Quality of Postoperative Analgesia and Functional Recovery After Elective Cesarean Delivery Adding Different Doses of Intrathecal Fentanyl to Spinal Anesthesia With Bupivacaine and Intrathecal Morphine. A Single Center, Randomized, Multiple Blinded, Controlled Trial

In the study intervention group every patient will receive a spinal anesthesia composed by hyperbaric bupivacaine 12 mg 0,5 %, morphine sulfate 100 mcg and an added randomized dose of 10 or 20 mcg IT fentanyl. The spinal anesthetic will be administered with a 27 gauge Whitacre needle at the L2-3 or L3-4 intervertebral space with the patient in sitting position. Sterile saline will be used to dilute the mixture to a final volume of 3.1 mL. The allocated treatment will be kept a secret from the patient, the anesthesiologist managing the patient, and the entire study team. The fentanyl doses will be prepared by an anesthesiologist who will not be involved in the study or the patient's treatment. For 24 hours following surgery, each patient would receive intravenous patient-controlled morphine analgesia. In the control group every patient will receive a spinal anesthesia composed by hyperbaric bupivacaine 12 mg 0,5 % and morphine sulfate 100 mcg. The spinal anesthetic will be administered with a 27- gauge Whitacre needle at the L2-3 or L3-4 intervertebral space with the patient in sitting position. Sterile saline will be used to dilute the mixture to a final volume of 3.1 mL. The allocated treatment will be kept a secret from the patient, the anesthesiologist managing the patient, and the entire study team. For 24 hours following surgery, each patient would receive intravenous patient- controlled morphine analgesia.