- Children age one (1) day to eighteen (18) years, requiring admission to the Pediatric ICU, requiring continuous infusion of Fentanyl analgesic anticipated to last greater than 4 days will be eligible for enrollment. Patients from both genders, all races and ethnic backgrounds will be eligible. Patients meeting the above criteria will be eligible regardless of nutritional status, performance status or recovery from prior medical treatment. They will not be excluded if they require simultaneous infusions of sedation with Midazolam. Enrollment will require parental consent.