Rapid Sequence Intubation Medicines

Rapid sequence intubation (RSI) medicines allow a secure airway in patients at risk of aspiration or who cannot protect their airway. A sedative induction agent and a neuromuscular blocker are given together within seconds, with preparation of oxygen, equipment and drugs to manage haemodynamic collapse. The choice of drug depends on blood pressure, the condition and the operator’s experience.

Classification. Induction agents (ketamine, propofol, etomidate, thiopental); neuromuscular blockers (suxamethonium, rocuronium); opioids and adjuncts (fentanyl, lidocaine, atropine); vasopressors; reversal (sugammadex).

Mechanism. Induction agents cause rapid loss of consciousness through GABA enhancement (propofol, etomidate, thiopental) or NMDA blockade (ketamine). Suxamethonium depolarises the motor end plate. Rocuronium blocks the acetylcholine receptor competitively.

Pharmacokinetics. Induction agents act in 15 to 60 seconds and last 5 to 15 minutes. Suxamethonium acts in 45 seconds and lasts 6 to 10 minutes. Rocuronium 1.2 mg/kg acts in 60 seconds and lasts 45 to 70 minutes unless reversed.

Preparation.

• Preoxygenate with high-flow oxygen for 3 minutes or more, with apnoeic oxygenation.
• Resuscitate first: correct hypotension, hypovolaemia and hypoxia.
• Have a vasopressor ready (phenylephrine or noradrenaline), a plan for failed intubation and suction.
• Reduce the induction dose in shock and older patients; do not reduce the paralytic dose.

Malignant hyperthermia. Stop triggers, give dantrolene 2.5 mg/kg intravenously, cool, treat hyperkalaemia, and call for help.

• First-line. Ketamine or etomidate with rocuronium or suxamethonium in emergency intubation; propofol in stable patients.
• Alternative. Thiopental when others are unavailable; fentanyl added in raised intracranial pressure or aortic pathology.
• Specialist. Sugammadex for failed intubation with rocuronium; awake intubation; delayed sequence techniques.
• Emergency. Respiratory failure, airway compromise, depressed consciousness, severe trauma, status epilepticus not controlled.

Selection. Choose by haemodynamics: ketamine or etomidate in shock, propofol in stable patients. Use rocuronium when suxamethonium is contraindicated.

Contraindications. Suxamethonium: hyperkalaemia, burns or crush injury after 24 to 72 hours, spinal cord injury or denervation after 3 days, neuromuscular disease, malignant hyperthermia history, pseudocholinesterase deficiency. Etomidate: adrenal failure (relative). Ketamine: raised intraocular pressure (relative). Propofol: severe hypotension.

Serious adverse effects.

• Hypotension and cardiac arrest at induction, hypoxia and failed airway.
• Hyperkalaemia, arrhythmia and rhabdomyolysis with suxamethonium.
• Awareness under paralysis if sedation is wearing off.
• Anaphylaxis (neuromuscular blockers); adrenal suppression (etomidate); emergence reactions (ketamine).

Major interactions. Opioids and benzodiazepines add to hypotension; magnesium and aminoglycosides prolong blockade; anticonvulsants may shorten rocuronium action; monoamine oxidase inhibitors and sympathomimetics with ketamine raise pressure.

Common prescribing errors.

• Induction without resuscitation of shock.
• Underdosing the paralytic.
• Forgetting post-intubation sedation after rocuronium.
• Giving suxamethonium in hyperkalaemia or long-standing denervation.
• Not preparing a failed airway plan.

Special groups.

• Pregnancy: higher aspiration and failed airway risk; left tilt and experienced operator; usual doses.
• Breastfeeding: no interruption needed.
• Children: weight-based; atropine for bradycardia; sizes of equipment.
• Older adults: reduce induction dose and expect hypotension.
• Kidney: avoid suxamethonium in hyperkalaemia; rocuronium duration can be longer.
• Liver: rocuronium duration longer; titrate sedative.
• East Africa: ketamine and suxamethonium are widely available and widely used; sugammadex and etomidate are often absent, so plan for a longer rocuronium block and sustained sedation, and ensure oxygen supply and suction are reliable before starting.

Monitoring. Oxygen saturation, end-tidal carbon dioxide, blood pressure every minute, ECG, and depth of sedation after intubation.

Referral and escalation. Failed intubation, desaturation, cardiac arrest, suspected malignant hyperthermia or anaphylaxis.

Comparison with alternative classes. RSI drugs give the fastest conditions for intubation but carry high risk when patients are shocked or hypoxic. Awake or spontaneously breathing techniques are safer in a predicted difficult airway.