Magnesium Sulphate Versus Dexamethasone With TAP Block for Post-Cesarean Analgesia

Post-cesarean pain can affect maternal comfort, mobility, breastfeeding and postoperative recovery. Effective postoperative analgesia is therefore an important component of care following cesarean section. Ultrasound-guided transversus abdominis plane (TAP) block is used as part of multimodal analgesia to provide abdominal wall somatic analgesia and may reduce the requirement for systemic opioid analgesics.

This study will evaluate whether the addition of a single intravenous dose of magnesium sulphate or dexamethasone provides better postoperative analgesia when used as an adjunct to ultrasound-guided TAP block in women undergoing elective cesarean section.

The study will be conducted as a randomized, double-blind, controlled clinical trial in the Department of Anesthesia, Khyber Teaching Hospital, Peshawar. A total of 80 women will be included, with 40 participants allocated to the magnesium sulphate group (Group M) and 40 participants allocated to the dexamethasone group (Group D).

Eligible participants will be women aged 18-40 years undergoing elective lower-segment cesarean section under spinal anesthesia, with ASA physical status I or II, singleton full-term pregnancy of at least 37 weeks, and willingness to provide written informed consent.

Participants with known allergy or contraindication to magnesium sulphate, dexamethasone or local anesthetics; chronic pain disorders or regular analgesic/opioid use; neurological, renal, hepatic or cardiovascular disease; pregnancy complications such as pre-eclampsia, eclampsia or placenta previa; conversion to general anesthesia; inadequate spinal anesthesia or failed TAP block; or refusal to participate will be excluded.

Following enrollment and informed consent, participants will be randomly allocated using a computer-generated randomization list. Group M will receive a single intravenous dose of magnesium sulphate 50 mg/kg diluted in 100 mL normal saline 15 minutes before the TAP block. Group D will receive a single intravenous dose of dexamethasone 8 mg diluted in 100 mL normal saline 15 minutes before the TAP block.

All participants will receive spinal anesthesia at the L3-L4 interspace using a 25-G spinal needle and 0.5% hyperbaric bupivacaine at a dose of 10-12 mg under aseptic conditions.

Following cesarean section and stabilization in the recovery area, all participants will receive a bilateral ultrasound-guided TAP block using 20 mL of 0.25% bupivacaine on each side. The block will be performed by a skilled anesthesiologist using a high-frequency linear ultrasound probe.

Patients will be monitored during the perioperative period for heart rate, blood pressure, respiratory rate and oxygen saturation. Postoperative pain will be assessed using the Visual Analog Scale, with 0 representing no pain and 10 representing the worst imaginable pain. Pain will be assessed at 2, 4, 8, 12 and 24 hours after surgery, both at rest and on movement.

The duration of analgesia will be assessed as the time from administration of the TAP block until the patient's first request for rescue analgesia. Rescue analgesic requirement will be assessed by recording the number of rescue analgesic doses and total tramadol consumption during the first 24 postoperative hours. Each rescue dose of tramadol will be recorded as 50 mg intravenously according to the study protocol.

Adverse effects including nausea, vomiting, dizziness, sedation and allergic reactions will also be recorded. Patient satisfaction with postoperative pain control may also be assessed.

Data collection will be performed by qualified anesthesiology residents who will remain blinded to group allocation. The primary investigator will review completed data collection forms for accuracy and completeness.

The collected data will be entered and analyzed using SPSS version 26.0. Quantitative variables including age, weight, duration of analgesia and total tramadol consumption will be summarized using mean and standard deviation where appropriate. The Shapiro-Wilk test will be used to assess normality. The independent-samples t-test will be used for normally distributed continuous variables, while the Mann-Whitney U test will be used for non-normally distributed variables. Categorical variables, including adverse effects, will be presented as frequencies and percentages and compared using the Chi-square test or Fisher's exact test as appropriate. A p-value of less than 0.05 will be considered statistically significant.

The study will compare the postoperative analgesic effectiveness of intravenous magnesium sulphate and dexamethasone when used as adjuvants to ultrasound-guided TAP block. The outcomes will provide information regarding postoperative pain scores, duration of analgesia, rescue analgesic requirement, total tramadol consumption and adverse effects in women undergoing elective cesarean section.

Inclusion criteria

• Women aged 18-40 years.
• Undergoing elective lower-segment cesarean section under spinal anesthesia.
• American Society of Anesthesiologists (ASA) physical status I or II.
• Singleton, full-term pregnancy with gestational age of at least 37 weeks.
• Willing to provide written informed consent.

Exclusion criteria

• Known allergy or contraindication to magnesium sulphate, dexamethasone, or local anesthetics.
• History of chronic pain disorders or regular use of analgesics or opioids.
• Neurological, renal, hepatic, or cardiovascular disease.
• Pregnancy complications such as pre-eclampsia, eclampsia, or placenta previa.
• Intraoperative conversion to general anesthesia.
• Inadequate spinal block or failed TAP block.
• Refusal to participate in the study.