Anesth Analg 2002;95:1067-1070
© 2002 International Anesthesia Research Society
REGIONAL ANESTHESIA
The Median Approach to Transsacral Epidural Block
Tomoki Nishiyama, MD PhD*,
Kazuo Hanaoka, MD PhD
, and
Youji Ochiai, MD PhD
*Surgical Center, The Institute of Medical Science, Department of Anesthesiology, The University of Tokyo; and Department of Anesthesiology, Matsuda Hospital, Kurashiki, Japan
Address correspondence and reprint requests to Tomoki Nishiyama, MD, PhD, Surgical Center, The Institute of Medical Science, The University of Tokyo, 4-6-1, Shirokanedai, Minato-ku, 108-8639, Tokyo, Japan. Address e-mail to nishiyam{at}ims.u- tokyo.ac.jp.
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Abstract
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Transsacral epidural block may be useful for surgery or cancer pain affecting the rectal, anal, or urethral region. The procedure through the dorsal sacral foramen is difficult because of the long insertion route. We investigated whether the transsacral epidural block could be simplified by using a median approach instead of a lateral approach through the foramen. Thirty patients for transurethral resection of bladder tumor had a catheter placed 5 cm cephalad at S2-3 (15 patients) or caudal (15 patients) epidural space using a 19-gauge Tuohy needle by the median approach. Lidocaine 2% 15 mL was administered for anesthesia. Anesthesia level (sensory block to cold), hemodynamics, and side effects were compared between the two approaches. The success rate of anesthesia was 87% for transurethral resection of bladder tumor (proximal anesthesia level higher than T10) and 100% for the sacral region (S1-5) in both groups. The highest level of anesthesia (median, T8 in the S2-3 group and T9 in the caudal group) was obtained in 20 min in both groups. No side effects were observed. We conclude that the median transsacral epidural approach is technically feasible in adults and presents an alternative to caudal block.
IMPLICATIONS: The median approach to transsacral epidural block has been described in children. We found that it is technically feasible in adults and presents an alternative to caudal block for procedures on the rectal, anal, or urethral region.
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Introduction
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Complete analgesia is required or desirable during and after rectal, anal, or urethral surgery or for cancer pain in these regions. Lumbar epidural block sometimes fails to produce analgesia in the sacral region (1). Even when local anesthetic was injected through a Tuohy needle into the epidural space at the L3-4 interspace with the bevel pointed caudad, complete analgesia in the sacral area was not consistently obtained (1). Analgesia in the sacral region can be provided by caudal block. However, there are many anatomical variations of the sacral hiatus, and caudal block is contraindicated when the puncture site is included in the surgical area or contaminated. For surgical anesthesia, spinal anesthesia is also useful. However, it has a limited duration and may not be ideal for outpatient surgery or the pain clinic.
Transsacral epidural block provides anesthesia of the rectal, anal, or urethral region and has been performed through the dorsal sacral foramen. This foramen approach is difficult because of the long and oblique insertion route. Epidural block using a median approach at L5-S1 has been reported in children (2). In infants and children, the sacrum is not fused and consists of five distinct vertebrae, thus allowing an easy sacral intervertebral approach (3). There has been no report of a median approach to transsacral epidural block in adults. It has been thought that the median transsacral epidural puncture would be difficult or impossible in adults because of bony fusion. We investigated whether this approach could be performed successfully and compared it with standard caudal block.
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Materials and Methods
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Informed consent from the patients and approval by the research committee were obtained. Thirty male patients aged 50–75 yr old, with standard body weight, without pathology in the thoracic, lumbar, or sacral region, and scheduled for transurethral resection of bladder tumor (TUR) were randomly divided into two groups, S2-3 group and caudal group, using an envelope method. With the patient positioned in the lateral position with the legs flexed, a 19-gauge Tuohy needle was inserted into the epidural space of S2-3 or caudal space at the midline using a loss of resistance method. A Tuohy needle was inserted at an angle of approximately 60–90 degrees against the body surface for transsacral approach and approximately 45–60 degrees for the caudal approach. The distance between the epidural space and body surface was measured. A catheter was inserted 5 cm cephalad through the Tuohy needle. After returning to the supine position, 15 mL of 2% lidocaine was administered through the catheter using a disposable 20-mL syringe. Arterial blood pressure, heart rate, and level of anesthesia to cold were monitored for 30 min after the injection by the anesthesiologist who inserted the catheter. After the observation period, 2% lidocaine or 0.5% bupivacaine was used for additional surgical anesthesia. Patients with a T10 or higher anesthesia level at 30 min were counted as a success for TUR and with analgesia in S1-5 as success for the sacral region. A nurse recorded side effects, such as pain at the insertion site, headache, or nausea, for 3 days after surgery.
Demographic data and the distance between the epidural space and body surface were compared with the Student’s t-test. Blood pressure and heart rate were analyzed with the two-way repeated-measures analysis of variance. The level of anesthesia was analyzed with the Mann-Whitney U-test and the Friedman test. Power analysis was performed after the study using a post hoc power analysis for the success rate and anesthesia level using the G-Power version 2.1.2. A P < 0.05 was considered statistically significant.
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Results
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Age (68 ± 6 yr and 66 ± 7 yr, respectively; mean ± SD), body weight (60 ± 7 kg and 62 ± 6 kg, respectively), height (162 ± 5 cm and 160 ± 6 cm, respectively), and duration of surgery (75 ± 18 min and 67 ± 15 min, respectively) were not different between the S2-3 group and caudal group.
The highest level of anesthesia (sensory block, median; T8 in the S2-3 group and T9 in the caudal group) was obtained 20 min after the epidural lidocaine administration in both groups. The sacral region was anesthetized in 10 min. The anesthesia level was not different between the two groups (Fig. 1) while the power of analysis was 0.453. In two of the 15 patients in both groups, sufficient analgesia for TUR was not produced (success rate, 87%), whereas all patients in both groups showed analgesia in the sacral area (success rate, 100%) with the power of analysis of 0.29. The distance from the skin surface to the epidural space was 4.7 ± 1.6 cm in the S2-3 group and 4.9 ± 1.4 cm in the caudal group, which was not different between the two groups. Blood pressure and heart rate did not change significantly in either group and was not different between groups. No patients complained of pain at the insertion site, headache, or nausea for 3 days after surgery in both groups.
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Figure 1. Proximal anesthesia level. Median value and range (in parenthesis) of the upper level of anesthesia are shown. All patients showed analgesia in the sacral area in both groups. Black column is the S2-3 group and the white column is the caudal group. *P < 0.05 versus the value at 5 min. No difference was seen between the two groups.
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Discussion
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The success rate of the median transsacral epidural block through S2-3 was 87% for TUR (higher level of sensory block than T10) and 100% for the sacral region in patients with standard body weight. These were similar to standard caudal block. In the present study, we used a cold test to check the level of anesthesia. Although the cold test does not really address anesthesia, the pinprick test, which does, is invasive to patients.
Spinal anesthesia is usually used for TUR. We do not recommend sacral epidural block as the first choice for this procedure, but we chose to study this population because the patients have similar demographics, and the surgical site lends itself to frequent anesthesia level measurement. The indication for sacral epidural block may be prolonged surgery or cancer pain in the rectal, anal, or urethral region.
The sacral intervertebral approach for epidural block is considered easy in infants and children (4). Because of the rudimentary spinous process of the first sacral vertebra and the less prominent sacral angle, an appropriate upward inclination of the Tuohy needle in the midline is always possible in infants and small children (2). It is said that the 5 sacral vertebral bodies begin to fuse from below upward at approximately 17–18 years of age, with fusion being complete by 23 years of age (5).
In a preliminary study, we examined 5 dry sacral bone specimens and attempted insertion of a 23-gauge IV injecting needle (Top Co Ltd, Osaka, Japan) through the median sacral intervertebral space at midline in S1-2, S2-3, S3-4, and S4-5. We found that we could easily insert the needle at midline through the intervertebral spaces of S1-2, S2-3, S3-4, or S4-5 in all specimens (Fig. 2). The bony fusion was not tightly fused, or there was a thin bony membrane. We checked only a few dry bone specimens; therefore, we cannot confirm that there might be tight bony fusion in the sacral intervertebral space in some adults.
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Figure 2. Bone specimen seen from cephalad. A 23-gauge needle went through the fusion of sacral bone (S2-3) easily at midline (arrow).
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In two patients, we also examined whether the median approach was clinically possible. An 81-year-old woman with back and leg pain received an epidural injection of 60% amidotrizoic acid (UrografinTM, Japan Schering Co Ltd, Osaka) 5 mL for contrast enhanced radiograph. Epidural puncture was performed with a 21-gauge epidural needle at the midline of S1-2 in the lateral position using a loss-of-resistance method. A plain radiograph showed a clear border of the fusion of the sacral vertebrae (i.e., L5-S1, S1-2, S2-3, S3-4, and S4-5; Fig. 3). Contrast enhanced radiograph showed that UrographinTM spread into the epidural space cephalad from S1-2 to L5 (Fig. 4). Bupivacaine 0.25% (MarcainTM, Astra-Zeneca, Osaka) 5 mL was administered epidurally, and her back and leg pain decreased. A 76-year-old woman with back and leg pain received an epidural injection of 60% UrografinTM 5 mL for contrast enhanced computed tomography. Epidural puncture was performed at S2-3 in the same way as the former patient. UrographinTM was detected in the epidural space in contrast enhanced computed tomography (Fig. 5). Bupivacaine 0.25% 5 mL was administered epidurally, and her back and leg pain decreased. In both cases, we did not measure the visual analog scale scores but recorded patients’ verbal assessment of pain.
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Figure 3. Plain radiograph. One can see a clear border of each fusion of the sacral bone at L5-S1, S1-2, S2-3, S3-4, and S4-5 intervertebral spaces (arrows).
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Figure 5. Contrast enhanced computed tomography scan seen from caudad at S2 level. UrographinTM is detected in the epidural space (arrow).
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Epidural catheterization in the sacral region avoids the risk of puncture of the dural sac, which usually ends at S1-2 (6,7). The lumbosacral approach is widely used because the L5-S1 interspace is the largest in the vertebral column (2). The transsacral approach through the dorsal sacral foramen is difficult and also risks oblique penetration of the ligamentum flavum with vascular or neural damage. In addition, it has a risk of advancing the needle too deeply into the colon, rectum, or bladder. This risk would be reduced with the present median approach where the needle is more likely to contact bone or lineae transversae than a foramen.
Usually, epidurally-administered drugs tend to spread more cephalad (8) during the lumbar than during the caudal approach (9). This might prevent adequate caudad spread of analgesia during lumbar epidural block. It takes longer to develop analgesia in the S1 than in the S2 and S3 because the S1 nerve root is larger (10,11). In the present study, both approaches provided analgesia in the sacral region in 10 minutes. High thoracic block (T3-5) may occur after the lumbar injections, whereas minimal abdominal anesthesia develops after injections at the L5-S1 interspace (8). The extent of anesthesia obtained from the L5-S1 injection tends to be similar to that from caudal injection (12) and may reflect the relative spinal stenosis observed frequently in the lower lumbar vertebrae in the elderly (13). Such resistance could limit the cephalic spread of the drug in sacral epidural block.
In 13% of the patients in both groups, the anesthesia level did not reach T10. However, we could confirm that the catheters were in the epidural space in these patients because the sacral region was anesthetized. The reason for the failure of sufficient anesthesia might be because of adhesions in the epidural space.
In the present study, blood pressure and heart rate did not change significantly even when the anesthesia level reached the thoracic region. In addition, no side effects were observed. Therefore, transsacral epidural block may be as safe as caudal block in terms of cardiovascular function, although the number of patients in this study might not be enough to detect differences between the two groups. If there is a bony membrane at the intervertebral space, theoretically, bone substance may be transferred with the needle into the epidural space with this procedure. Further study is required to elucidate the safety of this procedure including detailed anatomical research. We conclude that the median transsacral epidural approach is technically feasible in adults and presents an alternative to caudal block.
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Acknowledgments
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Funded, in part, by the Department of Anesthesiology, The University of Tokyo.
We thank Chingmuh Lee, MD, Department of Anesthesiology, Harbor-UCLA Medical Center, Los Angeles, CA, for his comments and editing the manuscript and Mr Mori, Clinical Research Administration Department, Toray Industries Inc, Tokyo, Japan, for his help performing power analysis.
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References
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Accepted for publication May 20, 2002.
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Abstract
Introduction
