Anesthesia Considerations 

Postoperative Nerve Injury 

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Background

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• Third-most common cause of anesthesia-related medical litigation

• Most common nerves injured:

  • Ulnar nerve, brachial plexus, lumbosacral nerve roots, spinal cord

• Grade of injury:

  • Grade I - Neurapraxia (compression) - Focal segmental demyelination (i.e. myelin sheath only)

  • Grade II - Axonotmesis (crush) - Damaged axon with intact endoneurium

  • Grade III - Axonotmesis (crush) - Damaged axon and endoneurium with intact perineurium

  • Grade IV - Axonotmesis (crush) - Damaged axon, endoneurium, perineurium with intact epineurium

  • Grade V - Neurotmesis (transection) - Complete nerve transection

 

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Considerations

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• Very rare event (incidence ~ 0.03%)

• U/S use in regional does NOT ↓ risk of nerve injury

• Important to document pre-existing neurological deficits

• Mechanisms:

  • Direct nerve damage from trauma

  • Stretch and compression

  • Ischemia

  • Toxicity from injected solutions

  • Second-hit on nerve with pre-existing injury

• Risk factors:

  • Neuro, cardiac, GI, ortho sx

  • HTN, DM, smoking

  • Pre-existing peripheral neuropathies

  • GA, epidural

  • ↓ Fluid status, ↓BP, electrolyte abn, ↓ temp

• Signs / symptoms depend on specific nerve injured (see below)

  • Anesthesia, paresthesia, hypo/hyperasthesia, pain, motor deficit

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Prevention 

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• Understand which nerves are at risk with each procedure/position

• Avoid ↓BP, ↓temp, dehydration

• Careful positioning and judicious padding

• Avoidance of contact of susceptible nerves to hard surfaces

• Regional techniques:

  • Use less toxic LAs + vasoconstrictors for regional techniques (i.e. use Ropivicaine)

  • Avoid injecting during pain or paresthesia (likely perineurial injection)

• Lower limb nerves:

  • Adequate padding when patient is in lithotomy, prone or lateral positions (hip flexion > 120 deg)

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Management 

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• Clinical exam/history to localize lesion and identify pre-existing lesions

• Document sensory/motor deficits as well as severity of each

  • Important for prognosis

• Consult neurology

• Request EMG + nerve conduction studies to determine:

  • Complete vs incomplete lesion

  • Localization of lesion

  • Severity and age of lesion

  • Guide prognosis + recovery course

• MRI +/- high-res U/S may help further localize otherwise ambiguous lesions

 

Prevention 
 

• Understand which nerves are at risk with each procedure/position

• Avoid ↓BP, ↓temp, dehydration

• Careful positioning and judicious padding

• Avoidance of contact of susceptible nerves to hard surfaces

• Regional techniques:

  • Use less toxic LAs + vasoconstrictors for regional techniques (i.e. use ropivicaine)

  • Avoid injecting during pain or paresthesia (likely perineurial injection)

 

• Lower limb nerves:

  • Adequate padding when patient is in lithotomy, prone or lateral positions (hip flexion > 120 deg)

 

 

Specific Nerve Injuries 

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• Ulnar Nerve Injury (C7, C8-T1)

  • Most common --> superficial + close to medial condyle 

  • Men > women

  • Possible pre-existing subclinical neuropathy exacerbated by surgery

  • Symptoms can present up to 28 days post-op

  • Mechanism:

    • direct pressure on ulnar groove

    • prolonged forearm flexion

  • Signs/symptoms:

    • tingling/numbness along pink finger

    • weak add/abduction o fingers

    • hyperextension of MTP joints

    • flexion at distal + proximal ITP joints of ring + little finger

  • Prevention:

    • General considerations above

    • Mandatory padding

    • Keep forearm in supine/neutral position

    • Maintain flexion/extension of elbow < 90 deg

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• Brachial Plexus Injury (C5-T1)

  • Common --> superficial structure which runs btw two fixed points (intervertebral foramen + axillary sheath)

  • Mechanism:

    • Compression (e.g. retraction during median sternotomy or lateral decubitus position)

    • Stretching (i.e. Arm abduction + external rotation + posterior shoulder displacement)

    • Direct trauma during regional technique

  • Signs/symptoms:

    • C5-C6 lesions: Waiter's tip = arm hangs by side, medially rotated + pronated

    • C8-T1 lesions: flexion of small muscles of hand ("claw hand"), numbness in ulnar area

  • Prevention:

    • General considerations as described above

    • Maintain arm ABduction < 90 deg

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• Radial Nerve Injury (C5-T1)

  • Usually injured at spiral groove of the humerus

  • Mechanism:

    • Tourniquets/BP cuff compression

    • Arm board at incorrect height creating a step

  • Signs/symptoms:

    • Wrist drop

    • Numbness along:

      • Posterior + distal surface of arm

      • Posterior surface of forearm

      • Dorsum of hand + lateral 3 1/2 fingers

  • Prevention:

    • General considerations as described above

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• Median Nerve Injury (C5-T1)

  • Mechanism:

    • Direct trauma during regional technique

    • Surgical procedures on elbow

    • Compression in the carpal tunnel

  • Signs/symptoms:

    • Paresthesias: lateral 3 1/2 fingers + palmar aspect of hand

    • Supinated forearm

    • Weakness:

      • Abd + opposition of thumb

      • Wrist flexion

  • Prevention:

    • General considerations as described above

    • Mandatory padding

    • Keep forearm in supine/neutral position

    • Maintain flexion/extension of elbow < 90 deg

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• Axillary Nerve Injury (C5, 6)

  • Mechanism:

    • Shoulder dislocation

    • Shoulder surgery

  • Signs/symptoms:

    • Weakness: shoulder abduction

    • Numbness: upper lateral border of arm

  • Prevention:

    • General considerations as described above

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• Musculocutaneous Nerve Injury (C5-7)

  • Mechanism:

    • Shoulder dislocation

    • Shoulder surgery

  • Signs/symptoms:

    • Weakness: flexion of elbow

    • Numbness: lateral border of forearm 

  • Prevention:

    • General considerations as described above

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• Sciatic Nerve Injury (L4-S3)

  • Men > women, T2DM

  • Mechanisms:

    • Lithotomy, frog leg and seated positions (hyperflexion of hip, ABduction + extension off leg

    • Direct damage during: regional techniques + hip replacement surgery

  • Signs/symptoms:

    • Hamstring muscle paralysis

    • Weak knee flexion

    • Foot drop

    • Numbness: below knee in all areas except medial aspect of leg+foot

  • Prevention:

    • General considerations as described above

    • Adequate padding when patient is in lithotomy, prone or lateral positions (hip flexion > 120 deg)

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• Femoral Nerve Injury (L2-4)

  • Mechanisms:

    • Pelvic brim injury due to retractors in abdo/pelvic surgery

    • Ischemia during aortic cross clamp

    • Lithotomy position: extreme ABduction of thigh + ext rotation of hip

    • Direct damage during: vascular sx involving femoral vessels + hip replacement

  • Signs/symptoms:

    • Numbness: anterior thigh, medial leg

    • Weakness: hip flexion, knee extension

    • Absent knee jerk reflex

  • Prevention:

    • General considerations as described above

    • Adequate padding when patient is in lithotomy, prone or lateral positions (hip flexion > 120 deg)

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• Superficial Peroneal Nerve Injury (L4-S2)

  • Commonly compressed against the fibular head

  • Mechanism:

    • Direct trauma during knee arthroplasty

    • Lithotomy / lateral position

  • Signs / symptoms:

    • Weakness: dorsiflexion + eversion of the foot

    • Numbness: antero-lateral leg + dorsum of digits

  • Prevention:

    • General considerations as described above

    • Adequate padding when patient is in lithotomy, prone or lateral positions (hip flexion > 120 deg)

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References 

• ​Abdul Ghaaliq Lalkhen, Kailash Bhatia. Perioperative peripheral nerve injuries. Continuing Education in Anaesthesia Critical Care and Pain. Volume 12, Issue 1, 2012. Pages 38-42.

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