What are the considerations prior to initiating Mannitol (mannitol) therapy in patients with severe Traumatic Brain Injury (TBI)?

Pre-Initiation Considerations for Mannitol in Severe TBI

Before administering mannitol in severe traumatic brain injury, you must assess hemodynamic stability, renal function, serum osmolality, and ensure the patient has clear clinical indications such as signs of herniation or neurological deterioration not attributable to systemic causes. 1, 2

Critical Hemodynamic Assessment

Avoid mannitol in hypotension or hypovolemia - this is an absolute priority consideration. 2 The key concern is that mannitol induces significant osmotic diuresis requiring volume compensation, which can worsen hypotension and compromise cerebral perfusion pressure (CPP). 1, 3

• If systolic BP <90 mmHg or signs of hypovolemia exist, choose hypertonic saline instead - it has comparable efficacy at equiosmotic doses (~250 mOsm) but increases blood pressure rather than causing diuresis. 1, 2, 3
• Initiate aggressive fluid resuscitation with crystalloids before or concurrent with mannitol if hemodynamic instability is present. 1
• Maintain CPP between 60-70 mmHg during therapy, as CPP <60 mmHg is associated with poor neurological outcomes. 1, 2

Renal Function Evaluation

Assess baseline renal function before administration - mannitol is substantially excreted by the kidney and carries increased risk of renal failure in compromised patients. 4

• Patients with pre-existing renal disease, conditions putting them at high risk for renal failure, or those receiving nephrotoxic drugs are at increased risk. 4
• Evaluate and correct fluid and electrolyte imbalances prior to administration. 4
• Place a urinary catheter before administration due to expected osmotic diuresis. 2, 3

Serum Osmolality Monitoring

Check baseline serum osmolality and plan for serial monitoring - discontinue mannitol if serum osmolality exceeds 320 mOsm/L to prevent renal failure. 1, 2, 3

• Serum osmolality increases of ≥10 mOsm are associated with effective ICP reduction, but excessive elevation increases risk of complications. 3
• Monitor fluid, sodium, and chloride balance throughout therapy. 2
• If hypernatremia already exists, mannitol is preferred over hypertonic saline. 2, 3

Clinical Indications Verification

Confirm appropriate clinical indications before initiating therapy. 1 Mannitol should be administered when:

• Obvious neurological signs of increased ICP exist, such as pupillary abnormalities or neurological worsening not attributable to systemic causes. 1
• Signs of brain herniation are present - mannitol is the treatment of choice for this indication. 1, 3
• GCS ≤8 with abnormal initial CT scan in patients unable to undergo neurological assessment. 1

Studies show that 72% of patients receiving mannitol during interfacility transfer had clear indications, but 28% did not meet guideline criteria, highlighting the importance of verification. 5

Dosing Preparation and Administration Planning

Prepare for proper dosing to avoid common errors - a 22% dosing error rate has been documented at peripheral hospitals, including 8.3% underdosing and 7.5% overdosing. 5

• Standard dose: 0.25-1 g/kg IV over 15-20 minutes for acute ICP crisis. 1, 2, 4
• Smaller doses (0.25 g/kg) are as effective as larger doses for acute ICP reduction while minimizing osmotic complications. 2, 3
• For debilitated patients, 500 mg/kg may be sufficient. 4
• Never administer if solution contains crystals - use a filter for administration. 2, 4
• Do not place 25% mannitol in PVC bags as white precipitate may form. 4

Cardiac and Pulmonary Status

Evaluate cardiac and pulmonary status before administration, particularly in elderly patients who are at greater risk of adverse reactions. 4

• Careful evaluation of circulatory reserve is required prior to administration at higher doses and rapid infusion rates. 4
• Monitor body weight and total input/output before and after infusion. 4

Special Contraindications

Avoid mannitol entirely in specific clinical contexts:

• Perioperative moyamoya disease - mannitol should be avoided entirely per American Stroke Association guidelines. 1
• Never add mannitol to whole blood for transfusion. 4

Alternative Agent Consideration

Have hypertonic saline available as an alternative when mannitol is contraindicated or less optimal. 1, 2, 3 Choose hypertonic saline when:

• Hypovolemia or hypotension is present. 1, 2, 3
• Hypernatremia exists (choose mannitol instead). 2, 3
• Improved blood pressure support is needed alongside ICP reduction. 3