A 3-year-old child with tetralogy of Fallot is found cyanosed, distressed, squatting and crying inconsolably after waking up. SpO2 is 60%. Heart murmur is now absent. This is a hypercyanotic spell. The FIRST pharmacological intervention is:
- A IV propranolol
- B IV digoxin
- C IV morphine sulphate 0.1–0.2 mg/kg ✓
- D IV sodium bicarbonate only
Correct answer: C. IV morphine sulphate 0.1–0.2 mg/kg
Explanation
In a Tet spell (hypercyanotic episode), the immediate management sequence is: knee-chest position + oxygen → IV morphine (0.1–0.2 mg/kg, reduces pulmonary vascular resistance, sedates, suppresses hyperpnea, and reduces dynamic RVOTO) → IV sodium bicarbonate for metabolic acidosis → IV phenylephrine (raises systemic vascular resistance) → IV propranolol (for recurrent spells). The disappearance of the murmur indicates near-complete dynamic RVOTO (no flow across the pulmonary outflow tract). Morphine is the first pharmacological step after positioning and oxygen.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.