Tourniquet-Induced Nerve Injury

Tourniquet induced nerve injury is neuropraxia or axonotmesis from compression and ischaemia beneath or distal to a limb tourniquet. The radial nerve (arm) and sciatic and peroneal nerves (leg) are most often affected.

Epidemiology. Incidence is about 1 in 8,000 to 1 in 10,000 tourniquet applications for clinically significant injury (higher with neurological symptoms of 0.1% to 7.7% in some studies). Most injuries are neuropraxia and recover in weeks to months.

Risk factors. Duration over 2 hours, high pressure (over 300 mmHg in the leg, over 250 mmHg in the arm), narrow cuff, cuff placed over a nerve with little soft tissue, poor padding, thin patients, repeated inflation without reperfusion, diabetes, peripheral neuropathy and peripheral vascular disease.

Pathophysiology.

Maximum mechanical injury lies at the cuff edges (shear force). Ischaemia of the nerve beyond 2 hours causes conduction failure and myelin damage. Direct pressure produces demyelination, and more severe injury causes axonal loss.

Numbness, paraesthesia, weakness (wrist drop, foot drop) and pain distal to the cuff after the block should have worn off (often 1 to 2 days). Pressure injury of skin (blister, bruise) may coexist.

Red flags.

• Complete paralysis.
• Expanding swelling or loss of pulses.
• Severe pain out of proportion (compartment syndrome).

Document deficits and examine pulses, compartments and skin. Nerve conduction studies and electromyography at 3 weeks classify injury and prognosis. Ultrasound or MRI for haematoma or nerve injury. Exclude nerve block injury and surgical injury.

Differential diagnosis.

• Compartment syndrome.
• Regional anaesthesia injury.
• Surgical nerve damage.
• Positional neuropathy.
• Vascular insufficiency.

Exclude compartment syndrome and vascular injury at once (fasciotomy for compartment syndrome). Protect the limb, splint to prevent contracture (ankle foot orthosis for foot drop, wrist splint for wrist drop) and begin physiotherapy.

• Gabapentin: 300 mg orally, titrated every 3 days to 900 to 1,800 mg daily in three divided doses; maximum 3.6 g daily; monitor sedation and renal function; reduce in creatinine clearance under 60 mL/min.
• Amitriptyline: 10 mg orally at night, titrated to 75 mg; maximum 150 mg daily; monitor ECG and anticholinergic effects; avoid in recent myocardial infarction and arrhythmia.

Most neuropraxias recover over 6 to 12 weeks, and axonotmesis recovers at about 1 mm daily over months. Consider exploration if no improvement at 3 to 6 months.

Prevention. Use the lowest effective pressure, wide cuffs, adequate padding, inflation under 2 hours with reperfusion break of 10 to 15 minutes, and record inflation times and pressures.

Monitoring. Neurological examination at 24 hours, 1 week, 6 weeks and 3 months, with electrophysiology at 3 weeks.

Referral and escalation. Neurology, orthopaedic or nerve surgery review. Disclosure and reporting.