Comparative Analysis of Analgesic Efficacy: by Single Shot Intrathecal Analgesia (SSSA) in Normal Labor

on arrival to the operating room, the demographic and baseline data will be collected, which include sections about age, height, weight, primigravida or multigravida, cervical dilation at the time of performing labor analgesia, fetus presentation, presence of rupture of membrane, baseline pain scores will be assessed using a 10-cm VAS (0 = no pain and 10 = worst imaginable pain) before SSSA. Intravenous access will be achieved in all patients loading will be undertaken using 500 ml Ringer's solution, baseline values of pulse rate (PR), respiratory rate (RR), hemoglobin oxygen saturation (SpO2), and arterial blood pressure (ABP) will be recorded. SSSA will be performed with the parturient in the sitting position under complete aseptic precautions at the L3-L4 level using a 25-gauge spinal needles. The correct positioning of the needle tip in the intrathecal space will be confirmed by the observation of a free flow of cerebrospinal fluid, and then the prefilled study drug will be injected intrathecally which is 2.5 mg bupivacaine plus 25 mic fentanyl or 5 mic dexmedetomidine or 0.5 ml saline according to different groups.

parturient will then turn to the supine position, and a wedge will be placed under the right buttocks to prevent aortocaval compression. VAS will be evaluated every 5 min for the first 30 min, followed by every 20 min for 3 hours then every 30 min for next 3 hours. If VAS 8 or more the instigators will give the patient 50 mg intramuscular pethidine.

Maternal blood pressure, heart rate, respiratory rate, and oxygen saturation will be measured and recorded noninvasively every 5 min for the first half hour, followed by every 20 min for 3 hours, then every 1 h for next 3 hours. the investigators will give 5 mg ephedrine if there is hypotension ( decrease in ABP more than 25% of the baseline ABP) and .5 mg atropine if there is bradycardia (HR less than 50 beats per minute). Side effects such as hypotension, nausea, vomiting, bradycardia, shivering, pruritus, and tachycardia will be recorded. The first- and fifth-minute Apgar scores will also be recorded. The onset, duration of analgesia, and obstetric and neonatal outcomes will be compared.