RSI Drugs Explained for FRCEM Exams

Rapid sequence induction is a core Emergency Medicine topic because it sits at the junction of airway management, resuscitation, pharmacology and human factors. In exams, candidates are rarely rewarded for naming drugs alone. Marks come from choosing the right induction agent and neuromuscular blocker for the physiology in front of you, reducing dose when appropriate, anticipating peri-intubation hypotension, recognising when succinylcholine is unsafe, and planning immediate post-intubation sedation and analgesia. In practice, these same decisions affect first-pass success, haemodynamic stability and prevention of secondary brain injury.

Why RSI Drugs Matter for FRCEM

Emergency Department intubation is usually performed in patients who are physiologically unstable rather than anatomically straightforward. Common scenarios include major trauma, sepsis, severe hypoxia, status asthmaticus, reduced conscious level, agitation preventing preoxygenation, and peri-arrest physiology.

Drug choice matters because:

• Induction can precipitate hypotension or cardiac arrest in shocked patients.
• Positive pressure ventilation can worsen venous return and blood pressure.
• A poor paralytic choice can create avoidable harm, especially with succinylcholine contraindications.
• Rocuronium produces prolonged paralysis, so failure to provide immediate sedation is a major safety error.
• In neurocritical patients, hypoxia and hypotension worsen outcome more than most theoretical drug effects.

For FRCEM and MRCEM, the expected standard is safe UK ED reasoning: optimise first, intubate well, and think beyond the tube.

Key Definitions

Essential Pathophysiology

RSI pharmacology only makes sense when linked to physiology.

• Shock reduces physiological reserve. Standard induction doses may be excessive in sepsis, haemorrhage, dehydration, frailty and peri-arrest states.
• Induction agents can reduce sympathetic tone, cause vasodilation, depress myocardium, or unmask cardiovascular collapse.
• Positive pressure ventilation reduces venous return and may worsen hypotension after intubation.
• Hypoxia, hypercapnia and acidosis increase peri-intubation risk.
• Succinylcholine causes depolarisation and potassium efflux. In receptor upregulation states, this can trigger life-threatening hyperkalaemia.
• Rocuronium causes prolonged paralysis. The induction agent wears off long before the paralysis does, so sedation and analgesia must continue.

The key physiological priorities are:

• Prevent hypoxia.
• Prevent hypotension.
• Maximise first-pass success.
• Avoid awareness while paralysed.

Clinical Presentation

Patients needing RSI present with a clinical problem, not a pharmacology problem. Typical ED presentations include:

• Failure to maintain or protect the airway
• Failure of oxygenation or ventilation
• Reduced conscious level
• Severe agitation preventing safe assessment or oxygenation
• Major trauma requiring airway control
• Status epilepticus
• Severe asthma or exhaustion
• Sepsis with respiratory failure
• Peri-arrest deterioration

The exam often embeds the drug question inside one of these scenarios.

Red Flags and High-Risk Features

These features should immediately influence RSI drug choice and preparation:

• Shock, severe hypotension or rising lactate
• Peri-arrest physiology
• Severe hypoxia with poor reserve
• Severe metabolic acidosis
• Raised aspiration risk
• Traumatic brain injury or other neurocritical state
• Status asthmaticus
• Known or suspected hyperkalaemia
• Established burns, crush injury, denervation, neuromuscular disease, prolonged critical illness or major immobility
• Previous malignant hyperthermia
• Pseudocholinesterase deficiency
• Anticipated difficult airway
• Need for early neurological reassessment after intubation

Exam point: if the stem contains a succinylcholine contraindication, that is usually the key discriminator.

Differential Diagnosis

In an RSI pharmacology article, the practical differential is not the disease itself but the reason the patient may deteriorate with induction.

• Hypotension due to sepsis, haemorrhage, dehydration, cardiogenic shock or obstructive shock
• Hypoxia due to pneumonia, pulmonary oedema, asthma, trauma or airway obstruction
• Agitation due to hypoxia, intoxication, delirium, head injury or psychiatric illness
• Reduced GCS due to trauma, stroke, seizure, sepsis, overdose or metabolic disturbance
• Hyperkalaemia risk due to renal failure, crush injury, burns, neuromuscular disease or prolonged immobilisation

Good candidates identify the physiology driving the drug choice.

Initial ED Assessment

Assessment should be structured and rapid.

Airway

• Is the airway patent?
• Is there contamination, blood, vomit or facial trauma?
• Is a difficult airway predicted?

Breathing

• Oxygen saturation, respiratory rate, work of breathing
• Need for preoxygenation strategy, NIV, HFNO or apnoeic oxygenation according to local practice
• Risk of rapid desaturation

Circulation

• Blood pressure, heart rate, capillary refill, shock index
• Need for blood products, fluids, vasopressors or inotropes
• Likelihood of peri-intubation collapse

Disability

• GCS, pupils, seizure activity, agitation
• Need for neuroprotection through avoidance of hypoxia and hypotension

Exposure

• Burns, crush injury, signs of sepsis, trauma pattern, pregnancy, obesity

Before drugs are given, define:

• Plan A, B and C airway strategy
• Who is intubating
• What drugs and doses will be used
• What the haemodynamic rescue plan is
• What post-intubation sedation and analgesia will be started

Investigations

RSI is usually a clinical decision. Investigations should not delay a necessary airway, but some results influence drug choice.

• Blood gas: hypoxia, hypercapnia, acidosis, lactate
• Urea and electrolytes: especially potassium if hyperkalaemia is suspected
• Glucose
• ECG: hyperkalaemia features, arrhythmia, ischaemia
• Group and save or crossmatch in trauma or haemorrhage
• Imaging as clinically indicated, but not before a needed airway

Exam point: if the stem gives hyperkalaemia, crush injury, established burns or neuromuscular disease, avoid succinylcholine.

Management in the Emergency Department

Management is not just choosing a drug. It is a sequence.

1. Prepare and optimise before induction

• Use an RSI checklist.
• Call for appropriate help early, including anaesthetic support if needed and according to local pathways.
• Preoxygenate properly. Use the best tolerated method for the patient and pathology.
• Position the patient appropriately, including ramping in obesity and left lateral tilt where relevant in pregnancy.
• Suction ready and working.
• Prepare difficult airway equipment and rescue oxygenation plan.
• Resuscitate before induction where possible:
  • control haemorrhage
  • give blood products or fluids when appropriate
  • start vasopressor support according to local governance if shock is present
• Reduce induction dose in shock, frailty, old age or peri-arrest physiology.
• Draw up post-intubation sedation and analgesia before induction.

2. Choose the induction agent

The best induction agent depends on haemodynamics, pathology and local familiarity.

Ketamine

Ketamine is one of the commonest ED induction agents and a frequent best answer in exam stems.

• Useful in trauma, sepsis, asthma and DSI.
• Bronchodilation is helpful in severe bronchospasm.
• Often preserves blood pressure better than propofol.
• Not universally haemodynamically protective. In profound shock or catecholamine depletion, hypotension can still occur.

Exam phrasing: ketamine is often preferred in hypotensive or bronchospastic patients, but dose reduction may still be required.

Etomidate

Etomidate remains exam-relevant and clinically valid, although UK availability and routine use vary between departments.

• Useful when haemodynamic stability is the main concern.
• Single-dose adrenal suppression does not mean the drug is banned.
• Routine steroid administration solely because etomidate was used is not standard UK practice.

Exam phrasing: etomidate is an acceptable haemodynamically stable induction option, not a forbidden drug.

Propofol

Propofol is entirely reasonable in selected stable patients, but is often a poor choice in emergency shock states.

• Can produce significant hypotension through vasodilation and myocardial depression.
• Older, frail and shocked patients need substantial dose reduction if it is used at all.

Exam phrasing: propofol is acceptable in a genuinely stable patient, but often wrong in sepsis, trauma or hypovolaemia.

Midazolam

Midazolam is not usually the preferred induction agent for standard adult ED RSI.

• Onset is slower and less predictable.
• Can cause hypotension.
• More relevant as part of post-intubation sedation than as first-line induction.

Thiopentone

Thiopentone is now mainly of historical or exam-bank relevance.

• Rapid onset, but haemodynamic depression limits usefulness in unstable ED patients.
• If it appears in a shocked patient stem, it is usually not the best answer.

3. Choose the neuromuscular blocker

Succinylcholine

Succinylcholine remains high-yield because it is fast, familiar and dangerous in the wrong patient.

Main contraindications and high-risk situations:

• Known hyperkalaemia
• Established burns
• Established crush injury
• Major denervation syndromes such as spinal cord injury
• Neuromuscular disease
• Prolonged critical illness or significant immobility with receptor upregulation
• Previous malignant hyperthermia
• Pseudocholinesterase deficiency

Important timing nuance:

• Immediately after a burn or crush injury, succinylcholine is not automatically contraindicated.
• Risk rises once receptor upregulation develops.
• For exam purposes, if the stem says established burns, established crush injury, denervation or prolonged immobility, avoid succinylcholine.

Other points:

• Can cause bradycardia, especially with repeated doses.
• Can trigger malignant hyperthermia in susceptible patients.
• Fasciculations are common but usually not the key exam issue.

Exam phrasing: succinylcholine is acceptable only when there is no contraindication and short paralysis is genuinely useful.

Rocuronium

Rocuronium is the standard non-depolarising alternative and is commonly used in modern UK ED RSI.

• RSI dose is usually 1.0–1.2 mg/kg IV.
• At RSI dose, onset is rapid and intubating conditions are good.
• Duration is much longer than succinylcholine.

Main advantages:

• Safe choice when succinylcholine is contraindicated.
• Widely used in contemporary practice.
• Avoids succinylcholine-related hyperkalaemia and malignant hyperthermia trigger risk.

Main cautions:

• Paralysis lasts far longer than the induction agent.
• Immediate post-intubation sedation and analgesia are mandatory.
• Early neurological examination is delayed.
• Sugammadex does not make rocuronium risk-free and does not replace good planning.

Exam phrasing: if succinylcholine is contraindicated, rocuronium is usually the best answer in UK ED practice.

Succinylcholine versus rocuronium

4. Pretreatment and adjuncts

Pretreatment drugs are not routine requirements in every RSI.

Fentanyl

• May be used selectively by experienced clinicians to blunt sympathetic response, for example in some neurocritical or severe hypertensive scenarios.
• Not a routine “ICP protection” drug.
• Can worsen hypotension.

Vasopressors

• If peri-intubation hypotension is likely, prepare haemodynamic support according to local governance and departmental SOP.
• The key principle is anticipation rather than rescue after collapse.

Atropine

• Not a routine adult RSI pretreatment drug.
• May be relevant in selected paediatric practice, but use should follow local paediatric airway guidance.

5. Dose reduction in shock, frailty and peri-arrest

This is a major exam discriminator.

• Standard textbook induction doses may be excessive in shocked, elderly, frail or peri-arrest patients.
• Reduced-dose induction is often safer than full-dose induction.
• The exact dose depends on physiology, not memorised dogma.

Good viva wording:

• I would reduce the induction dose because this patient is shocked and may not tolerate standard dosing.
• I would optimise circulation before induction and have vasopressor support ready according to local practice.

6. Delayed sequence intubation and modified RSI

Delayed sequence intubation

DSI is useful when the patient needs intubation but cannot tolerate preoxygenation because of agitation, delirium or severe distress.

• Ketamine is commonly used to facilitate oxygenation and preparation while preserving respiratory drive.
• Once preoxygenation is achieved and the team is ready, paralysis and intubation proceed.

Classic exam stem: agitated hypoxic patient repeatedly removing oxygen mask. Best answer may be ketamine to facilitate DSI.

Modified RSI

Modified RSI refers to adapting the standard sequence for physiology or aspiration risk.

• May include gentle ventilation before laryngoscopy if severe hypoxia makes apnoea unsafe.
• May include altered drug dosing and more active haemodynamic support.
• Should still aim for first-pass success and aspiration minimisation.

7. Immediate post-intubation care

The RSI sequence does not end with tube placement.

Immediately after tube confirmation:

• Start sedation and analgesia without delay.
• Secure the tube.
• Set ventilation appropriately for the pathology.
• Reassess blood pressure and treat hypotension promptly.
• Obtain post-intubation blood gas and chest radiograph when appropriate.

Post-intubation sedation and analgesia

Key principle: analgesia and sedation should be prepared before induction and started immediately after confirmation of tracheal tube placement.

Common UK-compatible approach:

• Analgesia-first strategy, often opioid-based, if pain is likely
• Continuous sedative infusion or repeated boluses according to local protocol
• Common agents include fentanyl, morphine, midazolam, propofol or ketamine depending on haemodynamics and local practice

Exam point: if you choose rocuronium and do not mention immediate sedation and analgesia, that is a major safety omission.

8. Scenario-based drug choice