Which type of fluid to use perioperatively?

Fluid administration in the perioperative period is daily clinical practice for all anesthesiologists. The goal of fluid administration is to increase cardiac output in order to ultimately improve oxygen delivery to the tissues. Fluid therapy can be given as maintenance or as replacement fluid therapy. For both of these therapies balanced crystalloids belong to the first line of treatment. Colloids are used for fluid replacement as well, but are given for more specific indications such as hypovolemia as a consequence of blood loss. Fluids, as any other intravenous drug, have indications, contra-indications, and potential side-effects. No conclusive evidence exists over the way and amount of fluids that should be administered, and several strategies have been developed, e.g., restrictive or liberal fluid therapy or perioperative goal-directed therapy (PGDT). Restrictive fluid therapy uses limited amounts of fluid compared to liberal fluid therapy, however no clear definitions of restricted or liberal fluid therapy are available. PGDT uses hemodynamic variables to assess fluid responsiveness and to guide fluid therapy in order to optimize the hemodynamic status of the patient. Future directions in fluid administration are to use personalized hemodynamic target values and to use PGDT in closed-loop systems. Most important, fluids should be administered with the same caution that is used with any intravenous drug.