II. Preparations: Hypotonic Solutions

  1. Dextrose in Water (D5W)
    1. Osmolality: 252 mOsm/L
    2. Glucose: 50 g/L
    3. Contains no Sodium or chloride
    4. Primarily used to deliver intravenous medications in small volume fluid infusions (<100 ml)
  2. Half Normal Saline (0.45 NaCl or 1/2NS)
    1. Osmolality: 154 mOsm/L
    2. Sodium: 77 mEq/L (with equivalent chloride)
    3. Equivalent of administering half free water and half Isotonic Saline
    4. Consider in Hypernatremia with volume depletion
    5. Risk of Hyponatremia
      1. Prolonged use
      2. Impaired water excretion (e.g. GFR <20%, CHF, Cirrhosis, Nephrosis)

III. Preparations: Isotonic Solutions

  1. See Crystalloid Isotonic Solution
  2. General
    1. NS or LR is the typical replacement in most volume depleted cases
    2. LR may be preferred as more physiologic (pH neutral) compared with the acidic NS
    3. Hypovolemia due to Hemorrhage should be replaced with blood (as indicated)
  3. Normal Saline (0.9% NaCl or NS)
    1. Osmolality: 308 mOsm/L
    2. Sodium: 154 mEq/L (with equivalent chloride)
    3. pH: 5-6
  4. Lactated Ringers (LR)
    1. Osmolality: 272 mOsm/L
    2. Sodium: 130 mEq/L
    3. Chloride: 109 mEq/L
    4. Lactate: 28 mEq/L (buffer)
    5. Also contains Potassium (4 mEq/L) and Calcium (3 mEq/L)
    6. pH: 6.5

IV. Preparations: Hypertonic Solutions

  1. Hypertonic Saline (3% NaCl)
    1. Osmolality: 1026 mOsm/L
    2. Sodium: 513 mEq/L (with equivalent chloride)
    3. pH: 5
    4. Exercise caution and dose very carefully (risk of Central Pontine Myelinolysis)
    5. Five fold greater effect of expanding extracellular space than Isotonic Solutions given the same fluid volume
      1. However, no survival benefit over Isotonic Solutions (with the added risk)
    6. Indications
      1. Severe symptomatic Hyponatremia
      2. Severe cerebral edema with risk of Herniation (Traumatic Brain Injury)

V. References

  1. Loflin (2015) Crit Dec Emerg Med 29(9): 11-18
  2. Marino (2014) The ICU Book, Wolters Kluwer, Philadelphia, p. 217-37
  3. Preston (2011) Acid-Base, Fluids and Electrolytes, Medmaster, Miami, p. 30-4

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