Hypokalemia

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  • Topic: Hypokalemia, Potassium, Hyperkalemia
  • Pages : 7 (1730 words )
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  • Published : December 13, 2012
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Potassium is one of the body's major ions. Nearly 98% of the body's potassium is intracellular. The ratio of intracellular to extracellular potassium is important in determining the cellular membrane potential. Small changes in the extracellular potassium level can have profound effects on the function of the cardiovascular and neuromuscular systems. The kidney determines potassium homeostasis, and excess potassium is excreted in the urine. The reference range for serum potassium level is 3.5-5 mEq/L, with total body potassium stores of approximately 50 mEq/kg (ie, approximately 3500 mEq in a 70-kg person). Hypokalemia is defined as a potassium level less than 3.5 mEq/L. Moderate hypokalemia is a serum level of 2.5-3 mEq/L.

Severe hypokalemia is defined as a level less than 2.5 mEq/L. Pathophysiology
Hypokalemia may result from conditions as varied as renal or GI losses, inadequate diet, transcellular shift (movement of potassium from serum into cells), and medications. Frequency
United States
As many as 20% of hospitalized patients are hypokalemic; however, hypokalemia is clinically significant in only about 4-5% of these patients. Severe hypokalemia is relatively uncommon. Up to 14% of outpatients who undergo laboratory testing are found to be mildly hypokalemic. Approximately 80% of patients who are receiving diuretics become hypokalemic. Sex

Incidence is equal in males and females.
Clinical
History
The history may be vague. Patients are often asymptomatic, particularly with mild hypokalemia. Symptoms are often due to the underlying cause of the hypokalemia rather than the hypokalemia itself. Hypokalemia should be suggested by a constellation of symptoms that involve the GI, renal, musculoskeletal, cardiac, and nervous systems. The patient's medications should be reviewed to ascertain whether any of them could cause hypokalemia. Common symptoms include the following:

Palpitations
Skeletal muscle weakness or cramping
Paralysis, paresthesias
Constipation4
Nausea or vomiting
Abdominal cramping
Polyuria, nocturia, or polydipsia
Psychosis, delirium, or hallucinations
Depression
Physical
Findings that are consistent with severe hypokalemia may include the following:

Signs of ileus
Hypotension
Ventricular arrhythmias5
Cardiac arrest
Bradycardia or tachycardia
Premature atrial or ventricular beats
Hypoventilation, respiratory distress
Respiratory failure
Lethargy or other mental status changes
Decreased muscle strength, fasciculations, or tetany
Decreased tendon reflexes
Cushingoid appearance (eg, edema)
Causes
Renal losses
Renal tubular acidosis
Hyperaldosteronism
Magnesium depletion
Leukemia (mechanism uncertain)
GI losses (source may be medical or psychiatric6 , ie, anorexia or bulimia) Vomiting or nasogastric suctioning
Diarrhea
Enemas or laxative use
Ileal loop
Medication effects
Diuretics (most common cause)
Beta-adrenergic agonists
Steroids
Theophylline
Aminoglycosides
Transcellular shift
Insulin
Alkalosis
Malnutrition or decreased dietary intake, parenteral nutrition

Hypokalemia (American English) or hypokalaemia (British English), also hypopotassemia or hypopotassaemia (ICD-9), refers to the condition in which the concentration of potassium (K+) in the blood is low. The prefix hypo- means "under" (contrast with hyper-, meaning "over"); kal- refers to kalium, the Neo-Latin for potassium, and -emia means "condition of the blood." Normal plasma potassium levels are between 3.5 to 5.0 mEq/L; at least 95% of the body's potassium is found inside cells, with the remainder in the blood. This concentration gradient is maintained principally by the Na+/K+ pump. Signs and symptoms

Mild hypokalemia is often without symptoms, although it may cause a small elevation of blood pressure, and can occasionally provoke cardiac arrhythmias. Moderate hypokalemia, with serum potassium concentrations of 2.5-3 mEq/L (Nl: 3.5-5.0 mEq/L), may cause muscular weakness,...
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