Tourniquet Syndrome

Tourniquet syndrome is the group of systemic and local effects occurring after limb tourniquet inflation or release: pain, hypertension, hypotension after release, acidosis, hyperkalaemia, arrhythmia, hypercarbia, and in the limb, ischaemia reperfusion injury and swelling.

Epidemiology. Tourniquet pain affects up to 66% of patients under regional anaesthesia after 45 to 60 minutes. Haemodynamic changes after release occur in most patients, and are clinically important with long inflation (over 2 hours), bilateral tourniquets and cardiac disease.

Risk factors. Duration over 2 hours, high pressure, bilateral limbs, large limb, vascular disease, diabetes, renal failure, sickle cell disease, and cardiac or pulmonary disease.

Pathophysiology.

During inflation, ischaemia causes anaerobic metabolism, local acidosis, potassium and lactate accumulation, and sympathetic response with hypertension (tourniquet hypertension). On release, venous return and washout of acid, potassium, carbon dioxide and free radicals cause a fall in blood pressure, rise in end tidal carbon dioxide, rise in temperature and potassium, and reperfusion injury. Prolonged ischaemia causes muscle necrosis and compartment syndrome.

During inflation: dull pain in the limb (after 30 to 60 minutes), hypertension, tachycardia. On release: hypotension, rise in end tidal carbon dioxide (3 to 8 mmHg), transient acidosis, hyperkalaemia, arrhythmia, limb swelling, pallor then hyperaemia, and in severe cases rhabdomyolysis.

Red flags.

• Arrhythmia or peaked T waves after release.
• Tense limb swelling or neurovascular deficit.
• Dark urine.

Clinical. Blood gas with potassium and lactate after release for prolonged ischaemia, creatine kinase at 6 to 24 hours (limb muscle injury), urine myoglobin and renal function. ECG for hyperkalaemia. Examine the limb for pulses, compartments and nerve function.

Differential diagnosis.

• Light anaesthesia.
• Pain (inadequate block).
• Hyperkalaemia from other cause.
• Pulmonary embolism (after release).
• Malignant hyperthermia.
• Compartment syndrome.

Treat hypertension by deepening anaesthesia or analgesia (opioid), and give a vasodilator only if severe.

• Fentanyl: 25 to 50 microgram IV, repeated every 5 minutes; maximum 200 microgram for this episode; monitor respiratory rate and sedation; reduce in older adults and hepatic impairment.

Before release, warn the team, increase ventilation if appropriate, give fluids, and release slowly (stagger release in bilateral surgery).

Hypotension after release: fluid 250 to 500 mL crystalloid and phenylephrine 50 to 100 microgram IV (maximum 200 microgram/min infusion; monitor blood pressure).

Hyperkalaemia and acidosis: calcium chloride 10% 10 mL IV, insulin 10 units with glucose 25 g IV, and salbutamol 10 to 20 mg nebulised (monitor ECG and potassium; avoid insulin overdose; check glucose hourly for 6 hours).

Rhabdomyolysis: crystalloid 1 to 2 L in the first hour and then 200 to 300 mL/h to maintain urine output of 1 to 2 mL/kg/h; monitor creatine kinase, renal function, potassium and calcium.

Prevention. Use the lowest effective pressure (limb occlusion pressure plus 40 mmHg for arm and plus 50 to 75 mmHg for leg, or 250 mmHg in arm and 300 to 350 mmHg in thigh), limit inflation to 2 hours (reperfuse for 10 to 15 minutes if longer), and pad skin.

Monitoring. ECG, blood pressure, end tidal carbon dioxide and urine output for 30 minutes after release; limb checks for 24 hours.

Referral and escalation. Orthopaedic and vascular input for limb ischaemia. Nephrology for renal injury.