Postoperative pain after hallux valgus repair can be severe and difficult to control with oral analgesics. Regional anesthesia provides good postoperative pain relief after foot surgery . In our orthopedics department, a standard thigh tourniquet is used for hallux valgus repair. Combined peripheral nerve block of the sciatic and femoral nerves is a widely used anesthetic technique for leg surgery when a thigh tourniquet is used [2-4]. The expected duration of postoperative analgesia ranges between 14 and 18 h when bupivacaine is used ; although mepivacaine has a faster onset time of surgical anesthesia than bupivacaine, it provides a shorter duration of postoperative pain relief [6,7]. Ropivacaine is a new, long-acting local anesthetic with a favorable toxicity profile compared with bupivacaine . It has been reported that the use of either bupivacaine or ropivacaine produces similar anesthetic characteristics during brachial plexus blockade [8-12]. However, no study has addressed the perioperative clinical properties of ropivacaine when used for combined sciatic-femoral nerve block.
The goal of the present prospective, double-blind study was to compare intraoperative and postoperative clinical properties of ropivacaine, bupivacaine, and mepivacaine when used for peripheral block of sciatic and femoral nerves.
The study protocol was approved by our hospital ethical committee, and informed consent was obtained from each patient. Forty-five ASA physical status I or II patients, aged 25-65 yr, scheduled for elective hallux valgus repair under combined sciatic-femoral nerve block were enrolled in the study. Patients receiving chronic analgesic therapy, as well as patients with diabetes or peripheral neuropathies, were excluded.
No premedication was administered before the block, and standard ASA monitors were used during surgical procedures. Baseline arterial blood pressure and heart rate were recorded, a 20-gauge IV cannula was inserted into the forearm, and all patients received a 5-mL [center dot] kg-1 [center dot] h-1 infusion of lactated Ringer's solution. Surgery was performed in all patients using a standard thigh tourniquet inflated 100 mm Hg higher than systolic arterial blood pressure.
Patients were randomized to receive 0.75% ropivacaine (ROPI, n = 15), 0.5% bupivacaine (BUPI, n = 15), or 2% mepivacaine (MEPI, n = 15). Sterile syringes containing a local anesthetic solution were prepared in a double-blind fashion by one of the authors not involved in the management of studied patients. For the femoral block, 10 mL of anesthetic solution was used; for the sciatic block, 15 mL of the same solution was used. Nerve blocks were performed with the aid of a nerve stimulator (Plexival, Medival, Italy) using a short-beveled, Teflon-coated stimulating needle (Locoplex, Vygon, France) (3.5 cm long, 25-gauge for femoral nerve block and 12 cm long, 22-gauge for sciatic nerve block). Stimulation frequency was set at 2 Hz. The intensity of the stimulating current was initially set to deliver 1 mA, and then gradually decreased to <0.5 mA. Paresthesia was never intentionally sought. A multiple injection technique was used to elicit specific twitches on nerve stimulation to confirm exact needle location [3,4,13]. First, we performed the femoral nerve block, which was followed by the sciatic nerve block. For the femoral nerve block, the needle was inserted lateral to the femoral artery at the intersection between the femoral artery and a line connecting the anterior superior iliac spine to the pubic tubercle. The stimulating needle was then inserted and redirected to elicit contraction of vastus medialis, vastus intermedius, and vastus lateralis. Sciatic nerve block was performed according to the classic Labat approach: a line was drawn from the posterior superior iliac spine to the midpoint of the greater trochanter. A perpendicular line was drawn bisecting this line, which extended 5 cm caudally. A second line was drawn from the greater trochanter to the sacral hiatus. The intersection of this line with the perpendicular line indicated the point of needle entry. Even for sciatic nerve block, the stimulating needle was inserted and redirected to elicit flexion of the foot, extension of the foot, and contraction of biceps femoris. If the injection of 1 mL of the study solution immediately stopped the muscular twitch, the needle location was considered adequate, and the remaining volume of anesthetic solution was injected. For both femoral and sciatic nerve blocks, the total volume of anesthetic solution was equally divided among each of considered twitches.
Onset time of surgical anesthesia for the operated limb was recorded by an observer blinded to the anesthetic solution. Time 0 for clinical assessments was the completion of anesthetic injection at the sciatic nerve. Because a thigh tourniquet was always inflated, we considered adequate surgical anesthesia (readiness for surgery) to be the loss of pinprick sensation (22-gauge) for both femoral and sciatic distributions and the presence of complete motor blockade at the knee, ankle, and toes of the operated limb.
The quality of the block was judged according to the need for supplementary IV analgesics and sedation: satisfactory = neither sedation nor IV fentanyl; unsatisfactory = need for additional IV fentanyl >or=to0.1 mg and sedation (continuous IV propofol infusion 2 mg [center dot] kg-1 [center dot] h-1); failed block = general anesthesia. Patients with a failed nerve block were excluded from the study.
Arterial blood pressure, heart rate, and hemoglobin oxygen saturation were recorded at 5, 10, 15, and 30 min.
Resolution of motor block for the knee and the foot of the operated leg, as well as onset time of postsurgical pain and first pain medication administration, were recorded. Postoperative analgesia consisted of ketoprofen 100 mg IV if required. Degree of pain was measured by using a 100-mm visual analog scale (VAS) at the onset of postsurgical pain. Acceptance of the anesthetic technique was assessed 24 h postoperatively using a 2-point score: 1 = good, if necessary, I will repeat it; 2 = bad, I will never repeat it again. Patients were questioned regarding neurological complications at discharge from the orthopedic ward and 1 wk after hospital discharge (at first routine postoperative orthopedic examination).
Statistical analysis was performed using Stat-View 3.0 (Abacus Concepts, Berkeley, CA). Demographic data, onset and resolution of sensory and motor block, and duration of postoperative analgesia were analyzed by using analysis of variance. Dunnett's and Scheffe's tests were used for multiple comparisons. Analysis of variance for repeated measures was used to analyze changes of hemodynamic variables compared with baseline. Adequacy of intraoperative anesthesia and acceptance of anesthetic technique were analyzed by using contingency Table analysiswith Fisher's exact test. A value of P < 0.05 was considered significant. Continuous variables are presented as mean +/- SD; ordinal data are presented as median (range).
The three groups of patients were similar with respect to age, weight, height, ASA physical status, male/female ratio, and surgical times (Table 1). Sensory block for sciatic and femoral nerve distributions required 14 +/- 17 min in Group ROPI, 12 +/- 8 min in Group MEPI, and 37 +/- 27 min in Group BUPI (P = 0.002) (Figure 1). Even the onset of motor block was significantly shorter in Group ROPI (14 +/- 8 min) and in Group MEPI (15 +/- 9 min) compared with Group BUPI (51 +/- 32 min) (P = 0.001) (Figure 1).
Two patients in Group BUPI (13.3%) and one patient in Group MEPI (6.6%) demonstrated unsatisfactory blocks manifested by tourniquet pain at the thigh (P > 0.05); however, general anesthesia was never required.
No significant changes in arterial blood pressure, heart rate, or hemoglobin oxygen saturation were observed during the first 30 min after block placement in the three groups of patients.
(Table 2) shows the duration of motor block of the knee and foot of the operated leg and time from the end of anesthetic injection to onset of postsurgical pain (duration of analgesia) in the three groups of patients. Resolution of motor block was similar in Groups ROPI and BUPI but significantly longer than that observed in Group MEPI (P = 0.005 for knee and P = 0.0001 for foot, respectively).
The degree of pain measured at the onset of postsurgical pain was similar in the three groups (ROPI 52 +/- 21 mm, BUPI 60 +/- 25 min, MEPI 68 +/- 32 min). However, the duration of postoperative analgesia was statistically and clinically shorter in Group MEPI than in the other two groups (P = 0.0001). Patients in Group ROPI showed an intermediate duration of postoperative analgesia (Table 2). Postoperative analgesic consumption was significantly reduced in Groups ROPI and BUPI compared with Group MEPI. During the first 24 h after surgery, seven patients in Group ROPI (46%) and six patients of Group BUPI (40%) did not require pain medication, whereas all patients in Group MEPI required postoperative analgesics.
Acceptance of the anesthetic technique was good in all patients, and no significant differences were observed among the three groups. One patient in Group BUPI reported prolonged hypesthesia of the operated leg, which spontaneously resolved 5 days after surgery. However, no persistent neurologic deficit was observed in any studied patients 1 wk after surgery.
The most interesting finding of this study is that 0.75% ropivacaine has an onset time significantly shorter than 0.5% bupivacaine and similar to that provided by 2% mepivacaine when used for combined sciatic-femoral nerve block. Postoperatively, 0.75% ropivacaine and 0.5% bupivacaine allowed prolonged analgesia with a significant decrease in analgesic requirements compared with 2% mepivacaine.
Hallux valgus repair is a minor orthopedic procedure; however, it produces significant postoperative pain that can be difficult to control with oral analgesics . For this reason, the use of a long-acting local anesthetic should be advocated to improve the quality of postoperative analgesia.
Our study demonstrated that 0.5% bupivacaine, when used for combined sciatic-femoral nerve block, may require up to 50 min to produce adequate surgical anesthesia. Although both the addition of vasoconstrictors and alkalinization significantly reduce bupivacaine onset times for sciatic block , the wide and unpredictable latency of the block conveyed with this drug may be unfavorable. Previous studies of epidural and brachial plexus blockade reported no significant differences in median onset time of similar concentrations of ropivacaine and bupivacaine [10-12,14,15]. However, no studies have compared the clinical properties of ropivacaine or bupivacaine when used for combined sciatic-femoral nerve block.
In a study evaluating the local anesthetic efficacy of ropivacaine, Nolte et al.  reported that plain ropivacaine is optimally effective at concentrations between 0.5% and 0.75%. However, the equipotency ratio between ropivacaine and bupivacaine, when used for peripheral nerve block, is not available. A reasonable explanation for the differences in the onset of the block observed between ropivacaine and bupivacaine might be the different solution concentration of the two local anesthetics used in the present study . It has been demonstrated that the depth of anesthetic block is intensified as the dose of ropivacaine is increased [8,18]. The lower potential for systemic toxicity compared with bupivacaine [18,19,20], enables ropivacaine to be used for surgical anesthesia in concentrations up to 1%. This higher gradient of concentration may facilitate diffusion of local anesthetic molecules into peripheral nervous tissue compared with 0.5% bupivacaine, thus improving the onset of nerve block.
Because quick onset of the block and prolonged postoperative analgesia are important goals in regional anesthesia, results of the present study suggest that 0.75% ropivacaine is the most suitable choice of local anesthetic for combined sciatic-femoral block, providing an onset similar to mepivacaine and postoperative analgesia intermediate between bupivacaine and mepivacaine.
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© 1998 International Anesthesia Research Society
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