Experimental: Hyperhydration

In this study arm, all eligible children are admitted for the administration of intravenous fluids.~The following specifics will form the basis of the fluid management protocol:~1. Reversal of dehydration: Initial ED rehydration strategies should focus on rapidly reversing dehydration.~2. Infusion of 200% of maintenance fluids x 24 hours~3. If hematocrit reduction \< 20% from initial value, repeat step #2 \[infusion of 200% maintenance fluids x 24 hours\].~4. Oral fluids permitted ad lib.~5. Once the target hematocrit reduction is achieved (20% decrement in initial HCT) AND a 10% weight gain, adjust total IV fluid volume to maintain targeted weight gain: insensible plus output (i.e., urine plus stool).

Active_comparator: Conservative Fluid Management

The conservative fluid management arm has been designed to align and integrate into existing local practice patterns. Implementation of this approach will allow institutions and their practitioners to choose their management of protocol eligible children. All children will undergo a protocolized baseline evaluation that includes reversal of dehydration (if present) and follow-up plan (see Pre-Pathway care). The fluid management decision in the ED (i.e., to treat dehydration) will be at the discretion of the clinical care team. In the absence of evidence of microangiopathy (i.e., normal urinalysis, LDH, hemoglobin and platelet counts, and creatinine concentrations), the decision to admit the child to hospital or discharge the child to home will be at the discretion of the clinical care team. If microangiopathy is present (i.e., abnormal urinalysis, LDH, hemoglobin or platelet counts, or creatinine concentrations) admission for monitoring will be required.