Fluids, Electrolytes and Shock
Tom Archer, MD, MBA
OutlineThree fluid compartments (ICF, ISF, IVF)
Osmosis– theory and clinical
Shock-- tissue needs and cardiac output
Water and electrolytes in general (3 overlapping systems)
Hyponatremia– appropriate and inappropriate secretion of ADH
Hypernatremia and K+ disorders Three fluid compartments
Intracellular fluid (ICF)
Interstitial fluid (ISF)
Intravascular fluid (IVF)
Fractions to remember:
2/3, 2/3, 3/4TBW (42 L) = 2/3 of body weight (70 kg).
ICF (28 L) = 2/3 of TBW.
ECF (14 L) = 1/3 of TBW.
Interstitial fluid (ISF, 10.5 L) = ¾ of ECF
Intravascular fluid (IVF, 3.5 L) = ¼ of ECF.
Non- brain capillary endothelium
Brain capillary endothelium (“blood-brain barrier– BBB”) Solutes
Ions: Na+ , Cl-, K+, PO4---
Sugars: glucose, mannitol
Large molecules (colloids): albumin, hetastarch Two types of membranes
Non-brain capillary endothelium is permeable to everything but colloid, therefore, only colloid is osmotically active at non-brain capillary membrane. Two types of membranes
Cell membrane and healthy BBB are only permeable to water, therefore, all ions, sugars and large molecules are osmotically active at cell membrane and BBB.