High potassium (hyperkalemia) occurs when the level of potassium in the blood is higher than normal. Hyperkalemia is defined as plasma potassium greater than 5 mEq/L. It is virtually always due to difficulty eliminating potassium by the kidneys. According to Dr. Peter Ahee's review article published in the "Journal of Accident & Emergency Medicine" in May 2000, life-threatening hyperkalemia occurs when potassium is greater than 7 mEq/L and is commonly associated with acute renal failure. Acute treatment of life-threatening hyperkalemia depends on electrocardiogram (EKG) changes caused by the condition and the severity of the condition. The main drugs that treat high potassium stabilize cell membranes, drive potassium into cells or block its absorption.
The initial treatment of hyperkalemia should be the protection of the heart. In hyperkalemia, calcium gluconate works by diminishing the cardiac toxicity of excess potassium and stabilizing heart muscles to protect against arrhythmias, such as ventricular fibrillation and asystolic arrest. Its effect is rapid (within minutes), but is short lived (up to one hour).
Calcium has no effect on potassium levels in the blood.
The next goal of treatment of hyperkalemia is promoting the shift of potassium from extracelluar fluid into cells throughout the body. This is most often done by giving insulin, which temporarily lowers the level of potassium in the blood. Insulin is given with glucose to prevent a drop in blood sugar; patients who have high blood sugar levels should not be given glucose. Insulin is effective in 15 to 30 minutes and lasts for several hours.
The final task in treating patients with severe hyperkalemia is to remove potassium from the body. Sodium polystyrene sulfonate (kayexalate), which is not absorbed, binds excess potassium in the colon, carrying it out of the body. Kayexalate can be administered orally or rectally (as a retention enema). Because the major site of action for kayexalate is the colon, rectal administration is preferred for severe hyperkalemia. This lowers potassium within one to two hours and lasts for four to six hours.