Fluid therapy: Too much or too little

There is much debate regarding the amount of perioperative fluid administration in relation to patient outcome.Fluid shifting towards the interstitial space is of two types (physiologic and pathologic) across the vascular endothelial membrane. This membrane, of 1 μm thickness, is formed of an endothelial layer coated by glycocalyx, a small concentration of albumin, and a non-circulating part of plasma. It acts as a gateway to the interstitial space with a primary molecular filler function, generating an effective molecular filter function, generating an effective molecular gradient across its thickness.Since the early sixties, perioperative fluid requirements were calculated by considering pre-existing deficits, maintenance volumes, and third-spaces loss, depending on the type of surgery. Based on this, a goal-directed “liberal” fluid approach was modulated. On the other hand, a “restrictive” fluid approach was later suggested to achieve better patient outcome. Extremes of either approach were shown to induce hyper- or hypovolemia, respectively. However, there are no clear definitions to describe the volume status of patients.The literature is currently characterized by inconsistency and contradiction regarding patient outcome parallel to perioperative “too much” or “too little” fluid administration. There is no single fluid regimen which provides optimal fluid volumes to all surgical patients all the times. So, available literature is discussed in this article with an early evidence of a preferred “adequate” rather than a “liberal” or a “restrictive” fluid approach.Further systematic reviews of randomized controlled trials are recommended to predict the volumes and types of administered fluids, and its timing as important determinants of postoperative patient outcome. Special evidence is also needed for “liberal” versus “restrictive” hemoglobin therapy to determine the same goals.