Ultrasound-Guided Posterior Quadratus Lumborum Block With Bupivacaine and Dexmedetomidine Versus Intrathecal Morphine for Postoperative Analgesia After Cesarean Delivery

Ultrasound-Guided Posterior Quadratus Lumborum Block With Bupivacaine and Dexmedetomidine Versus Intrathecal Morphine for Postoperative Analgesia After Cesarean Delivery

Cesarean delivery (CD) is one of the most commonly performed surgical procedures worldwide, with millions of women undergoing the procedure annually (1). Despite advances in surgical techniques and perioperative care, postoperative pain management remains a significant clinical challenge (2). Moderate to severe postoperative pain is commonly reported following CD, which can seriously impair daily activities, hinder maternal-infant bonding, delay recovery, and increase the risk of negative psychological outcomes, including postpartum depression and chronic pain syndromes. Effective postoperative analgesia is crucial not only for maternal comfort but also for optimizing recovery outcomes. Adequate pain control facilitates early mobilization, reduces hospital length of stay, promotes breastfeeding initiation, and strengthens the maternal-infant relationship Consequently, clinicians continuously refine postoperative analgesic protocols to enhance both effectiveness and safety while minimizing adverse effects that could compromise maternal and neonatal well-being. The Challenge of Post-Cesarean Analgesia Intrathecal morphine (ITM) has long been considered the "gold standard" for postoperative analgesia following cesarean delivery due to its excellent analgesic efficacy and prolonged duration of action (3). Administered as a single injection during spinal anesthesia, ITM provides effective pain relief for 12-24 hours postoperatively, making it a cornerstone of enhanced recovery after cesarean (ERAC) protocols. However, ITM is associated with a significant side-effect profile that limits its clinical utility. Higher doses, while offering superior pain control, substantially increase the risk of adverse effects including pruritus, postoperative nausea and vomiting (PONV), urinary retention, and potentially life-threatening respiratory depression. Studies have demonstrated that pruritus occurs in up to 91% of patients receiving 200 mcg of ITM, while respiratory depression risk increases significantly with doses exceeding 0.3 mg (6). Although dose reduction can mitigate these effects, the optimal dose that balances analgesia with an acceptable side-effect profile remains controversial. Some evidence suggests that doses as low as 0.025-0.075 mg may be sufficient when combined with multimodal analgesia (5,6). ltrasound-guided regional nerve blocks have emerged as valuable components of multimodal analgesia, offering the potential for effective pain relief while reducing systemic opioid exposure. Among these techniques, the quadratus lumborum block (QLB) has gained significant attention for abdominal surgeries, including cesarean delivery. The QLB targets the fascial planes surrounding the quadratus lumborum muscle. Unlike the transversus abdominis plane (TAP) block, which primarily provides somatic analgesia of the anterolateral abdominal wall, the QLB offers potential advantages including more extensive sensory blockade (T6-L3) and the ability to address both somatic and visceral pain components through spread of local anesthetic to the paravertebral space (4,7) between groups. Evidence suggests that bilateral QLB provides more effective postoperative pain relief than TAP blocks for cesarean delivery, with better visceral pain control and greater opioid-sparing effects. The addition of dexmedetomidine as an adjuvant to local anesthetics in QLB has shown promising results. Dexmedetomidine, a selective alpha-2 adrenergic agonist, possesses analgesic and sedative properties without respiratory depression. Studies have demonstrated that perineural dexmedetomidine prolongs the duration of local anesthetic action, likely through localized vasoconstriction and inhibition of nerve fiber action potentials. Clinical trials have found that adding dexmedetomidine to bupivacaine in QLB significantly prolongs the time to first rescue analgesia request Study Aims and Hypotheses Primary Aim: To compare the analgesic efficacy of ultrasound-guided bilateral QLB with bupivacaine and dexmedetomidine versus intrathecal morphine for postoperative analgesia following elective cesarean delivery.

Inclusion Criteria:

• Age ≥ 18 years • Singleton pregnancy • Term pregnancy (≥ 37 weeks gestation) • Scheduled for elective cesarean delivery under spinal anesthesia • American Society of Anesthesiologists (ASA) physical status II or III • Ability to provide written informed consent

Exclusion Criteria:

• Contraindication to spinal anesthesia or regional nerve blockade • Known hypersensitivity to any study medication (bupivacaine, dexmedetomidine, morphine) • Significant cardiovascular, pulmonary, hepatic, or renal disease • Preeclampsia or eclampsia • Coagulopathy or bleeding diathesis • Infection at the injection site • Chronic pain conditions • Current opioid use or substance abuse • History of psychiatric illness that may interfere with pain assessment • Emergency cesarean delivery