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Effect of bupivicaine dose in combined spinal epidurals in laboring parturients: A randomized double-blinded prospective study
Abstract Number: O2-6
Abstract Type: Original Research
Background: Combined spinal epidural anesthesia (CSE) is a safe and simple procedure which provides adequate analgesia in laboring patients. Two possible complications of this technique are maternal hypotension and fetal bradycardia, which have been demonstrated to result from both rapid pain relief and sympathetic blockade (1). Previous studies have shown the ED95 of bupivacaine to be 1.66mg (less than the standard 2.5mg often being used) (2).
Material and Methods: Two hundred patients between 37-42 weeks gestational age were sought from Labor and Delivery patients who expressed interest labor analgesia. Patients with pre-eclampsia, gestational hypertension, and parturients in whom spinal anesthetics are contraindicated or cannot be performed we excluded. Patients were administered a spinal dose that was labeled only with a numerical code dispensed from pharmacy. The dose contained 20mcg of fentanyl with 2.5mg, 1.66mg, or 1.25 mg of bupivacaine. VAS pain score, fetal heart rate, and maternal blood pressure were recorded prior to administration and regularly for the first hour afterwards. Additionally delivery method was recorded, along with doses of required vasopressors and nitroglycerin.
Results: The three groups were compared with respect to the primary variables of maternal hypotension and fetal bradycardia. The 2.5 mg bupivacaine group had significantly more hypotension than the two lower dose groups. Accordingly, there was increased vasopressor use in highest dose group. Fetal bradycardia was a rare event in the study overall, so it was not possible to compare between the three groups. Additionally, VAS pain scores were compared between the groups. The pain reduction and overall pain scores were equivalent between all groups. Finally, the three dose groups had no difference in method of delivery.
Conclusions: CSE with 20mcg of fentanyl and 1.25mg of bupivacaine provided the least amount of hypotension and equivalent pain scores as the highest dose. This dose was the safest dose overall. There was no advantage to using higher doses with regards to pain scores or hemodynamic measures. All doses demonstrated remarkable safety with regards to fetal bradycardia, despite the fact that VAS pain scores saw a significant decrease after CSE dosing (and this has been linked to fetal bradycardia elsewhere (3)). Lastly, the dose of bupivacaine in the CSE had no relationship to the method of delivery.
1) Clarke VT, Smiley RM, Finster M. Uterine hyperactivity after intrathecal injection of fentanyl for analgesia during labor: a cause of fetal bradycardia? Anesth 1994; 81(4):108.
2) Whitty R, et al. Determination of the ED95 for intrathecal plain bupivacaine combined with fentanyl in active labor. IJOA 2007; 16.4: 341-345.
3) Cheng SL, Bautista D, Leo S, Sia TH. Factors effecting fetal bradycardia following combined spinal epidural for labor analgesia: a matched case-control study. J Anesth 2013 Apr; 27 (2): 169-174.