RSI Induction Agents in Melatonin, Quetiapine & Risperidone Overdose

Key Pharmacological Concerns of This Overdose Combination

Induction Agent Recommendations

✅ Ketamine — Preferred first-line

• Sympathomimetic — maintains or increases BP, heart rate, and cardiac output; ideal when alpha-1-mediated hypotension is present
• Bronchodilator — beneficial in obtunded patients
• Preserves airway reflexes relatively better than other agents
• QTc caveat: Ketamine itself has minimal direct QTc effect, but the sympathetic stimulation is generally safe in this context
• Dose: 1–2 mg/kg IV

✅ Etomidate — Acceptable alternative

• Haemodynamically neutral — minimal effect on BP or HR
• Short duration, predictable
• Suitable when cardiac stability is the priority and ketamine is unavailable or contraindicated
• Avoids adrenal suppression concerns (single dose acceptable acutely)
• Dose: 0.3 mg/kg IV

⚠️ Propofol — Use with caution / avoid if hypotensive

• Causes significant vasodilation and myocardial depression — will worsen alpha-1 blockade-induced hypotension
• May precipitate cardiovascular collapse in this overdose context
• If used, reduce dose significantly and have vasopressors ready
• Not recommended as first choice

⚠️ Midazolam — Avoid or minimise

• Additional CNS and respiratory depression on top of existing overdose
• Further vasodilation and hypotension
• If used, very low dose only (0.05 mg/kg)

❌ High-dose barbiturates (thiopentone) — Avoid

• Profound hypotension, cardiac depression
• May worsen QTc effects

Neuromuscular Blockade (for RSI)

• Succinylcholine: Generally acceptable unless contraindications exist (hyperkalemia risk, burns, etc.). Note: succinylcholine itself can cause transient QTc changes, but this is not a strong contraindication in acute RSI — the risk of failed airway outweighs theoretical QTc concerns.
• Rocuronium 1.2 mg/kg: Preferred if succinylcholine is contraindicated or QTc is already critically prolonged (>500 ms); can be reversed with sugammadex. This is a reasonable first choice given the QTc concerns.

Practical RSI Approach in This Overdose

1. Pre-oxygenate aggressively (apnoeic oxygenation if possible)
2. Have vasopressors drawn up — noradrenaline/phenylephrine for anticipated hypotension post-induction
3. Induction: Ketamine 1–2 mg/kg IV (preferred) or Etomidate 0.3 mg/kg IV
4. NMB: Rocuronium 1.2 mg/kg IV (preferred given QTc) or succinylcholine 1.5 mg/kg
5. Post-intubation: Avoid QTc-prolonging agents for sedation where possible — use propofol infusion at low dose (with vasopressor cover) or ketamine infusion
6. Continuous cardiac monitoring for torsades — have magnesium sulphate (2g IV) and defibrillator ready
7. Check and correct electrolytes (K⁺, Mg²⁺) — hypokalaemia and hypomagnesaemia potentiate QTc prolongation

Summary Table