USMLE/COMLEX 1 - Hyponatremia Management

Here are key facts for USMLE Step 1 & COMLEX-USA Level 1 from the Acute Hyponatremia Management tutorial, as well as points of interest at the end of this document that are not directly addressed in this tutorial but should help you prepare for the boards. See the tutorial notes for further details and relevant links.

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1. Definition: Developed within the last 48 hours (versus chronic >48 hours). 2. Key symptoms: GI (nausea, vomiting), motor (ataxia, tremor), cognitive (confusion, seizures, coma). 3. Key physical findings: Peripheral edema from volume overload, cerebral edema with neurological signs of coma. 4. Severity classification: Severe (<120 mEq/L), moderate (120-130 mEq/L), mild (130-135 mEq/L). 5. Treatment goal: Initial 5 mEq/L increase over first few hours, avoiding over-correction over 24 hours. 6. Symptomatic management: Rapid 100 mL 3% hypertonic saline infusion (over 10 minutes) for any symptomatic patient. 7. Complication concern: Osmotic demyelination from overly rapid correction.

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1. Common causes: IV fluid overload in surgery, water intoxication (marathon runners, psychotic polydipsia). 2. Treatment indication: Treat when sodium is < 130 mEq/L (if acute). 3. Autocorrection management: If already autocorrecting (from water diuresis), no saline bolus needed, monitor hourly. 4. Asymptomatic patients: Use 50 mL of 3% saline, check sodium hourly, repeat bolus if needed. 5. Additional management: Stop other IV fluids, restrict electrolyte-free water intake. 6. Underlying causes: Look for contributing medications (thiazide diuretics), possible SIADH (recent surgery, pain, certain medications). 7. Treatment principle: Treat rapidly early, monitor closely (hourly), then level off to allow brain adaptation. 1. Main pathophysiologic concern: Development of cerebral edema in acute cases. 2. Treatment strategy: "Treat rapidly, early, monitor closely (hourly) and then level off to give the brain a chance to adapt."

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Below is information not explicitly contained within the tutorial but important for USMLE & COMLEX 1. 1. Brain adaptation: In acute hyponatremia, the brain has not had time to adapt through solute loss. 2. Cerebral edema mechanism: Hypotonic extracellular fluid causes osmotic water movement into brain cells. 3. Central pontine myelinolysis: Risk increases with correction rates >10-12 mEq/L/24h. 1. Laboratory workup: Serum and urine osmolality, urine sodium to differentiate between SIADH, psychogenic polydipsia, and salt-wasting. 2. Volume status assessment: Critical for determining underlying cause and appropriate treatment. 3. Pseudohyponatremia: Caused by hyperlipidemia or hyperproteinemia - important differential to consider.