Rocuronium

Rocuronium is an aminosteroid non-depolarising neuromuscular blocking drug with the fastest onset of its class. At high dose it gives intubating conditions close to those of suxamethonium, and its effect can be reversed rapidly with sugammadex. It is the usual alternative to suxamethonium in rapid sequence induction, with a duration of action that needs planning for reversal.

Class. Non-depolarising neuromuscular blocking drug (aminosteroid).

Mechanism. Competitive antagonism of acetylcholine at the nicotinic receptor of the motor end plate, without depolarisation.

Pharmacokinetics. Onset 60 to 90 seconds at 0.9 to 1.2 mg/kg and 90 to 120 seconds at 0.6 mg/kg. Clinical duration 30 to 40 minutes at 0.6 mg/kg and 45 to 70 minutes at 1.2 mg/kg. Elimination half-life about 1.5 hours, longer in older adults and in liver disease. Eliminated mainly unchanged by the liver and bile, with 10 to 30% in urine. Minimal metabolism and no active metabolites of clinical importance.

Indications are tracheal intubation, rapid sequence induction, maintenance of relaxation during surgery, and short term paralysis in intensive care.

Adults

• Routine intubation: 0.6 mg/kg intravenously (range 0.45 to 0.6 mg/kg).
• Rapid sequence induction: 1 to 1.2 mg/kg intravenously.
• Maintenance: 0.1 to 0.15 mg/kg boluses as required, or infusion 0.3 to 0.6 mg/kg/hour (5 to 10 micrograms/kg/minute) once recovery has started.
• Intensive care infusion: 0.3 to 0.6 mg/kg/hour, adjusted by train-of-four monitoring to a count of 1 to 2.
• Obesity: dose maintenance by ideal body weight. The weight to use for rapid sequence induction is contested; lean body weight is a reasonable basis, and conditions should be confirmed before laryngoscopy.
• Older adults: onset slower and duration longer; use the lower end of the range and titrate.
• No fixed maximum dose; titrate to effect.

Children

• Intubation: 0.6 mg/kg intravenously; neonates and young infants 0.45 to 0.6 mg/kg with a longer duration.
• Rapid sequence induction: 1 mg/kg.
• Maintenance: 0.075 to 0.15 mg/kg boluses or infusion 0.3 to 0.6 mg/kg/hour.

Reversal. Sugammadex 2 mg/kg (shallow block), 4 mg/kg (deep block) or 16 mg/kg (immediate reversal 3 minutes after rocuronium 1.2 mg/kg), or neostigmine 50 micrograms/kg with glycopyrronium 10 micrograms/kg when the train-of-four count is at least 2.

Contraindications. Hypersensitivity to rocuronium or other neuromuscular blocking drugs; absence of airway skills, ventilation equipment and reversal agents; myasthenia gravis (use only with specialist advice and a much lower dose).

Boxed-warning-level risks. Anaphylaxis; residual paralysis if not reversed or monitored; awareness during paralysis if anaesthesia is inadequate.

Adverse effects. Common: transient injection pain, tachycardia, small rise in blood pressure. Serious: anaphylaxis, prolonged block in liver disease or with interacting drugs, residual paralysis with aspiration risk, prolonged weakness after long intensive care use (especially with corticosteroids).

Interactions. Volatile anaesthetics increase potency by 25 to 50% and prolong the block. Aminoglycosides, clindamycin, polymyxins, magnesium, lithium, local anaesthetics and calcium channel blockers prolong it. Long term phenytoin and carbamazepine reduce the effect. Previous suxamethonium can potentiate the block. Sugammadex reverses it rapidly.

Common prescribing errors. Using the full intubating dose in a patient with myasthenia gravis; not reversing; reversing too early with neostigmine at a deep block; under-dosing in rapid sequence induction; no ventilation plan after a failed intubation.

Special groups

• Pregnancy: used for caesarean section; placental transfer is small.
• Breastfeeding: compatible after recovery.
• Older adults: slower onset, longer duration.
• Kidney impairment: slight prolongation; reduce maintenance doses if the creatinine clearance is under 30 mL/minute.
• Liver impairment: prolonged duration; use smaller maintenance doses and monitor.
• Regional: store at 2 to 8 degrees Celsius; many labels allow up to 60 days at room temperature. Where sugammadex is unavailable, plan for the longer duration at 1 to 1.2 mg/kg and keep ventilating until adequate spontaneous recovery.

Formulations. Injection 10 mg/mL (25 mg in 2.5 mL and 50 mg in 5 mL vials).

Administration. Give as an intravenous bolus followed by a flush. Dilute for infusion in 0.9% sodium chloride or 5% glucose; do not mix with alkaline solutions.

Baseline. Allergy history to neuromuscular blocking drugs, weight (ideal, lean and actual in obesity), neuromuscular disease, liver and kidney function, current medicines.

Monitoring. Continuous electrocardiogram, oxygen saturation and capnography. Train-of-four monitoring during and after use, with extubation only when the train-of-four ratio is at least 0.9.

Therapeutic drug monitoring. Not used.

Dose reduction and stopping thresholds. Reduce doses in older adults, liver disease, electrolyte disturbance and when interacting drugs are present. Stop and reverse when surgery is complete.

Referral and escalation. Anaphylaxis needs intramuscular adrenaline, fluids and intensive care. Residual paralysis needs ventilatory support, sedation, and reversal. A patient unable to be intubated or ventilated after a rapid sequence dose needs an emergency front of neck airway and sugammadex 16 mg/kg if available.