Hypokalemia

From Anvita Health Wiki

Contents 1 Etiology 2 Epidemiology 3 Clinical-manifestations 4 Laboratory 5 Diagnostic-procedures 6 Complications 7 Management 8 More General Terms 9 Additional Terms 10 References

Etiology

• renal

• osmotic diuresis, i.e. diabetes mellitus
• pharmacologic agents:

• diuretics (most common cause)
• amphotericin B
• gentamicin
• mineralocorticoids
• glucocorticoids (some)
• osmotic diuretics
• tetracycline
• theophylline
• vitamin B12
• carbenicillin

• excessive mineralocorticoids

• primary hyperaldosteronism ( Conn's syndrome)
• secondary hyperaldosteronism

• Bartter's syndrome
• Gitelman syndrome
• renal artery stenosis

• glucocorticoid excess

• Cushing's disease
• ectopic ACTH production
• exogenous steroids

• distal renal tubular acidosis ( RTA-1)

• gastrointestinal

• decreased dietary intake

• starvation
• clay ingestion

• gastrointestinal ( GI) loss of K+

• vomiting
• diarrhea
• villous adenoma
• fistula
• laxative abuse

• intracellular shift of K+

• metabolic alkalosis
• pharmacologic agents

• insulin
• beta-adrenergic receptor agonists
• ritodrine
• theophylline

• familial hypokalemic periodic paralysis

• insensible losses

• sweating

Epidemiology

• 90% of hypertensive patients with hyperaldosteronism

Clinical-manifestations

• signs/symptoms depend upon acute vs chronic nature of hypokalemia
• musculoskeletal dysfunction

• muscle weakness
• flaccid paralysis (including respiratory paralysis)
• hypotonia
• hyporeflexia
• rhabdomyolysis

• smooth muscle dysfunction

• paralytic ileus
• muscle cramps

• renal failure
• renal tubular dysfunction

• polydipsia
• polyuria

• glucose intolerance [3]
• cardiac ventricular arrhythmias (especially in patients on digoxin)

Laboratory

• serum K+ < 3.5 meq/L
• increased serum glucose

• hypokalemia impairs insulin secretion

• urine K+

• > 20 meq/L suggests renal origin

• blood gas: pH

• metabolic alkalosis -> urine Cl- < 20 meq/L -> vomiting, NG suction, diarrhea, previous diuretics -> urine Cl- > 20 meq/L -> high blood pressure -> excess glucocorticoids, mineralocorticoids (urine Cl- generally > 40 meq/L) -> normal blood pressure -> Bartter's syndrome, Gitelman's syndrome, current use of diuretics
• renal tubular acidosis

• < 20 meq/L non-renal origin

• diarrhea, vomiting, laxative abuse, villous adenoma

• serum Mg+2: low in Gitelman's syndrome

Diagnostic-procedures

• electrocardiogram ( EKG)

• flattening of T waves or inverted T waves
• ST segment depression [3]
• increased prominence of U wave
• ventricular arrhythmias

• severe hypokalemia
• in patients taking digoxin

Complications

• exacerbation of digitalis toxicity
• glucose intolerance from impaired insulin secretion

Management

• fatal arrhythmias may occur in patients taking digoxin even if hypokalemia is mild
• oral KCl (first resort)
• intravenous KCl, potassium phosphate

• do not exceed 40 meq/L
• do not exceed 20 meq/ hr
• EKG monitoring during rapid K+ infusion

• potassium sparing diuretics

• amiloride
• triamterene
• spironolactone

• hypomagnesemia & magnesium deficiency MUST be corrected before K+ depletion can be corrected

More General Terms

• sign/symptom

Additional Terms

• Bartter syndrome
• familial periodic paralysis (hyperkalemic, normokalemic, hypokalemic, HYPP, NKPP, HYPOPP)
• Gitelman syndrome
• potassium (K+) in serum/plasma

References

1. Harrison's Principles of Internal Medicine, 13th ed. Companion Handbook, Isselbacher et al (eds), McGraw-Hill Inc. NY, 1995, pg 831
2. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 674-676
3. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 15, American College of Physicians, Philadelphia 1998, 2006, 2009

hypokalemia