Do not treat factitious hyperkalemia, treat the underlying disorder
Author:
Craig DeWolfe, MD
What to Do - Make a Decision
Although hyperkalemia can be a serious disorder associated with serious
consequences, the inattention to, or inappropriate treatment of, factitious
hyperkalemia can result in its own set of unnecessary and potentially dangerous interventions. One should suspect factitious hyperkalemia when the
patient lacks kidney disease and does not show the typical signs and symptoms of muscle weakness or electrocardiographic abnormalities associated
with true hyperkalemia. If suspicious, the clinician should obtain a more
accurate specimen or account for leukocytosis, thrombocytosis, or genetic
factors when weighing the importance of the measured value. Secondary,
nonrenal causes of hyperkalemia should also be considered since the disruption may be iatrogenic or a result of an equally serious underlying
disorder.
Factitious hyperkalemia, or pseudohyperkalemia, reflects an artificially
high measured potassium level resulting from its release just before or after
phlebotomy. Venous stasis from a tourniquet, fist clenching, straining, or hyperventilating can cause a potassium efflux from cells. Specimens obtained
using a small-gauge needle, stored on ice, or processed after a considerable
delay may also cause falsely elevated potassium results. In vitro potassium
will be released from clots of white blood cells and platelets once the blood
has been drawn and will be exacerbated by significant cases of leukocytosis
(>100 × 109/L) or thrombocytosis (>1,000 × 109/L) commonly found in
myeloproliferativedisordersorKawasakisyndrome.Finally,familialpseudohyperkalemia, a genetic condition passed as an autosomal dominant trait on
chromosome 16 may predispose affected patients to factitious hyperkalemia
as a result of an abnormal leakage of ions across the red blood cell membranes. Any combination of these factors may raise the measured potassium
level by 2 mEq/L; the practitioner should consider how the specimen was
processed while examining the patient for symptoms. Important diagnostic
studies include measures of renal function tests, an electrocardiogram, and
a repeat specimen. If the repeat level is normal, the practitioner should be
reassured; however, if the potassium remains persistently elevated, further
investigation and treatment may be warranted.
Secondary, nonrenal causes of hyperkalemia are extensive. Often these
disruptions are mild, but in patients with renal insufficiency or when known
causes of hyperkalemia are left unmonitored and unmanaged, the elevations
inpotassiumcanresultinsignificantmorbidityormortality.Iatrogeniccauses
of hyperkalemia include medications and the induction of metabolic acidosis. Acute metabolic acidosis may result in hyperkalemia due to an efflux of
potassium ions out of the cells, as excess protons are buffered inside the cells.
The use of ammonium chloride to manage alkalosis can cause up to a 1.5
mEq/L rise in the potassium concentration for every 0.1 unit reduction in
arterial blood pH.Otherdrugsmay temper thebody'snormal catecholamine
andmineralocorticoidresponsetohyperkalemia.Forexample,beta-blockers,
angiotensin-converting enzyme inhibitors, or angiotensin-receptor antagonists may precipitate hyperkalemia in patients during periods of exercise.
Cytotoxic drugs may cause a tumor lysis syndrome in patients with a significant tumor burden found in certain cases of lymphoma or neuroblastoma.
Succinylcholine works as a muscle relaxant by depolarizing muscle cells and
can lead to significant increases in potassium in susceptible patients including those with neuromuscular disease or extensive burns cannot handle a
significant potassium load. In fact, elevations of 6 mEq/L have been documented. Finally, digoxin toxicity inhibits the cellular Na+-K+-ATPase and
can cause a potassium leak from cells.
Exogenousandendogenouspotassiumloadsarealsoofconcern.Clearly,
overdoses of oral or intravenous potassium are concerning, but intravenous
penicillin preparations and red blood cell products over 5 days old may
result in markedly elevated potassium levels. Also, endogenous potassium
loads after intravascular coagulation, sickle cell hemolysis crisis, rhabdomyolysis, trauma, burns, and massive gastrointestinal bleeds may result in
hyperkalemia. In these cases, the practitioner should treat the underlying cause of the disruption while surveying the risk of the potassium
level.
Generally, potassium levels >8 mEq/L with electrocardiographic
changesandmuscleweaknessshouldbeconsideredanemergencyandtreated
with a combination of potassium antagonists (calcium gluconate), redistribution compounds (glucose and insulin, sodium bicarbonate), and agents
directed at eliminating the potassium (sodium polystyrene sulfonate resin,
furosemide, albuterol). A combination of treatments is recommended due
to the variable onsets of action and the ultimate need to eliminate the excess
potassium.
In cases where cardiac complications are not of immediate concern,
the practitioner should quickly investigate the etiology of hyperkalemia by
recognizing the various factitious and reversible secondary causes and treat
them accordingly.
Suggested Readings
Schwartz GJ. Potassium. In: Avner ED, et al. eds. Pediatric Nephrology. 5th ed. Philadelphia:
Lippincott Williams & Wilkins; 2004;147–188.
Wiederkehr MR, Moe OW. Factitious hyperkalemia. Am J Kidney Dis. 2000;36:1049–1053.
Book Source Details
- Book Title: Avoiding Common Pediatric Errors
- Author(s): Anthony D Slonim MD, DrPH; Lisa Marcucci MD
- Year of Publication: 2008
- Copyright Details: Avoiding Common Pediatric Errors, Copyright © 2008 Lippincott Williams & Wilkins.
Other Book Chapters Related to Hyperkalemia
Read excerpts from these other book chapters related to Hyperkalemia:
Medical Books Excerpts
- Hyperkalemia
- "The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter" (2000)
- [ read ]
Copyright Details: Avoiding Common Pediatric Errors, Copyright © 2008 Williams & Wilkins.
More About Causes of Hyperkalemia
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More About This Book:
Title: Avoiding Common Pediatric Errors
Authors: Anthony D Slonim MD, DrPH; Lisa Marcucci MD
Publisher: Lippincott Williams & Wilkins
Copyright: 2008
ISBN: 0-7817-7489-6
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