Sevoflurane and Success of External Cephalic Version (ECV)

Overview

External cephalic version (ECV) is noninvasive procedure aiming to turn the fetus to cephalic presentation, thereby enabling vaginal delivery and avoiding unnecessary cesarean delivery. The American College of Obstetricians and Gynecologists (ACOG) suggested that all women near term with breech presentation should be offered a version (9). Its success rate depends on the experience of obstetrician in addition to maternal factors. Several interventions have been tried to increase the success rate of ECV, including but not limited to tocolytics and neuraxial anesthesia. Although parenteral β stimulants and spinal anesthesia proved to be effective for increasing the success rate ECV, their success rates are still not high (10, 11) Sevoflurane's pleasant odor, lack of pungency, and potent bronchodilating characteristics make sevoflurane administration via the facemask for either sedation or induction of anesthesia is suitable. Sevoflurane has sedative and uterine relaxation effects all together would facilitate ECV and consequently would increase its success rate. To the best our knowledge sevoflurane has never been studied for ECV. Up to 1% concentration of sevoflurane has been used for labor analgesia without excessive sedation (8). Therefore, the investigators aim at comparing the success rate of ECV at 36-40 weeks of gestation under 1% of sevoflurane with a control group (received no anesthetic or other obstetric interventions). Other outcomes such as pain score and maternal and fetal complications will also be evaluated.

Pre- procedure all parturients will be asked to be fasting for 8 hours for solid and 2 hours for clear liquids. Before ECV (as routinely done in ECV procedure), a cardiotocogram (CTG) and obstetric ultrasound will be done to confirm the fetal wellbeing and fetal position prior to procedure. The mother and fetus were monitored for at least 30 min before attempting ECV. The procedure will be performed by one of two experienced obstetricians. Fetal heart rate will be recorded throughout the procedure. In the operating room, standard monitoring will be placed, as well as intravenous line will be established on an upper limb. Baseline measures of BP, HR, O2 Saturation will be taken before proceeding to inhalation sedation, including 3 baseline blood pressure readings to determine baseline values. A circle system, including antibacterial filter and scavenging system is connected to the anesthesia machine (Datex-Ohmeda). If the parturient is assigned to the control (nonintervention) group, the participants will not receive any medications neither tocolytics nor analgesics as we do routinely in our hospital. However, these participants will be monitored throughout the procedure for vital signs and for pains scores as in the intervention group (see below). In the intervention group, each participant started by preoxygenation of 100% oxygen for 3minutes. Then, parturients breath 1% of sevoflurane in mixture of oxygen and air (FIO2 0.5) by tight face mask with a gas flow of 6 L/min. Values of inspired (FI) and end-tidal (FET) concentrations of sevoflurane, oxygen and respiratory rate (RR) measured by end-tidal carbon dioxide (EtC02) were monitored continuously and recorded at 30 seconds intervals by a gas analyzer. Thirty seconds after stating inhalation sedation, the obstetrician will be asked to start the procedure. HR, FI and FET concentration of sevoflurane, Sp02 and EtC02 will be recorded at 30 seconds intervals during ECV. Non-invasive BP will be recorded every one minute. The duration of ECV in addition to the level of difficulty estimated by obstetrician will be recorded. In noninterventional (control) group, the patients will not receive any medication or anesthetic intervention however their vital signs including Sp02, BP and HR will be monitored throughout the procedure at the same interval used for the intervention group, their pain score will be measured as in the intervention group (see below). A hypotensive episode will be defined as 2 consecutive systolic BP (SBP) measurements less than 20% below the baseline value. The treatment of hypotension consists of Phenylephrine 1 mcg/kg IV bolus will be administered if HR \> 60 bpm or Ephedrine 5 mg IV bolus if HR is \< 60 bpm. If only the HR is \< 55 bpm, but SBP is normal, Glycopyrrolate 0.2 mg IV bolus will be administered. ECV considered successful when a cephalic presentation, confirmed by ultrasound scan, achieved. Pain intensity measured by VAS will be recorded at the end of procedure and 10 minutes after. In addition, the women's level of satisfaction with the procedure will be assessed using another numerical rating scale (0 = completely dissatisfied, 10 = completely satisfied) 10 min after the end of attempted ECV. The intervention will be stopped if the woman reported severe pain, if the version could not be achieved readily, or if prolonged fetal bradycardia, uterine bleeding or placental abruption occurred. Parturient will be kept in the Post Anesthesia Care Unit (PACU) for 45minutes. CTG will be monitored during PACU stay. Maternal oxygen saturation will be measured continuously using pulse oximetry, episodes of hypoxia (Sp02 ≤95%) and need for oxygen therapy will be recorded. Blood pressure will be measured every 5 min; hypotension was defined as a fall in blood pressure of \>20% from baseline and will be treated as perioperative period (see above). Isolated bradycardia with HR \< 50 bpm will be treated by glycopyrrolate 0.2mg IV bolus. Nausea and vomiting will be documented as adverse effects, regardless of when they occurred, and were treated with intravenous ondansetron 4 mg. Other maternal side effects including drowsiness and dizziness were also documented. Data Collection Pre-procedure and intra-procedure and post-procedure data will be collected by an anesthesia resident, or an anesthesiologist Not involved in the procedure. * Pre-procedure data: * Age, weight, height, gestation, gravida, parity * Estimated fetal weight * Number of prior cesarean deliveries * Reason for the ECV * Intra-procedure data: * HR, Sp02, EtC02 for RR, FI and FET concentration of sevoflurane will be recorder every 30 seconds * BP every one minute * Episode of tachycardia * Episode of hypotension * Episode of desaturation (Sp02 ≤95%) * Nausea or vomiting * Use of ondansetron * Pain intensity measured by VAS * Transient fetal bradycardia * Emergency Cesarean delivery * Post-procedure data: * HR, RR, Sp02, BP will be recorded every 5 minutes * Pain score measured by VAS 10 minutes after ECV * Episodes of desaturation * Episodes of hypotension * Nausea or vomiting * Drowsiness * Dizziness * Fetal bradycardia * Maternal satisfaction by using numerical rating scale 0-10 (see above) 10 min after the end of attempted ECV * Mode of delivery after successful and failed ECV will be recorded by reviewing the electronic medical records Randomization: \- Randomization will be achieved by a statistician using an online random number generator Sample Size Estimation A sample size of 40 parturients (20 per group) would give 80% power to detect a difference of 0.2 in the change in successful ECV rate. Assuming the use of sevoflurane will have 65% success rate and confidence interval 95% with 5% margin of error and total number of cases per year in our center is 45 patients. The average success rate of ECV in patients who either did not receive any intervention or just receive intravenous analgesia is 43.1% (10). So, we are aiming to increase the success rate of ECV by using Sevoflurane to be more than or equal to 65%. The sample size calculation will be 40 cases. The sample size was calculated by the help of this website (http://www.raosoft.com/samplesize.html). Statistical Analysis This prospective randomized controlled study will compare the difference in success rate of ECV when a subject receives a sevoflurane or not. Other covariable like pain scores and adverse effects will also be recorded. Data will be stored in an excel database and analyzed with SPSS statistical software. Demographic data and intraoperative and PACU continuous and categorical data will be analyzed by Student t-test, ANOVA for repeated measures, or Chi-Squared test, accordingly. A P-value \< 0.05 will be considered statistically significant.