Introduction
Hypokalemia is one of the common electrolyte imbalances seen in hospitalized patients. It is a drop in serum potassium levels than the normal range. This may alter the normal homeostasis of the body as potassium is one of the integral components in maintaining the body's physiological functions. Hypokalemia mainly affects the functions of the heart, nerves, and muscles. The treatment depends on the severity of the condition, whether it is mild or severe. Severe cases would need emergency management as it could increase the risk of other complications.
What Is Hypokalemia?
The word hypo means less or under, kalium- potassium, emia - blood. Hypokalemia is the reduction in serum potassium levels. The normal levels of potassium in the blood range from 3.5 mmol/l to 5.0 mmol/l. When the serum levels of potassium drop below 3.5 mmol/l, it is called hypokalemia.
What Is Hyperkalemia?
Hyperkalemia is the increased serum potassium levels than the normal range, to levels of more than 5.0 mmol/l.
What Is Pseudohypokalemia?
Pseudo hypokalemia is not true hypokalemia, here decrease in serum potassium levels occurs in the collected laboratory blood samples as a result of metabolically active cells uptaking the potassium in the blood.
What Is the Epidemiology of Hypokalemia?
Studies have shown that around 14 % of patients undergoing laboratory tests seem to have mild hypokalemia. 20 % of hospitalized patients are reported to develop hypokalemia. It has been reported that around 80 % of patients under diuretics develop hypokalemia due to excessive urinary potassium loss. There is no reported gender predilection.
What Are the Types of Hypokalemia?
It can be classified into two types,
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Mild Hypokalemia - When the serum potassium levels decrease below 5.0 mmol/l and not below 2.5 mmol/l, it is called mild hypokalemia.
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Severe Hypokalemia - When the serum potassium levels drop below 2.5 mmol/l, it is called severe hypokalemia. It is a serious condition and has to be addressed immediately.
What Is the Etiology of Hypokalemia?
Hypokalemia is mainly caused due to two reasons: either decreased intake of potassium or increased excretion of potassium.
Decreased Potassium Intake:
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Dietary Deficiency of Potassium - Eating potassium-less foods.
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Starvation or Fasting - This can gradually decrease the potassium levels.
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Anorexia Nervosa - This is an eating disorder, patients with this disorder develop the fear of gaining weight, and they avoid eating foods leading to hypokalemia.
Increased Loss of Potassium:
Potassium loss from the body can occur in three ways, through the skin, the gastrointestinal tract, and the urine.
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Loss of Potassium Through the Gastrointestinal Tract And Skin - This includes conditions such as diarrhea, vomiting, surgical procedures, intestinal obstructions, infections, chronic usage of laxatives, excessive sweating, pancreatic fistula, adenomas of the GI tract, etc.,
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Loss of Potassium Through Urine Medications - Diuretics such as Furosemide and Thiazide diuretics are the main cause of hypokalemia. Other drugs such as Amphotericin B, Penicillin, Insulin, Xanthines, Epinephrine, and Beta Agonists are also reported to cause hypokalemia.
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Alkalosis - This is the increase in the blood pH that causes the potassium to shift from the plasma and the interstitial fluid into the urine and is excreted via urine.
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Hypomagnesemia - Reduced serum magnesium levels will indirectly cause hypokalemia as magnesium is required for the processing of potassium.
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Hereditary Syndromes - Syndromes such as Gitelman Syndrome (it is a rare kidney disorder that causes an imbalance of the charged ions such as potassium, magnesium, and calcium). Cushing’s syndrome, in which excess cortisol binding with sodium and potassium, would lead to hypokalemia.
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Hyperaldosteronism - Increased levels of aldosterone in the blood due to various disease conditions would cause hypertension which in turn leads to the increased loss of potassium.
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Diabetic Ketoacidosis - In this condition, the urinary loss of potassium occurs in addition to the loss of potassium from the kidney tubules.
What Is the Pathophysiology of Hypokalemia?
Potassium is essential for maintaining the normal functioning of the cell. 98 % of potassium is found inside the cell, with the remaining two percent in the extracellular fluid. It maintains muscle and nerve function and regulates the heartbeat. Decreased potassium levels will alter the functions of the nerves causing hyperpolarization and thus affecting nerve function. Reduced potassium levels will affect the contraction of the skeletal and smooth muscles and the release of certain hormones.
What Are the Signs and Symptoms of Hypokalemia?
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Fatigue.
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Muscle weakness.
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Leg cramps.
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Constipation.
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Tingling or numbness.
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Palpitations.
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Cardiac arrhythmias (irregular heartbeat).
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Metabolic acidosis (build-up of acid in the body).
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Rhabdomyolysis (is characterized by muscle breakdown and muscle death).
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Respiratory failure.
How Is Hypokalemia Diagnosed?
Blood Test:
- Serum Potassium Levels - Serum investigation would reveal decreased potassium levels with a range between 3.5 to 2.5 mmol/l in case of mild hypokalemia and levels less than 2.5 mmol/l in case of severe hypokalemia.
- Serum Urea and Creatinine Levels - To rule out the presence of chronic kidney disease.
Electrocardiogram: ECG may reveal the findings of cardiac arrhythmias such as suppression of ST-segment and increased amplitude of the T and U waves.
Computed Tomography Scan or Magnetic Resonance Imaging: CT scans and MRI Imaging are done to rule out the causes of hypokalemia due to Cushing's syndrome (MRI of the pituitary gland), CT of the adrenal gland, and CT of the abdomen are carried out.
How Is Hypokalemia Treated?
The goal of treating hypokalemia is to treat the underlying cause, correct the potassium levels, and stop or discontinue the offending medications.
Stopping the Offending Drugs
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The drugs such as Diuretics, Amphotericin B, Penicillin, Beta-agonists, etc., causing hypokalemia should be discontinued immediately and replaced with alternative drugs.
Dietary Potassium Intake
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In patients with mild hypokalemia due to dietary insufficiency, they are advised to take foods rich in potassium such as green leafy vegetables, broccoli, spinach, carrot, beans, legumes, cauliflower, potatoes, etc., and fruits like mangoes, kiwis, bananas, etc.
Oral Potassium Supplementation
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In patients with mild hypokalemia, oral supplementation of potassium is given in the form of tablets. It is better to give oral potassium supplements after food, along with adequate water.
Intravenous Replacement of Potassium
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In the case of patients with potassium levels ranging from 2.5 to 3.5 mmol/l oral supplementation and dietary intake is sufficient. In case of severe hypokalemia with levels less than 2.5 mmol/l, it is recommended to give intravenous potassium replacement therapy. The potassium administration should be done with careful monitoring of the patient's heart rate and rhythm through ECG monitoring, and the serum potassium levels should be monitored frequently.
Conclusion
Hypokalemia is one of the common electrolyte imbalances. The decreased potassium levels will affect the normal physiological functions of the body as it is involved in many physiological functions. Muscles, nerves, and the heart are mainly in need of potassium for their normal functioning. The severe decrease in potassium levels will end up in life-threatening conditions; hence the proper management of hypokalemia is of prime importance to maintain normal body functions.
