, levobupivacaine was associated with a reduced depressant effect on the cardiovascular function than both dex- and racemic bupivacaine (18,19), whereas in healthy volunteers levobupivacaine produced significantly less depression of the cardiac output than bupivacaine (20). Although our data suggest that levobupivacaine is safe, the study was not powered to evaluate the relative safety of levobupivacaine compared with ropivacaine. Properly powered studies with a much larger sample size are required to confirm that levobupivacaine may increase patient safety and compare its toxic potential with that of ropivacaine.

It must also be pointed out that, although our study provides valuable information about the clinical profile of levobupivacaine for sciatic nerve blocks using a posterior approach, our findings may not apply to the use of levobupivacaine with other approaches to the sciatic blocks nor to the use of this drug for the block of the lumbar plexus. Therefore, additional studies might be required to better evaluate the clinical use of levobupivacaine for peripheral nerve blocks. Nonetheless, results of this study demonstrate that sciatic nerve block produced by 0.5% levobupivacaine has similar onset, duration, and intensity as that produced by the same volume and concentration of ropivacaine.

	References

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Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999