Polypharmacy-related Adverse Events in Critically Ill Children

Inclusion Criteria: * Ages 2-\<18 at the time of enrollment * Admitted to the Duke PICU or PCICU * Planned or anticipated mechanically ventilation for ≥2 days * Require sedation to maintain mechanical ventilation * No contraindication to receipt of fentanyl or dexmedetomidine per clinician judgment * Availability and willingness of the parent/legal guardian to provide written informed consent Exclusion Criteria: * Any concomitant condition, which in the opinion of the investigator would preclude a subject's participation in the study. * Previous participation in this study * Planned receipt of sedatives other than fentanyl or dexmedetomidine * Participants with any of the following diagnoses: traumatic brain injury, intracranial hemorrhage, baseline neurodevelopmental delay, status epilepticus, or requiring inotropic support for hemodynamic stability. * Renal failure requiring renal replacement therapy * Hepatic failure * Support with extracorporeal membrane oxygenation