Part 10.1: Life-Threatening Electrolyte Abnormalities

Electrolyte abnormalities are commonly associated with cardiovascular emergencies. These abnormalities may cause or contribute to cardiac arrest and may hinder resuscitative efforts. In some cases therapy for life-threatening electrolyte disorders should be initiated before laboratory results become available.The magnitude of the potassium gradient across cell membranes determines excitability of nerve and muscle cells, including the myocardium. Rapid or significant changes in the serum potassium concentration can have life-threatening consequences.Evaluation of serum potassium must consider the effects of changes in serum pH. When serum pH falls, serum potassium rises because potassium shifts from the cellular to the vascular space. When serum pH rises, serum potassium falls because potassium shifts from the vascular space into the cells. Effects of pH changes on serum potassium should be anticipated during therapy for hyperkalemia or hypokalemia and during any therapy that may cause changes in serum pH (eg, treatment of diabetic ketoacidosis). HyperkalemiaAlthough hyperkalemia is defined as a serum potassium concentration >5 mEq/L, it is moderate (6 to 7 mEq/L) and severe (>7 mEq/L) hyperkalemia that are life-threatening and require immediate therapy. Hyperkalemia is most commonly seen in patients with end-stage renal disease. Other causes are listed in the Table. Many medications can contribute to the development of hyperkalemia. Identification of potential causes of hyperkalemia will contribute to rapid identification and treatment.1–3 View this table:TABLE. Common Causes of Hyperkalemia Signs and symptoms of hyperkalemia include weakness, ascending paralysis, and respiratory failure. A variety of electrocardiographic (ECG) changes suggest hyperkalemia. Early findings include peaked T waves (tenting). As the serum potassium rises further, flattened P waves, prolonged PR interval (first-degree heart block), widened QRS complex, deepened S waves, and merging of S and T waves can be seen. If hyperkalemia is left untreated, a sine-wave pattern, idioventricular rhythms, and asystolic cardiac arrest may develop. …