Why this drug is interesting

Propofol is the drug that made day-case anaesthesia and emergency department procedural sedation practical. It works within one arm–brain circulation, wears off by redistribution rather than metabolism, produces a clear-headed recovery, and suppresses airway reflexes enough to permit instrumentation. No other induction agent does all of that.

It also causes dose-dependent vasodilatation, myocardial depression and apnoea. In a fit patient on a theatre list, these are manageable and expected. In a hypovolaemic, septic or shocked emergency patient — someone whose blood pressure is being held up entirely by sympathetic tone that propofol abolishes — the same dose can produce cardiovascular collapse.

Dosing

Induction of anaesthesia

Titrate against the patient's response "until the clinical signs show the onset of anaesthesia"
"Most adult patients aged less than 55 years are likely to require 1.5–2.5 mg/kg of Propofol 1%"¹
The total dose required can be reduced by slower administration — 2–5 mL/min (20–50 mg/min)
Over 55 years the requirement is generally less
In ASA grades 3 and 4, use lower rates of administration — approximately 2 mL (20 mg) every 10 seconds

Sedation

Sedation of ventilated patients in intensive care: 0.3–4 mg/kg/h, with the rate determined by the desired depth¹
Propofol 1% is not indicated for sedation in intensive care in patients aged 16 years or younger — this is a contraindication, not a caution
Procedural sedation in the emergency department is a separate, senior-led practice with its own monitoring and staffing requirements

Pharmacology

Mechanism

Propofol potentiates GABA-A receptor activity, increasing chloride conductance and hyperpolarising neurones. It is a hypnotic and amnestic agent with no analgesic properties whatever — which is why an opioid such as fentanyl is usually given alongside it for intubation.

Kinetics

Onset: One arm–brain circulation — 30–45 seconds
Offset after a bolus: By redistribution, not metabolism — around 5–10 minutes
Metabolism: Hepatic conjugation, with significant extrahepatic clearance
Context-sensitive half-time: Rises with prolonged infusion, though less than most alternatives

Useful properties beyond hypnosis

Anticonvulsant — propofol terminates seizures and is used in refractory status epilepticus
Antiemetic at sub-hypnotic doses
Reduces cerebral metabolic rate, cerebral blood flow and intracranial pressure — attractive in head injury, provided the cerebral perfusion pressure survives the fall in mean arterial pressure
Bronchodilator, and it obtunds airway reflexes better than the alternatives

Propofol infusion syndrome

A rare, late and frequently fatal complication of prolonged infusion

Propofol infusion syndrome is characterised by metabolic acidosis, rhabdomyolysis, hyperkalaemia, hepatomegaly, renal failure, lipaemia, cardiac failure and arrhythmia. The proposed mechanism is impairment of mitochondrial fatty acid oxidation.

The label’s own risk factors are "decreased oxygen delivery to tissues; serious neurological injury and/or sepsis; high dosages of one or more of the following pharmacological agents — vasoconstrictors, steroids, inotropes and/or Propofol 1% (usually at dose rates greater than 4mg/kg/h for more than 48 hours)", with the instruction that "treating physicians are reminded if possible not to exceed the dosage of 4 mg/kg/h."¹ Young age and inadequate carbohydrate intake are commonly cited in the literature but are not label factors. The 4 mg/kg/h for more than 48 hours threshold is the number worth carrying.

The practical implications for emergency practice are modest — this is a critical care complication of days, not hours — but two things carry over. An unexplained metabolic acidosis in a patient on a propofol infusion should prompt the thought, and a rising lactate in that context is not automatically sepsis.

Note also the caloric load: propofol 1% delivers a substantial amount of lipid, which matters for feeding calculations and for triglyceride levels during long infusions.

Practical use in the ED

Fix the physiology before you induce. Fluid, blood, or a vasopressor running before induction changes the risk more than any choice of agent does. Induction is not the moment to discover the patient was hypovolaemic.
Reduce the dose and slow the delivery in the shocked patient. Then wait. The circulation time is prolonged and the effect is late.
Have a vasopressor drawn up and immediately available at every emergency induction. Post-induction hypotension is predictable; treating it should not require someone leaving the room.
Give an analgesic. Propofol does not obtund the sympathetic response to laryngoscopy on its own.
Plan the sedation that follows. A single induction bolus wears off in minutes, and the rocuronium will not.

Allergy and the formulation

The emulsion also contains purified egg phosphatide. The relevant allergens in egg allergy are usually egg white proteins rather than the phospholipid, and egg allergy is not a labelled contraindication — but soya and peanut are, and that distinction is worth carrying. In an emergency airway the risk calculus may still favour proceeding with an alternative agent rather than delaying; that is a decision to take knowingly.

Propofol is not lipid emulsion

Adverse effects

Hypotension — dose-dependent, and the principal hazard in emergency use
Apnoea — expected at induction doses, and common at sedation doses
Bradycardia, occasionally profound; propofol blunts the baroreceptor response
Pain on injection
Involuntary movements and myoclonus at induction
Propofol infusion syndrome with prolonged high-rate infusion
Hypertriglyceridaemia and lipid load with prolonged infusion
Green or cloudy urine — harmless, occasionally alarming

Critical appraisal

The induction agent debate is less important than the induction technique. Comparisons of propofol, etomidate and ketamine for emergency intubation have not produced convincing mortality differences. What consistently does matter is pre-induction resuscitation, dose reduction in shock, and having a vasopressor ready — none of which is a choice of drug.
Dose reduction in shock is universally taught and inconsistently done. The weight-based number is on the syringe and in everyone's head; the correction factor for physiology is a judgement, and judgements are what degrade under pressure.
Procedural sedation with propofol is safe in systems, not in individuals. Its safety record in the emergency department rests on monitoring, staffing, capnography and airway skills. The drug is the least interesting part of that arrangement.
Propofol infusion syndrome is rare enough to be forgotten and serious enough that forgetting it matters. It is worth keeping in the differential of an unexplained acidosis in a ventilated patient, which is precisely when nobody thinks of the sedative.

References

1
Propofol 10mg/ml (1%) emulsion for injection or infusion — Summary of Product Characteristics, Aspen. electronic Medicines Compendium. Sections 4.1–4.4, 4.8. Verified 24 Aug 2026. Compare B.Braun, emc.
2
Royal College of Anaesthetists and Difficult Airway Society. NAP4: Major complications of airway management in the United Kingdom. nationalauditprojects.org.uk
3
Association of Anaesthetists. Quick Reference Handbook, 3-10 Local anaesthetic toxicity, version 2, June 2023. anaesthetists.org/qrh
4
Royal College of Emergency Medicine. Best Practice Guideline: Pharmacological Agents for Procedural Sedation and Analgesia in the Emergency Department. rcem.ac.uk
5
Propofol — dosing and safety monograph. BNF, NICE. bnf.nice.org.uk

Propofol

At a glance