Hypokalemia and hyperkalemia refer to disorders in which blood levels of potassium are below and above normal, respectively. Potassium is essential for maintaining healthy physiology. Most of the potassium in the body is stored within cells rather than in the blood. The level of potassium in the blood is determined by the amount consumed, the amount stored in cells and the amount lost in the urine. Both hypokalemia and hyperkalemia can be serious, even life-threatening, conditions.
Normal Role of Potassium
Potassium is an electrolyte that plays an important role in several body functions. It helps maintain normal electrical conduction in the heart, which helps synchronize heart beats. It plays a role in muscle contraction and helps maintain normal acidity of the blood. Potassium is also important in the transport of substances in and out of cells.
Causes of Hypokalemia
Hypokalemia can occur when not enough potassium is consumed in the diet. However, the body can usually compensate by decreasing potassium output. Potassium can be lost from the gut, especially with vomiting, leading to hypokalemia. Some medications called diuretics ("water pills") can increase the amount of potassium lost in the urine. Certain conditions cause potassium to move from the blood into the cells, causing hypokalemia. This occurs when blood insulin is too high, the blood becomes less acidic or in hypothermia. Other causes of hypokalemia include excessive sweating and diseases of the gut such as Crohn's disease.
Causes of Hyperkalemia
Hyperkalemia can occur when too much potassium is consumed, but this increase is usually well-regulated. In kidney disease, which occurs in uncontrolled diabetes, the body can become unable to properly eliminate potassium into the urine, resulting in hyperkalemia. When muscle tissue breaks down in response to injury, it releases large stores of potassium into the blood. Hyperkalemia can also result as a side effect of certain medications or from a complication of genetic diseases that affect the kidney.
Clinical Symptoms
The symptoms of hypokalemia and hyperkalemia are similar and are related to the effects of potassium on the heart and muscles. Since potassium controls electrical conduction in the heart, hypokalemia or hyperkalemia can result in arrhythmias, or skipped heart beats. In severe cases, the heart may become unable to adequately pump blood or go into cardiac arrest. Both disorders of blood potassium can cause muscle weakness and fatigue. Hypokalemia may also result in kidney disorders, which cause increased urination. In severe hypokalemia, muscle cramping and muscle breakdown occur in a process called rhabdomyolysis.
Diagnosis and Treatment
Hypokalemia and hyperkalemia are both diagnosed using a simple blood test. An electrocardiogram (EKG) may also be obtained to determine if the heart is affected. In hypokalemia, treatment may include giving potassium. Hyperkalemia can be treated with drugs such as calcium and insulin. In severe cases, a procedure called dialysis can remove excess potassium from the blood. Ultimately, treatment of hypokalemia and hyperkalemia involve treating the underlying cause.
References
- "Harrison's Principles of Internal Medicine, 17th Edition"; Anthony Fauci MD, Eugene Braunwald MD, Dennis Kasper MD, et al; 2008
- "Rosen's Emergency Medicine, 7th Edition"; John Marx, MD; 2008
- "Brenner and Rector's The Kidney, 8th Edition"; Barry Brenner, MD; 2008
