What are the three phases of RSI drug dosing?

Rapid sequence intubation uses pre-treatment or adjunct drugs (such as fentanyl or lidocaine), an induction agent to produce unconsciousness (ketamine, propofol, etomidate or midazolam), and a neuromuscular blocker to achieve paralysis (suxamethonium or rocuronium). This tool calculates all three from one weight.

How should I dose induction agents in shock?

Reduce induction doses substantially in haemodynamic instability. Ketamine is often halved, and propofol can cause profound hypotension so is reduced markedly or avoided. Etomidate is comparatively haemodynamically stable. The aim is to avoid peri-intubation cardiovascular collapse.

When should suxamethonium be avoided?

Suxamethonium can cause dangerous hyperkalaemia and should be avoided in patients with pre-existing hyperkalaemia, burns or crush injury beyond about 24 to 48 hours, denervation injuries, prolonged immobility, and known malignant hyperthermia. Rocuronium at 1.2 mg/kg is the usual alternative for RSI.

Why is rocuronium dosed higher for RSI than maintenance?

For rapid sequence intubation rocuronium is given at 1.2 mg/kg, roughly double the standard intubating dose, to shorten the onset time so intubating conditions match suxamethonium. The trade-off is a longer duration of paralysis, which sugammadex can reverse if needed.

Are the volumes based on standard concentrations?

Yes. Where a drug has a standard ampoule concentration the tool divides the calculated dose by that concentration to show the millilitres to draw up. Concentrations vary between products, so always confirm against the actual ampoule label before drawing up.

RSI Drug Dosing Calculator

Rapid sequence intubation, dosed from one weight

Emergency airway management is high-stakes and time-critical. This calculator takes a single weight and produces the full RSI drug set across all three phases — pre-treatment adjuncts, induction and paralysis — with both the milligram (or microgram) dose and the volume to draw up from a standard ampoule.

How it works

Every agent is dosed per kilogram, and where a standard concentration exists the volume follows directly:

dose   = per_kg_dose × weight
volume = dose ÷ concentration

The three phases map onto the RSI sequence:

Pre-treatment / adjuncts — fentanyl (blunts the sympathetic response), lidocaine (optional for raised ICP or reactive airway), and atropine in young children.
Induction — ketamine, propofol, etomidate or midazolam. Pick one based on haemodynamics.
Paralysis — suxamethonium (fast on, fast off) or rocuronium at the higher 1.2 mg/kg RSI dose.

Notes and safety

Doses follow standard emergency-medicine and anaesthesia references. Choose a single induction agent and a single paralytic, and tailor the induction dose to the patient’s circulation — halve ketamine and reduce propofol heavily in shock to avoid peri-intubation collapse.

Avoid suxamethonium where hyperkalaemia is a risk and use rocuronium instead. The displayed volumes assume the concentrations shown; always verify against the actual ampoule and apply a second checker before administration.