An abnormally high level of the mineral potassium is called hyperkalemia, and it is defined in the medical textbook "Harrison's Principles of Internal Medicine" as a potassium concentration greater than 5.0 millimoles per liter, or mmol/L. The medical reference UpToDate lists several possible causes for hyperkalemia, including kidney disease and medications; giving a person with low potassium too much potassium can also cause this problem. There are risks for several problems in a person with hyperkalemia.
Muscle Weakness
One of the many processes in which potassium is involved is that of muscle function. An elevated level of potassium disturbs the balance of chemicals involved in the ability of muscles to work properly, and muscle weakness results. UpToDate informs readers that in hyperkalemia, the muscle problems usually begin with the legs, then ascend to affect the arms and the trunk. In severe cases, a condition called "flaccid paralysis" may develop, in which the muscles are floppy and loose, and the limbs are not able to move because of this.
Changes on the Electrocardiogram
The electrocardiogram, or ECG, is described by the National Heart, Blood and Lung Institute as an easy, non-invasive test that simply records the electrical activity of the heart. The readings on the ECG allow cardiologists and other health care professionals to determine if the heart is healthy or if there is damaged to the heart, just by looking at the recordings, called tracings, of the ECG. A person suffering from elevated potassium is at risk for several changes on the ECG. One common finding, according to "Harrison's Principles of Internal Medicine," is a phenomenon known as "peaked T waves." While the appearance of tall, narrow "T waves" may be considered a non-specific change on the ECG -- other diseases may show this change as well --it is usually the first change seen on the ECG in patients with hyperkalemia. If left untreated, the hyperkalemia will worsen and the ECG will show other changes as well; in extreme cases, the ECG will show a "flat line" indicating that no electrical activity of the heart is occurring.
Abnormal Heart Rhythms
An abnormality in the way the heart is beating is known as an arrhythmia. Either the rate at which the heart is beating, or the pattern of the heart beat itself, may be the problem in an arrhythmia. Patients with hyperkalemia may have several different types of arrhythmias develop. UpToDate reports that sinus bradycardia, in which the heart is beating more slowly than normal, is one possible abnormality. A more dangerous arrhythmia is ventricular fibrillation, in which the muscle fibers within the ventricles of the heart begin contracting in a random fashion. This can result in blood remaining within the ventricles rather than being pumped throughout the body; cardiac death can be the unfortunate result of this arrhythmia. Finally, asystole may occur as the hyperkalemia becomes worse. In asystole, the patient's heart is no longer beating at all -- cardiac arrest has developed and no blood is being pumped through the body.
References
- "UpToDate;" Clinical Manifestations of Hyperkalemia; D. Mount, June 2010
- "Harrison's Principles of Internal Medicine;" A. Fauci et. al.; 2008
- National Heart Lung and Blood Institute: What is an Electrogcardiogram?
- MedlinePlus: Arrhythmias
- MedlinePlus: Ventricular Fibrillation
- "Tintinalli's Emergency Medicine;" J. Tintinalli et. al.; 2004
