TNS..When spinal causes Harm

Increased awareness of TNS beginning in early 1990s

Incidence dependent on type of surgery:

Patient in lithotomy or gynecologic position at highest risk (≈40%).

Next highest group appears to be knee arthroscopy (due to positioning and manipulation).

Group with lowest incidence (4%-8%) are those having spinal anesthesia and placed in supine position (eg, inguinal hernia repair, umbilical hernia repair).

Potential causes of TNS

Local anesthetic toxicity (all local anesthetics toxic)
Neural ischemia related to stretching (particularly of sciatic nerve)
Needle trauma, maldistribution, patient positioning, muscle spasm, and early ambulation have all been discounted as causes.

Recommendation

Lidocaine can be used in patients in supine, but not lithotomy position; also avoid in knee arthroscopy
Uses less lidocaine than in past (rarely uses >60 mg)
No difference in incidence based on needle type; dilution probably not helpful

Comments

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