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.

Selecting an induction agent

Each agent has a distinct haemodynamic and pharmacological profile:

In haemodynamic instability, ketamine at a reduced dose or etomidate are the two most reliably safe choices. Propofol should be significantly reduced or avoided in shock.

Suxamethonium vs rocuronium for RSI

• Suxamethonium (1–1.5 mg/kg) achieves intubating conditions within about 60 seconds and wears off in 10–12 minutes. That short duration is a safety margin if intubation fails. It is contraindicated when hyperkalaemia is a risk: burns beyond 24–48 hours, crush injury, denervation, prolonged immobility, and known malignant hyperthermia susceptibility.
• Rocuronium at 1.2 mg/kg achieves onset roughly equivalent to suxamethonium and is the standard RSI alternative when suxamethonium is contraindicated. The trade-off is a longer duration (45–60 minutes), which sugammadex can reverse rapidly if needed.

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.

The displayed volumes assume the concentrations shown; always verify against the actual ampoule label before drawing up, and apply a second checker before administration. This tool is a clinical decision support aid, not a substitute for direct supervision and local guidelines.

Pre-oxygenation and sequence timing

The RSI drug sequence matters as much as the individual doses. Standard RSI procedure runs as follows:

1. Pre-oxygenate for 3–5 minutes on high-flow oxygen, or use 8 vital-capacity breaths if time is short. The goal is to build an oxygen reserve (apnoeic oxygenation) that extends safe apnoea time.
2. Position the patient: ramped positioning with the ear-to-sternal-notch horizontal is preferred, especially in obese patients and those at risk of aspiration.
3. Draw up and label all three phases of drugs before induction begins. The calculator gives you the doses; the label and the second check happen before the needle goes in, not during the sequence.
4. Pre-treatment (fentanyl, lidocaine, atropine where indicated) is given 3–5 minutes before induction if time allows, or omitted in true crash airways.
5. Induction agent, followed immediately by the neuromuscular blocker — the “rapid sequence” in RSI means no bag-mask ventilation in between (except in modified or delayed-sequence intubation protocols for specific situations).
6. Intubation at approximately 60 seconds for suxamethonium, or at 60–90 seconds for rocuronium 1.2 mg/kg.
7. Confirm tube position by waveform capnography, auscultation, and clinical signs before releasing cricoid pressure if it was applied.

Post-intubation management — sedation, analgesia, neuromuscular blockade maintenance, ventilator settings, and haemodynamic support — falls outside the scope of the pre-intubation drug dosing this calculator covers.