Hypokalemia (low potassium) Therapy Calculator
Potassium related content
Background
Hypokalemia (defined as a serum potassium level of less than 3.5
mmol/L) is one of the most common electrolyte abnormalities
encountered in clinical practice with more than 20% of hospitalized patients
affected and approximately 40% of ICU patients.
Hypokalemia reflects either total body potassium depletion
or redistribution from extracellular fluid to intracellular
fluid without potassium depletion.
The most common causes include:
- Nonrenal losses (urine K+ < 20 mmol/L):
Examples include:
diarrhea, vomiting,
nasogastric drainage,
laxative abuse.
- Renal losses (urine K+ ≥ 20 mmol/L):
Loop diuretics (furosemide, bumetanide, torsemide).
Thiazide diuretics.
Osmotic diuresis e.g. uncontrolled diabetes.
- Mineralocorticoid excess
- Primary and secondary hyperaldosteronism
- Magnesium depletion
- Transcellular Shifts:
Insulin administration,
β-Adrenergic agonists,
Acute catecholamine surges,
Other.
Note: Increased potassium loss (through the kidneys or gastrointestinal
tract) is the most common cause of hypokalemia.
Diagnostic workup:
- Initially, determine if the patient is symptomatic or arrhythmias
are present. Also look for weakness or palpitations, ECG changes, severe
hypokalemia (less than 2.5 mEq/L (mmol/L), rapid-onset hypokalemia, or
if the patient has underlying heart disease or cirrhosis. This will help determine the acuity of the interventions
required.
- Perform a history and physical examination to look for relevant
clinical clues including offending medications, conditions, possible GI
losses, and whether
or not factitious/spurious hypokalemia is present. Most cases of hypokalemia-induced rhythm disturbances occur in
individuals with underlying heart disease.
- Determine if the lower potassium levels were caused by a
transcellular shift (managed by treating the underlying condition or
removing the offending agent) or a decrease in total body potassium. A
history of paralysis, hyperthyroidism, or use of insulin or beta
agonists suggests possible transcellular shifts leading to
redistributive hypokalemia.
- Evaluating the urine potassium,
fractional excretion of potassium (FEK) and the
Transtubular
Potassium Gradient can help differentiate between renal and nonrenal
causes of hypokalemia.
- Urinary potassium levels higher than 20 mmol/L are suggestive of
renal causes and levels lower than 20 mmol/L are suggestive of nonrenal
causes.
-
Identification and treatment of concurrent hypomagnesemia:
Magnesium depletion reduces the intracellular potassium concentration
and causes renal potassium wasting.
-
The diagnosis should be confirmed with a repeat serum
potassium measurement. Other laboratory tests include serum
glucose and magnesium levels, urine electrolyte and creatinine
levels, and acid-base balance.
Required
Entries
Data points:
Weight:
Current Potassium Level:
[
Value below 3.9 mEq/L (mmol/L]
Describe current symptoms of hypokalemia:
[
Severe symptoms include:
cardiac arrhythmias,
pronounced muscle weakness, paralysis, or ECG changes.
ECG changes may include: prominent U
wave, flattened or inverted T waves, ST segment depression, T and U wave
fusion giving appearance of QT interval prolongation.
Arrhythmias: atrial
tachycardia, PVCs,
ventricular tachycardia and/or fibrillation, torsades de pointes.]
Select any that apply
Patient is able to take oral
medications?
Magnesium level is in the normal range?
Hypokalemia predisposes
to cardiac arrhythmias by several mechanisms including increased
cardiac automaticity, slowed conduction, and delayed ventricular
repolarization, predominantly in patients with ischemic heart
disease or on digitalis.
Symptoms of
Hypokalemia
Symptoms of mild hypokalemia:
- Fatigue
- Weakness
- Respiratory difficulty
- Constipation
- Paralytic ileus
- Leg cramps
- Other
Examples of symptoms by system due to hypokalemia:
Cardiovascular System:
-
Worsening hypertension
- ECG changes
- Arrhythmias (especially
ventricular arrhythmias), PEA, Aystole.
- Sudden death
Kidney:
-
Polyuria due to decreased concentrating ability
-
Hypokalemic nephropathy
-
Chloride-depletion metabolic alkalosis
-
Increased risk of nephrolithiasis
Neuromuscular:
- Cramping
-
myalgia
-
weakness
-
rhabdomyolysis
-
paresthesias
-
paralysis
Gastrointestinal tract:
-
Altered gastrointestinal motility (nausea, vomiting, constipation,
paralytic ileus)
-
Worsening of hepatic encephalopathy
Genitourinary tract:
Respiratory System:
-
Respiratory acidosis secondary to respiratory muscle weakness
Endocrine System:
- Insulin resistance and impairment in insulin release
References
-
Aboujamous et al. Evaluation of the Change in Serum Potassium Levels after
Potassium Administration. J Clin Nephrol Ren Care 2016, 2:013,
-
Asmar A, Mohandas R, Wingo CS. A Physiologic-Based Approach to the Treatment
of a Patient With Hypokalemia. Am J Kidney Dis. 2012 September ; 60(3):
492–497.
-
Cohn JN, Kowey PR, et al. New guidelines for potassium replacement in
clinical practice: A contemporary review by the National Council on
Potassium in Clinical Practice. Arch Intern MED/VOL 160, SEP 11, 2000.
-
Gennari FJ. Disorders of potassium homeostasis: Hypokalemia and
hyperkalemia. Crit Care Clin. 2002;18(2):273-288.
-
Gennari FJ. Hypokalemia. N Engl J Med. 1998;339(7):451-458.
-
Kamel KS, Quaggin S, Scheich A, et al. Disorders of potassium homeostasis:
an approach based on pathophysiology. Am J Kidney Dis 1994;24:597–613.
-
Kardalas E, et al. Hypokalemia: a clinical update. Endocrine Connections
(2018) 7, R135–R146.
-
Kim GH, Han JS. Therapeutic approach to hypokalemia. Nephron. 2002;92(suppl
1):28-32.
-
Lippi G, Favaloro EJ, Montagnana M, Guidi GC. Prevalence of hypokalaemia:the
experience of a large academic hospital. Intern Med J. 2010;40(4):315-316.
-
Rastergar A, Soleimani M. Hypokalaemia and hyperkalaemia. Postgrad Med J
2001;77:759–764.
- Viera AJ, Wouk N. Potassium Disorders:
Hypokalemia and Hyperkalemia.Am Fam Physician. 2015;92(6):487-495.
- Weiner ID, Wingo CS.
Hypokalemia-consequences, causes, and correction. J Am Soc Nephrol.
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