Hyperkalemia overview

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Jogeet Singh Sekhon, M.D. [2] Syed Ahsan Hussain, M.D.[3]

Historical Perspective

• Potassium was discovered in 1807 by Sir Humphry Davy in 1807 in England.
• He discovered potassium by means of electrolysis from potash.
• It was the first alkali metal to be discovered.

Classification

Hyperkalemia develops when blood potassium levels are more than 5.1meq/L. Hyperkalemia can be classified based on the potassium levels, duration of onset and the cause of hyperkalemia.

Pathophysiology

Potassium is the most abundant intracellular cation and is critically important for many physiologic processes. The normal range of potassium in blood is 3.5-5.1mEq/L . Hyperkalemia develops when the level of potassium exceeds 5.5 meq/L in blood which can be due to an increase in intake of potassium, excessive production as seen in tissue breakdown, ineffective elimination of potassium or some drugs. The potassium levels in the body are highly regulated mainly by kidneys. The gut excretes a minimal amount of dietary potassium (approximately 10%) . Hyperkalemia is very common in patients with chronic kidney disease as potassium is not effectively excreted from the bod y.Potassium is involved in maintaining transmembrane potentials of cell s,so imbalance in potassium levels can lead to disruption of cell membrane potentials and can cause hyperexcitablity leading to fatal cardiac arrhythmias and effecting nervous system.

Causes

Hyperkalemia is an elevated blood level (above 5.1 mmol/L) of the electrolyte potassium. Hyperkalemia can be caused by reasons that include increased uptake, extracellular shift, tissue breakdown and impaired excretion from the body.

Differentiating Hyperkalemia from Other Diseases

Hyperkalemia is a laboratory finding that is a result of several conditions. These conditions must be differentiated as a cause of hyperkalemia.

Epidemiology and Demographics

The exact prevalence of hyperkalemia is unknown. It changes between inpatient and outpatient cases. In one study in USA, the prevalence was 1.57

Risk Factors

The kidneys normally remove excess potassium from the body. Most cases of hyperkalemia are caused by disorders that reduce the kidneys' ability to get rid of potassium. This may result from disorders such as acute kidney failure, chronic kidney failure and glomerulonephritis.

Screening

There is insufficient evidence to recommend routine screening for hyperkalemia. However, potassium levels are routinely monitored in patients with chronic kidney diseases.

Natural History, Complications, and Prognosis

Extreme degrees of hyperkalemia are considered a medical emergency. If left untreated hyperkalemia can cause cardiac rhythm disorders and eventually cardiac arrest leading to death. Complications that can develop as a result of hyperkalemia are arrhythmia, cardiac arrest, and neuromuscular weakness. The outcome with this condition varies. In some people, the disorder causes deadly complications, while others tolerate it well.

Diagnosis

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Diagnostic Study of Choice

Serum potassium is the gold standard test for the diagnosis of hyperkalemia. Pseudohyperkalemia needs to be ruled out whenever hyperkalemia is diagnosed. Pseudohyperkalemia is defined when serum potassium concentration exceeds that of plasma. Different etiologies of hyperkalemia can be assessed by using the diagnostic criteria.

History and Symptoms

Hyperkalemia often has no symptoms. Occasionally, people may have the following symptoms: irregular heartbeat, nausea, slow, weak, or absent pulse. Extreme degrees of hyperkalemia are considered a medical emergency due to the risk of potentially fatal arrhythmias. A detailed history taking is very helpful in diagnosing the cause of hyperkalemia.

Physical Examination

In patients with hyperkalemia, physical examination may vary from normal to bradycardia (heart block), tachypnea due to respiratory muscle weakness and absent tendon reflexes. Evaluation of vital signs plays a key role in determining hemodynamic stability and identifying the presence of cardiac arrhythmias due to the hyperkalemia.

Laboratory Findings

In a patient who does not have a risk for hyperkalemia, repeating the blood test is indicated before taking any actions unless changes are present on electrocardiography.

Electrocardiogram

Extreme degrees of hyperkalemia are considered a medical emergency due to the risk of potentially fatal arrhythmias. The EKG is an important tool in evaluating a patient who has hyperkalemia as well as in diagnosing hyperkalemia. However, EKG changes do not always correlate with the degree of hyperkalemia. Some of the EKG changes that can be seen associated with hyperkalemia include peaked T waves, PR interval prolongation, QRS complex widening, absence of P waves, sine wave pattern and sinus arrest.

X-ray

There are no x-ray findings associated with hyperkalemia.

Echocardiography and Ultrasound

There are no echocardiography/ultrasound findings associated with hyperkalemia. However depending on the cause of hyperkalemia ultrasound findings of the particular cause might be present.

CT scan

There are no CT scan findings associated with hyperkalemia.

MRI

There are no MRI findings associated with hyperkalemia

Other Imaging Findings

There are no other imaging findings associated with hyperkalemia

Other Diagnostic Studies

There are no other diagnostic studies associated with hyperkalemia

Treatment

Medical Therapy

When arrhythmias occur, or when potassium levels exceed 6.5 mmol/l, emergency lowering of potassium levels is mandated. Several agents are used to lower potassium levels. Choice depends on the degree and cause of the hyperkalemia, and other aspects of the patient's condition.

References

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