Seminar 1: Sodium and Potassium

Seminar 1: Sodium and Potassium – The Giants of Osmolality and Excitability Differentiate between isotonic, hypotonic, and hypertonic hyponatremia using serum osmolality. • Hypotonic hyponatremia = low sodium with low serum osmolality (true hyponatremia; most common). • Isotonic hyponatremia = normal osmolality; usually pseudohyponatremia from high lipids/ proteins. • Hypertonic hyponatremia = low sodium due to osmotic substances (e.g., severe hyperglycemia). Assess a patient’s volume status clinically to categorize the etiology of hyponatremia. • Hypovolemic: dehydration, low BP, dry mucosa. • Euvolemic: normal exam, often SIADH. • Hypervolemic: edema, ascites, heart failure, cirrhosis. Calculate the appropriate rate of sodium correction to prevent Osmotic Demyelination Syndrome. • Main principle: correct slowly. • Overly rapid correction causes ODS. • Generally do not exceed about 8–10 mEq/L/day. Identify the indications for the use of 3% hypertonic saline in symptomatic hyponatremia. • Severe symptoms: Seizures ◦ Coma ◦ Severe confusion ◦ Marked neurological symptoms ◦ Explain the pathophysiology of Diabetes Insipidus in the context of hypernatremia. • ADH deficiency or resistance → inability to concentrate urine → excessive water loss → hypernatremia. Recognize the sequential ECG changes associated with progressive hyperkalemia. • Peaked T waves • PR prolongation • QRS widening • Sine-wave pattern • Cardiac arrest Administer calcium gluconate correctly as a first-line treatment for potassium-induced cardiotoxicity. • First treatment when hyperkalemia causes ECG changes. • Stabilizes cardiac membranes. • Does not lower potassium. Distinguish between various causes of hypokalemia, including renal losses vs. gastrointestinal losses. • GI losses: vomiting, diarrhea. • Renal losses: diuretics, hyperaldosteronism, renal disease. Describe the relationship between magnesium deficiency and refractory hypokalemia. • Low magnesium causes continued urinary potassium loss. • Potassium replacement often fails unless magnesium is corrected. Formulate a clinical plan for the safe intravenous replacement of potassium in severe depletion. • ECG monitoring. • Controlled infusion rates. • Avoid rapid administration because it may cause fatal arrhythmias.