Intravenous literature: Cook, S-C. and Brown, J. (2009) Perioperative fluid therapy. Anaesthesia and Intensive Care Medicine. 10(12), p.573-575.
Perioperative fluid therapy remains a controversial topic despite much research. Here, we review the different types of fluids, what to use in different circumstances and some of the controversies associated with fluid use. Crystalloids are fluids with small water-soluble molecules that can easily cross semi-permeable membranes. Saline-based fluids stay mainly within the extracellular compartment. Glucose solutions provide free water that diffuses across all the fluid compartments of the body. Colloids are fluids with larger, more insoluble molecules that do not readily cross membranes. Gelatins, dextrans and hydroxyethyl starches are effective intravascular volume expanders but are associated with numerous complications including anaphylaxis, renal failure and coagulation changes. Balanced solutions have low chloride content to avoid producing hyperchloreamic acidosis with extensive fluid use. Maintenance requirements can be met by providing water, sodium and potassium. Replacement for third space and insensible losses should use a â€˜balancedâ€™ crystalloid. The type of fluid used for hypovolaemia resuscitation can be crystalloid or colloid, with neither proven to be better than the other. Goal-directed therapy has shown that giving surgical patients the optimal amount of fluid that they require, as guided by cardiac-output monitoring, is associated with better outcomes.