Nerve/plexus injuries:
- Due to either direct surgical injury, or excessive stretch or compression from positioning or retractors
- Neuropathies are usually temporary but can be debilitating and are avoidable
Upper limb:
Brachial plexus:
- Vulnerable as it is fixed to fasciae in close proximity to bony structures
- In lateral position, downside arm vulnerable to compression, upside arm vulnerable to stretch
- Presentation variable depending on level
- Weakness of deltoid/biceps/brachioradialis/triceps/wrist and finger flexors
- Decreased sensation along a dermatome
- Absent reflexes
Other peripheral nerves:
- Usually from arm falling off arm board in supine, or from compression against IV pole etc
Lower limb:
Femoral nerve:
- S2 – S4, formed within psoas passing inferolaterally within psoas before emerging superior to inguinal ligament
- Injury results in weakness of hip flexion, knee extension, adduction and external rotation – difficulty ambulating post-operatively, or with stairs at home
- Also may have numbness/paraesthesias of anteromedial thigh
- Most commonly injured due to compression by self-retaining retractors
- Retractor directly placed onto psoas, typically in longer procedures i.e. cystectomy
- Directly compresses nerve, or indirectly trapped against pelvic side wall
- May also compress iliolumbar artery compromising femoral nerve blood supply
- Thin patients at higher risk
Common peroneal nerve:
- Common peroneal nerve arises from sciatic and wraps around fibular head – at risk of compression -> foot drop
Sciatic nerve:
- Can be excessively stretched by overflexion of the hip and overextension of the knee
Common surgical positions:
Supine:
- Avoid > 90 degree abduction of arms -> brachial plexus injury
- Use gutters to reduce pressure on ulnar nerve, and radial nerve running past humerus
Lithotomy:
- Manipulate both legs simultaneously with hip flexion 80 – 100° and 30 – 45° abduction (practically point stirrups towards contralateral shoulder)
- Padded to avoid compression of common peroneal nerve around neck of fibula
- foot drop, loss of eversion, loss of dorsal foot sensation
- Watch for hand injury from stirrup attachments
- Sciatic nerve can be stretched in excessive hip flexion or knee extension during positioning, or in the popliteal fossa resting against the stirrups
Lateral:
- GA and airway secured supine
- Then rolled on to side, with operative side upwards
- Lower leg is flexed at hip and knee, pillow between legs to avoid pressure points
- Heels and knees padded to avoid
- Watch the arms
- Ipsilateral arm on elevated arm rest/gel pad – not abducted > 90°, avoid excessive shoulder stretch
- Contralateral arm on arm rest 90° to table with ulnar padding/gutter
- Axillary roll (“chest roll” more correct) just caudal to axilla to avoid brachial plexus compression
- Adequately secured to avoid falling off – 2 x braces with tape
- Consider securing head to avoid further brachial plexus stretch
- Break table (at or just above iliac crest) to maximise separation of costal margin and iliac crest
Prone:
- Pad the torso, hips, elbows and legs
- Ensure tube secured – loss of ETT not uncommon (reinforced ETT preferred)
- Pressure areas
- Rare but documented risk of ischaemic optic neuropathy
Steep Trendelenburg:
- Increased central venous and intracranial pressures
- Increased intraocular pressure -> potential optic neuropathy
- Difficulty with ventilation and therefore respiratory gas exchange
- Ensure well secured and padded – beanbag
- Fixed shoulder braces should be avoided due to brachial plexus injury
- NB in RALP risks associated with lithotomy also
- Compartment syndrome and rhabdomyolysis also reported due to legs being elevated above heart, with direct pressure of muscles for prolonged period
