Cognitive changes after saline or Plasmalyte infusion in healthy volunteers: blinded, randomized cross-over trial

Intravenous crytsalloid fluids are one of the mainstays of in-hospital patient treatment with fluid intervention being ubiquitous for surgical and critical care patients. Cognitive changes such as a perceived difficulty in abstract thinking or mental arithmetic has been reported in subjects exposed to a commonly prescribed crystalloid solution - Normal Saline (0.9%). The postulated mechanism for the altered cognition is unclear but could be a result of NS 0.9% induced hyperchloraemia or NS 0.9% induced acidaemia (normal anion gap metabolic acidosis) that frequently occurs following saline administration. No study has attempted to formally investigate cognitive changes after the administration of saline or other commonly administered crystalloid solutions. Plasmalyte solution is a frequently used crystalloid solution with similiar properties to saline. However it is a more physiological and balanced crystalloid solution compared to saline as it has a significantly lower chloride concentration and physiochemical profile similar to normal plasma. Study hypothesis: Is normal saline associated with greater cognitive changes than Plasmalyte in healthy volunteers?