Anesth Analg 2003;97:56-61
© 2003 International Anesthesia Research Society
AMBULATORY ANESTHESIA
Subarachnoid Small-Dose Bupivacaine Versus Lidocaine for Cervical Cerclage
Yaakov Beilin, MD*,
,
Jeffrey Zahn, MD*,
Sharon Abramovitz, MD
,
Howard H. Bernstein, MD*,,
Sabera Hossain, MS
, and
Carol Bodian, DrPH
Departments of *Anesthesiology,
Obstetrics, Gynecology, and Reproductive Sciences, and
Biomathematical Sciences, Mount Sinai School of Medicine, New York University, New York, New York; and
Department of Anesthesiology, Weill Medical College of Cornell University, New York, New York
Address correspondence and reprint requests to Yaakov Beilin, MD, Mount Sinai School of Medicine, Department of Anesthesiology, Box 1010, One Gustave L. Levy Place, New York, NY 10029-6574. Address e-mail to Yaakov.Beilin{at}mountsinai.org
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Abstract
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Cervical cerclage is often performed as an outpatient procedure under subarachnoid anesthesia. Lidocaine was historically the drug of choice for short procedures but has fallen out of favor because of concerns of transient neurologic symptoms (TNS). We performed this study to determine whether small-dose bupivacaine is an acceptable alternative to lidocaine for cervical cerclage. We randomized 59 women to receive either subarachnoid isobaric lidocaine 30 mg or hyperbaric bupivacaine 5.25 mg. Fentanyl 20 µg was added to both local anesthetics, and the total volume was diluted to 3 mL with 0.9% saline. Onset and highest dermatomal level of sensory block; quality of anesthesia; hypotension; and times until T12 regression, return of lower extremity motor function, ambulation, and micturition were recorded. Symptoms of TNS were evaluated by telephone interview 24 h after surgery. We did not find any significant difference in onset or recovery times between the groups, with the exception of a longer duration until return of lower extremity motor strength in the lidocaine group. Symptoms consistent with TNS that resolved spontaneously within 48 h were reported by two women in the lidocaine group but by none in the bupivacaine group. We conclude that subarachnoid bupivacaine offers a satisfactory alternative to subarachnoid lidocaine for cervical cerclage.
IMPLICATIONS: We found that small-dose subarachnoid bupivacaine (5.25 mg) with fentanyl 20 µg provides reliable anesthesia for cervical cerclage and exhibits a pharmacodynamic profile similar to that of small-dose lidocaine.
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Introduction
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Cervical cerclage is an ambulatory surgical procedure performed to correct an incompetent cervix in the pregnant woman. The operation is usually of short duration, lasting <30 min, and is often accomplished under a subarachnoid anesthetic (1).
Lidocaine is often used as the local anesthetic for subarachnoid anesthesia when a short duration of action is desired. However, lidocaine may be associated with transient neurologic symptoms (TNS), a condition characterized by transient pain or dysesthesias in the buttock or leg (2,3). Because lidocaine is associated with TNS, it might be preferable to use a different short-acting local anesthetic with an infrequent incidence of TNS for brief surgical procedures (4).
Bupivacaine, a local anesthetic with significantly less associated risk of TNS than lidocaine (2,3), is generally considered a long-acting local anesthetic that can provide anesthesia for up to 4 h after a single subarachnoid dose (5). Decreasing the dose of bupivacaine and combining it with an opioid will shorten the duration of action but still provide adequate subarachnoid anesthesia for some surgical procedures, including knee arthroscopy and in vitro fertilization (6,7). This study was performed to determine whether small-dose bupivacaine, combined with fentanyl, can provide adequate subarachnoid anesthesia for cervical cerclage with a similar pharmacodynamic profile to that of lidocaine and with a decrease in anesthetic complications.
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Methods
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The protocol was approved by the IRB of Mount Sinai School of Medicine of New York University, and written, informed consent was obtained from each subject. All subjects were women scheduled to undergo elective cervical cerclage during the first or second trimester (between the 1st and 26th weeks of pregnancy). Those with preexisting neurologic disease or back pain were excluded. All women had agreed to receive a combined spinal-epidural (CSE) technique for the cerclage procedure.
Before placement of the CSE, each subject was randomly assigned to one of two groups on the basis of the local anesthetic to be used for the subarachnoid block. Women in the lidocaine group received 2 mL of lidocaine 1.5% (30 mg) with fentanyl 20 µg and 0.6 mL of 0.9% saline, for a total injectate volume of 3 mL. Women in the bupivacaine group received 0.7 mL of bupivacaine 0.75% (5.25 mg) in dextrose 8.25% with fentanyl 20 µg and 1.9 mL of 0.9% saline, for a total injectate volume of 3 mL. All medication was drawn into a 3-mL syringe that had markings at 0.1-mL intervals.
A computer-generated random number program was used to assign each subject to her study group. The results of the randomization were sealed in opaque envelopes and opened sequentially immediately before the CSE procedure. The study medication was prepared by an anesthesiologist who was involved neither in the study nor in the clinical care of the patient. Neither the research assistant who performed all of the subsequent assessments nor the women were aware of study group assignment.
After prehydration with 500–1000 mL of a crystalloid solution and with the woman seated perpendicular to the long axis of the operating room table, a CSE anesthetic was placed at the L2-3 or L3-4 interspace by using the loss-of-resistance-to-air technique. Once the epidural space was identified with an 18-gauge Hustead needle, a 123-mm long 25-gauge Sprotte needle was inserted through the epidural needle into the subarachnoid space. Both the epidural needle and the spinal needle were directed with the bevel in a cephalad direction. On aspiration of cerebrospinal fluid, the anesthetic solution was administered, and the spinal needle was removed. A 20-gauge epidural catheter was inserted into the epidural space and secured with tape. Immediately after the epidural catheter was secured, the patient was positioned supine.
The time of injection of subarachnoid medication was recorded and noted as t0. Sensory level was assessed every 3 min thereafter by using an alcohol swab to detect differences in cold perception. The level was assessed bilaterally in the midclavicular line. A T12 sensory level was considered adequate for cervical cerclage (8). Once a T12 level was achieved, the woman was positioned in the lithotomy position, and the obstetrician was allowed to proceed. All patients were catheterized with a urinary catheter before the onset of the procedure, per the obstetric protocol. The adequacy of the anesthetic was further evaluated by asking the woman at the start of the procedure to rate her level of comfort as complete, adequate, or inadequate, in which case any supplemental analgesic medication—epidural or IV—was recorded. The highest dermatomal level of sensory block was determined by repeating the alcohol swab test every 3 min until the level was constant for 2 consecutive tests. Thereafter, the dermatomal level was tested every 15 min until the level receded to T12 (T12 regression). The presence of pruritus, nausea, or vomiting and their intensity (mild, moderate, or severe) were recorded every 15 min until the end of the study. A noninvasively measured blood pressure (BP) was recorded every 5 min, and any decrease in systolic BP of more than 20% was noted as a complication. Treatment of a decrease in BP with ephedrine was at the discretion of the anesthesiologist.
When the cerclage procedure was completed, motor block was assessed every 15 min by using the modified Bromage scale (0, no motor block; 1, unable to raise extended leg, able to move knee and foot; 2, unable to raise extended leg or knee, able to move foot; 3, complete motor block of lower limb) until the woman had no motor block (score of 0). Once this score was achieved, the research assistant encouraged the woman every 15 min to ambulate and urinate. When ambulation and urination were accomplished, the initial phase of the study was completed.
On postoperative Day 1, approximately 24 h after surgery, a research assistant blinded to study group contacted each patient by telephone to inquire about any anesthetic complications, with a particular focus on TNS. A standardized questionnaire designed to ensure uniformity was used by the research assistant (Fig. 1). All women were first asked whether they had recovered completely from their anesthetic. Regardless of a yes or no answer to the first question, all women were asked a series of questions to assess neurologic symptoms, including TNS. TNS was defined as pain or dysesthesia in the legs or buttock after recovery from the anesthetic (9). Women were asked to rate the intensity of any symptom on a 0 to 10 verbal scale, with 0 representing no problem and 10 representing the worst imaginable intensity. If any complication was noted, including TNS, the woman was contacted daily thereafter until resolution of the complication.
All data were entered into an Excel database (Microsoft, Redmond, WA) and converted to a SAS file (SAS Institute Inc., Cary, NC) for statistical analysis (10). The primary goal of this study was to determine whether there was a difference in the duration of action (t0 until anesthetic recovery) between the bupivacaine and the lidocaine groups. We expected times to have a log-normal distribution. Sample size estimates for log-normal variables were derived by the method of van Belle and Martin (11). Assuming the duration of action of the bupivacaine group to be 150 min and that of lidocaine to be 120 min, and assuming the coefficient of variation (SD/mean) in each group to be 0.30, it was predicted that the study would require 29 women in each group to provide 80% power to detect a 30-min difference in recovery times, by using a two-tailed test at the 5% level of significance.
Once data were collected, nonparametric tests were performed for group comparisons, because the log-normal assumption could not be validated for all time points. Wilcoxon-Mann-Whitney tests were performed to compare the times between the two groups. The 95% confidence intervals of the median times in the lidocaine group versus the bupivacaine group were estimated by the Hodges-Lehmann technique with StatXact 4 for Windows (Cytel Software Corp., Cambridge, MA).
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Results
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We enrolled 59 women in the study: 30 women in the bupivacaine group and 29 in the lidocaine group. Demographic data of the women in the two groups are presented in Table 1. All 59 women had at least a T12 dermatomal level of sensory anesthesia before the onset of the procedure. In the lidocaine group, all 29 women rated their analgesia as complete at the beginning of the procedure, and none required supplemental analgesia. In the bupivacaine group, 29 of 30 rated their analgesia as complete at the beginning of the procedure, and 1 rated the analgesia as incomplete. This woman achieved a T12 level of anesthesia 14 min after the subarachnoid block was placed, but she felt the surgical stimulation and required additional epidural local anesthetic (8 mL of lidocaine 2%) to achieve adequate surgical anesthesia (Table 2). An additional woman in the bupivacaine group required additional epidural medication during the procedure, 45 min after the subarachnoid medication had been administered. Both these patients were included in all subsequent analyses. The highest dermatomal level was the same on the right and left sides within groups: T7 in the bupivacaine group and T6 in the lidocaine group (P = not significant). The highest level occurred within 9 min in the bupivacaine group and within 6 min in the lidocaine group (P = not significant).
For the study variables measured, the order of recovery from fastest to slowest in both groups was a Bromage score of 0, T12 regression, ambulation, and micturition. Between groups there was no significant difference in the time until T12 regression (median time was 90 min in both groups) and the time until ambulation (median time was 117 min in both groups). The median time until a Bromage score of 0 was less in the bupivacaine group than in the lidocaine group (56 versus 75 min; P = 0.04), but the median time until micturition was more in the bupivacaine group than in the lidocaine group (164 versus 133 min; P = 0.12; 95% CI for difference in medians, -5 to 65) (Table 2).
There were three cases, all mild, of nausea in the bupivacaine group and five in the lidocaine group, of which three were mild and two were moderate. All cases of nausea occurred after surgery, except for one in the lidocaine group that occurred intraoperatively 9 min after the subarachnoid medication was administered. One woman in each group vomited. Pruritus was a frequent complaint, affecting 16 patients in the bupivacaine group and 15 in the lidocaine group. Most cases of pruritus occurred after surgery, except for three in the lidocaine group and two in the bupivacaine group that occurred intraoperatively. All cases of pruritus were mild except for three in the bupivacaine group; two cases were moderate, but one was severe and required postoperative IV naloxone 40 µg. There were two moderate cases of pruritus in the lidocaine group, neither of which required treatment. The woman who required naloxone did not require supplemental analgesia. Few women developed hypotension in either group (two in the lidocaine group and three in the bupivacaine group), and only one in the bupivacaine group received ephedrine 10 mg IV.
On postoperative Day 1, all women reported that they had recovered completely from their anesthetic. However, when questioned about neurologic symptoms, two women in the lidocaine group reported symptoms consistent with TNS. Both reported pain in the buttocks that radiated into the right thigh, with a numeric score rating of 2. No woman reported back pain or difficulty with either ambulation or urination. One woman in the lidocaine group complained of a mild postdural puncture headache (score of 2). All complaints resolved spontaneously by postoperative Day 2.
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Discussion
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We found that women who received small-dose bupivacaine with fentanyl reported adequate anesthesia for cervical cerclage, with a recovery profile similar to that of women who received small-dose lidocaine with fentanyl and without an increase in complications. Lidocaine has a short duration of action, making it an excellent choice for a short operative procedure. However, lidocaine is associated with TNS, a syndrome marked by transient pain or dysesthesia in the buttock or leg after recovery from the anesthetic (2,3). At first, the concern of TNS primarily centered on the use of lidocaine 5% and not smaller concentrations of lidocaine (12,13). When those concerns were reported, we changed to 2 mL of lidocaine 1.5% for cervical cerclage, with satisfactory outcome. However, subsequent reports in the literature suggested that the incidence of TNS with lidocaine is not reduced by either decreasing the total milligram dose or the concentration of lidocaine (9,14) and that the neurotoxic potential of lidocaine can occur even in clinically used concentrations (15,16). When these reports were released, we stopped using subarachnoid lidocaine entirely and started our search for a suitable replacement.
Bupivacaine is generally considered a long-acting local anesthetic. Reports suggest that decreasing the dose of bupivacaine while combining it with an opioid can decrease the duration of action of the local anesthetic, yet still provide adequate subarachnoid anesthesia (7). We chose bupivacaine 5.25 mg on the basis of the results of previous studies. Ben-David et al. (7) found that bupivacaine 5 mg with fentanyl 10 µg was an adequate subarachnoid dose for knee arthroscopy, but without fentanyl, at least 7.5 mg was required for the same procedure (17). Tsen et al. (6) reported a 20% failure rate with only 3.75 mg of bupivacaine. We therefore considered that approximately 5 mg was a reasonable dose. This dose can be practically achieved by using 0.7 mL of the 0.75% hyperbaric bupivacaine typically used in the United States. We diluted the bupivacaine and fentanyl to a total injectate volume of 3 mL. This was based on our past experience (unpublished data) that increasing the injected volume of subarachnoid local anesthetic enhances the spread of anesthesia and therefore allows the use of smaller doses of local anesthetic. Whether this is indeed the case deserves further study. We compared the bupivacaine with lidocaine 30 mg because we had been successfully using this dose of lidocaine for cervical cerclage. In this study, we used a CSE technique for this short procedure so that the epidural catheter could be used to administer a rescue anesthetic in the event that bupivacaine 5.25 mg was not adequate. However, on the basis of the results of this study (close to 100% success), we do not deem a CSE necessary for cervical cerclage with bupivacaine 5.25 mg and would use a single-shot spinal technique.
Only one patient required additional medication before the onset of the procedure, and this occurred in the bupivacaine group 14 minutes after the subarachnoid medication was given. It is possible that, had we waited longer, the anesthetic block might have been sufficient. However, per study protocol, we allowed the surgeon to start when the patient had a T12 level of anesthesia rather than on the basis of an arbitrary time. We found that the median time until the return of motor function (Bromage score of 0) occurred significantly faster in the bupivacaine group than in the lidocaine group (56 versus 75 minutes; P = 0.04), although the time until ambulation did not differ significantly between groups.
In our study, the ability to urinate was the last of the measured variables to recover from the anesthetic on the day of surgery and occurred earlier in the lidocaine group than the bupivacaine group (133 versus 164 minutes; P = 0.12). This finding has been confirmed by others who compared lidocaine with bupivacaine (6,18). The reason for the delay in urination associated with bupivacaine may be related to our study design, in that prehydration was not controlled. We did not control the amount of prehydration because it is controversial how much fluid to use before subarachnoid anesthesia. Therefore, we left this decision to the individual anesthesiologist. Another possibility as to why there was a difference in the ability to urinate is that bupivacaine impairs bladder function more than lidocaine (19). The delay in the ability to urinate should not affect the choice of bupivacaine for short procedures because it is not an absolute requirement for hospital discharge after ambulatory procedures, and the delay in micturition is not associated with any long-term sequelae (20).
The incidence of the complications of nausea, vomiting, pruritus, hypotension, and the need for ephedrine did not differ significantly between the bupivacaine and lidocaine groups. We found two cases (7%) of TNS with lidocaine and no cases with bupivacaine (P = not significant). In both of our cases of TNS, the symptoms were mild and were acknowledged only when the woman was specifically asked if she had pain radiating into the buttock or leg. Our study lacks adequate power to determine whether there is a difference between bupivacaine and lidocaine in the incidence of TNS. However, the anesthesia community has already been alerted to the concerns about TNS with lidocaine that either does not occur with bupivacaine (2,6,21) or occurs at a smaller rate (22–24). It should be noted that these studies (2,7,21–24) evaluated hyperbaric bupivacaine 0.5% or 0.75%. It is possible that larger concentrations of hyperbaric bupivacaine may be associated with an increased rate of TNS. Indeed, Runza et al. (25) found a more frequent incidence of backache and postdural puncture headache in women who received hyperbaric bupivacaine 1% than in women who received the 0.75% formulation. Because of the risk of TNS with lidocaine, it is preferable that a clinically useful dose of a local anesthetic other than lidocaine be used for procedures of short duration. On the basis of the results of this study, bupivacaine appears to be an appropriate choice.
In conclusion, the administration of small-dose subarachnoid bupivacaine with fentanyl provides reliable anesthesia for cervical cerclage and exhibits a pharmacodynamic profile similar to that of small-dose lidocaine. This combination reduces the concerns about TNS that may exist with lidocaine and is an acceptable alternative for cervical cerclage.
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Acknowledgments
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Supported solely by the Department of Anesthesiology, Mount Sinai School of Medicine, New York University.
The authors express appreciation to James B. Eisenkraft, MD, for his help with the study design and for his critical review of the manuscript.
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Footnotes
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Presented in part at the meeting of the Society for Obstetric Anesthesia and Perinatology, Denver, CO, May 22, 1999.
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References
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Accepted for publication March 10, 2003.
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Abstract
Introduction
