Sam Galvagno- Osmotherapy: Agents to know for your next "Brain Code"

Today we are once again excited to have Dr./LtCol/All-around critical care guru Sam Galvagno. In addition to publishing in multiple major journals, defending the country, maintaining FOUR board certifications, AND maintaining a PhD in Clinical Research; Dr. Galvagno somehow finds time away from his job as Associate Director of the University of Maryland SICU to do what he does best: share his advanced knowledge of critical care. It is an honor and a privilege to share with you a lecture topic that Dr. Galvagno has spent many years researching: Osmotherapy. I assure you, no matter what your level of exposure is to this topic I GUARANTEE you will take away a TON of new clinical pearls!!

Podcast: Play in new window | Download

Subscribe: Apple Podcasts | RSS

Key points

• Pearl #1: Egress of water = Loss of volume in the cranial vault
  • Monroe-Kelley Doctrine!
  • This is a BRIDGE to definitive therapy!
• Pearl #2: Water movement in the brain is NOT PASSIVE
  • Need to physically alter the osmotic equilibrium with:
    • A non-toxic, inert, object with COMPLETE exclusion from the brain
• Pearl #3: A 1.6% reduction in brain volume = 90 ml of brain tissue saved!! 
  • An Osm of 300-320 will:
    • Allow active egress of water from the brain tissue → decreased intracranial volume
    • Improve elasticity of the cranial vault
• Pearl #4: There is NO JUSTIFICATION in withholding an osmolar agent due to lack of central access
  • NO study shows significant harm is caused by using PIV
• Pearl #5: Osmotherapy agent effects extend beyond simply osmotic action:

Mannitol

• 1100 mOsm/L
• Dose: 0.25-1.5g/kg
• Takes 15-30 minutes for full effect, i.e.: takes time to lower ICP
  • Lasts 2-4 hours
• Effects:
  • Concentration gradient → egress of intracranial fluid
  • Volume expansion (detrimental in CHF) → increased CO → improved CPP
  • Vasoconstriction + decreased viscosity → improved CBF
  • Proximal tubule diuretic (detrimental in AKI/CKD)
  • Free radical scavenger
• Goal:
  • DO NOT worry about a desired serum osm goal (i.e. <320…)
  • Calculate Serum Osm Gap 
    • Renal failure rare with Osm Gap < 55!!
• Adverse effects:
  • #1 side effect- diuresis → hypovolemia and hypotension
  • Pulmonary edema, metabolic acidosis, hemolysis, AKI, hyperkalemia

Hypertonic Saline

• 3% 1027 mOsm/L, 5% 1711 mOsm/L, 23.4% 8000 mOsm/L
• Dose: 1-2 cc/kg/hr 3% or 4-6cc/kg/hr 2% (Ideal Body Weight)
  • Lasts 48 to 72 hours
• Rise in Sodium can be augmented with simultaneous use of loop diuretic
• CAUTION:
  • Chloride load leads to SEVERE hyperchloremic metabolic acidosis
  • Sudden rise in sodium can lead to Central Pontine Myelinolysis (but…. only one documented case)
• Effects:

• Goal:
  • Na level 145-160 (i.e. Osm 300-320)
• Adverse effects:
  • In addition to acidosis and CPM, a rapid ICP drop can tear bridging veins and lead to a SDH

Hypertonic Saline vs. Mannitol

• No study has ever shown a remarkable difference (yet….)