Dose-Response Study of Sodium Nitroprusside in Children Requiring Controlled Hypotension in the Operating Room

Inclusion Criteria: Study subjects must meet all of the following criteria: Subject is less than 17 years of age Neonates must be full-term gestation and have a body weight of at least 2.5 kg Subject requires pharmacologically-induced hypotension for acute blood pressure management for surgery or other invasive procedure, e.g., cerebral artery embolization Duration of the subject's controlled hypotension is expected to be ≥ 2 hours Subject requires general anesthesia with endotracheal intubation Subject requires placement of intra-arterial line during the surgical or medical procedure The subject's parent or legal guardian gives permission (informed consent) and subject gives assent when appropriate. Exclusion Criteria: Subjects will be excluded if any of the following criteria exist: Subject has a known allergy to SNP Subject has a known mitochondrial cytopathy with a disorder of oxidative phosphorylation or of respiratory chain enzymes Subject has a contraindication to vasodilator therapy for control of blood pressure during surgery or procedures Subject has participated in other clinical trials for investigational drugs and/or devices within 30 days prior to enrollment Subject has any serious medical condition which, in the opinion of the investigator, is likely to interfere with study procedures Subject is moribund (death likely to occur within 48 hours) Subject has a positive result for the urine or serum human chorionic gonadotropin (HCG) test administered at screening.