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
]. 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-through-needle 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
], was injected over 10 seconds without barbotage or aspiration. Immediately after intrathecal injection, the epidural needle was removed without inserting an epidural catheter. All parturients were promptly placed in a supine position with left uterine displacement.
A second anesthesiologist recorded vital signs at two-minute intervals for 20 minutes. IV phenylephrine 100μ
g was administrated for a decrease in systolic blood pressure (SBP) to less than 90
mmHg or a 30% reduction in SBP and was repeated as necessary. Bradycardia with less than 50 beats per minute was treated with IV atropine 0.3
mg. Sensory level of the block was assessed bilaterally at two-minute intervals using alcohol swab (sensory blockade level to cold ) and 25-gauge hypodermic needle (sensory blockade level to pinprick) in the cephalad direction. The degree of motor blockade was evaluated bilaterally using the modified Bromage scale [5
]. The peak sensory and motor blockade and the amount of time taken to achieve it were compared. Other side effects such as shivering, nausea, and vomiting were recorded.
Skin incisions were made 20 minutes after intrathecal injection. Prior to delivery of the fetuses, any reaction to surgical stimulation (including any verbal complaint of pain or withdrawal of extremities to pinprick) was supplemented with IV ketamine at a dose of 0.5
mg/kg each time until adequate anesthesia was achieved. After childbirth, midazolam 0.03
mg/kg was administrated to all parturients, and IV pethidine 0.5
mg/kg each time was also utilized according to parturient's reaction to ensure adequate anesthesia. General anesthesia was reserved as a back-up plan. Time intervals from skin incision to uterine incision, from uterine incision to fetus delivery, and surgical time were collected. The Apgar scores and parturients' satisfaction with anesthesia care were recorded. All parturients were followed for three days postoperatively.
2.1. Statistical Analysis
Statistical analysis was performed using SPSS Version 13.0 software. One-sample Kolmogorov-Smirnov test was applied to analyze the distribution of the data. Student's unpaired t-test was used to examine the differences of quantitative data between groups. The Mann-Whitney U test was performed to analyze the ordered variables, such as median sensory levels, VAS scores, modified Bromage scores, and those skewed quantitative data. The incidences of hypotension, shivering, and nausea/vomiting between the two groups were compared with Fisher's exact test. The correlations between sensory blockade level and cervical dilation or labor pain scores were analyzed with Spearman's rank correlation. A P value <0.05 was considered statistically significant.