What is the recommended dose of mannitol in mL for a 72 kg adult patient with a massive bleed?

Mannitol Dosing in mL for a 72 kg Adult with Massive Hemorrhage

For a 72 kg adult with massive hemorrhage, administer 18-36 mL of 25% mannitol (or 90-180 mL of 20% mannitol) intravenously over 20 minutes, which can be repeated every 6 hours as needed, with a maximum total daily dose of 144 g (576 mL of 25% solution or 720 mL of 20% solution).

Standard Dosing Calculation

The recommended dose is 0.25 to 0.5 g/kg body weight administered over 20-30 minutes 1, 2. For a 72 kg patient:

• Minimum dose: 0.25 g/kg × 72 kg = 18 g
• Maximum dose: 0.5 g/kg × 72 kg = 36 g

Volume Conversions by Concentration:

For 25% mannitol (250 mg/mL):

• Minimum: 18 g ÷ 0.25 g/mL = 72 mL
• Maximum: 36 g ÷ 0.25 g/mL = 144 mL

For 20% mannitol (200 mg/mL):

• Minimum: 18 g ÷ 0.20 g/mL = 90 mL
• Maximum: 36 g ÷ 0.20 g/mL = 180 mL

1, 3

Critical Considerations for Massive Hemorrhage

Mannitol should only be used if there are clinical signs of elevated intracranial pressure or impending herniation (declining consciousness, pupillary changes, decerebrate posturing), not routinely in all massive hemorrhage cases 2, 4. In the context of massive hemorrhage without intracranial pathology, mannitol is not indicated and may worsen outcomes by causing osmotic diuresis and exacerbating hypovolemia 5.

If Hemorrhage is Intracranial:

• Initial bolus: 72-144 mL of 25% mannitol (or 90-180 mL of 20% solution) over 20 minutes 1, 2
• Repeat dosing: Can be given every 6 hours as needed 1, 2
• Maximum daily dose: 2 g/kg = 144 g for 72 kg patient = 576 mL of 25% solution or 720 mL of 20% solution 1, 2

Mandatory Monitoring and Discontinuation Criteria

Stop mannitol immediately if:

• Serum osmolality exceeds 320 mOsm/L 2, 6, 1, 3
• No clinical improvement after 2-4 doses 6
• Clinical deterioration despite treatment 6

Monitor every 6 hours:

• Serum osmolality 4
• Electrolytes (particularly sodium) 2
• Neurological status 4
• Fluid balance 2

Essential Pre-Administration Steps

Before giving mannitol:

• Insert Foley catheter (mannitol causes profound osmotic diuresis) 3
• Ensure patient is not severely hypovolemic from the massive bleed 1
• Confirm clinical signs of elevated ICP or herniation 2, 4
• Avoid if patient has well-established anuria, severe pulmonary edema, or severe dehydration 1

Important Caveats for Massive Hemorrhage Context

In massive hemorrhage WITHOUT intracranial involvement, focus should be on:

• Fresh frozen plasma (FFP) at 15-30 mL/kg (1,080-2,160 mL for 72 kg patient) to prevent dilutional coagulopathy 5
• Maintaining platelet count ≥75 × 10⁹/L 5
• Maintaining fibrinogen ≥1.5 g/L 5

Mannitol is contraindicated in hypovolemic shock and should never be used as volume replacement in massive hemorrhage 1. If the massive bleed has caused hypovolemia, correct this with crystalloids and blood products first before considering mannitol for any intracranial indication 3.

Alternative Therapy

Hypertonic saline (3% or 23.4%) is an equally effective alternative with potentially longer duration of action and may be safer in hemorrhagic contexts 2, 4, 7. Consider this if mannitol is contraindicated or ineffective.