A crucial electrolyte, potassium levels are normally kept within a narrow range, according to "Harrison's Principles of Internal Medicine." This mineral is the major cation inside the cells responsible for the relaxation phase of muscle contraction. Abnormalities in potassium result in severe and even deadly heart conduction problems, paralysis and death.
Significance
Homeostasis of potassium is crucial to healthy heart action. Imbalances in this electrolyte affect the relaxation phase of cardiac muscles, hindering the filling capacity of the chambers of the heart. For instance, hyperkalemic conditions--high potassium levels--produce serious electrical conduction delays which lead to cardiac arrest and death, according to "Harrison's Principles of Internal Medicine."
"Rapid Interpretation of EKG's" states that low serum levels of potassium or hypokalemia result in spontaneous and extremely rapid ventricular arrhythmias that can cause the heart to beat up to 350 beats per minute. Normal heart rate is 70 to 100 beats per minute.
Normal Levels in the Blood
Serum potassium levels are one of the most monitored lab tests in the hospital setting. According to "Harrison's Principles of Internal Medicine," the normal range for an adult falls between 3.5 and 5.0 mmol/L, millimoles per liter fluid.
Children should have higher potassium levels, especially newborns, according to "The Johns Hopkins Hospital: The Harriet Lane Handbook." In fact, newborn levels range from 3.7 to 5.9 mmol/L.
Normal Levels in the Urine
Urine potassium levels are tested over a 24-hour period, usually to help practitioners determine the cause of abnormal levels in the blood. The kidneys are the major elimination pathway for potassium, filtering approximately 90 percent of potassium. Renal elimination is followed second by the gastrointestinal system, which accounts for the remainder, according to "Step-Up to Medicine" authored by Drs. Steven Agabegi and Elizabeth Agabegi.
"Harrison's Principles of Internal Medicine" states that normal levels within the urine range from 25 to 120 milliequivalents per liter per 24-hours, mEq/L/24-hr.
Normal Levels in the Stool
A secondarily means of potassium secretion, the gastrointestinal tract normally filters between 5 and 10 mmol/day within every 100 to 200 milliliters of feces. This rate remarkably increases in situations of large-volume diarrhea and chronic renal insufficiency, according to "Harrison's Principles of Internal Medicine."
Imbalances
Hyperkalemia produces a variety of severe problems including cardiac arrest, muscle paralysis and death, according to "2007 Current Consult Medicine." These conditions can be treated by administering intravenous calcium gluconate, insulin and glucose.
Hypokalemia results in heart palpitations, muscle paralysis, constipation due to ileus, tetany and rhabdomyolysis. Low levels of potassium are treated by administration of oral potassium.
References
- "Harrison's Principles of Internal Medicine" 17th ed.; Anthony Fauci, M.D., et al., eds.; 2008
- "Rapid Interpretation of EKG's"; Dale Dubin, M.D.; 2000
- "Step-Up to Medicine" 2nd ed.; Steven Agabegi, M.D. and Elizabeth Agabegi, M.D.; 2008
- "2007 Current Consult Medicine"; Maxine Papadakis, M.D. and Stephen McPhee, M.D.; 2007
- "The Johns Hopkins Hospital: The Harriet Lane Handbook" 17th ed.; Jason Roberston, M.D. and Nicole Shilkofski, M.D.; 2005
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