Many reports demonstrate improved outcomes in critically ill adults who develop hyperglycemia by rigorous glycemic. Medical oversight committees (including the Institutes of Healthcare Improvement, the American Diabetes Association, and Society of Critical Care Medicine, among others) recommend routine glycemic control during critical illness. Some studies show high rates of hypoglycemia and have highlighted the concern of this approach to care. Little data exists on how hyperglycemia and glycemic control affects critically ill children. Our practice group has developed a regular approach to glycemic control that appears effective and safe and controlling hyperglycemia and the investigators believe that due to our unique experience and expertise in this field, the investigators are well-poised to conduct further much needed studies regarding glycemic control in children. To specifically address the void of knowledge regarding glycemic control in critically ill children, the investigators will conduct a single-center randomized controlled trial to ascertain whether there is vital organ system, outcome, and resource utilization benefit to strict glycemic control vs. more conservative control in children requiring intensive care. The "PedETrol" (the "Pediatric ICUs at Emory-Children's Center Glycemic Control) Trial will study 1,004 children admitted to the ICU for medical, surgical, or cardiac conditions requiring mechanical ventilation and/or vasopressor/i support who develop hyperglycemia, defined as persistent blood glucose >140 mg/dL). Participants will be randomized to either receive strict glycemic control (80-140 mg/dL) or more conservative control (190-220 mg/dL). Insulin infusions will be used to maintain blood glucose in these ranges. In addition to assessing organ and outcome specific efficacy parameters, the investigators will meticulously evaluate for untoward effects including hypoglycemia, and determine the impact of this practice on costly medical resources. All children <1 year old and 25% of those >1 year old, will be able to receive continuous glucose monitoring via interstitial glucometry. This appears to be the first glycemic control trial in any critical care population to make use of continuous glucose monitoring.