• Perioperative nerve injury
    • Mechanisms
      • Direct nerve damage
        • Surgery
        • Needle
        • Trauma
      • Stretch and compression
        • Poor padding
        • Limb positioning
      • Ischaemia
        • Tourniquets
        • Haematomas
        • LA drugs
      • Toxicity of solutions
        • LA can cause cytotoxic axonal damage
        • Higher incidence if pre-existing neuropathy
      • Unknown factors play a role
    • Classification
      • Neuropraxia
        • Local myelin damage with nerve intact
      • Axonotmesis
        • Continuity of axon lost but intact epineurium; Wallerian degeneration occurs due to axoplasmic flow disruption
      • Neurotmesis
        • Complete division of he entire nerve trunk
    • Diagnosis
      • History and examination vital
      • Assess degree of impairment
      • Liase with neurologist
      • EMG
        • Reduced recruitment of motor units
        • Abnormal spontaneous activity (reduces with re-innervation)
      • Nerve conduction studies
        • Looks at conduction velocity and size of the response to evaluate functional integrity ane allow localisation
      • MRI
        • 3T MRI can show nerves, best used when NCS have located likely site of lesion
    • Prevention measures
      • Thorough pre-op assessment for existing nerve damage or predisposing conditions
      • Avoid dehydration, hypotension, hypothermia
      • Careful positioning with padding, padded arm boards, avoid contact with hard surfaces
      • Limit arm abduction to <90 degrees
      • Adequate documentation
      • Consider avoidng more potent LA, and avoid adrenaline if high risk
      • Pain or paraesthesia on injection - abandon or reposition needle
    • Nerve injuries
      • Upper limb
        • Ulnar nerve
          • Commoner in men, less adipose tissue. Often subclinical but can progress over next 4/52
          • Direct pressure in the ulnar groove is the proposed mechanism
          • Presents as paraesthesia, 'ulnar clawing' of the hand
        • Brachial plexus
          • Relatively fixed between intervertebral foramen and axillary sheath, so traction can occur
          • Caused by sternal retraction, compression against humeral head (lateral position), extreme arm abduction/external rotation
          • Upper roots (C5/6) affects musculocutaneous, axillary and suprascapular nerve so the arm adopts the 'Waitor's tip' position. C8-T1 affects the ulnar nerve and so 'claw hand' is seen
        • Radial nerve
          • Caused by pressure cuffs or direct compression
          • Wrist drop and posterior aspect of the forearm numbness seen
        • Median nerve
          • Direct damage around carpal tunnel, elbow procedures and regional techniques are causes
          • Numbness of palmer aspect of lateral 3 and a half fingers, weakness of wrist flexion, abduction and opposition of thumb, wasted thenar eminence
        • Axillary nerve
          • Shoulder dislocation, shoulder surgery are causes
          • Causes weakness of shoulder abduction, numbness over 'badge' area
        • Musculocutaneous nerve
          • Numbness of lateral border of the arm and weakness of elbow flexion
      • Lower Limb
        • Sciatic nerve
          • Stretch, compression, ischaemia, direct damage
          • Weakness of hamstring and all muscles below the knee and numbness below the knee except medial aspect of leg and foot
        • Femoral nerve
          • Compression, ischaemia (aortic cross clamp), lithotomy position, hip procedures implicated
          • Loss of sensation anterior thigh, and medial aspect of leg, weak hip flexion and knee extension
        • Common peroneal nerve
          • Due to knee surgery, lithotomy or lateral positioning
          • Foot drop with anterolateral leg and dorsum of the foot paraesthesia
    • USS does not seem to reduce the incidence of nerve injuries
    • CEACCP
      Link:ceaccp.oxfordjournals.org/content/12/1/38.full.pdf