This single-center, retrospective cohort study was conducted in Juntendo University Hospital, a teaching hospital in where 1200 deliveries, including 850 deliveries receiving epidural labor analgesia, are carried out annually. We collected data from medical records, anesthetic records, labor analgesia records, and partographs.
From September 2015 to May 2019, term parturients who were aged > 20 years and who underwent cesarean sections while receiving labor analgesia were enrolled in this study. We excluded those parturients who required stat cesarean sections (category 1, NICE classification ), those who underwent surgery within 2 h of induction of epidural labor analgesia, and those who were not given any local anesthetics via epidural catheter because of the subjective definition of the anesthesiologist to choose an alternate anesthetic route to provide operative anesthesia.
Standard protocol for labor epidural analgesia
Although this study was performed as a retrospective one, our standard protocol for labor analgesia and anesthetic management of cesarean section for parturient after induction of labor analgesia were as follows. During the study period, all case was managed under the supervision of our senior staff. Obstetric anesthesiologists performed all the anesthetic procedures in this study. The standard ways of induction of labor analgesia are combined spinal and epidural anesthesia (CSEA), dural puncture epidural (DPE), or epidural anesthesia (EPI). Anesthesiologists decided which ways to perform as the initial technique. Labor analgesia was initiated to all women upon request, regardless of the degree of cervical dilation. For induction of CSEA, 10 μg of fentanyl and 2.5 mg of bupivacaine were administered intrathecally via the L3–L4 interspace. Then, an epidural catheter was placed by needle through needle technique. The DPE technique is a modification of the CSEA technique, where a dural perforation is created with a spinal needle, but intrathecal medication is withheld . For induction of EPI and DPE, levobupivacaine (0.125%) with fentanyl (5 μg/mL) was administered incrementally (10-20 ml). For maintenance of labor analgesia, 0.1% ropivacaine or 0.08% levobupivacaine, with fentanyl (2 μg/mL) was administered using a patient-controlled epidural analgesia (PCEA) device regardless of the induction technique. Settings for PCEA were a bolus dose of 5 ml, a lockout time of 15 min, and no background infusion. Pain intensity was measured using numerical rating scales of 0 to 10 points (0 = no pain, 10 = worst pain). Scores of ≤ 4 were considered to be adequate pain relief. Anesthesiologists checked for the adequate block every one to two hours during labor analgesia, even with PCEA. When cesarean section was decided, 10 ml of 2% lidocaine, 1 ml of 7% bicarbonate were administered, and another 5 ml of 2% lidocaine with 100 micrograms of fentanyl was added when needed.
All cases during the studying period were examined if it fulfilled the criteria of chorioamnionitis, regardless of the proposed indication for cesarean section for the purpose of this study. We defined CAM as suspected Triple I  (intrauterine infection or inflammation or both) (Additional Table 1). The criteria are as follows.
Fever without a clear source plus any of the following
- baseline fetal tachycardia (>160 bpm) for 10 minutes or longer, excluding accelerations, decelerations and periods of marked variability
- maternal WBC > 15,000 per mm³ in the absence of corticosteroids
- definite purulent fluid from the cervical os
We collected laboratory data, symptoms, and vital signs from delivery records and electronic medical records, and the parturients whose data were complete for the criteria were classified into CAM (+) group. All the parturients were retrospectively classified into CAM (+) or CAM (-) group.
The primary outcome was failure of conversion of epidural labor analgesia to cesarean delivery anesthesia. We defined this failure as the inability of anesthesiologists to provide adequate anesthesia until the end of surgery using only local anesthetics via the epidural catheter inserted for epidural labor analgesia and/or the need to administer a sedative agent or intravenous analgesics.
The secondary outcomes included the following variables regarding labor analgesia; the number of PCEA request that parturient pushed the PCEA button, number of PCEA bolus, hourly consumption of PCEA solution, and the number of rescue by an anesthesiologist. In addition, we checked the intervertebral range of ‘loss of cold’ level from L3/4.
We listed age, body mass index (BMI), whether the patient was parous or not, and the duration between the induction of labor analgesia and entry into the operating room as potential confounders.
The degree of urgency and the type of anesthesia are considered potential effect modifiers. We exclude the cases of stat cesarean section (category 1 of the NICE classification); therefore, the degree of urgency was unified. The types of anesthesia were divided into subgroups (CSEA or non CSEA). Non CSEA subgroup was small to analyze; therefore, the results of CSEA subgroup analysis is shown as Additional Tables. We categorized some quantitative variables, age, BMI, and duration of anesthesia, into some groups in analyzing.
Statistical analysis was performed with JMP software package (JMP 12 pro; SAS Inc., Cary, NC, USA). The results were expressed as median (interquartile range; IQR) or count (%). Univariate analysis was performed by the χ² test or Fisher’s exact test for categorical variables and Wilcoxon rank-sum test for continuous variables. Multivariable logistic regression was used to estimate multivariable-adjusted odds ratios and 95% confidence intervals (CI). The multivariable analysis was adjusted for age, BMI, multiparity, and duration for epidural labor analgesia. We considered the type of anesthesia as an effect modifier and analyzed the association between factors and outcomes as a subgroup analysis. Statistical significance was set at two-tailed p values less than 0.05.