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Chapter 121. Neuraxial Anesthesia

Toni Torrillo, MD

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Contraindications to Neuraxial Anesthesia
AbsoluteRelativeControversial
  • Patient refusal
  • Infection at injection site
  • Increased ICP
  • Coagulopathy (cutoff for PTT, INR, platelet values unclear)
  • Antiplatelet medications (e.g., clopidogrel [Plavix], ticlopidine [Ticlid])
  • Critical aortic or mitral stenosis
  • Severe spinal deformity or pathology (complete spina bifida, meningocele)
  • Uncooperative patient
  • Sepsis
  • Preexisting neurological deficits,1 hydrocephalus, severe convulsive disorders
  • Complicated surgery (major EBL, potential for respiratory compromise)
  • Stenotic heart valve—weigh risk/benefit. Consider patient functional status
  • Severe hypovolemia
  • Spinal deformity or pathology not at injection site
  • Inability to communicate with patient
  • Demyelinating lesions1 (multiple sclerosis)
  • Prior back surgery or fusion
  • Spinal anesthesia following failed epidural anesthesia

1Concern may be more medicolegal than medical.

  • Platelets, PTT, INR, platelets, except in ASA 1 patients
  • Reassure patients they may have sedation or general anesthesia to supplement neuraxial technique
  • Explain risks, benefits, and alternatives
  • Adverse effects:
    • Happen on occasion but not serious:
      • Headache, hypotension, nausea, itching if opioids used, risks of long-acting drugs such as preservative-free morphine, failed attempt, need to try a different level, inability to perform spinal or epidural and need for general anesthesia, difficult/lengthy surgery necessitating conversion to general anesthesia despite working neuraxial technique
    • Rare but serious:
      • Bleeding, infection, nerve injury, high anesthetic level, respiratory, or cardiovascular compromise

  • Anatomy:
    • Spinal cord from foramen magnum → L1 (adults) or L3 (children)
    • Dural sac/subarachnoid/subdural space → S2 (adults) or S3 (children)
  • Surface landmarks (Figure 121-1)
  • Spine anatomy (Figure 121-2):
    • Ligaments:
      • Supraspinous
      • Interspinous
      • Ligamentum flavum—thickest (3–5 mm) and furthest from meninges (4–6 mm) at midline, thus less likely to get accidental dural puncture with midline approach
  • Landmarks for testing level of anesthesia:
    • T4—nipple
    • T7—xiphoid process
    • T10—umbilicus
    • L1—inguinal ligament
  • Gentle pinprick (sensory test) or cold alcohol swab (sympathetic):
    • Sympathetic block 2 levels > sensory block 2 levels > motor block
    • Monitor BP q1 minute initially (level stabilizes at 10–15 minutes for short-acting locals and 20-30 minutes for longer-acting locals)
  • Positioning:
    • Sitting:
      • Easier to appreciate midline (obese, scoliotic)
      • Chin down, shoulders relaxed, back flexed (angry cat/shrimp)
    • Lateral:
      • Patient on his or her side, chin down, knees flexed (fetal position)
      • Note that males and females have different shoulder/hip width ratios, with the spine typically not horizontal
      • CSF flow typically slower
    • Prone:
      • Spinal anesthesia for anorectal procedures with hypobaric anesthetic and jackknife position or when fluoroscopic guidance used for neuraxial technique
      • CSF may not flow freely and may need to be aspirated
  • Approaches (Figure 121-3):
    • Midline:
      • Identify spinous process above and below level to be used
      • Depression between spinous processes is needle entry point
      • Spinous processes course downward; needle direction should aim slightly cephalad for lumbar procedures and fairly acute (30–50°) for thoracic epidural
    • Paramedian (Figure 121-4):
      • Useful in patients who are difficult to position (inability to flex spine) or with calcified interspinous ligaments
      • Identify upper and lower spinous processes at desired level
      • Insert needle 1 cm lateral to the lower spinous process
      • Needle should enter skin at ...

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