The effects of Sterofundin versus Ringer's Lactate on Acid-base balance and electrolyte status in paediatric patients undergoing major urogenital surgery.

Perioperative fluid comprises of basic maintenance requirement, replacement of fluid losses and fasting deficits. The aims of perioperative fluid therapy are to maintain correct fluid and electrolyte balance and adequate vascular volume which will ensure cardiovascular stability, organ perfusion and adequate tissue oxygenation . Most of the fluids given perioperatively are used for replacing deficits and third space losses which consist mainly of extra cellular fluid . Therefore the hydrating solution should ideally have a composition of electrolytes as similar to plasma as possible. This favours crystalloids which are high in sodium and chloride concentration and have low concentrations of potassium, bicarbonate and calcium. Examples of crystalloids that approximate these ideals are ringer’s lactate and sterofundin. The two fluids used in this study, sterofundin and ringer’s lactate are balanced crystalloids. The composition of which is very similar to plasma composition. Sterofundin or ringerfundin is a balanced isotonic solution for intravenous infusion with electrolyte composition very similar to plasma (Na 140, k 4.0, Ca 2.5, Mg 1, Cl 127mmol/l. It also has a potential base excess of zero and contains acetate (24mmol/l) and malate(5mmol/l) which is widely metabolized in all organs and muscles, resulting in low oxygen consumption (1.4l oxygen per litre solution). Ringer’s lactate is a balanced solution containing sodium (130mmol/l), potassium (5mmol/l), calcium and magnesium (both at 1mmol/l), chloride (112mmol/l) and lactate (27mmol/l) therefore it is actually slightly hypotonic. Its osmolarity is 276mOsm/l which renders it slightly hypo-osmolar to plasma. Its potential base excess is 3 mmol/l and oxygen consumption is higher than that of sterofundin at 1.8l oxygen per litre solution. This minor difference in oxygen consumption would be actually significant in a perioperative paediatric patient who has to cope with other stresses of surgery and anaesthesia. The lactate in ringer’s lactate was added in order to reduce the chloride load and act as a bicarbonate precursor, therefore reducing likelihood of hyperchloraemic acidosis seen after large infusions of normal saline. However, the metabolism of lactate is dependent on the kidney and liver, and as such, when the functions of these organs are compromised, there will be lactate accumulation as well as reduction in production of bicarbonate resulting in lactic acidosis.Sterofundin has been compared with ringer’s lactate use for resuscitation in septic oncologic adult patients where it has been found to be associated with a better preservation of electrolyte and acid-base pattern . However, few data exist on perioperative use of sterofundin in children. This study aims to elicit any significant changes in sodium, chloride, pH and base excess levels when sterofundin is used in paediatric patients undergoing major surgery as compared to ringer’s lactate usage. Ideally, there should be minimal changes in these parameters as compared to the baseline levels as there are many undesirable and dangerous effects associated with moderate to severe derangement of acid base and electrolytes.