Pilot Study Assessing Oxidative Stress in Children

Inclusion Criteria: Critically Ill subjects: 1. All patients, birth-18 years, admitted to the pediatric intensive care unit that require blood to be drawn as part of medical management consistent with "standard of care". 2. Admission to the PICU within the last 24 hours. 3. Subjects' legal guardian shall possess the ability to understand the purposes and risks of the study and provide an informed consent signature. Healthy control subjects: 1\. All healthy children, birth-18 years, who are having semi-elective magnetic resonance imaging (MRI) that require peripheral intravenous (PIV) catheters placed to provide sedation. Exclusion Criteria: Critically Ill subjects: 1. Have received steroids within the last 30 days. 2. Pre-existing/known neuroendocrine disorder, including but not limited to disorders of the hypothalamus, pituitary, adrenal, pancreas, or thyroid gland. 3. Have been treated at anytime with antipsychotic medication. 4. Human immunodeficiency virus (HIV) positive. 5. Patients who have received etomidate. 6. Patients weighing less than or equal to 6 kilograms. 7. Developmentally delayed. 8. Medical urgency preventing timely administration of the consenting process, or any condition that, in the opinion of the attending physician, would place the patient at undue risk by participating. 9. Other technical considerations that would prevent the timely acquisition of sufficient samples such as (but not limited to) hour of admission or absence of a study team member. 10. Parent or legal guardian (or patient when applicable) refuses to sign informed consent. Healthy control subjects: 1. Have received steroids within the last 30 days. 2. Have a pre-existing/known neuroendocrine disorder, including but not limited to disorders of the hypothalamus, pituitary, adrenal, pancreas, or thyroid gland. 3. Have been treated at anytime with antipsychotic medication. 4. Human immunodeficiency virus (HIV) positive. 5. Patients who have received etomidate. 6. Patients weighing less than or equal to 6 kilograms. 7. Developmentally delayed. 8. Medical urgency preventing timely administration of the consenting process, or any condition that, in the opinion of the attending physician, would place the patient at undue risk by participating. 9. Other technical considerations that would prevent the timely acquisition of sufficient samples such as (but not limited to) hour of admission or absence of a study team member. 10. Parent or legal guardian (or patient when applicable) refuses to sign informed consent.