Abstract
Aim & Background: Pediatric MRI sedation often requires atraumatic, needleless techniques to facilitate IV access and minimize anxiety. We aimed to evaluate the efficacy and safety of intranasal dexmedetomidine (DEX) 2 mcg/kg combined with intranasal ketamine (KET) in a dose-finding case series of 50 children aged 2–5 years undergoing elective MRI.
Methods: Prospective case series using Dixon up-and-down methodology with 0.5 mg/kg KET dose steps (range 2.0–4.0 mg/kg). Success was redefined as successful MRI completion, noting the requirement for rescue propofol, rather than a strictly rescue-free interval. ED50/ED95 estimated via centered isotonic regression. Ethics approved by institutional committee; informed consent obtained.
Results: Fifty children (mean age 3.4 ± 1.1 years, weight 14.3 ± 5.2 kg, ASA II 92%) underwent MRI (mean duration 47.7 ± 15.3 minutes). Mean sedation onset was 12.9 ± 3.8 minutes; parent separation at 21.1 ± 5.2 minutes; recovery to discharge readiness was 3.2 ± 2.8 minutes. Only 6% (3/50) completed MRI without rescue propofol; 94% required incremental propofol (mean 2.13 ± 1.47 mg/kg) to achieve motion-free imaging. ED50 KET was 4.79 mg/kg (95% CI 3.57–6.90); ED95 6.61 mg/kg (95% CI 4.43–8.80). Importantly, the calculated ED95 exceeds the tested dose range. No bradycardia, desaturation <94%, nausea, vomiting, or hypersalivation occurred. No patients required airway intervention or unplanned admission.
Conclusion: Intranasal DEX–KET provided rapid pre-sedation and excellent safety but was insufficient as a standalone regimen at the tested doses, frequently requiring low-dose IV propofol rescue for motion-free MRI. Because the estimated ED95 extrapolates beyond the tested maximum dose, clinical recommendations for this higher dose are premature without further validation.
Keywords
Pediatrics, Magnetic Resonance Imaging, Conscious sedation, Dexmedetomidine, Ketamine, Intranasal administration, Dose-response relationship