Water and Electrolytes II PDF

Water and electrolytes II Dr Xikombiso Nkuna Chemical Pathology Department Objectives Explain the basic concepts of water and salt loss Explain potassium disturbances Understand electrolytes imbalance conditions such as: Hypernatremia Hyponatremia Hyperkalemia Hypokalemia...

Water and electrolytes II Dr Xikombiso Nkuna Chemical Pathology Department Objectives Explain the basic concepts of water and salt loss Explain potassium disturbances Understand electrolytes imbalance conditions such as: Hypernatremia Hyponatremia Hyperkalemia Hypokalemia Understand the clinical effects and management of electrolytes in the body fluids. Sodium balance The volume of the extracellular fluid (ECF) is directly dependent on the total body Na+ content. Sodium is mainly confined to the ECF. Water intake and loss are regulated to maintain a constant ECF osmolality and sodium concentration. Sodium balance is maintained by regulation of its excretion by the kidneys. Renal handling of sodium Hyponatraemia Hyponatremia is defined as a decreased plasma sodium concen tration (30 mmol/L) No clinical evidence of volume depletion or oedema Normal renal, adrenal and thyroid function SIADH management Restrict water intake Hypertonic saline risk of fluid overload→ pulmonary oedema In chronic dilutional hyponatraemia: correct the sodium slowly to avoid causing central pontine myelinolysis Treat the underlying cause Hypernatraemia Hypernatremia (defined as plasma Na>145 mmol/L) is always hyperosmolar and is less common than hyponatremia. Hypernatremia occurs frequently in critically ill patients, where patients may be unable to drink water. Symptoms of hypernatremia are primarily neurologic (because of neuronal cell loss of H2O to the ECF) including tremors, irritability, ataxia, confusion and coma. Hypernatraemia Diabetes insipidus DI is characterized by dilute urine (osmolality