What are the standard weight‑based doses for rapid‑sequence intubation agents in adults and children, and how should they be adjusted for elderly patients, severe cardiac dysfunction, pregnancy, or hemodynamic instability?

Rapid Sequence Intubation Medication Dosing

Standard Adult Dosing

For critically ill adults undergoing RSI, administer etomidate 0.3 mg/kg IV followed immediately by either succinylcholine 1-1.5 mg/kg IV or rocuronium 1.0-1.2 mg/kg IV, with the sedative-hypnotic agent always given before the neuromuscular blocker to prevent awareness during paralysis. 1, 2

Induction Agent Selection and Dosing

• Etomidate 0.3 mg/kg IV is the preferred first-line induction agent due to its superior hemodynamic stability in critically ill patients 1, 2
• Ketamine 1-2 mg/kg IV serves as an alternative when etomidate is contraindicated, though recent evidence shows higher peri-intubation hypotension rates (18.3% vs 12.4%) compared to etomidate 1, 2
• The sedative-hypnotic agent MUST be administered before the neuromuscular blocking agent to prevent awareness during paralysis, which occurs in approximately 2.6% of emergency department intubations when this sequence is violated 1, 3

Neuromuscular Blocking Agent Selection and Dosing

• Succinylcholine 1-1.5 mg/kg IV is the first-line NMBA when no contraindications exist, with onset in 30-45 seconds and duration of 5-10 minutes 1, 4
• Rocuronium 1.0-1.2 mg/kg IV should be used when succinylcholine is contraindicated, with higher doses (≥1.4 mg/kg) associated with improved first-pass success when using direct laryngoscopy (OR 1.9,95% CI 1.3-2.7) 1, 5
• Sugammadex must be immediately available when using high-dose rocuronium for reversal in "cannot intubate, cannot ventilate" scenarios 1, 2

Pediatric Dosing

Induction Agents

• Etomidate 0.3 mg/kg IV followed immediately by neuromuscular blockade 4
• Ketamine 1-2 mg/kg IV is preferred in pediatric septic shock patients, as etomidate is explicitly contraindicated due to adrenal suppression concerns 1

Neuromuscular Blocking Agents

• Succinylcholine dosing: 2 mg/kg IV for infants <6 months, 1-2 mg/kg IV for older children, or 4-5 mg/kg IM if IV access unavailable 4
• Atropine 0.02 mg/kg (minimum 0.1 mg, maximum 1 mg) must be administered before succinylcholine in all pediatric patients to prevent bradycardia or asystole 4
• Rocuronium 0.6 mg/kg IV is the standard pediatric dose, though 0.45 mg/kg may be used depending on anesthetic technique; rocuronium is NOT recommended for rapid sequence intubation in pediatric patients per FDA labeling 6

Critical Pediatric Contraindications

• Succinylcholine is contraindicated in patients with malignant hyperthermia history, severe burns or crush injury, spinal cord injury, or hyperkalemia risk (particularly boys <9 years old) 4

Dose Adjustments for Special Populations

Elderly Patients (≥65 years)

• Reduce etomidate to 0.15-0.2 mg/kg in elderly patients, as doses ≥0.23 mg/kg in patients >55 years were associated with oxygen desaturation requiring bag-assisted ventilation in 80% of cases 1
• Geriatric patients exhibit prolonged clinical duration with rocuronium (median 46-94 minutes depending on dose under opioid/nitrous oxide/oxygen anesthesia) 6

Hemodynamically Unstable Patients

• Etomidate 0.15-0.3 mg/kg IV is preferred due to its favorable hemodynamic profile 1, 2
• If using ketamine as an alternative, consider the lower end of the dosing range (1 mg/kg) to minimize hemodynamic effects, though be aware that in critically ill patients with depleted catecholamine stores, ketamine may paradoxically cause hypotension 1, 2
• Patients with pre-intubation hypotension (SBP <100 mmHg) had higher first-attempt success (94.9% vs 88.6%) when higher doses of rocuronium (≥1.4 mg/kg) were used 5

Pregnancy

• Standard RSI dosing applies, with etomidate 0.3 mg/kg IV or ketamine 1-2 mg/kg IV followed by succinylcholine 1-1.5 mg/kg IV or rocuronium 1.0-1.2 mg/kg IV 1, 2

Severe Cardiac Dysfunction

• Etomidate 0.2-0.3 mg/kg IV provides the most stable hemodynamics 1, 2
• Avoid ketamine in patients with severe coronary artery disease or uncontrolled hypertension due to its sympathomimetic effects 1

Obese Patients (≥120 kg)

• Succinylcholine should be dosed based on actual body weight at 1.5 mg/kg to ensure adequate neuromuscular blockade, as underdosing is common in heavier patients (median dose 1.0 mg/kg in ≥120 kg patients vs 1.5 mg/kg in <80 kg patients) 7
• Rocuronium 0.6 mg/kg should be based on actual body weight per FDA labeling, with pharmacodynamics not differing between obese and non-obese patients when dosed appropriately 6
• Very heavy patients (≥120 kg) have reduced first-pass success (76% vs 90-91% in lighter patients), likely due to underdosing of NMBAs 7
• Etomidate dosing: Patients ≥100 kg are significantly more likely to receive underdosing (68% received <0.2 mg/kg vs 2% in <100 kg patients), so ensure weight-based dosing of 0.3 mg/kg based on actual body weight 8

Hepatic Dysfunction

• Standard etomidate and ketamine dosing can be used 1, 2
• Rocuronium clinical duration is approximately 1.5 times longer in patients with hepatic disease compared to normal hepatic function 6

Renal Dysfunction

• Standard dosing for induction agents 1, 2
• Rocuronium duration is similar in end-stage renal disease patients undergoing renal transplant, though greater variation in duration may occur 6

Critical Timing and Administration Considerations

Medication Sequence

• Always administer the sedative-hypnotic agent BEFORE the neuromuscular blocking agent to prevent awareness during paralysis 1, 3, 2
• Wait at least 60 seconds after rocuronium administration before attempting intubation, or use a peripheral nerve stimulator to confirm adequate blockade 1
• For succinylcholine, onset is 30-45 seconds IV, allowing for intubation within 60 seconds 4

Medication-Assisted Preoxygenation

• In agitated or uncooperative patients who cannot tolerate preoxygenation, consider ketamine 1 mg/kg IV with subsequent 0.5 mg/kg doses until dissociative state is achieved (mean total dose 1.4 mg/kg), administered 3 minutes before NMBA 4
• This approach increased mean oxygen saturation by 8.9% (95% CI 6.4-10.9%) before NMBA administration 4

Common Pitfalls and How to Avoid Them

Underdosing in Heavy Patients

• Always calculate doses based on actual body weight for both induction agents and NMBAs to avoid underdosing, which is the most common error in patients ≥100 kg 8, 7
• Succinylcholine is particularly prone to underdosing in heavier patients, with median doses dropping to 1.0 mg/kg in ≥120 kg patients when 1.5 mg/kg is recommended 7

Awareness During Paralysis

• Never administer the NMBA before adequate sedation is achieved, as this causes awareness during paralysis in 2.6% of cases 1, 3
• Ensure loss of consciousness before administering the neuromuscular blocker 2

Respiratory Depression in Elderly

• Avoid doses of etomidate >0.3 mg/kg in patients >55 years, as doses ≥0.23 mg/kg were associated with oxygen desaturation requiring bag-assisted ventilation 1
• Have bag-valve-mask ventilation immediately available 4

Paradoxical Hypotension with Ketamine

• In critically ill patients with depleted catecholamine stores (severe sepsis, cardiogenic shock), ketamine may cause paradoxical hypotension despite its sympathomimetic properties 1, 2
• Have vasopressors immediately available during RSI 1

Inadequate Neuromuscular Blockade

• Ensure full neuromuscular blockade before attempting intubation to prevent coughing or movement that increases aspiration risk 1, 2
• Use a peripheral nerve stimulator to confirm adequate blockade if uncertain, particularly when using rocuronium 1