Optimal Dose of Spinal Bupivacaine on Maternal and Fetal Outcomes in Parturients Undergoing Combined Technique for Labor Analgesia: A Randomized Double Blinded Prospective Study

Study Objectives: Maternal hypotension and fetal bradycardia (FB) are recognized complications of combined spinal epidural. Our purpose was to ascertain which of 3 common doses of spinal bupivacaine results in optimal analgesia with minimal side effects, assuming the lowest dose fills all criteria. Design: Prospective, randomized clinical trial. Setting: Labor and Delivery Unit of 514-bed urban teaching hospital. Patients, Interventions and Measurements: Patients were assigned to receive an intrathecal dose of 20 mcg of fentanyl with either 2.5 mg, 1.66 mg, or 1.25 mg of isobaric bupivacaine. Visual Analog Scale (VAS) Pain Score, fetal heart rate (FHR), maternal blood pressure (BP), number of hypotensive episodes, doses of vasopressors, nitroglycerin and mode of delivery were recorded at various time points. Main results: 164 patients were enrolled: 66 receiving 1.25 mg, 50 in the 1.66 mg group and 48 in the 2.5 mg. At 6 and 10 minutes, we recorded in the 1.66 mg group: 4.7% and 4.6%, 18.9% and 23.9% fewer hypotensive episodes compared with the 1.25 mg and the 2.5 mg groups respectively and significantly more hypotensive episodes in the 2.5 mg group (p = 0.025 and 0.019 respectively). There was no statistical difference in vasopressors use, mode of delivery or FB. The VAS decreased equally by an average of 7–10 points among all groups. Conclusion: The 1.66 mg spinal dose was associated with the least hypotensive episodes and equivalent pain relief as the 2.5 mg. The 1.25 mg and 1.66 mg doses allowed for adequate BP and FHR stability. Clinical Trial: Study registered on the ClinicalTrial.gov website under the NCT number NCT02159807