Causes, diagnosis, and evaluation of hyperkalemia in children
- Michael J Somers, MD
Michael J Somers, MD
- Associate Professor of Pediatrics
- Harvard Medical School
Hyperkalemia is defined as a serum or plasma potassium that is higher than the upper limit of normal potassium, which typically is considered to be 5.5 mEq/L (mmol/L) (table 1). Although children are less likely to develop hyperkalemia than adults, pediatric hyperkalemia is not an uncommon occurrence, and severe hyperkalemia (potassium level greater than 7 mEq/L [mmol/L]) is a serious medical problem that needs immediate attention.
The etiology, clinical findings, diagnosis, and evaluation of pediatric hyperkalemia are reviewed here. The management of hyperkalemia in children is presented separately. (See "Management of hyperkalemia in children".)
NORMAL POTASSIUM BALANCE AND LEVELS
Homeostatic mechanisms regulate potassium balance in order to maintain high intracellular levels required for cellular functions (eg, metabolism and growth), and low extracellular concentration to preserve the steep concentration gradient across the cell membrane needed for nerve excitation and muscle contraction. After a bolus of potassium intake, these normal physiologic processes preserve the intra- and extracellular balance via transcellular potassium movement regulated by cell membrane Na-K-ATPase (mediated by insulin and alpha and beta-2 adrenergic agonists), and urinary potassium excretion (mostly mediated by aldosterone). In children, positive potassium balance is needed for growth, whereas in adults, homeostasis is directed towards a zero potassium balance.
Normal serum and plasma potassium concentrations in children and adolescents are similar to levels in adults. However, infants have a higher normal range of potassium because of their reduced urinary potassium excretion caused by their relatively increased aldosterone insensitivity and decreased glomerular filtration rate (table 1). (See "Causes and evaluation of hyperkalemia in adults", section on 'Brief review of potassium physiology'.)
Hyperkalemia in children is caused by derangements of the homeostatic mechanisms that normally regulate potassium balance, which are the same as those that occur in adults. Understanding the underlying physiology is helpful in the diagnostic evaluation and treatment of children with hyperkalemia. (See "Causes and evaluation of hyperkalemia in adults", section on 'Brief review of potassium physiology'.)
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- NORMAL POTASSIUM BALANCE AND LEVELS
- Increased potassium intake
- Transcellular movement of potassium
- - Cellular injury
- - Metabolic acidosis
- - Hyperkalemic periodic paralysis
- Abnormalities in renal excretion
- - Acute and chronic kidney disease
- Glomerular filtration rate
- Tubular dysfunction
- - Decreased effective arterial blood volume
- - Decreased activity of the renin-angiotensin-aldosterone system
- CLINICAL MANIFESTATIONS
- Asymptomatic patients
- Symptomatic patients
- Cardiac conduction abnormalities
- DIFFERENTIAL DIAGNOSIS
- EVALUATION TO DETERMINE UNDERLYING ETIOLOGY
- Initial management
- History and physical examination
- - Historical clues
- - Physical findings
- - Further laboratory testing
- SUMMARY AND RECOMMENDATIONS