Intravenous fluid administration in pregnancy: maintenance and acute hydration

Abstract

Pregnancy is characterised by a hyperdynamic output state, low blood viscosity and haematocrit, reduced blood and tissue buffering capacity, increased tendency to both sodium and water retention, an exaggerated ketotic and hypoglycaemic response to dehydration and increased insensible losses and decreased heat tolerance. These changes are relevant to anaesthetists attempting to restore and maintain fluid, electrolyte, glucose and metabolic balance in labour and during anaesthesia, resuscitation and critical care. Fluid maintenance and replacement in pregnancy follow the basic principle of replacing what is lost in both quantity and quality, remembering the specific requirements of the individual patient and situation. The altered milieu of pregnancy makes the use of most crystalloid containing fluids somewhat controversial particularly for acute hydration (fluid loading) in association with central neural blockage or resuscitation. Normal saline and lactate tend to worsen reduced buffer base capacity and cause further dilution of plasma proteins in an already low blood glucose level, so potentiating the efforts of highlevel epidural or spinal sympathetic blockade. Glucose loads can cause fetal hyperinsulinaemia, rapid‐onset neonatal hypoglycaemia and jaundice. A balanced approach of fluid administration using colloids, crystalloids and vasopressors will be discussed.