Regional Anesthesia in Obstetrics

Regional Anesthesia in Obstetrics

Regional Anesthesia in Obstetrics

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Physiology & RA Choices - Bump & Block Basics

  • Physiological Changes (Pregnancy & RA):
    • CV: ↑CO, ↓SVR. Aortocaval compression (LUD vital!).
    • Resp: ↓FRC, ↑O₂ demand (rapid desaturation risk).
    • GI: ↓Gastric emptying, ↓LES tone (↑aspiration risk).
    • Nervous: ↑LA sensitivity (↓dose ~30%); engorged epidural veins (↓epidural volume).
  • RA Advantages (Obstetrics):
    • Maternal: Superior analgesia, awake patient, ↓aspiration, ↓opioids.
    • Fetal: Minimal drug transfer, better uteroplacental perfusion (normotension).
  • Indications: Labor analgesia (epidural, CSE); C-section (spinal, epidural, CSE).
  • Contraindications (Absolute): 📌 I CHOP: Infection (site), Coagulopathy (Plt < 80,000/µL)/Severe Hypovolemia, ↑ICP, Patient refusal.
  • Techniques & Levels:
    • Epidural: Slower, titratable. Labor: T10-L1. C-section: T4.
    • Spinal: Rapid, dense. C-section: T4.
    • CSE: Spinal speed + epidural flexibility.

Manual uterine displacement techniques

⭐ Aortocaval compression by the gravid uterus causes supine hypotension syndrome; left uterine displacement (LUD) is crucial.

Pharmacology of RA - Mommy's Magic Mix

Local Anesthetics (LAs):

  • Bupivacaine: Potent, long-acting; racemic ↑cardiotoxicity.
  • Levobupivacaine: S-enantiomer of bupivacaine, ↓cardiotoxicity.
  • Ropivacaine: ↓cardiotoxicity & ↓motor block vs Bupivacaine.
  • Lidocaine: Fast onset, short duration; for surgical epidurals.
  • Properties: pKa (onset), Lipid Sol. (potency/duration), Protein Bind. (duration).
  • Differential Block: Sensory > Motor.
  • Cardiac Toxicity: Bupivacaine > Ropivacaine/Levobupivacaine.
  • Placental Transfer & Ion Trapping: LAs cross placenta; fetal acidosis → LA accumulation in fetus.

⭐ Levobupivacaine and Ropivacaine have a better safety profile (less cardiotoxic) than racemic Bupivacaine.

Properties of Local Anesthetics for Regional Anesthesia

Neuraxial Opioids:

  • Lipophilic (fast onset, short duration): Fentanyl (Epidural 50-100 mcg, IT 10-25 mcg), Sufentanil (Epidural 5-20 mcg, IT 1-5 mcg).
  • Hydrophilic (slow onset, long duration): Morphine (IT 50-150 mcg).
  • Benefits: Synergy with LAs (↓LA dose).
  • Side Effects: 📌 Pruritus (common), N/V, Resp. Depression (early-lipo, delayed-hydro).

Adjuvants:

  • Epinephrine: Test dose marker (15 mcg), prolongs block (e.g., 1:200,000 / 5 mcg/mL).
  • Clonidine ($\alpha_2$-agonist): Prolongs analgesia (Epidural 75-150 mcg).

Patient-Controlled Epidural Analgesia (PCEA):

  • Concept: Patient-controlled epidural boluses for labor.
  • Advantages: ↑Maternal satisfaction, ↓motor block, ↓total drug.
  • Typical Mix: Bupivacaine 0.0625%-0.125% + Fentanyl 1-2 mcg/mL.

Complications & Special Cases - Wobbly Walk & Woes

  • Maternal Hypotension: Common. Prevent: LUD, IV fluid co-load. Manage: Phenylephrine 50-100 mcg IV.

  • PDPH (Post-Dural Puncture Headache): Postural headache. Prevent: Atraumatic needles. Manage: Conservative; EBP (15-20 mL blood).

  • High/Total Spinal: Rapid ↑ block, respiratory distress, ↓BP. Manage: ABCs, intubate if needed.

  • LAST (Local Anesthetic Systemic Toxicity): 📌 SAMS (Slurred speech, Agitation, Metallic taste, Seizures). Manage: Stop LA, ACLS, Intralipid 20% (1.5 mL/kg bolus, 0.25 mL/kg/min infusion).

    ⭐ For LAST management, lipid emulsion therapy (Intralipid 20%) should be initiated early along with standard ACLS protocols, avoiding vasopressin, CCBs, beta-blockers or lidocaine for arrhythmias.

    LAST Management Algorithm

  • Neuro Complications: Rare. Nerve injury, epidural hematoma/abscess (urgent MRI).

  • Failed Block: Troubleshoot: reposition, supplemental LA, convert to GA.

  • Special Cases:

    • Preeclampsia: Platelets >80,000/µL for neuraxial.
    • Cardiac disease: Careful titration.
    • Coagulopathy: Contraindication if significant for neuraxial anesthesia.

High‑Yield Points - ⚡ Biggest Takeaways

  • Epidural analgesia is the gold standard for labor pain relief.
  • Spinal anesthesia is preferred for elective Cesarean sections due to rapid onset and dense block.
  • Combined Spinal-Epidural (CSE) offers rapid onset of spinal with prolonged analgesia via epidural catheter.
  • Hypotension is the most common side effect of neuraxial anesthesia; manage with IV fluids and vasopressors.
  • Bupivacaine is commonly used; ropivacaine and levobupivacaine offer ↑ cardiac safety.
  • PDPH is a key complication; manage conservatively, then epidural blood patch.
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_____ needle is used in epidural anesthesia and has a blunt curved tip (Huber tip), which helps prevent accidental dural rupture

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_____ needle is used in epidural anesthesia and has a blunt curved tip (Huber tip), which helps prevent accidental dural rupture

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