Hypertonic Saline

HYPERTONIC SALINE

  • Brain Trauma Foundation – start treatment for increased ICP at pressures >20mm Hg
  • Hyperosmolar therapy:
    1. Mannitol vs HTS
      1. Mannitol
        • BTF recommends mannitol as mainstay in management of intracranial HTN
        • Considered first choice in immediate treatment of increased ICP
        • Even for cases requiring emergent surgery, mannitol is a good temporizing choice
        • Is the standard treatment of choice, so any Level 1 evidence should compare HTS to mannitol
      2. HTS
        • 2%-23.5%
        • More effective than mannitol for reduction of ICP
  • Side effect profile of HTS more favorable
    • Mannitol causes delayed hypovolemia due to diuretic effect (not good in trauma patients); hypotension due to osmotic diuresis, compromises renal function
    • Mannitol may exacerbate cerebral edema if administered late after cerebral injury due to disrupted BBB
    • HTS improves MAP and increases circulating blood volume
  1. Mechanism of action
    1. Classic theory: reduced brain water content through osmotic effects
      • Na has reflection coefficient of nearly 1 (with intact BBB, very little Na crosses barrier, pulls fluid out of interstitial space)
      • BUT
        • studies show equal decrease in ICP in those with and without a decrease in brain volume after HTS treatment
        • studies show sustained decrease in ICP even at serum Na levels that will not have osmotic effect
  1. Other mechanisms:
    • VASOCONSTRICTION: Early after administration, HTS reduces blood viscosity, increases rheological properties, improves CBF and cerebral oxygenation causing autoregulatory vasoconstriction, reduced ICP.
    • ENDOTHELIAL SHRINKAGE: HTS induces endothelial cell shrinkage, improves circulation
    • IMMUNOMODULATORY ROLE?
    • REDUCED CSF PRODUCTION?
  • Cerebral edema:
Type Mechanism Conditions Timing Notes
Cytotoxic Cellular swelling due to ischemic or toxic injury Trauma Minutes to hours Resistant to treatment
Vasogenic Extracellular edema due to capillary disruption / breakdown of BBB Trauma, tumors, abscess Hours to days

 

  • Questions:
    1. What is the role of HTS in intracranial hypertension due to trauma, SAH, mass lesions? HTS appears to have a favorable outcome in all types of intracranial hypertension, no matter the origin
    2. What is the most optimal concentration for HTS? There is no consensus on the most optimal concentration – all concentrations appear to have favorable effects on ICP
    3. Is there an advantage of continuous drip or bolus administration? Meta analysis shows more favorable short term ICP outcome for HTS, regardless of concentration or administration mode (continuous drip or bolus)
    4. What is the optimal length of treatment? Is there a rebound effect with HTS? Studies looking into rebound risk of HTS are lacking. The few studies that mentioned rebound phenomenon have inadequate monitoring
  • Take home:
    1. Decreasing ICP: HTS is superior to mannitol
    2. Neurological outcome: no clear benefit, but positive trend for HTS

Mortazavi, Martin M, Andrew K Romeo, Aman Deep, Christoph J Griessenauer, Mohammadali M Shoja, R Shane Tubbs, and Winfield Fisher. 2012. ‘Hypertonic Saline For Treating Raised Intracranial Pressure: Literature Review With Meta-Analysis: A Review’. Journal Of Neurosurgery 116 (1): 210–221.

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