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OBSTETRIC ANESTHESIA

Combined Spinal-Epidural Anesthesia Using Epidural Volume Extension Leads to Faster Motor Recovery After Elective Cesarean Delivery: A Prospective, Randomized, Double-Blind Study

From the Department of Anaesthesia (Obstetrics and Gynaecology), KK Women’s and Children’s Hospital, Singapore

Address correspondence and reprint requests to Eileen Lew, Department of Anaesthesia (Obstetrics and Gynaecology), KK Women’s and Children’s Hospital, 100 Bukit Timah Road, Singapore 229899, Republic of Singapore. Address email to Eileen.Lew{at}kkh.com.sg or elewtan@yahoo.com.sg.

	Abstract

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Epidural volume extension (EVE) via a combined spinal-epidural (CSE) technique is the enhancement of a small-dose intrathecal block by epidural saline boluses. In this prospective, randomized, double-blind study, we compared the EVE technique with single-shot spinal anesthesia with respect to its sensory and motor block profile and hemodynamic stability. Sixty-two parturients (n = 31 in each group) undergoing elective cesarean deliveries were administered either spinal anesthesia with hyperbaric 0.5% bupivacaine 9 mg and fentanyl 10 µg or CSE comprising intrathecal hyperbaric 0.5% bupivacaine 5 mg with fentanyl 10 µg, followed by 0.9% saline 6.0 mL through the epidural catheter 5 min thereafter. In each group, the lowest systolic blood pressure (SBP), sensory block level to loss of pain from pinprick, and modified Bromage scores were recorded at 2.5-min intervals. The visual analog pain score (VAS), peak sensory block height, highest modified Bromage motor score, time for sensory regression to the tenth thoracic dermatome (T10), and motor block recovery were compared between groups. Both groups were comparable in demographic data, VAS scores, peak sensory block height, time for sensory regression to T10, and lowest SBP recorded. Patients in the EVE group demonstrated significantly faster motor recovery to modified Bromage 0 (73 ± 33 min versus 136 ± 32 min, P < 0.05).

IMPLICATIONS: When compared with conventional, single-shot spinal anesthesia, epidural volume extension of a small-dose spinal block provides satisfactory anesthesia for cesarean delivery with only 55% of the bupivacaine dose required and is associated with faster motor recovery of the lower limbs.

	Introduction

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The combined spinal-epidural anesthetic technique (CSE) has the reliability of a subarachnoid block as well as the flexibility conferred by an epidural catheter (1). Recently, the technique has undergone several modifications designed to increase its safety and efficacy. A modification of the conventional CSE is the sequential CSE technique, in which spinal anesthesia is induced with a small-dose intrathecal local anesthetic and opioids to produce a limited block that can be extended with epidural top-ups of local anesthetic (2). In addition, epidurally-administered saline can be used to extend the spinal block (2–7).

At our institution, it is standard practice to administer single-shot spinal anesthesia for patients undergoing elective cesarean delivery. Although spinal anesthesia provides a reliable block of rapid onset, it can be very intense and may persist long after surgery.

We postulate that epidural volume extension (EVE) (8) of a small-dose spinal block could provide adequate anesthesia for cesarean delivery while allowing faster motor recovery of the lower limbs. In this prospective, randomized, double-blind study, we compared the EVE technique with single-shot spinal anesthesia for cesarean delivery in terms of its sensory and motor block profile and hemodynamic stability.

	Methods

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After hospital ethics committee approval and written informed consent, 62 patients (ASA physical status I–II, body weight 50–95 kg, height 150–170 cm, singleton pregnancies) scheduled for elective cesarean delivery were randomized (by computer-generated random tables) to receive either single-shot spinal anesthesia or a CSE technique with EVE.

We excluded patients with contraindications to regional anesthesia, emergent cesarean deliveries, hypertensive disorders, and peripartum hemorrhagic conditions.

All the patients were premedicated orally with ranitidine and sodium citrate. On arrival in the induction room, standard monitoring was applied with automated noninvasive blood pressure measurement, electrocardiography and pulse oximetry. Baseline mean arterial blood pressure (MAP) and heart rate (HR) were recorded. All patients were prehydrated with 500 mL of lactated Ringer’s solution before induction of the allocated regional anesthetic technique. The regional anesthesia was performed with the patient in the right lateral position at the fourth lumbar interspace using a midline approach.

Patients in the spinal group were administered 9.0 mg of hyperbaric 0.5% bupivacaine and fentanyl 10 µg through a 27-gauge Whitacre spinal needle via a 20-gauge introducer after free flow of cerebrospinal fluid (CSF) was obtained. The intrathecal drugs were injected over 10 s without barbotage. The point at which the spinal needle was removed marked the completion of spinal anesthesia. Immediately, patients were turned supine with left uterine displacement using a wedge pillow under the right hip.

For patients in the EVE group, a 17-gauge Tuohy needle was introduced into the fourth lumbar intervertebral space and the epidural space identified by a loss of resistance to air. Care was taken to limit the injection of air on entry into the epidural space. Using the needle-through-needle technique, an adjustable 27-gauge Whitacre spinal needle (BD Durasafe; Becton-Dickinson, Franklin Lakes, NJ) was inserted into the subarachnoid space via the Tuohy needle and after CSF was obtained, 5.0 mg of hyperbaric 0.5% bupivacaine and fentanyl 10 µg were injected over 10 s without barbotage. After withdrawal of the spinal needle, a 19-gauge multiorificed catheter was placed 4 cm into the epidural space and the Tuohy needle was removed. Patients were then turned supine with left uterine displacement. Five minutes from completion of the intrathecal injection (taken as the point of removal of the spinal needle), 6.0 mL of 0.9% saline was injected through the catheter over 30 s. The completion of this saline injection marked the completion of regional anesthesia for patients in the EVE group.

At the end of each regional technique (taken as time 0 min), an observer who was unaware of the technique received by each patient recorded the HR, systolic blood pressure (SBP), MAP, level of sensory block to loss of pain from pinprick induced by a 25-gauge hypodermic needle, and the modified Bromage motor score (0 = able to move hip, knee and ankle; 1 = unable to move hip, able to move knee and ankle; 2 = unable to move hip and knee, able to move ankle; 3 = unable to move hip, knee and ankle) at 2.5 min intervals until there was no change in 3 consecutive readings or 30 min had passed.

Surgery was allowed to commence as soon as the sensory block height reached the fifth thoracic dermatome (T5) or 10 min had elapsed. At the point of surgical incision, the intraoperative visual analog pain score (VAS) was assessed on a 101-point scale and repeated intraoperatively whenever pain or discomfort was experienced. If VAS was more than 30, analgesia was supplemented with epidural boluses of 3 mL of 1.5% lidocaine (for the EVE group) or IV adjuncts such as fentanyl 25 µg boluses and ketorolac 30 mg (for both groups) after delivery of the baby. If these failed to reduce pain to less than VAS of 30, general anesthesia would be offered to the patient.

Hypotension (defined as SBP <100 mm Hg or a reduction in MAP of more than 20% from baseline determined just before the administration of regional anesthesia) was treated with ephedrine boluses of 6 mg. The presence of intraoperative nausea, vomiting, pruritus, and shivering were also noted and treated appropriately. Rescue antiemetic drugs using a combination of IV ondansetron 4–8 mg, metoclopramide 10 mg, and dexamethasone 4 mg were administered at the discretion of the anesthesiologist. Discomfort from shivering was treated with IV meperidine 25 mg after delivery of the baby. The baby’s Apgar scores at 1 min and 5 min thereafter were noted. At the end of surgery, patients in the EVE group had their epidural catheters removed before being transported to the recovery room.

At the recovery room, all patients were monitored by trained nurses blinded as to the type of anesthetic technique administered. The time intervals for sensory recovery to the tenth thoracic dermatome (T10) and motor recovery to modified Bromage score 0 were ascertained by testing for sensory loss to pinprick and getting the patients to perform straight leg raise and knee bends respectively every 15 min.

A 24-h postoperative review was also conducted in which the occurrence of postspinal headache, time to the first request for postoperative IM meperidine injection, and the degree of maternal satisfaction graded on a 4-point scale (4 = excellent, 3 = good, 2 = satisfactory, 1 = poor) were noted.

We determined from a pilot study of 30 patients that a sample size of 30 in each group would confer a 90% power to detect a 25% difference in SBP and a difference in motor block duration of 60 min between the two groups. Statistical analyses were performed using the SPSS version 9.0 for windows (SPSS Inc., Chicago, IL) with Student’s t-test, Mann-Whitney U-test, and ² test, where appropriate. Statistical significance was assumed when P < 0.05.

	Results

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All patients enrolled completed the study successfully. No technical difficulty or block failure was encountered. There was no inadvertent dural puncture in the patients who received CSE. Surgery was commenced in all the patients by 10 min from the completion of the regional anesthetic technique, which was consistent with our standard of practice in the elective setting. Patients in the two groups were comparable in terms of demographic data and duration of surgery (Table 1).

There was no difference in the intergroup sensory block duration and time interval to the first request for postoperative meperidine injection.

With regards to the hemodynamic profile (Table 3), the lowest SBP attained and the total ephedrine dose required were comparable between the two groups. The Apgar scores of the newborns and incidence of nausea, vomiting, pruritus, and shivering were also similar. None of the patients developed a postspinal headache, and maternal satisfaction was comparable in both groups.

	Discussion

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In our study, the epidural catheter was not used to provide analgesia postoperatively, as there was inadequate specialized monitoring facilities in the postnatal wards. This practice is being reevaluated at our institution to allow mothers to use their epidural catheters for analgesia after cesarean delivery.

A limitation of our study is the failure to include a control group of patients who are administered the CSE technique solely with the intrathecal drug combination of hyperbaric 0.5% bupivacaine 5 mg and fentanyl 10 µg, which would then demonstrate unequivocally whether a sensory level of T5 could be obtained without EVE. We omitted this group of patients because a previous study has established that adequate anesthesia may not be consistently attained with this small-dose drug combination (11). Using intrathecal 5 mg isobaric bupivacaine and 25 µg fentanyl as part of a CSE technique for cesarean delivery, 50% of the parturients (8 of 16) in that study complained of transient mild pain or pressure with stretching of the incision and/or with fundal pressure. The median peak sensory level was T4.5, but a range T2 to T7 was attained, implying that some patients did not achieve the minimum sensory level of T5 required for a pain-free cesarean delivery. Although our study differed from the earlier study in that the hyperbaric preparation was used, we excluded the small-dose spinal anesthesia group for practical reasons.

Several mechanisms have been described in the literature to explain the enhancement of a spinal block by an epidural top-up of saline, including the "volume effect," in which the theca is compressed by epidural saline, resulting in the "squeezing" of cerebrospinal fluid and more extensive spread of subarachnoid local anesthetic (2–7). This effect is distinct from the block enhancement after an epidural top-up of local anesthetic in that saline extends the block height by a mechanical "volume effect" and does not prolong the block duration. The volume effect appears to be time-dependent. Beyond 30 minutes or after two-segment regression has begun, any epidural top-up of saline would have no effect on block extension and may even accelerate spinal block regression (6,12). The delayed administration of epidural saline beyond 10 minutes could have accounted for the frequent failure reported by Choi et al. (13) in their use of EVE of a spinal block induced with 8 mg of hyperbaric bupivacaine. The incidence of intraoperative pain in his study exceeded 50%. Another factor that might have contributed to the failure rate of his study was the omission of the use of intrathecal opioids, which have a dose-sparing effect on the local anesthetic (14).

These findings may have clinical significance. Conventional doses of drugs used in spinal anesthesia for cesarean delivery often produce rapid onset of a dense block that lasts beyond the duration of surgery and is associated with delayed ambulation resulting from residual motor blockade. At our institution, the duration of a cesarean delivery rarely exceeds 60 minutes, even in the hands of residents. However, the average time taken for our patients to achieve a modified Bromage score of 0 after a single-shot spinal was at least 120 minutes. The CSE technique using EVE produced a more rapid motor block regression time by approximately 60 minutes. This 1-hour difference may not seem clinically important, as it is routine for cesarean patients to be hospitalized for a few days. However, the faster motor recovery profile may have an impact on reducing or bypassing postanesthesia care unit (PACU) stay (15). This, in turn, may imply better resource use and cost-savings for both the patient and the hospital. Very few studies have compared spinal, CSE, and epidural anesthetic techniques with regard to the use of operating rooms (ORs) and discharge from the PACU (15,16). This may be attributable to the complexity involved in calculating health care cost. In future research, it would be of interest to evaluate these anesthetic techniques with respect to OR use and PACU discharge times.

This study demonstrated a relatively frequent incidence of hypotension in both patient groups. This could be a result of inadequate uterine displacement and fluid preloading. Various maternal positions have been adopted to minimize the effects of aortocaval compression, including the supine wedged position (wedge placed under the right hip), a 12°–15° left lateral tilt, and the left lateral position. In a study comparing the effects of various tilting angles, up to 12.5° of left lateral tilt failed to produce any significant improvement in the cardiac output of parturients (17). In our study, the same wedge pillow was used for each patient and a hanging angle measure was not used for accurate quantification of the resultant angle of tilt. Hence, we might not have achieved the 12°–15° left tilt necessary to reduce aortocaval compression by the gravid uterus. The incidence of hypotension in our study is comparable to that reported by Mendonca et al. (18) in parturients who assumed the 12° tilted supine position after CSE anesthesia for cesarean delivery. Their study demonstrated a significantly less frequent incidence of early maternal hypotension associated with the left lateral position, but in this position, surgical access is difficult.

It remains debatable whether the frequent incidence of hypotension could have been reduced by a larger volume of fluid preload. We administered only 500 mL of lactated Ringer’s solution for preload, as the literature does not support the routine practice of preloading large volumes of crystalloid solution to prevent hypotension related to central neuraxial blocks (19–21). Colloids may be more reliable than crystalloids in maintaining hemodynamic stability after spinal anesthesia but are associated with increased costs and risks (22). A prophylactic dose of IV ephedrine may be effective in preventing hypotension in healthy parturients undergoing spinal anesthesia for elective cesarean delivery, although it may not change the neonatal outcome and may actually have detrimental effects (23,24).

Finally, single-shot spinal anesthesia with conventional doses of hyperbaric 0.5% bupivacaine has a definite role in cesarean delivery. It is a simple, fast, and highly reliable technique. However, it has disadvantages, such as a finite block duration that may not always correspond with the duration of surgery. The study shows that CSE with EVE provided adequate anesthesia for elective cesarean delivery with only 55% of the bupivacaine dose and allows a more rapid motor recovery of the lower limbs, which may have an impact on shortening PACU stay. Moreover, the use of saline for epidural boluses is economical. With modification, the epidural catheter could be retained to provide postoperative analgesia.

These data suggest that CSE with EVE should be considered a novel alternative to spinal anesthesia for cesarean delivery.

	Footnotes

 
Presented, in part, as a poster at the First World Congress in Regional Anesthesia and Pain Therapy, May 30, 2002 in Barcelona, Spain.

	References

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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