Intrathecal Morphine for Cesarean Section: Recommendations and Contraindications
Primary Recommendation
Intrathecal morphine at doses of 50-100 μg is strongly recommended for postoperative pain management in elective cesarean sections performed under neuraxial anesthesia. 1
This recommendation is based on the 2021 PROSPECT (Procedure Specific Postoperative Pain Management) guidelines published in Anaesthesia, which represent the highest quality, most recent evidence-based consensus for cesarean section analgesia. 1
Optimal Dosing Strategy
Use intrathecal morphine doses ≤100 μg to maximize analgesia while minimizing side effects. 1, 2
- Doses of 50-100 μg provide adequate analgesia with reduced incidence of side effects compared to higher doses. 1
- Lower doses (even 25 μg) combined with multimodal analgesia can be effective, reducing opioid-related adverse effects like pruritus. 3
- The safety of intrathecal morphine in cesarean patients has been confirmed in large-scale studies. 1
Essential Multimodal Approach
Intrathecal morphine must always be combined with basic analgesics—never use it as monotherapy. 1
The complete regimen includes:
- Paracetamol (oral pre-operatively or IV intra-operatively after delivery) 1, 4
- NSAIDs (IV intra-operatively after delivery, continued postoperatively) 1, 4
- IV dexamethasone (intra-operatively after delivery for both analgesia and antiemetic effects) 1, 4
- Postoperative continuation of scheduled paracetamol and NSAIDs with opioids reserved for rescue only 1, 2
This multimodal approach is critical because studies demonstrate that NSAIDs provide pain control comparable to opioids, and regular administration limits rescue opioid requirements. 1
Absolute Contraindications to Intrathecal Morphine
Based on FDA labeling and clinical guidelines, do NOT use intrathecal morphine in the following situations: 5
From FDA Drug Label:
- Hypersensitivity to morphine 5
- Convulsive states (status epilepticus, tetanus, strychnine poisoning) due to morphine's stimulating effect on the spinal cord 5
- Diarrhea caused by poisoning until toxic material is eliminated from the GI tract 5
From Clinical Guidelines:
- Coagulopathy or hemostasis disorders (absolute contraindication to neuraxial anesthesia itself) 2
- When spinal anesthesia is not possible (in these cases, use epidural morphine or diamorphine 2-3 mg instead) 1
- Emergency or unplanned cesarean sections (these guidelines apply specifically to elective cases under neuraxial anesthesia) 1
- Cesarean sections performed under general anesthesia (recommendations do not apply) 1
Side Effect Profile and Management
Common side effects are generally manageable and short-lived, but require monitoring. 6
Expected Side Effects:
- Pruritus (most common, dose-dependent; higher incidence with doses ≥100 μg) 3, 7, 8
- Nausea and vomiting (reduced by concurrent IV dexamethasone) 1, 6
- Urinary retention 6
Serious but Rare Complication:
- Delayed respiratory depression (incidence approximately 0.26% with 150 μg dose; severe cases requiring naloxone occur in ~0.05% of patients) 9
- Respiratory monitoring for 24 hours post-administration is standard practice 9
- One case series reported oxygen desaturation requiring naloxone in 1/1915 patients receiving 150 μg 9
The lower recommended doses (50-100 μg) have superior safety profiles compared to historical higher doses. 1, 7
Alternative When Intrathecal Morphine Cannot Be Used
If intrathecal morphine is contraindicated or spinal anesthesia is not possible, use alternative regional techniques: 1
- Epidural morphine or diamorphine 2-3 mg (when epidural catheter is in situ) 1
- Intrathecal diamorphine 300 μg (alternative to morphine, recommended by NICE guidelines in UK) 1
- Local anesthetic wound infiltration (single-shot or continuous infusion) 1
- Fascial plane blocks (TAP blocks, quadratus lumborum blocks) 1, 8
Important caveat: Regional blocks like TAP provide inferior analgesia compared to intrathecal morphine (higher supplemental morphine requirements and pain scores) but have fewer opioid-related side effects. 8 Therefore, these blocks should be administered only if intrathecal morphine is not used—their additional benefit when combined with intrathecal morphine is minimal. 1
Critical Clinical Pitfalls to Avoid
- Do NOT omit basic analgesics (paracetamol/NSAIDs) when using intrathecal morphine—this is a fundamental error that increases opioid requirements. 1
- Do NOT use gabapentinoids pre-operatively due to limited evidence and concerns about sedation and respiratory depression. 1, 2
- Do NOT apply these recommendations to emergency cesarean sections or those under general anesthesia—the evidence base is specific to elective cases under neuraxial anesthesia. 1
- Monitor for hypotension after spinal anesthesia and treat promptly with vasopressors. 2
- Exercise caution with IV dexamethasone in patients with glucose intolerance. 1
Scope of Application
These recommendations apply specifically to: 1
- Elective cesarean sections
- Procedures performed under neuraxial (spinal or epidural) anesthesia
- Healthy, full-term parturients
These recommendations may NOT be applicable to: 1
- Parturients with morbid obesity
- Patients with chronic pain conditions
- Preterm deliveries
- Patients with co-existing medical conditions