Comparison of Intrathecal Versus Epidural Fentanyl on Fetal Bradycardia in Labor Combined Spinal Epidural Analgesia

After approval by the Institutional Review Board and written informed consent, we plan to prospectively study pregnant patients who undergo neuraxial labor analgesia. All patients will receive combined-spinal-epidural analgesia. Patients will be randomly assigned to one of four groups by means of sealed envelope technique. Group A will receive a spinal dose of preservative-free fentanyl 25 mcg. Group B will receive one dose of spinal preservative-free 0.25% bupivacaine. Group C will receive a spinal combination of preservative-free 0.25% bupivacaine and fentanyl 25 mcg. Group D will receive spinal preservative-free 0.25% bupivacaine and epidural fentanyl 100 mcg. After the procedure, we will monitor the fetal heart rate and tocometry tracings for 20 min. Thereafter, an epidural infusion with a solution containing 0.125% bupivacaine and 2mcg/mL of fentanyl will be started. We will record demographic variables (age, and BMI), obstetric variables (parity, gestational age, cervical dilation, oxytocin infusion) and anesthetic variables (level of insertion of epidural catheter). Primary outcomes: Fetal heart rate (baseline, minimal and abnormal patterns) Secondary outcomes: * Blood pressure (systolic, diastolic and mean) measured at baseline and every 5 minutes after administration of medication. * Dermatomal level measured after 20 minutes of medication administration. * Pain level (visual analogue scale) after 20 minutes of medication administration. * Patient satisfaction level (1-10 scale) after 20 minutes of medication administration. * Uterine tone measured with tocometer at baseline and during 20 minutes after medication administration.