[Hydroelectrolytic requirements during the first week of life in premature infants weighing less than 1000 g. Physiopathology and recommendations].

Fluid and electrolyte maintenance in very low birth weight infants during the first week of life must be adapted to their physiological characteristics and to pathological events. Insensible water losses are elevated and may reach 100 mL/kg/24 h depending upon many factors, such as type of incubator, phototherapy, presence of respiratory distress syndrome, changes in transepidermal water losses and renal water and electrolyte regulation (prediuretic, diuretic and postdiuretic phases); there is also a major risk of hypernatremia and hyperkaliema. In cases of insufficient fluid intake the main complication is dehydration with hypernatremia. Excessive fluid intake results in increased incidence of bronchopulmonary dysplasia, patent ductus arteriosus and necrotizing enterocolitis. Hypernatremia is a major risk factor of intracranial hemorrhage. A careful management of water and electrolyte requirements is therefore mandatory in very low birth weight infants. Guidelines on daily maintenance and management are presented.