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AMBULATORY ANESTHESIA

A Prospective, Randomized, Double-Blind Comparison of Unilateral Spinal Anesthesia with Hyperbaric Bupivacaine, Ropivacaine, or Levobupivacaine for Inguinal Herniorrhaphy

Andrea Casati, MD, Elena Moizo, MD^*, Chiara Marchetti, MD^*, and Federico Vinciguerra, MD^*

*Department of Anesthesiology, Vita-Salute University of Milano, IRCCS H San Raffaele, Milano, Italy; and Department of Anesthesiology, University of Parma, Azienda Ospedaliera Parma, Parma, Italy

Address correspondence and reprint requests to Dr. Andrea Casati, Department of Anesthesiology, University of Parma, Azienda Ospedaliera di Parma, Via Gramsci 13-33100 Parma, Italy. Address e-mail to acasati{at}ao.pr.it

	Abstract

Top Abstract Introduction Methods Results Discussion References

 
In 60 patients undergoing inguinal hernia repair, we compared the clinical profile of unilateral spinal anesthesia produced with either 8 mg of hyperbaric bupivacaine 0.5% (n = 20), 8 mg of hyperbaric levobupivacaine 0.5% (n = 20), or 12 mg of hyperbaric ropivacaine 0.5% (n = 20). The study drug was injected slowly through a 25-gauge Whitacre directional needle and patients maintained the lateral decubitus position for 15 min. The onset time and intraoperative efficacy were similar in the three groups. The maximal level of sensory block on the operative and nonoperative sides was T6 (T12–5) and L3 (/[no sensory level detectable]–T4) with bupivacaine, T8 (T12–5) and L3 (/–T3) with levobupivacaine, T5 (T10–2) and T11 (/–T3) with ropivacaine (P = 0.11, P = 0.23, respectively). Complete regression of spinal anesthesia occurred after 166 ± 42 min with ropivacaine, 210 ± 63 min with levobupivacaine, and 190 ± 51 min with bupivacaine (P = 0.03 and P = 0.04, respectively); however, no differences were observed in time for home discharge (329 ± 89 min with bupivacaine, 261 ± 112 min with levobupivacaine, and 332 ± 57 min with ropivacaine [P = 0.28]). We conclude that 8 mg of levobupivacaine or 12 mg of ropivacaine are acceptable alternatives to 8 mg of bupivacaine when limiting spinal block at the operative side for inguinal hernia repair.

IMPLICATIONS: Comparing spinal block produced with 8 mg of hyperbaric bupivacaine 0.5%, 8 mg of hyperbaric levobupivacaine 0.5%, and 12 mg of hyperbaric ropivacaine 0.5%, this prospective, randomized, double-blind study demonstrated that all 3 local anesthetics have similarly short clinical profiles.

	Introduction

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Spinal anesthesia is widely used for inguinal hernia repair, providing a fast onset and effective sensory and motor blockade. Small doses of a long-acting local anesthetic have been used to provide a short-lasting spinal block (1,2). Limiting the block at the operative side (unilateral spinal anesthesia) using hyperbaric solutions, directional needles, and lateral decubitus position maintained for a certain period has been proposed as a means to obtain a high-quality and long-duration analgesia, mainly on the operative side, when small doses of bupivacaine are used (3–5).

Pure S-enantiomers, ropivacaine and levobupivacaine, have been introduced into clinical practice. The clinical profile of spinal ropivacaine and levobupivacaine has been evaluated in volunteers (6,7) and clinical studies (8,9); however, no direct comparative data are available on the use of these two new drugs to produce a preferential distribution of spinal anesthesia to the operative side for inguinal hernia repair. The aim of this prospective, randomized, double-blind study was to compare the use of relatively small equipotent doses of hyperbaric bupivacaine, levobupivacaine, and ropivacaine when providing unilateral spinal anesthesia.

	Methods

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With the approval of the Institutional Ethical Committee and written informed consent of the patient, 60 ASA physical status I–II patients, scheduled for elective inguinal hernia repair under spinal anesthesia, were prospectively enrolled. After standard volume expansion with 10 mL/kg Ringer’s acetate solution, patients were premedicated with IV midazolam (0.03 mg/kg). Standard monitoring was used. Baseline arterial blood pressure was recorded at the end of volume expansion, before inducing spinal block.

All patients were placed in a lateral position with the side to be operated on dependent whereas the vertebral column was kept as horizontal as possible by tilting the table. Dural puncture was performed with the midline approach at the L1-2 or L2-3 interspace using a 25-gauge Whitacre spinal needle. According to a computer-generated randomization sequence, patients were randomly allocated to receive 8 mg of hyperbaric bupivacaine 0.5% (group bupivacaine, n = 20), 8 mg of hyperbaric levobupivacaine 0.5% (group levobupivacaine, n = 20), or 12 mg of hyperbaric ropivacaine 0.5% (group ropivacaine, n = 20). The 1:1.5 equipotency ratio between levobupivacaine, bupivacaine, and ropivacaine on the other side was based on what has been reported in previous dose-finding studies in volunteers (6,7).

Hyperbaric solutions of ropivacaine and levobupivacaine were obtained by one of the authors, not involved in further patient evaluation, by diluting 20 mg of the plain 0.75% solution with glucose and sterile water to obtain a 0.5% concentration of local anesthetic with 8% glucose. After free flow of cerebrospinal fluid was observed, the opening of the spinal needle was turned toward the dependent side and the designated dose of local anesthetic solution was injected slowly (injection speed: 2 mL/min) without further aspiration maneuvers (3,4). As is routine at our Institution, all spinal blocks were placed outside the operating room (OR) in a properly designed block room. The lateral decubitus position was maintained for a 15-min period; afterward, patients were turned supine, transferred to the OR, and surgery was started.

An independent, blinded observer evaluated the evolution of sensory and motor blocks on both sides every 5 min until achieving readiness for surgery, and then every 30 min until complete regression of spinal block. At the same times cardiovascular variables were also recorded. Sensory block was assessed as complete loss of pinprick sensation (22-gauge hypodermic needle). Motor block was assessed using a modified Bromage scale by asking the patient to flex the limb at the hip, knee, and ankle joints (0 = no motor block, 1 = hip blocked, 2 = hip and knee blocked, 3 = hip, knee, and ankle blocked). The patient, surgeon, and nursing staff taking care of the patients throughout the study were blinded to patient grouping.

Patients were judged ready for surgery when complete loss of pinprick sensation at T10 was reported on the operative side with concomitant complete motor block of the ipsilateral leg. The inability to reach a sensory block at T10 within 30 min after spinal injection was considered as a technical block failure, and the patient was excluded from further analysis.

Clinically relevant hypotension (decrease in systolic arterial blood pressure >30% of baseline) was initially treated with a rapid infusion of 200 mL of normal saline over 10 min. If this was ineffective, 5 mg of etilephrine (Effortil; Boehringer Ingelheim, Italy) was given IV. Bradycardia (decrease in heart rate to <45 bpm) was treated with 0.5 mg of atropine IV.

Times from the end of the spinal injection to readiness for surgery (onset time), as well as the maximal level of sensory block on both sides, time for complete regression of spinal block, and eligibility for home discharge were also recorded. Criteria for home discharge were stable vital signs, ability to tolerate liquids by mouth, and to walk and void spontaneously, with no nausea or pain.

Propofol sedation was provided (continuous infusion of 2–3 mg · kg^–1 · h^–1) if required by the patient.

The occurrence of adverse events, including nausea, vomiting, and itching was also recorded. Patient acceptance with the anesthesia technique was evaluated using a 2-point scale: 1) satisfied: "I will accept the same procedure if required in the future"; 2) unsatisfied: "I would prefer a different anesthesia technique for future operations." Postoperative analgesia consisted of 10 mg of oral ketorolac (Lixidol; Roche, Monza, Italy) at request.

A follow-up evaluation was performed the day after surgery by asking patients about occurrence of pain, postdural puncture headache, and dysesthesia in the lower limbs or buttocks.

The calculation of the required sample size was based on mean and standard deviation of complete regression of spinal block after unilateral spinal anesthesia for outpatient knee arthroscopy reported in previous investigations (6–8): 20 patients per group were required to detect a 30-min difference in time for complete regression of spinal anesthesia with an expected effect size to standard deviation ratio of 0.9, and accepting a two-tailed error of 5% and a ß error of 20% (10).

Statistical analysis was performed using the program Systat 7.0 (SPSS Inc., Chicago, IL). Data distribution was first evaluated using the Kolmogorov-Smirnov test. Anthropometric data, onset times of surgical block, and surgery times were analyzed with the analysis of variance, whereas changes over time were analyzed with a two-way analysis of variance for repeated measures. The Dunnett and Scheffé tests were also used for "post hoc" comparisons. Categorical variables were analyzed using the contingency tables analysis and the ² test with the appropriate corrections. A P value 5% was considered as significant. Continuous variables were presented as mean ± SD or as median (range); categorical data were presented as number (%).

	Results

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No differences in age, weight, height, male-to-female ratio, ASA physical status distribution, as well as surgical and OR times were observed among the three groups (Table 1).

Figure 1 shows the evolution of sensory block on both the operative and nonoperative sides in all groups. In each of the 3 groups, the maximal level of sensory block was higher on the operative than nonoperative side (P = 0.0005, P = 0.0005, and P = 0.0005 in group bupivacaine, levobupivacaine, and ropivacaine, respectively). No differences in the maximal level of sensory block were observed among groups on both the operative (group bupivacaine: T6 [T12–5]; group levobupivacaine: T8 [T12–5]; group ropivacaine: T5 [T10–2] [P = 0.11]) and nonoperative sides (group bupivacaine: L3 [/(no sensory level detectable)–T4]; group levobupivacaine: L3 [/–T3]; group ropivacaine: T11 [/–T3] [P = 0.23]). A strictly unilateral sensory block (no sensory block detectable at all on the nonoperative side throughout the study period) was observed in 6 patients of group bupivacaine (30%), 9 patients of group levobupivacaine (45%), and 7 patients of group ropivacaine (35%) (P = 0.605), whereas a strictly unilateral motor block (Bromage score = 0 on the nonoperative side throughout the study period) was observed in 14 patients of group bupivacaine (70%), 16 patients of group levobupivacaine (80%), and 16 patients of group ropivacaine (80%) (P = 0.68).

View larger version (26K): [in this window] [in a new window]   Figure 1. Evolution of sensory block on both operative and nonoperative sides after unilateral spinal anesthesia performed with 8 mg of 0.5% hyperbaric bupivacaine (group bupivacaine, n = 20), 8 mg of 0.5% hyperbaric levobupivacaine (group levobupivacaine, n = 20), or 12 mg of 0.5% hyperbaric ropivacaine (group ropivacaine, n = 20) for inguinal herniorrhaphy. *P < 0.05 versus operative side.

Complete regression of spinal anesthesia was faster in patients receiving ropivacaine (166 ± 42 min; range, 107–278 min) than in those receiving levobupivacaine (210 ± 63 min; range, 130–332 min) or bupivacaine (190 ± 51 min; range, 104–281 min) (P = 0.03 and P = 0.04, respectively). Complete regression of motor block 180 min after spinal injection was observed in 16 patients of group levobupivacaine (84%) and 19 patients of group ropivacaine (95%) but only in 11 patients of group bupivacaine (55%) (P = 0.02).

In no case was urinary retention reported, and time to micturition was 298 ± 68 min in group bupivacaine, 255 ± 58 min in group levobupivacaine, and 302 ± 48 min in group ropivacaine (P = 0.32). Criteria for home discharge were fulfilled after 329 ± 89 min in group bupivacaine, 261 ± 112 min in group levobupivacaine, and 332 ± 57 min in group ropivacaine (P = 0.28). Eighteen patients in groups levobupivacaine (90%) and ropivacaine (90%), and 16 patients in group bupivacaine (80%) requested ketorolac pain medication (P = 0.89), whereas none of the studied patients requested tramadol administration.

	Discussion

Top Abstract Introduction Methods Results Discussion References

 
Although the possibility and practicality of limiting a spinal block to the operative side is controversial, several groups described the use of this technique to limit the extent of spinal block to those dermatomes mainly involved in the surgery, and positive findings have been reported in terms of cardiovascular stability (3,11) and patient discharge (3,12–14). Results of this prospective, randomized, double-blind study demonstrated that 8 mg of hyperbaric levobupivacaine, 8 mg of hyperbaric bupivacaine, and 12 mg of hyperbaric ropivacaine produce a unilateral spinal block with a similar clinical profile, and similar restriction of both sensory and motor blocks to the operative side.

Based on reports in volunteer studies (6,7), we used the same dose of levobupivacaine and bupivacaine, but a 50% larger dose of ropivacaine. Interestingly, irrespective of the theoretically equipotent doses used in the present investigation, patients receiving ropivacaine showed a faster resolution of spinal anesthesia compared with the other two groups, even though this was not associated with a significant acceleration of home discharge. Even though complete resolution of spinal block occurred on average 3 hours after spinal injection, the recovery of spontaneous voiding significantly delayed fulfillment of home discharge criteria, and this could reduce the applicability of this technique to outpatient procedures. Mulroy et al. (15) suggested a relaxation of the requirements for voiding after short-duration spinal anesthesia in outpatients; however, inguinal hernia repair has been characterized as high risk for urinary retention (16), and further studies with smaller doses of the three drugs should be performed to evaluate the use of this technique for outpatient procedures. Nonetheless, Breebaart et al. (9), evaluating bladder function with urinary bladder scanning after day-case spinal anesthesia with 10 mg of levobupivacaine, 15 mg of ropivacaine, or 60 mg of lidocaine reported that the incidence and degree of micturition problems were not different with the 3 drugs. In their study, the authors also reported L2 regression of sensory block after 173 minutes and 167 minutes and home discharge after 311 minutes and 305 minutes with levobupivacaine and ropivacaine, respectively (9). In our study, the doses used were 20% smaller than those reported by Breebaart et al.: this resulted in faster regression of spinal block, but was not associated with an earlier fulfillment of home discharge criteria.

Evaluating the clinical profile of spinal anesthesia performed with 8, 10, 12, and 14 mg of ropivacaine and 8 mg of bupivacaine, Gautier et al. (8) reported that ropivacaine 10 mg induced a shorter-lasting block than bupivacaine 8 mg, but was also associated with a poorer quality of intraoperative anesthesia. However, when increasing the dose of ropivacaine to 12 mg (the same dose ratio we used in our study), these authors reported characteristics of sensory and motor blocks similar to those produced with 8 mg of bupivacaine.

In a dose-finding study on unilateral spinal block for outpatient knee arthroscopy, we recently demonstrated (14) that reducing the dose of hyperbaric bupivacaine from 8 mg to 4 mg can result in a similarly effective spinal block with a significant acceleration of home discharge. Dobrydnjov et al. (5) reported on restricted spinal block using 6 mg of hyperbaric bupivacaine with or without clonidine for inguinal hernia repair, and demonstrated complete regression of sensory and motor blocks after 209 ± 57 minutes, and home discharge after 432 ± 67 minutes. In their study, the authors reported a strictly unilateral spinal block in 47% of patients; however, they also reported an insufficient level of analgesia in up to 33% of cases. The success rate of spinal block we observed when using a nearly 30% larger dose of bupivacaine was higher than that reported in the study by Dobrydnjov et al., without being associated with a significant prolongation of the time for home discharge.

Buckenmaier et al. (17) described the use of doses of ropivacaine as small as 4 mg with the addition of 20 µg of fentanyl for anorectal surgery in an ambulatory setting, and observed complete regression of spinal block after <2 hours, with the patient discharged home nearly 3 hours after spinal injection. However, anorectal procedures require a lower level of spinal anesthesia compared with inguinal hernia repair, and this can account for the acceptable success rate reported by Buckenmaier et al. when using such a small dose of ropivacaine. Further dose-finding studies with smaller doses of both ropivacaine and levobupivacaine should be performed to better evaluate the clinical profile of these two drugs for inguinal hernia repair.

Limiting the block to the operative side by just using small doses of local anesthetic, injected slowly through pencil-point, directional needles in patients maintaining the lateral decubitus position for 10–15 minutes after the injection is a very simple and effective way to optimize the efficiency of spinal block when small doses of local anesthetic are used (3,18), and has also been demonstrated to be very effective and useful for outpatients (3–5,12–14,19). Nonetheless, most anesthesiologists are still concerned by the cost of "wasting" 15 minutes of the OR time. This disadvantage may be much more theoretical than practical, because comparing preparation times (from spinal injection to readiness for surgery) of either unilateral or conventional bilateral spinal block with the same small dose of bupivacaine resulted in only a 5-minute difference (12): statistically significant but clinically negligible (12,18). Moreover, this small disadvantage is also eliminated by the organization of our OR, because placing all regional anesthesia techniques (including spinal anesthesia) outside the OR in a properly designed block room has been clearly demonstrated to be associated with the least anesthesia-controlled time (20), with significant reduction of anesthesia-related costs.

The interest in using small doses of long-acting drugs to produce a short-duration spinal block has grown after the increasing evidence of the occurrence of transient neurologic symptoms (TNS) with spinal lidocaine (21,22). Reducing the dose of spinal lidocaine to 20 mg reduces the incidence of TNS from 32% to 3.6%; however, up to 25 µg of intrathecal fentanyl had to be administered to provide adequate analgesia, and this resulted in postoperative nausea and vomiting in 18% of cases and pruritus in up to 41% of patients (23), whereas the incidence of TNS was, however, nearly 3 times more frequent than that reported with bupivacaine (22). In our investigation, we did not report any TNS in any group. However, the study was not powered to detect such a complication, and further, adequately powered, randomized studies should be performed to evaluate the incidence of TNS associated with spinal levobupivacaine and ropivacaine.

In conclusion, results of this prospective, randomized, double-blind study demonstrate that 8 mg of levobupivacaine or 12 mg of ropivacaine are acceptable alternatives to 8 mg of bupivacaine when limiting spinal anesthesia at the operative side for inguinal hernia repair. Interestingly, the use of a 1.5 to 1 equipotency ratio between ropivacaine and levobupivacaine or bupivacaine resulted, nevertheless, in a shorter duration of spinal anesthesia, even if this was not associated with a shorter home discharge time.

	References

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (9) Citing Articles via Google Scholar Google Scholar Articles by Casati, A. Articles by Vinciguerra, F. Search for Related Content PubMed PubMed Citation Articles by Casati, A. Articles by Vinciguerra, F. Related Collections Regional Anesthesia Pharmacology

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