Comparison of Spinal Block Levels between Laboring and Nonlaboring Parturients Using Combined Spinal Epidural Technique with Intrathecal Plain Bupivacaine

Hindawi Publishing Corporation Anesthesiology Research and Practice Volume 2012, Article ID 187132, 5 pages doi:10.1155/2012/187132 Clinical Study Comparison of Spinal Block Levels between Laboring and Nonlaboring Parturients Using Combined Spinal Epidural Technique with Intrathecal Plain Bupivacaine Yu-Ying Tang,1 Jie Zhou,2 Xiao-Hui Ren,3 and Xue-Mei Lin1 1 Department of Anesthesiology, West China Second Hospital, Sichuan University, Sichuan, Chengdu 610041, China 2 Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women’s Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA 3 Department of Anesthesiology, Median Area of Maternal and Child Care Service Center, Sichuan, Neijiang 641000, China Correspondence should be addressed to Xue-Mei Lin, Received 26 February 2012; Revised 23 April 2012; Accepted 2 May 2012 Academic Editor: Takashi Nishino Copyright © 2012 Yu-Ying Tang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. It was suggested that labor may influence the spread of intrathecal bupivacaine using combined spinal epidural (CSE) technique. However, no previous studies investigated this proposition. We designed this study to investigate the spinal block characteristics of plain bupivacaine between nonlaboring and laboring parturients using CSE technique. Methods. Twenty-five nonlaboring (Group NL) and twenty-five laboring parturients (Group L) undergoing cesarean delivery were enrolled. Following identification of the epidural space at the L3-4 interspace, plain bupivacaine 10 mg was administered intrathecally using CSE technique. The level of sensory block, degree of motor block, and hemodynamic changes were assessed. Results. The baseline systolic blood pressure (SBP) and the maximal decrease of SBP in Group L were significantly higher than those in Group NL (P = 0.002 and P = 0.03, resp.). The median sensory level tested by cold stimulation was T6 for Group NL and T5 for Group L (P = 0.46). The median sensory level tested by pinprick was T7 for both groups (P = 0.35). The degree of motor block was comparable between the two groups (P = 0.85). Conclusion. We did not detect significant differences in the sensory block levels between laboring and nonlaboring parturients using CSE technique with intrathecal plain bupivacaine. 1. Introduction Combined spinal epidural (CSE) anesthesia is commonly used for cesarean delivery. It has been suggested that nonlaboring parturients have a higher sensory block level than those in labor during CSE anesthesia [1]. This proposition was derived from combining two independent randomized studies on spinal block levels designed separately for laboring and nonlaboring parturients [2, 3]. There was a 5-dermatome level difference between nonlaboring (C6) [2] and laboring (T3) [3] parturients using 10 mg hyperbaric bupivacaine with CSE technique. However, there has been no previous study examining the effect of labor on the level of the subarachnoid block during CSE. The effect of CSE technique on the spinal block level of hyperbaric bupivacaine in nonlaboring parturients was not consistent. Horstman et al. reported that sensory block level was at T3 with CSE in nonlaboring parturients using 20% higher dose of hyperbaric bupivacaine [4]. We speculate that baricity of the hyperbaric bupivacaine used by Ithnin et al. could be a confounding factor, because the block level could be easily manipulated with the positioning of the parturients when hyperbaric local anesthetic was used. The effect of labor on the spread of local anesthetics may be better examined by using plain or isobaric agents which hold the least gravity-generated flow dynamics in cerebrospinal fluid (CSF). This study was therefore designed to compare the spinal block characteristics between the laboring and nonlaboring parturients using plain bupivacaine injected intrathecally with the needle-through-needle CSE technique. 2 2. Methods This research was conducted at the West China Second Hospital of Sichuan University, Chengdu, Sichuan Province, China. With median two-segment dermatome blockade level difference to be clinically significant and variability (interquartile range) of two dermatomes in sensory block, 20 parturients in each group were required in each group to address a 2-segment difference with a power of 0.9 and a level of significance of 5%. Following the institutional research ethics board (IRB) approval and written informed consents, we enrolled two groups of parturients with 25 in each group. Group NL were 25 nonlaboring parturients undergoing elective cesarean delivery, and Group L were 25 parturients in spontaneous active labor (having regular uterine contractions and cervical dilation greater than 3 cm) undergoing cesarean delivery for failure to progress. All parturients were between 20 and 40 years of age, ASA physical status I-II with a singleton pregnancy at greater than 36 weeks gestation, and received a lower segment transverse incision for cesarean delivery. The decision for cesarean delivery was made by the obstetric team, independent of the study investigators. Exclusion criteria included parturient refusal, having received any analgesic treatment, any contraindication to CSE or general anesthesia, height less than 150 cm or greater than 175 cm, body weight greater than 100 kg, obstetric and/or medical comorbidities such as preeclampsia, any cardiac, renal, neurologic, or other systemic diseases, unilateral block, or maximal pinprick sensory block level below T10 at 20 min postspinal injection. Each parturient was preloaded with 500 mL of lactated Ringer’s solution intravenously (IV). On arrival in the operation room, baseline vital signs were recorded and the initial severity of labor pain for a laboring parturient was assessed on a 10 cm visual analog scale (VAS) before CSE anesthesia was placed. The degree of cervical dilations for laboring parturient was also recorded. One anesthesiologist performed all CSE procedures following previously published methodology [2, 3]. With the parturient in the right lateral decubitus position, epidural space was identified at the L3-4 interspace with a 17-gauge Tuohy needle using the loss of resistance to air technique. The L3-4 interspace was identified by the line connecting the iliac crests to cross the spine. The volume of air used was limited to no more than 2 mL. Using the needle-throughneedle technique, a 25-gauge Whitacre spinal needle (BD Durasafe) was advanced via the epidural needle with the orifice facing cephalad direction. When cerebrospinal fluid was detected, 10 mg plain bupivacaine (2 mL of 0.5% w/v bupivacaine), which was the same as the previously published studies by Ithnin and Lim et al. [2, 3], was injected over 10 seconds without barbotage or aspiration (...truncated)