USMLE/COMLEX 1 - Hypokalemia Management

Here are key facts for USMLE Step 1 & COMLEX-USA Level 1 from the Hypokalemia 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: K+ < 3.5 mEq/L. 2. Classification by Severity:

• Mild/Moderate: K+ 3.0-3.4 mEq/L
• Severe/Symptomatic: K+ < 3 mEq/L

1. Major causes:

• Gastrointestinal losses
• Renal losses
• Redistribution into cells
• Inadequate intake

1. Muscle symptoms: Cramps, weakness, rhabdomyolysis 2. Cardiac manifestations: Premature beats, arrhythmias 3. Diagnostic ECG changes: U waves, flattened T waves

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1. IV replacement: 20 to 60 mEq KCl in saline 2. Administration rate: Not more than 10-20 mEq/hr to avoid peripheral vein irritation 3. Monitoring requirements: Close monitoring, ECG monitoring if arrhythmias present 1. Oral replacement: K+ supplements – 10-20 mEq, 2-4× daily (max 80 mEq/day) 2. Dietary intervention: Increase intake of K+-rich foods 1. Target range: Maintain K+ between 3.5-5 mEq/L 2. Adjustment goal: Avoid hyperkalemia and arrhythmias 1. Address primary etiology: Gastrointestinal losses, diuretic therapy 2. Consider renal function: Important during replacement therapy 1. Magnesium status: Check for and correct magnesium deficiency 2. Pharmacologic intervention: Consider potassium-sparing diuretics in renal losses (e.g., amiloride) 3. Individualized approach: Based on comorbidities and clinical status

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Below is additional information not explicitly contained within the tutorial but important for USMLE Step 1. 1. Cellular membrane potential: Hypokalemia leads to hyperpolarization of cell membranes 2. Aldosterone effect: Promotes renal K+ excretion and Na+ retention 3. Acid-base disturbances: Metabolic alkalosis commonly coexists with hypokalemia 1. Diuretics: Loop and thiazide diuretics are common iatrogenic causes 2. Endocrine disorders: Cushing's syndrome, hyperaldosteronism 3. Medications: Beta-agonists, insulin, and theophylline can cause redistribution 4. Renal tubular acidosis: Type 1 (distal) and Type 2 (proximal) RTA 1. Glucose metabolism: Impaired insulin release and glucose intolerance 2. Neurologic: Paresthesias, tetany, and in severe cases, ascending paralysis 3. Renal effects: Polyuria, polydipsia, and nephrogenic diabetes insipidus 4. Gastrointestinal: Ileus, constipation