Morning Report 11/3 – Hyponatremia

Teaching Pearls:

  • Can be categorized into the following:
    • Hyperosmolar
      • Hyperglycemia, mannitol use
    • Iso-osmolar
      • Hypertriglyceridemia, hyperparaproteinemia
    • Hypo-osmolar
  • Hypo-osmolar hyponatremia can be divided into different categories based on volume status:
    • Hypovolemic
      • GI losses, diuretic use, blood loss
      • ↓↓salt/↓H2O
      • Urine osm >100mOsm/L
      • Urine Na <20 mmol/L
    • Euvolemic
      • siADH, psychogenic polydipsia, adrenal insufficiency, hypothyroidism, low solute intake (tea toast diet or beer potomania)
      • Salt/↑H2O
      • siADH
        • Urine osm >100mOsm/L
        • Urine Na >40 mmol/L
      • Psychogenic polydipsia
        • Urine osm<100mOsm/L
        • Urine Na >20mmol/L
    • Hypervolemic
      • CHF, nephrotic syndrome, cirrhosis
      • ↑Salt/↑↑H2O
      • Urine osm >100mOsm/L
      • Urine Na <20mmol/L
  • Hypothyroidism presents as a hypoosmolar euvolemic hyponatremia.
    • Can present with a clinical picture and urine studies similar to siADH
    • Can also present as a picture of CHF.
      • Often these patients have myxedema coma.
      • Theorized that the decreased cardiac output leads to decreased glomerular filtration, leading to poor excretion of free water.
  • Adrenal insufficiency commonly presents with hyponatremia, hyperkalemia, and metabolic acidosis.
  • Low solute diet (tea toast diet and/or beer potomania)
    • Kidneys can dilute urine to as low as 50mOsm/L.
    • If intake of solute is very low, then it limits the amount of free water that can be excreted.
  • For more teaching points, check out the hyponatremia section on http://www.professorebm.com.

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