II. Indication
- Analgesia and Anesthesia for First Stage of Labor
- Gives four hours of Labor Anesthesia
III. 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
IV. Labs
-
Complete Blood Count with Platelets
- Confirm no Coagulopathy
V. Advantages
- Single injection into the intrathecal space offers nearly immediate relief without retained catheter
VI. 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
- Site: L3-4 interspace
- Instill Intrathecal medications
VII. 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
VIII. Adverse Effects
- Maternal Hypotension
- Nausea or Vomiting
- Pruritus
- Skin Hypersensitivity
- Postdural Puncture Headache
- Associated with increased instrument-assisted Vaginal Delivery (vacuum or forceps)