Anesth Analg 2006;103:1540-1542
© 2006 International Anesthesia Research Society
doi: 10.1213/01.ane.0000243392.91765.52
OBSTETRIC ANESTHESIA
Combined Spinal Epidural Does Not Cause a Higher Sensory Block than Single Shot Spinal Technique for Cesarean Delivery in Laboring Women
Yvonne Lim, MMED,
Wendy Teoh, FANZCA, and
Alex T. Sia, MMED
From the Department of Women’s Anesthesia, KK Women’s and Children’s Hospital, Singapore 229899.
Address correspondence and reprint requests to Dr. Y. Lim, Department of Women’s Anesthesia, KK Women’s and Children’s Hospital, 100 Bukit Timah Road, Singapore 229899. Address e-mail to YVEL6{at}hotmail.com.
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Abstract
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BACKGROUND: The combined spinal epidural (CSE) technique has been shown to result in a higher sensory block than an equivalent single shot spinal (SSS) in women undergoing elective cesarean delivery. We tested whether this is true also in laboring women who may have variable epidural pressures.
METHODS: We randomized 40 ASA I parturients in established labor for cesarean delivery into our double-blind study. Group S (n = 20) intrathecally received 2 mL of 0.5% hyperbaric bupivacaine by SSS and group CS received CSE (n = 20) of an equivalent dose of hyperbaric bupivacaine.
RESULTS: We found that similar maximal sensory blocks were achieved in both groups (group S: median T3 [min–max] T6-1 versus group CS: median T3 [min–max] T4-C7, P = 0.517).
CONCLUSION: As compared with previous reports in nonlaboring parturients, the block characteristics of CSE in our study were indistinguishable from those of SSS in laboring parturients for cesarean delivery.
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Introduction
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Combined spinal epidural (CSE) anesthesia is an established technique for lower segment cesarean section (LSCS) delivery (1). However, in patients undergoing minor gynecological procedures and elective LSCS, the subarachnoid block from the CSE technique is associated with greater sensorimotor blockade compared with equivalent single shot spinal (SSS) anesthesia (2,3). It has been postulated that in SSS anesthetic the negative pressure of the epidural space was preserved, whereas in the CSE technique, the negative pressure in the epidural space was counterbalanced by the open connection to atmospheric pressure through the epidural needle, possibly resulting in a reduction of the dural sac volume, and consequently, a higher level of sensory block after a spinal dose of local anesthetic (LA) (4,5). We tested this hypothesis in laboring parturients, who may have a variable epidural space pressure (6). We hypothesized that the spinal block in laboring parturients from the CSE technique alone (without further administration of LA or saline into the epidural space) results in a similar spread of LA into the subarachnoid space when compared with the SSS technique.
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METHODS
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With the approval of the hospital research ethics committee and informed consent, we recruited 40 ASA I parturients in established labor (having regular uterine contractions and cervical dilation 
3 cm) scheduled for emergency LSCS delivery under regional anesthesia into our randomized, double-blind study. We excluded parturients with an allergy to the study drugs or contraindications to central neuraxial block.
All patients were placed in the right lateral decubitus position and the regional anesthesia was performed by the investigators (who had more than 3 yr of anesthetic experience). The patients were randomized using sealed opaque envelopes. Group S (n = 20) received intrathecal (IT) 10 mg hyperbaric bupivacaine (Marcain, Astrazeneca, Sweden) via a SSS technique performed at the L3-4 intervertebral space with a 27G Whitacre spinal needle. Group CS (n = 20) received IT 10 mg hyperbaric bupivacaine via a CSE technique. The CSE was performed with an 18G Tuohy needle (using loss-of-resistance to 1 mL of air) at the L3-4 intervertebral space. The dural puncture was performed by passing a 27G Whitacre spinal needle through the epidural needle (Espocan, B. Braun, Melsungen, Germany). We removed the Touhy needle immediately after the IT drug administration without inserting an epidural catheter.
After administration of the spinal drugs, the parturients were immediately placed supine with a 15° left tilt. An investigator blinded to the anesthetic technique used evaluated the patient’s hemodynamic status, maximal dermatomal sensory block achieved, maximum motor block of lower limb based on the modified Bromage scale (0 = no impairment, 1 = unable to raise extended legs but able to move knees and ankles, 2 = unable to raise extended legs as well as flex knees, able to move feet, 3 = not able to flex ankle, feet or knees), and the presence of side effects, e.g., hypotension, nausea, vomiting, bradycardia, and shivering.
On the basis of a previous study comparing SSS with CSE in elective obstetric patients (3), it was determined that a sample size of 40 patients was needed to detect a two segment difference in maximal dermatomal sensory block with a power of 0.9 and 
< 0.05. Results were analyzed with SPSS ver 11.5. We used the Student’s t-test to analyze parametric data and Mann–Whitney U-test to compare the nonparametric data between the two groups.
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RESULTS
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Both groups had similar demographic and baseline hemodynamic profiles (Table 1). There were no failed or inadequate blocks, and all patients achieved a sensory level T6. The maximal sensory block achieved in group CS and group S was similar (median T3 [min–max] T4 to C7 and median T3 [min–max] T6 to T1, P = 0.517) (Table 2). The time taken to reach maximal sensory block and for the block to recede were similar in both groups. There were no differences in the incidence of side effects, the maximal Bromage score, or time for the recovery of the motor block of the lower limb (Table 2).
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DISCUSSION
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Our results demonstrated that the CSE technique resulted in a similar level of sensory block when compared with the SSS technique when an equivalent dose of IT LA was given to laboring parturients for LSCS delivery. This may seem self-evident, but is contrary to previous studies demonstrating that the CSE technique without placement of an epidural catheter or administration of epidural medication resulted in a significantly higher level sensory block than SSS anesthesia (2,3). In a study comparing the CSE technique and SSS anesthesia in gynecological patients, the maximum sensory block level achieved was two segments higher in the group who received the CSE technique (2). The authors went on to investigate the median effective dose of IT bupivacaine in the CSE and SSS technique and found that a 20% decrement in the dose of bupivacaine may be necessary when the CSE technique is used (7). In our previous study (3) of parturients undergoing elective LSCS delivery, the CSE technique resulted in a maximal sensory block level 5 segments higher than SSS anesthesia. It was postulated that the negative pressure in the epidural space may be counterbalanced by the open connection to atmospheric pressure through the epidural needle, possibly resulting in a reduction of dural sac volume, and consequently, a higher level of sensory block after a spinal dose of LA. This effect did not appear to play an important role when the CSE was performed in laboring parturients. The explanation could be that the pressures in the epidural space of parturients in labor differ from that in nonlaboring parturients (6). Messih (6) found that in laboring parturients, the epidural pressures could be above the atmospheric pressure, with the increase of epidural space pressure synchronous with uterine contraction as a result of the reflex increase in abdominal muscle tone. This was also supported by another study that showed that the increase in intraperitoneal pressure played a role in producing an increased epidural pressure (8). With the variable epidural pressure during labor, performing the CSE technique in these parturients was unlikely to affect the epidural pressures, and subsequently, the maximal sensory block level achieved after a spinal dose of LA. We feel that this is a plausible explanation for why we did not find a significant difference in the maximal sensory block level between our parturients who received CSE and SSS anesthesia.
Many factors can play a role in the cephalad spread of LA in the subarachnoid space, including lumbosacral cerebrospinal fluid volume (5), increased intrabdominal pressures during labor (6), maternal position while performing the block (9,10), and the baracity of the LA. Without further studies, it is not possible to elucidate which of these factors is important in the spread of IT LA in laboring parturients.
In conclusion, spinal block from a CSE technique results in a similar spread of LA into the subarachnoid space and a similar level of block as the SSS technique when administered to laboring parturients for LSCS delivery. Administering IT 10 mg bupivacaine via the CSE and SSS techniques is equally effective for LSCS delivery, and a dose adjustment is not necessary.
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Footnotes
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Accepted for publication August 15, 2006.
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REFERENCES
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Abstract
Introduction
