Sodium Nitroprusside for Blood Pressure Reduction in the ICU (SNP2)

Inclusion Criteria:

   1. Subject is less than 17 years of age.

   2. An in-dwelling arterial line is clinically indicated.

   3. Subject's parent or legal guardian is willing and able to give informed parental
   permission signing and dating an IRB-approved informed parental permission containing
   all of the elements of informed consent, and subject provides assent, signing an
   IRB-approved and -required informed assent, if applicable.

   4. Subject is anticipated to require a minimum of 20 mm Hg (15 mm Hg for subjects < 2
   years old) reduction in MAP for at least 12 hours using SNP [i.e., MAPB1 - MAPB2 ≥ 20
   mm Hg (15 mm Hg for subjects < 2 years old)]

Exclusion criteria:

   1. Subject weighs < 3.0 kg.

   2. Subject has a known allergy to SNP.

   3. Subject has a known mitochondrial cytopathy with a disorder of oxidative
   phosphorylation or of respiratory chain enzymes.

   4. Subject has a contraindication to vasodilator therapy for control of blood pressure
   during surgery or in the intensive care unit.

   5. Subject has raised intracranial pressure.

   6. Subject is anticipated to need anti-hypertensive drugs other than Sodium Nitroprusside
   either IV (e.g. dexmedetomidine, esmolol, etc.) or epidural (e.g.local anesthetics,
   clonidine, etc.) within three terminal half-lives (3X T½ β) of the blinded study drug
   period. However, patients receiving stable doses of an anti-hypertensive drug(s) prior
   to the initiation of study drug may be enrolled.

   7. Subject has any serious medical condition which, in the opinion of the investigator,
   is likely to interfere with study procedures.

   8. Subject is moribund (death likely to occur within 48 hours).

   9. Subject has a positive result for the urine or serum HCG test administered at
   screening.

10. Subject has participated in other clinical trials for investigational drugs within 30
   days prior to enrollment

11. Subject has received or will have received Sodium Thiosulfate within 6 hours prior to
   the start of the open-label period.

12. Subject is either on, or anticipated to be on, ECMO.