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Intrathecal Morphine
Aka: Intrathecal Morphine, ITM, Spinal Anesthesia in Labor
- See Also
- Active Labor Anesthesia
- Latent Labor Anesthesia
- Non-Pharmacologic Pain Control in Labor
- Epidural Anesthesia
- Paracervical Block
- Pudendal Block
- Indication
- Analgesia and Anesthesia for First Stage of Labor
- Gives four hours of Labor Anesthesia
- Mechanism
- Acts at Opioid receptors
- Substantia gelatinosa of dorsal horn
- Affects afferent visceral pain impulses only
- Contrast with Epidural Anesthesia
- ITM does not affect second stage somatic pain
- ITM does not interfere with maternal pushing
- Does not inhibit efferent muscular paths
- Labs
- Complete Blood Count with Platelets
- Confirm no Coagulopathy
- Advantages
- Single injection into the intrathecal space offers nearly immediate relief without retained catheter
- Technique
- Patient lying in lateral decubitus position or seated
- Spinal needle Insertion
- Site: L3-4 interspace
- Insertion must be below L1-2 to prevent spinal cord injury
- Needle Gauge: 25 gauge ("Pencil point")
- Decreases Incidence of Postdural Puncture Headache
- Enter the dural sac as in Lumbar Puncture
- Clear Cerebrospinal Fluid should return promptly
- Instill Intrathecal medications
- Hyperbaric Lidocaine 25-50 mg
- Additional agents
- Fentanyl (Duragesic) 10-25 mcg
- Morphine (preservative-free) 0.25 mg
- Monitoring
- Initial
- Blood Pressure, Pulse every 5 minutes for 30 minutes
- Respiratory Rate every 15 minutes for 1 hour
- Later
- Monitor hourly for 24 hours
- Naloxone by bedside for respiratory depression
- Adverse Effects
- Maternal Hypotension
- Nausea or Vomiting
- Pruritus
- Skin Hypersensitivity
- Postdural Puncture Headache
- Associated with increased instrument-assisted Vaginal Delivery (vacuum or forceps)
- Reference
- Stephens (1997), Am Fam Physician 56(2):463-70 [PubMed]
- Schrock (2012) Am Fam Physician 85(5): 447-54 [PubMed]