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. • Medications are a common cause of hyperkalemia in susceptible individuals