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Postoperative Nerve Injury 

Background

  • 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

 

Considerations

  • 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

Prevention 

  • Manage patient expectations (explain GA vs MAC)

  • Recognize HR and BP alone are unreliable for determining anesthetic depth

  • Avoid muscle relaxants if possible, otherwise use twitch monitor

  • Consider use of BIS, raw EEG is even better

  • End-tidal monitoring of volatile agents

    • Aim for MAC>0.7

    • Provides safety margin b/c MAC-movement > MAC-awake & MAC-amnesia

  • Use target-controlled infusion (TCI) for TIVA

  • Use isolated forearm technique

    • Before NMBA given, tourniquet applied to a forearm, so that later an aware patient can alert team

Management 

  • 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 

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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)

  • 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)

  • 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)

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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