What is RSI Drug Dose Calculator (Adult)?
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Rapid Sequence Intubation (RSI) is the gold-standard emergency airway management technique that combines a sedative-hypnotic agent with a rapid-onset neuromuscular blocking agent (NMBA) to achieve loss of consciousness and complete muscle paralysis simultaneously, allowing immediate tracheal intubation with minimal risk of pulmonary aspiration. RSI is indicated whenever a patient requires immediate definitive airway protection and is presumed to have a full stomach. The technique was developed to minimise the window between loss of protective airway reflexes and placement of a cuffed endotracheal tube. Standard RSI includes pre-oxygenation for at least 3 minutes with 100% FiO2, optional pretreatment agents (fentanyl 3 mcg/kg IV to blunt intubating conditions, especially in head injury), simultaneous administration of the induction agent and NMBA, application of cricoid pressure (Sellick manoeuvre, though increasingly debated), and laryngoscopy without bag-mask ventilation during the apnoeic interval. Ketamine (1–2 mg/kg IV) is the preferred induction agent in haemodynamically unstable or asthmatic patients due to its sympathomimetic and bronchodilatory properties. Propofol (1.5–2 mg/kg IV) is preferred in haemodynamically stable patients with raised intracranial pressure due to its ICP-lowering effect. Etomidate (0.3 mg/kg IV) is used where haemodynamic stability is critical but adrenal suppression concerns exist. Succinylcholine (1.5 mg/kg IV) provides the fastest onset (45–60 seconds) and shortest duration (10–15 minutes) of paralysis. Rocuronium (1.2 mg/kg IV) is the preferred alternative when succinylcholine is contraindicated, with onset at 60–90 seconds; it can be reversed with sugammadex 16 mg/kg.
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Formula
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Ketamine dose = 1–2 mg/kg IV; Propofol dose = 1.5–2 mg/kg IV; Succinylcholine dose = 1.5 mg/kg IV; Rocuronium dose = 1.2 mg/kg IV; Fentanyl pretreatment = 3 mcg/kg IVVariable Legend
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| Symbol | Name | Unit | Description |
|---|---|---|---|
| W | Patient weight | kg | Used to calculate all weight-based drug doses in mg/kg or mcg/kg |
| D_rev | Sugammadex reversal dose | mg/kg | 16 mg/kg IV for immediate reversal of rocuronium in failed airway |
How to RSI Drug Dose Calculator (Adult)
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- 1Step 1 — Preparation: Assemble equipment (laryngoscope, ETT, suction, bag-mask, difficult airway trolley), draw up all drugs, confirm IV access, attach monitoring (SpO2, ECG, BP, EtCO2).
- 2Step 2 — Pre-oxygenation: Deliver 100% O2 via tight-fitting non-rebreather mask or BVM for at least 3 minutes (8 vital-capacity breaths accepted if time-critical) to maximise oxygen reserve.
- 3Step 3 — Pretreatment (optional): Give fentanyl 3 mcg/kg IV 3 minutes before induction to blunt the sympathetic response to laryngoscopy, particularly in traumatic brain injury.
- 4Step 4 — Induction agent: Administer the chosen sedative (ketamine 1–2 mg/kg, propofol 1.5–2 mg/kg, or etomidate 0.3 mg/kg) as a rapid IV bolus.
- 5Step 5 — Neuromuscular blockade: Immediately follow with succinylcholine 1.5 mg/kg IV or rocuronium 1.2 mg/kg IV; await complete fasciculations (succinylcholine) or 60 seconds (rocuronium).
- 6Step 6 — Laryngoscopy and intubation: With the patient paralysed and sedated, perform direct or video-assisted laryngoscopy and place a cuffed ETT; inflate cuff and confirm position with waveform capnography and bilateral auscultation.
- 7Step 7 — Post-intubation management: Secure the tube, initiate ventilator settings, obtain post-intubation CXR, and begin ongoing sedation and analgesia to maintain patient comfort.
Worked Examples
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Ketamine chosen for its ICP-neutral profile at standard doses; succinylcholine for fastest onset
Fentanyl 3 mcg/kg × 70 = 210 mcg; Ketamine 1–2 mg/kg × 70 = 70–140 mg; Succinylcholine 1.5 mg/kg × 70 = 105 mg. Rocuronium 1.2 × 70 = 84 mg if sux contraindicated.
Ketamine's sympathomimetic properties support blood pressure during induction
Propofol causes significant vasodilation and is avoided in hypotensive patients. Ketamine 1–2 mg/kg × 80 = 80–160 mg. Succinylcholine 1.5 × 80 = 120 mg.
Succinylcholine causes life-threatening K+ release in denervation/crush injuries >24 h old
Rocuronium 1.2 mg/kg × 60 = 72 mg. Sugammadex reversal dose = 16 mg/kg × 60 = 960 mg.
Ketamine is the induction agent of choice in bronchospasm due to bronchodilatory effect
Ketamine 1–2 mg/kg × 90 = 90–180 mg; Sux 1.5 × 90 = 135 mg. Avoid propofol which can trigger bronchospasm at induction.
Real-World Applications
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Emergency department management of patients with depressed consciousness, respiratory failure, or airway compromise, representing an important application area for the Rsi Adult Dose in professional and analytical contexts where accurate rsi adult dose calculations directly support informed decision-making, strategic planning, and performance optimization
Pre-hospital critical care intubation by paramedics and HEMS physicians in trauma and medical emergencies, representing an important application area for the Rsi Adult Dose in professional and analytical contexts where accurate rsi adult dose calculations directly support informed decision-making, strategic planning, and performance optimization
Operating theatre rapid sequence for patients at risk of aspiration (full stomach, pregnancy, bowel obstruction), representing an important application area for the Rsi Adult Dose in professional and analytical contexts where accurate rsi adult dose calculations directly support informed decision-making, strategic planning, and performance optimization
Intensive care unit intubation for deteriorating patients requiring mechanical ventilation, representing an important application area for the Rsi Adult Dose in professional and analytical contexts where accurate rsi adult dose calculations directly support informed decision-making, strategic planning, and performance optimization
Inter-hospital transfer preparation for patients who need a secured airway for safe transport, representing an important application area for the Rsi Adult Dose in professional and analytical contexts where accurate rsi adult dose calculations directly support informed decision-making, strategic planning, and performance optimization
Special Cases
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Traumatic Brain Injury
In the Rsi Adult Dose, this scenario requires additional caution when interpreting rsi adult dose results. The standard formula may not fully account for all factors present in this edge case, and supplementary analysis or expert consultation may be warranted. Professional best practice involves documenting assumptions, running sensitivity analyses, and cross-referencing results with alternative methods when rsi adult dose calculations fall into non-standard territory.
Haemodynamic Instability / Shock
In the Rsi Adult Dose, this scenario requires additional caution when interpreting rsi adult dose results. The standard formula may not fully account for all factors present in this edge case, and supplementary analysis or expert consultation may be warranted. Professional best practice involves documenting assumptions, running sensitivity analyses, and cross-referencing results with alternative methods when rsi adult dose calculations fall into non-standard territory.
Extremely large or small input values in the Rsi Adult Dose may push rsi adult
Extremely large or small input values in the Rsi Adult Dose may push rsi adult dose calculations beyond typical operating ranges. While mathematically valid, results from extreme inputs may not reflect realistic rsi adult dose scenarios and should be interpreted cautiously. In professional rsi adult dose settings, extreme values often indicate measurement errors, unusual conditions, or edge cases meriting additional analysis. Use sensitivity analysis to understand how results change across plausible input ranges rather than relying on single extreme-case calculations.
Pregnancy
In the Rsi Adult Dose, this scenario requires additional caution when interpreting rsi adult dose results. The standard formula may not fully account for all factors present in this edge case, and supplementary analysis or expert consultation may be warranted. Professional best practice involves documenting assumptions, running sensitivity analyses, and cross-referencing results with alternative methods when rsi adult dose calculations fall into non-standard territory.
Paediatric RSI
In the Rsi Adult Dose, this scenario requires additional caution when interpreting rsi adult dose results. The standard formula may not fully account for all factors present in this edge case, and supplementary analysis or expert consultation may be warranted. Professional best practice involves documenting assumptions, running sensitivity analyses, and cross-referencing results with alternative methods when rsi adult dose calculations fall into non-standard territory.
RSI Drug Doses by Weight
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| Drug | Dose | Onset | Duration | Notes |
|---|---|---|---|---|
| Ketamine | 1–2 mg/kg IV | 45–60 sec | 10–20 min | 1st choice in hypotension/asthma |
| Propofol | 1.5–2 mg/kg IV | 30–45 sec | 5–10 min | Avoid in haemodynamic instability |
| Etomidate | 0.3 mg/kg IV | 30–60 sec | 10–15 min | Adrenal suppression risk |
| Succinylcholine | 1.5 mg/kg IV | 45–60 sec | 10–15 min | Depolarising; many CI |
| Rocuronium | 1.2 mg/kg IV | 60–90 sec | 45–70 min | Reversed by sugammadex |
| Fentanyl (pre-Rx) | 3 mcg/kg IV | ~3 min | 30–60 min | Blunts sympathetic response |
| Sugammadex (reversal) | 16 mg/kg IV | 3 min | Full reversal | For rocuronium CICV rescue |
Frequently Asked Questions
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What is RSI and what medications are used for rapid sequence intubation?
RSI (Rapid Sequence Intubation/Induction) is a medical procedure to quickly secure an airway by administering a sedative (induction agent) and a neuromuscular blocking agent (paralytic) in rapid succession, followed by endotracheal intubation. The goal is to minimize the time between loss of consciousness and airway control, reducing aspiration risk. Standard RSI sequence: preoxygenation (3-5 minutes of 100% O₂), pretreatment (optional — fentanyl 1-3 mcg/kg for sympatholysis, lidocaine 1.5 mg/kg for ICP), induction agent, neuromuscular blocker (given immediately after or simultaneously), then intubation (typically 45-60 seconds after paralytic). Common induction agents: Etomidate: 0.3 mg/kg IV — hemodynamically stable, rapid onset (15-30 sec), short duration (5-10 min). Preferred in hemodynamically unstable patients. Concerns about adrenal suppression generally outweigh risks for single-dose RSI. Ketamine: 1-2 mg/kg IV — maintains hemodynamic stability, bronchodilator. Preferred in asthma/bronchospasm and hypotension. May increase ICP (debated). Propofol: 1-2 mg/kg IV — causes hypotension (avoid in shock). Good for status epilepticus. Midazolam: 0.1-0.3 mg/kg — slower onset, unpredictable, generally not first-line for RSI.
What are the adult doses for common RSI paralytic agents?
Two main categories of neuromuscular blocking agents (NMBAs) used in RSI: Depolarizing — Succinylcholine: 1-1.5 mg/kg IV (typical adult dose: 100-120 mg). Onset: 45-60 seconds. Duration: 6-10 minutes. Fastest onset and shortest duration of any NMBA — preferred when a short paralysis window is desired. Contraindications: hyperkalemia risk (burns >48hrs, crush injuries, chronic renal failure, neuromuscular diseases), personal/family history of malignant hyperthermia, penetrating eye injuries (increases intraocular pressure). Non-depolarizing — Rocuronium: 1-1.2 mg/kg IV for RSI (higher than the standard intubating dose of 0.6 mg/kg to achieve RSI-speed onset). Onset: 60-90 seconds at RSI dose. Duration: 45-70 minutes. Advantage: can be reversed with sugammadex (16 mg/kg for immediate reversal, 4 mg/kg for routine reversal), making it increasingly preferred over succinylcholine. Vecuronium: 0.15-0.25 mg/kg IV for RSI (standard dose 0.1 mg/kg). Onset: 90-120 seconds. Duration: 45-65 minutes. Slower onset makes it a second-line RSI choice. All doses should be based on ideal body weight for obese patients (neuromuscular blockers distribute to lean tissue, not fat). The availability of sugammadex has shifted many emergency departments and anesthesia practices toward rocuronium as the first-line paralytic, since its longer duration can now be reliably reversed if intubation fails — a significant safety improvement over the pre-sugammadex era.
What are the adult doses for common RSI sedative-hypnotic agents?
Propofol is typically dosed at 1.5-2.5 mg/kg IV, offering rapid onset and short duration. Etomidate is given at 0.2-0.4 mg/kg IV, known for its hemodynamic stability. Midazolam, a benzodiazepine, is used at 0.1-0.3 mg/kg IV, but has a slower onset and longer duration compared to propofol or etomidate. Ketamine is dosed at 1-2 mg/kg IV, providing dissociative anesthesia and maintaining hemodynamic stability.
How should adult RSI medication doses be adjusted for obese patients?
For lipophilic medications like propofol and ketamine, dosing based on ideal body weight (IBW) is often recommended to prevent oversedation and prolonged effects, especially in morbidly obese adults. IBW can be estimated using formulas such as Devine's: IBW (men) = 50 kg + 2.3 kg for each inch over 5 feet; IBW (women) = 45.5 kg + 2.3 kg for each inch over 5 feet. Neuromuscular blocking agents like succinylcholine and rocuronium are generally dosed on total body weight (TBW) up to a certain maximum, as their volume of distribution is less affected by obesity.
Are there specific adult dosing considerations for RSI medications in patients with renal or hepatic impairment?
For patients with renal impairment, succinylcholine is generally safe but can cause hyperkalemia if baseline potassium is elevated. Rocuronium and vecuronium are primarily hepatically metabolized and renally excreted, so their duration of action can be significantly prolonged in severe liver or kidney disease; reduced doses or careful titration may be necessary. Etomidate and propofol are largely metabolized by the liver, but their duration of action is less affected by hepatic impairment due to rapid redistribution, though lower doses might be considered in severe dysfunction.
Common Mistakes to Avoid
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- !Giving the induction agent without immediately following with the NMBA — loss of sequential administration defeats the purpose of RSI.
- !Using propofol in a hypotensive or volume-depleted patient, causing cardiovascular collapse at induction.
- !Forgetting to prepare a difficult airway plan and sugammadex before beginning RSI.
- !Neglecting pre-oxygenation — even 2–3 minutes of 100% O2 greatly extends safe apnoea time; skipping it leads to rapid desaturation.
- !Choosing succinylcholine in a patient with unrecognised contraindications (hyperkalaemia, myopathy, burns >24 h) leading to life-threatening hyperkalaemic arrest.
- !Not confirming ETT placement with waveform capnography — oesophageal intubation is fatal if not immediately recognised.
Pro Tip
The 'LOAD' mnemonic helps remember RSI pretreatment agents: Lidocaine (controversial, 1.5 mg/kg for bronchospasm), Opioid (fentanyl 3 mcg/kg for TBI/HTN), Atropine (children <5 yr pre-succinylcholine), Defasciculation (low-dose non-depolariser, rarely used). Always have your rescue plan — know your surgical airway approach before you start.
Did you know?
Succinylcholine was first synthesised in 1906 but not used clinically until 1951. It remains the fastest-acting neuromuscular blocker available 70 years later — no modern drug has beaten its 45-second onset to full paralysis in clinical use.
References
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