Inclusion Criteria:

• ≥ 18 years of age
• Catecholamine-resistant hypotension
  • Defined as requiring a total sum catecholamine dose of > 0.2 mcg/kg/min for a minimum of 6 hours and a maximum of 48 hours, to maintain a mean arterial pressure between 55-70 mmHg
• Required to have central venous access and an arterial line present, and these are expected to remain present for at least the initial 48 hours of study
• Required to have an indwelling urinary catheter present, and it is expected to remain present for at least the initial 48 hours of study
• Must have received at least 25 mL/kg of crystalloid or colloid equivalent over the previous 24-hour period, and be adequately volume resuscitated in the opinion of the treating investigator
• Must have clinical features of high-output shock by meeting one of the following criteria
  • Central venous oxygen saturation (ScvO2) > 70% (either by oximetry catheter or by central venous blood gas) and central venous pressure (CVP) > 8 mmHg
  • Cardiac Index (CI) > 2.3 L/min/1.73 m2
• Willing and able to provide written informed consent and comply with all protocol requirements

Exclusion Criteria

• < 18 years of age
• Has burns covering > 20% of total body surface area (TBSA)
• Has a Cardiovascular SOFA score ≤ 3
• Diagnosed with acute occlusive coronary syndrome requiring intervention
• On veno-arterial ECMO
• Have been on ECMO for less than 12 hours
• In liver failure with a Model for End-Stage Liver Disease (MELD) score of ≥ 30
• Have a history of asthma or are currently experiencing bronchospasm requiring the use of inhaled bronchodilators, if not mechanically ventilated
• Have acute mesenteric ischemia or a history of mesenteric ischemia
• Have a history of, presence of, or highly-suspected of having an aortic dissection or abdominal aortic aneurysm
• Require more than 500 mg daily of hydrocortisone or equivalent glucocorticoid medication as a standing dose
• Have Raynaud's phenomenon, systemic sclerosis or vasospastic disease
• Have an expected lifespan of < 12 hours
• Have active bleeding AND an anticipated need (within 48 hours of initiation of the study) for transfusion of > 4 units of packed red blood cells
• Have active bleeding AND hemoglobin < 7g/dL or any other condition that would contraindicate serial blood sampling
• Have an absolute neutrophil count (ANC) of < 1000 cells/mm3
• Have a known allergy to mannitol.
• Are current participating in another interventional clinical trial
• Are known to be pregnant at the time of screening