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Disorders of magnesium in the critically ill 

Disorders of magnesium in the critically ill
Chapter:
Disorders of magnesium in the critically ill
Author(s):

Figen Esen

DOI:
10.1093/med/9780199600830.003.0252
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date: 30 November 2020

Plasma potassium levels are maintained in health between 3.5 and 5.0 mmol/L, and reflect total body potassium only in stable states at normal pH. Most true hyperkalaemia results from renal insufficiency. The goals of therapy are myocardial protection and return of plasma potassium to a safe level. Measures are commonly initiated above 5.5 mmol/L; above 6.5 mmol/L, aggressive measures should be adopted and calcium salts given if there are cardiac dysrhythmias or QRS-broadening. Glucose-insulin infusions and beta-2-agonists promote potassium shifts into cells. Diuretics and sodium bicarbonate may be helpful, but persistent hyperkalaemia is an indication for renal replacement therapy. Hypokalaemia may lead to dangerous arrhythmias, skeletal muscle weakness, ileus, and reduced vascular smooth muscle contractility. Rapid replacement should only be undertaken for severe hypokalaemia or in the context of arrhythmias. Once the extracellular deficit is corrected, there will usually be a continuing need for potassium supplementation to replenish intracellular stores.

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