Crystalloid solutions

Crystalloid (salt) solutions are the cornerstone of clinical volume replacement, either during surgery or to treat traumatic blood loss. In contrast to blood transfusion, crystalloids are distributed significantly in the extravascular spaces, and the rates of distribution after infusion are not easily predictable. This chapter presents a theoretical basis for this phenomenon and explains why adequate replacement of blood losses with crystalloid requires infusion of between three and seven times the volume of loss. Infusion of large volumes can have undesired consequences, such as hypercoagulation, acidosis and tissue edema, particularly in the lung and gastrointestinal tract. It is important to understand the physiologic changes that follow infusion of these solutions. Furthermore, when blood substitutes are available, they will be used in combination with crystalloids. Although the overall safety of crystalloid fluids for blood replacement and perioperative fluid management appears to be outstanding, there remain several areas in which further information is necessary. The kinetics of crystalloids may favor interstitial accumulation during perioperative administration, and may be associated with postoperative complications in certain types of surgery such as bowel surgery. The effects of specific crystalloids on immune function, metabolic status and coagulation are potentially important and require continued study.