Diagnosis

Hypokalemia

Etiology

Cause [ot1]

1. Low intake (nutriotional disorders)

   • Anorexia, bulimia, starvation, pica, alcoholism, parenteral nutrition

2. Increased excretion

   • Gastric loss of potassium: vomiting, diarrhea

   • Renal loss of potassium: diuretics, osmotic diuresis: (mannitol and hyperglycemia)

   • Excessive sweating

   • Hyperreninism from renal artery stenosis

   • Mineralocorticoid excess

     • Cushing syndrome

     • Primary hyperaldosteronism (adrenal adenoma or bilateral adrenal hyperplasia)

     • Secondary hyperaldosteronism (volume depletion, congestive heart failure, cirrhosis, or vomiting)

     • Tumor producing adrenocorticotropic hormone

     • Genetic disorders

     • Steroid therapy

     • Licorice

     • Chinese herbal

     • Hypomagnesemia

   • Drugs that can cause hypokalemia

     • Diuretics

     • Methylxanthines (theophylline, aminophylline, caffeine)

     • Verapamil

     • Antipsychotic drugs: Risperidone, Quetiapine

     • Ampicillin, carbenicillin

     • Bicarbonate

     • Antifungal agents (amphotericin B, azoles, echinocandins)

     • Gentamicin

     • Cisplatin

     • Ephedrine

     • Beta-agonist intoxication

     • Chloroquin

   • Genetic disorders

     • Congenital adrenal hyperplasia

     • Glucocorticoid-remediable hypertension

     • Bartter syndrome

     • Gitelman syndrome

     • Liddle syndrome

     • Gullner syndrome

     • Glucocorticoid receptor deficiency

     • Hypokalemic period paralysis

     • Thyrotoxic periodic paralysis

     • SeSAME syndrome: Seizure, deafness, ataxia, intellectual disability, and electrolyte imbalance

3. Shift of potassium from extracellular to intracellular space:

   • Alkalosis

   • Insulin administration or glucose administration

   • Intensive beta-adrenergic stimulation

   • Hypothermia

   • Hypomagnesemia

Pathophysiology [mf9]

1. Potassium maintains cell membrane potential, nerve impulse conduction, muscle function (including skeletal, smooth, and cardiac muscles), and acid-base balance

2. Hypokalemia:

   • Muscle: impaired muscle contraction, muscle cramps, rhabdomyolysis, paralysis, respiratory failure

   • GI: impaired intestinal motility and constipation

   • Kidney: impaired concentrating ability, increased ammonia production, altered sodium reabsorption, and increased bicarbonate absorption

   • Heart: ventricular ectopy, atrial fibrillation, ventricular tachycardia or fibrillation

Risk factors: [mf9]

• Cardiac disease

• Renal failure

• Malnutrition

• Shock

• Hypothermia

• Increased blood cell production

Complications:

• Cardiac arrhythmias

• Cardiac failure

• Cardiac ischemia

• Left ventricular hypertrophy

• Muscular weakness

• Intestinal paralysis

• Respiratory compromise

Epidemiology

Incidence per 100.000 [uov][mqk][tmg][8i7]

Approach

• Blood test: Na, K, creatinine, renin, aldosterone, cortisol, 17-beta hydroxylase deficiency, thyroid function

• Urine: 24-hour urine aldosterone, cortisol, sodium, and potassium

• Blood gas: Alkalosis (Vomiting, Bartter syndrome, Gitelman syndrome, Mineralocorticoid excess), anion gap (toluene toxicity)

• ECG

• Drug screen in urine and/or serum for diuretics, amphetamine, Digitoxin

• CT caput: Pituitary (Cushing syndrome)

• CT abdomen: Adrenal adenoma, renal artery stenosis

Treatment

1. Stop potassium loss: [ot1]

   • Discontinue diuretics/laxatives

   • Use potassium-sparing diuretics

   • Treat diarrhea or vomiting

   • Treat hyperglycemia

2. Replenishment: [mf9]

   • K 2.5-3.5 mmol/L: oral potassium replacement 60-80 mmol/day upto weeks

   • K < 2.5 mmol/L:

     • Intravenous potassium chloride: 40 mmol KCl every 3 to 4 hours

     • Continuous ECG monitoring

3. Correct magnesium level

4. Surgical care:

   • Renal artery stenosis

   • Adrenal adenoma

   • Intestinal obstruction producing massive vomiting

   • Villous adenoma

Differential diagnoses

Alkalosis, Apparent mineralocorticoid excess syndrome, Colorectal polyp, Congenital adrenal hyperplasia, Conn syndrome, Cushing syndrome, Diabetes mellitus, Diabetic ketoacidosis, Drug side effects, Hyperaldosteronism, Hyperinsulinemia, Hyperthyroidism, Hypocalcemia, Hypomagnesemia, Hypovolemia, Metabolic alkalosis, Pancreatic fistula, Renal artery stenosis, Thyrotoxicosis, VIPoma