Crystalloid vs colloid rx

Crystalloids and colloids are the primary options for intravenous fluid resuscitation. Crystalloids fluids such as normal saline typically have a balanced electrolyte composition and expand total extracellular volume. Colloid solutions (broadly partitioned into synthetic fluids such as hetastarch and natural such as albumin) exert a high oncotic pressure and thus expand volume via oncotic drag. There are many clinical factors that may affect the decision to use a crystalloid versus colloid fluid. Crystalloids exert a significant hydrostatic effect on capillaries that may lead to extracellular fluid accumulation. This could lead to increased gastrointestinal wall edema, which may slow post-operative gastrointestinal recovery. It could also lead to significant pulmonary edema, especially in patients with underlying cardiac systolic dysfunction or renal disease. There is also a risk of hemodilution, which may occur with crystalloid administration.

Colloids, on the other hand, may (rarely) trigger an anaphylactic reaction. While low dose colloids typically preserve hematocrit and coagulation factor levels, there is a risk of abnormal hemostasis occurring if too much colloid is administered, especially synthetic colloids. Of note crystalloids are significantly cheaper than colloids.

In terms of selecting fluids in the perioperative period, most of the literature is extrapolated from critical care studies and there is no clear consensus. The CRISTAL trial did show a reduced 90-day mortality in patients with hypovolemic shock treated with colloids.1 However, according to a recent Cochrane review, there is no evidence that colloid resuscitation instead of crystalloids reduces mortality following trauma, burns, or surgery.2 One trial suggested that hydroxyethyl starch may actually increase 90-day incidence of death and renal replacement therapy compared to lactate ringers in patients with severe sepsis.3 Several studies have posited that albumin may exert a benefit to the microcirculation in certain conditions such as cirrhosis and spontaneous bacterial peritonitis that could in theory be beneficial in the perioperative period. In summary, crystalloids seem to be the best choice for replacing evaporative losses, providing maintenance fluids, and expanding total extracellular volume. Otherwise, the choice to use crystalloid versus colloid should be based upon the comorbidities of the patient and the overall clinical picture.

When replacing blood loss, you need to administer approximately 3x estimated blood loss volume when using a crystalloid solution. In the acute setting, you can replace blood loss with an equal volume of colloid solutions; however, as the half-life of all colloids is relatively short, patients will eventually require a greater volume of colloid solutions – nearly as great as would be required for a crystalloid resuscitation.