Disorders of Potassium Balance

Potassium homeostasis:  • K⁺ is the most essential intracellular cation, generating the resting potential in neuronal and muscle cells.  • Extracellular K⁺ levels are tightly regulated.  • Any disturbances of serum K⁺ levels can affect the resting potential and lead to arrhythmias or muscular abnormalities. Renal K⁺ handling and changes during maturation:  • The kidneys are primarily responsible for excreting excess K⁺.  • The goal of adult kidneys is to maintain a zero K⁺ balance, while newborn kidneys retain K⁺ to allow somatic growth.  • Premature infants are prone to develop hyperkalemia, because they cannot rapidly eliminate exogenous excess K⁺. Disturbances in K⁺ balance:  • Serum K⁺ levels can be abnormal due to abnormal intake or abnormal excretion of K⁺, but can also be caused by abnormal distribution of K⁺ between the extra- and intracellular space.  • Clinical symptoms vary and do not allow distinguishing between hypo- and hyperkalemia. Hypokalemia:  • Mild hypokalemia is a common finding in clinical practice.  • Administration of diuretics is the most common acquired cause of hypokalemia.  • Decreased intake of K⁺ can lead to total body K⁺ depletion and hypokalemia. Hyperkalemia:  • Hyperkalemia is rare in individuals with normal renal function.  • ECG findings with hyperkalemia occur individually and cannot be correlated with the serum K⁺ level per se.