In this episode, I’ll discuss mannitol extravasation.
When given as a bolus, mannitol is an osmotic diuretic that does not cross the blood-brain barrier. Mannitol lowers intracranial pressure by osmotically drawing free water out of the brain and into circulation where it can be eliminated. If given as a continuous infusion, mannitol will eventually cross the blood-brain barrier and have no effect on intracranial pressure.
This osmotic effect means that if even a small amount of mannitol extravasates, it can pull a large volume of free water with it and quickly turn into compartment syndrome.
Serious consequences of mannitol extravasation have been reported, including compartment syndrome in a patient’s forearm that required surgical treatment.
A case report in the journal Anesthesia and Analgesia describes the successful use of hyaluronidase to prevent complications from mannitol that had extravasated into a patient’s hand.
…150 units of hyaluronidase was mixed in 10 mL of normal saline. Using a 25-gauge needle, multiple subcutaneous injections of 0.5–1.0 mL were performed around the periphery of the extravasation…
…The hand was examined every hour. The swelling diminished after 6 h and was completely resolved by the next day.
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