Mechanically Ventilated, Critically Ill Children

The goal of a pilot study is to test a study plan to see if it is appropriate for a larger study. This study plan is looking at whether the use of inhaled sedatives (medications that help people be calm and sleep) can reduce delirium (extreme confusion) in children who need a ventilator (breathing machine) compared to IV or oral sedatives. The main question\[s\] it aims to answer are: * Will people join the study? (recruitment) * Will participants finish the study? * Will healthcare teams accept the study procedures? Participants will be randomized to receive study treatment (inhaled sedation) or standard of care (IV sedation). They will be monitored daily for up to 28 days. They will complete memory, thinking and behaviour tasks after 9-12 months.