Hyperosmolar therapy for intracranial hypertension [Neurosurgery Wiki]

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====== Hyperosmolar therapy for intracranial hypertension ======

see [[Hyperosmolar therapy for children]].

[[Hyperosmolar therapy]] has been the keystone of medical interventions used to control [[intracranial hypertension]]. 

As early as [[1783]], Monro, Kellie, and other investigators advanced the notion that the volume of the brain is constant. 

The landmark work of Weed and McKibben disproved this long-held dogma when they demonstrated dramatic changes in the volume of the brain resulting from administration of [[hypertonic]] or hypotonic intravenous solutions. Since that time, intravenous administration of hyperosmolar agents has become routine in the management of intracranial hypertension and herniation syndromes. However, the optimal agent, their optimal means of administration (i.e., dose and bolus vs. continuous infusion), and their precise mechanisms of action continue to be investigated.
----
In [[1919]] Weed and McKibben reported that hypertonic fluids could lower [[intracranial pressure]] and shrink nervous tissue
((Weed LH, McKibbens PR. Experimental Alterations of Brain Bulk. Am J Physiol. 1919;48:512–530)).

Shortly thereafter Fay reported on “the treatment of cerebral trauma, by methods of dehydration” using intravenous hypertonic sodium and magnesium solutions
((Fay T. The Treatment of Acute and Chronic Cases of Cerebral Trauma by Methods of Dehydration. Ann Surg. 1935;101:76–132)).

It was not until the early 1960s, following the introduction of ICP monitoring in head injury, that mannitol came into more widespread use 
((Shenkin HA, Goluboff B, Haft H. The Use of Mannitol for the Reduction of Intracranial Pressure in Intracranial Surgery. J Neurosurg. 1962;19:897–901.))
((Wise BL, Chater N. The Value of Hypertonic Mannitol Solution in Decreasing Brain Mass and Lowering Cerebro-Spinal-Fluid Pressure. J Neurosurg. 1962;19:1038–1043.))
and turn into the agent of choice. 

Recently, hypertonic saline has challenged mannitol’s role as the preferred osmotic agent
((Marko NF. Hypertonic Saline, Not Mannitol, Should Be Considered Gold-Standard Medical Therapy for Intracranial Hypertension. Crit Care. 2012;16:113. In this editorial the author makes the case for why HS should replace mannitol)).

A recent pro-con debate on osmotic therapy provides a complete summary of the argument for and against its use
((Grape S, Ravussin P. Pro: Osmotherapy for the Treatment of Acute Intracranial Hypertension. J Neurosurg Anesthesiol. 2012;24:402–406. A well -written option piece laying out the arguments in favor the use of osmotic therapy to treat elevated ICP))
((Grande PO, Romner B. Osmotherapy in Brain Edema: A Questionable Therapy. J Neurosurg Anesthesiol. 2012;24:407–412.)).


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Single doses of 3 ml/kg of 20% [[mannitol]] and 3% [[hypertonic saline]] (HS) are safe and effective for intraoperative brain debulking during elective supratentorial craniotomy, but less effective in patients with pre-existing mass effect and midline shift
((Hernández-Palazón J, Fuentes-García D, Doménech-Asensi P, Piqueras-Pérez C,
Falcón-Araña L, Burguillos-López S. A comparison of equivolume, equiosmolar
solutions of hypertonic saline and mannitol for brain relaxation during elective 
supratentorial craniotomy. Br J Neurosurg. 2015 Nov 16:1-6. [Epub ahead of print]
PubMed PMID: 26571037.
)).


Hyperosmolar therapy, using either [[hypertonic saline]] (HTS) or [[mannitol]] (MT), is considered the treatment of choice for [[intracranial hypertension]].

Results do not lend a specific recommendation to select [[hypertonic saline]] or [[mannitol]] as a first-line for the patients with elevated ICP caused by TBI. However, for the refractory intracranial hypertension, hypertonic saline seems to be preferred
((Gu J, Huang H, Huang Y, Sun H, Xu H. Hypertonic saline or mannitol for
treating elevated intracranial pressure in traumatic brain injury: a
meta-analysis of randomized controlled trials. Neurosurg Rev. 2018 Jun 15. doi:
10.1007/s10143-018-0991-8. [Epub ahead of print] PubMed PMID: 29905883.
)).

===== Complications =====

Hyperosmolar agents have been postulated to impair coagulation and platelet function.
 
Use of 3% HTS and 20% MT for the control of ICP did not significantly affect patients' coagulation function. Therefore, hyperosmotic solution is safe and does not increase the risk of intracranial rebleeding
((Wang H, Cao H, Zhang X, Ge L, Bie L. The effect of hypertonic saline and
mannitol on coagulation in moderate traumatic brain injury patients. Am J Emerg
Med. 2017 Oct;35(10):1404-1407. doi: 10.1016/j.ajem.2017.04.020. Epub 2017 Apr
14. PubMed PMID: 28431870.
))
((Hernández-Palazón J, Fuentes-García D, Doménech-Asensi P, Piqueras-Pérez C,
Falcón-Araña L, Burguillos-López S. Equiosmolar Solutions of Hypertonic Saline
and Mannitol Do Not Impair Blood Coagulation During Elective Intracranial
Surgery. J Neurosurg Anesthesiol. 2017 Jan;29(1):8-13. PubMed PMID: 26580123.
)).

Mannitol and hypertonic saline in equiosmolar concentrations produced comparable effects on ICP reduction, brain relaxation, and systemic hemodynamics
((Sokhal N, Rath GP, Chaturvedi A, Singh M, Dash HH. Comparison of 20% mannitol 
and 3% hypertonic saline on intracranial pressure and systemic hemodynamics. J
Clin Neurosci. 2017 Aug;42:148-154. doi: 10.1016/j.jocn.2017.03.016. Epub 2017
Mar 22. PubMed PMID: 28342705.
)).


===== Case series =====

see [[Hyperosmolar therapy for intracranial hypertension case series]]