Postoperative Nerve Injury

Question 1

You are asked to review a 41-year-old male patient in the anaesthetic clinic who presents with left arm weakness and numbness. He underwent left shoulder surgery 1 week ago with an interscalene nerve block and a general anaesthetic. He is otherwise well.

What are the potential causes of this patient’s symptoms?

Answer 1

Anaesthetic:
* Direct damage due to regional anaesthetic needling.

• Intraneural injection of local anaesthetic solution.
• Haematoma caused by needling.
• Perioperative hypotension (unlikely cause of local symptoms).

Surgical:
* Direct nerve or tissue damage due to surgical procedure or retractors.

• Pathology secondary to surgery, such as haematoma formation.
• Poor perioperative positioning/padding.

Other
* Cerebrovascular event (localised).

• Local nerve ischaemia secondary to haematoma formation.
• Exacerbation of pre-existing comorbidities e.g. carpal tunnel syndrome.

Question 2

How would you assess this patient in clinic?

Answer 2

• Take a full history of the patient’s symptoms including the duration, variation in symptoms over time, exacerbating or relieving factors and associated symptoms, as well as a medical and social history.
• Examine and document the current sensory and motor deficit. Attempt to localise symptoms to a particular nerve root or bundle in order to aid diagnosis. Examine the site of needling and operation; this may reveal a haematoma.
• Review the anaesthetic chart, operation note and postoperative observations chart.
• Discuss the patient with an anaesthetic consultant and the relevant surgical team following the initial assessment to determine the likely cause, any relevant investigations that should be done and how the patient should be managed, including an apology and the appropriate escalation if likely iatrogenic.
• Consider a referral to neurology if appropriate, and follow up.

Question 3

What are the risk factors associated with perioperative nerve injuries?

Answer 3

Patient factors:
* Comorbidities e.g. hypertension, peripheral vascular disease, diabetes mellitus, multiple sclerosis.

• Smoking.
• Anatomical variation in local structures.

Anaesthetic factors:
* Performing the block under general anaesthetic.

• Haemodynamic instability secondary to hypotension, hypovolaemia,
  hypoxia or hypothermia.
• Inexperience.

Surgical factors:
* Type of surgery: neurosurgery, cardiac, abdominal and orthopaedic surgical procedures.

Question 4

How can peripheral nerve injuries be classified?

Answer 4

The Seddon classification can be used to classify nerve injuries.

• Neuropraxia – damage to the myelin sheath only.
• Axonotmesis – damage to myelin sheath and axons.
• Neurotmesis – damage to myelin sheath, axons and nerve itself.

Question 5

What investigations may aid in the diagnosis of this patient’s symptoms?

Answer 5

• Electromyography.
• Nerve conduction studies.
• Magnetic resonance imaging.
• Ultrasound.

Question 6

How can the risk of peripheral nerve injuries be minimised in patients undergoing shoulder surgery?

Answer 6

• Thorough medical history preoperatively to detect high-risk patients.
• Avoidance of perioperative haemodynamic instability.
• If a regional technique is used, several strategies can be employed to
  reduce the risk of peripheral nerve injuries:
• Use of ultrasound with in-plane needling, ensuring that the
  needle shaft and tip are always visible.
• A regional nerve block can be carried out in awake patients, so
  they are able to identify paraesthesia or pain during the procedure.
• Use of a peripheral nerve stimulator.
• Adequate patient padding and neutral positioning, including limitation of excess movement at the shoulder joint, where the brachial plexus is at risk.
• Using alternative techniques to regional anaesthesia (although the benefits of a block must be considered as well as the risks when making an anaesthetic plan).