The perennial debate of which osmotic agent to use to reduce elevated ICP still rages on.
Who better than Mr Deranged Physiology himself, Aleks Yartsev, to take us through the pros and cons of each and work out a practical strategy.
This podcast was recorded at the Brain Symposium which took place in March 2023. Scroll down to read a summary of the talk and view the presentation slides.
SUMMARY
As Aleks says on DP, “Osmotherapy is a crude but effective means of desiccating the brain parenchyma and decreasing its contribution to intracranial pressure”, but when it comes to choosing which one, there’s a bit of nuance.
There’s a great page on osmotherapy on DR.
The history of osmotherapy stretches back to the early 20th century, when early cat-haters injected cats with hypertonic saline and noted that their thecal sacks had become flaccid, making it difficult to acquire CSF from them. Mannitol became popular later – if urea causes such splendid osmotic effects, then why not mannitol, Shenkin argued. Indeed, his patients demonstrated a rise in serum osmolality by 20-30 mOsm/L, and a fall in ICP by 30-60%.
Overall, it seems the trend these days is away from the mannitol, and towards the saline. Specifically, today’s public seem to favour super-high osmolarity saline solutions, such as 20% saline.
So, what are the advantages of saline over mannitol?
- Its cheap
- It does not cause massive diuresis and hypovolemia
- It is easy to monitor therapy with blood gases (aiming for a Na+ level around 145-155)
- It seems to have some sort of mysterious anti-inflammatory properties which decreases the permeability of the injured blood-brain barrier
