At what blood pressure should mannitol be stopped?

Blood Pressure Thresholds for Mannitol Administration

Mannitol should be avoided in patients with hypotension, and hypertonic saline should be used instead when systolic blood pressure is critically low or when hypovolemia is present. 1, 2

Critical Hemodynamic Requirements

Cerebral Perfusion Pressure (CPP) Must Be Maintained

• CPP must be maintained between 60-70 mmHg during mannitol administration. 1, 2, 3
• CPP below 60 mmHg is associated with poor neurological outcomes. 3
• CPP above 70 mmHg increases risk of respiratory distress syndrome without improving outcomes. 3

Blood Pressure Considerations

• With a blood pressure of 90/60 mmHg (MAP approximately 70 mmHg), if intracranial pressure is elevated, the CPP may already be critically low. 1
• Mannitol works optimally in patients with low CPP (<70 mmHg) because they have autoregulatory vasodilation that allows mannitol's vasoconstrictive mechanism to work effectively. 1, 4
• However, this does not mean mannitol should be used in hypotensive patients—rather, blood pressure must first be optimized. 1

Clinical Management Algorithm

When Blood Pressure Is Low (Systolic <90-100 mmHg or MAP <70 mmHg):

1. Initiate aggressive fluid resuscitation with crystalloids before or concurrent with osmotic therapy. 1
2. Choose hypertonic saline over mannitol as the superior option in hypotension or hypovolemia. 1, 2, 3
3. Mannitol induces osmotic diuresis requiring volume compensation, which can worsen hypotension. 1, 2

When Blood Pressure Is Adequate:

1. Mannitol can be safely administered at 0.25-1.0 g/kg (typically 0.5-1 g/kg as 20% solution) infused over 15-20 minutes. 1, 3
2. Monitor and maintain systolic blood pressure at or above baseline where the patient is asymptomatic. 5
3. Avoid systolic blood pressure >180 mmHg. 5

Specific Clinical Contexts

Perioperative Moyamoya Disease

• Mannitol should be avoided entirely in moyamoya patients perioperatively. 5
• Systolic blood pressure goal should be set at or above preoperative baseline. 5
• Patients should be kept euvolemic to mildly hypervolemic to avoid hypotension and decreased cerebral perfusion pressure. 5

Traumatic Brain Injury

• Control secondary brain insults (including hypotension) before administering mannitol. 3
• Hypotension is a critical secondary insult that must be addressed first. 1

Monitoring Requirements During Mannitol Use

• Serum osmolality must remain below 320 mOsm/L. 1, 2, 3
• Mannitol should be discontinued when serum osmolality exceeds 320 mOsm/L to prevent renal insufficiency. 3, 6
• Volume status must be monitored closely due to osmotic diuresis. 1, 2

Key Pitfalls to Avoid

• Do not use mannitol as first-line therapy in hypotensive patients—this can precipitate cardiovascular collapse due to osmotic diuresis and volume depletion. 1
• Do not assume higher doses are more effective—lower doses (0.25 g/kg) are as effective as higher doses (0.5-1 g/kg) for acute ICP reduction. 3
• Do not use mannitol in moyamoya patients perioperatively regardless of blood pressure. 5