Crystalloids versus Colloids for the Critical Care/ITU Patient
Introduction: Fluid Balance, Resuscitation, and the Crystalloid-Colloid Debate
Fluid imbalance in the critical care patient may result from several conditions including hypovolemia, normovolemia with maldistribution of fluid and hypervolemia (Kreimeier, 2000, p. 4). Hypovolemia is a common cause of fluid imbalance and may be induced by blood loss from trauma, or by dehydration due to fluid loss via gastrointestinal illness, fever, complications of diabetes mellitus, or renal dysfunction (Kreimeier, 2000). The resultant decrease in circulating blood volume may lead to decreased venous return, and in severe cases, to arterial ...view middle of the document...
305). The opposite of this is hydrostatic pressure where fluid moves through a capillary by outward force of the fluid on the membrane. Also during hypovolemia, activation of the renin-angiotensin system leads to peripheral vasoconstriction and the reabsorption by the kidney of sodium and water thereby increasing vascular volume (van Wissen & Breton, 2004, pp. 305-306).
Goals of fluid resuscitation. Sufficient oxygenation is the primary focus of fluid therapy. Thus, maintaining adequate pulmonary function and perfusion pressure are important (Kreimeier, 2000, p. 6). Most important is the maintenance of adequate circulatory volume (Kreimeier, 2000, p. 6). The main goal of fluid resuscitation is to maintain perfusion to the brain and heart by restoring intravascular volume (Diehl-Oplinger & Kaminski, 2004, p. 52). Two main factors that affect the choice of fluid for volume replacement are how the fluid was lost and which solutes need to be replaced (Diehl-Oplinger & Kaminski, 2004, p. 52).
The debate. The basic debate among proponents of each type of fluid is based on each side’s view of the potential negative effects of the other’s preferred fluid (Grocott & Hamilton, 2002, p. 5). Some argue that cost is central in the fluid resuscitation debate. It is reported that albumin is responsible for a substantial portion of some hospitals’ budgets (Vincern, 2000, p. S33). Those in the crystalloid camp also cite the hemodynamic derangements, increased potential for intravascular volume overload, and the potential for severe allergic reactions caused by colloids (Grocott & Hamilton, 2002, p. 5). Those who favor colloids point out the large volumes required to achieve the desired effect and the resultant tissue edema and potential for poor organ perfusion that may result from infusion of necessarily large volumes of crystalloid fluids (Grocott & Hamilton, 2002, p. 5).
Crystalloids are fluids, such as Ringers and 0.9% sodium chloride, that closely mimic the body’s extracellular fluid (ECF; Diehl-Oplinger & Kaminski, 2004, p. 53). These can be used to expand both intracellular and extracellular volume. Crystalloids can be isotonic, hypertonic, or hypotonic (Diehl-Oplinger & Kaminski, 2004, p. 53). Isotonic fluids—which have the same tonicity of as plasma—can be used to restore intravascular volume without changing plasma electrolyte concentration or altering fluid shifts between intracellular and extracellular spaces (Diehl-Oplinger & Kaminski, 2004, p. 53). Hypertonic fluids draw fluid from inside the cells into the extracellular space causing cells to shrink and increasing the volume of ECF (Diehl-Oplinger & Kaminski, 2004, p. 53). Conversely, hypotonic fluids help move fluid from the extracellular space into the cells. Overly aggressive use of crystalloids for fluid replacement may lead to volume overload, electrolyte imbalances, coagulopathy, and heart failure (Diehl-Oplinger & Kaminski, 2004, p. 54).
Colloids contain solutes that are...