Recurarisation

Recurarisation is the return of neuromuscular block after apparent recovery from reversal, usually seen as new weakness or hypoventilation in recovery or on the ward.

Epidemiology. It is uncommon with quantitative monitoring and sugammadex, and more frequent when neostigmine is given for deep block or when long acting relaxants are used.

Causes.

• Neostigmine wearing off before the relaxant (especially pancuronium) or given at too deep a block.
• Sugammadex underdosed for the depth of block, or given too early.
• Potentiating drugs: aminoglycosides, clindamycin, polymyxins, magnesium, calcium channel blockers, volatile agents.
• Hypothermia, acidosis, hypokalaemia and hypermagnesaemia.
• Re-administration of rocuronium within 24 hours of sugammadex, or displacement of sugammadex by toremifene, flucloxacillin or fusidic acid.

Pathophysiology.

Reversal agents act for a finite time. If free relaxant remains, or the sugammadex complex dissociates after drug displacement, receptors become blocked again once reversal effects wane.

Within minutes to 2 hours of extubation: weakness, shallow breathing, upper airway obstruction, stridor, desaturation, tachycardia, diplopia and anxiety with preserved consciousness.

Red flags.

• Hypoxaemia or hypoventilation.
• Respiratory arrest.
• Aspiration.
• A patient who is awake but cannot move.

Confirm with a train-of-four monitor (fade, ratio under 0.9). Review dose and timing of relaxant, reversal agent, temperature, electrolytes, acid base state and interacting drugs. Check potassium, magnesium, calcium and blood gas.

Differential diagnosis.

• Opioid induced respiratory depression.
• Upper airway obstruction.
• Residual volatile effect.
• Pulmonary oedema or aspiration.
• Myasthenic crisis.
• Stroke.

Support the airway and ventilation, give oxygen, and reintubate if needed. Sedate if awake and paralysed.

• Sugammadex (after rocuronium or vecuronium): 4 mg/kg IV once, repeated at the depth based dose (2 to 4 mg/kg, or 16 mg/kg for immediate reversal) once train-of-four is rechecked; maximum cumulative 16 mg/kg for each episode; monitor ratio, heart rate and hypersensitivity; avoid if creatinine clearance is under 30 mL/min.
• Propofol infusion (sedation while paralysed): 1 to 3 mg/kg/h IV until ratio is 0.9 or more; maximum 4 mg/kg/h and under 48 hours; monitor blood pressure, sedation depth and triglycerides if prolonged; reduce in older adults and instability.

Avoid a second neostigmine dose beyond a total of 5 mg. Correct hypothermia and electrolytes, and stop interacting drugs. If rocuronium is needed again within 24 hours of sugammadex, use a higher dose and expect slower onset, or choose a benzylisoquinolinium agent.

Prevention. Confirm quantitative recovery (ratio 0.9 or more) before extubation, and monitor for 30 minutes afterwards in at risk patients.

Monitoring. Train-of-four every 5 to 15 minutes, saturation, respiratory rate and end tidal carbon dioxide until recovery is sustained.

Referral and escalation. Senior anaesthetic help and critical care review for reintubation. Document and report the event.