Homeostatic mechanisms normally maintain the fluid and electrolyte levels of the body within narrow limits. However, intravenous fluid replacement may be required for circulatory shock, severe dehydration, or during the perioperative period. Crystalloid solutions containing dissolved salts are most commonly used for this purpose.

Colloids, containing particles suspended in solution, were developed to provide a more efficient option for replacing intravascular volume. The larger particle size of a colloid prevents redistribution into the interstitial space. Therefore lower volumes are required for a more sustained effect. However, this benefit may be reduced during septic shock and other conditions where capillary leakage is enhanced.

Table 1. Examples of crystalloid solutions and colloid solutions

Crystalloid Solutions

Colloid Solutions

Normal saline Albumin
Hartmann’s solution Dextrans
Ringer’s solution Hydroxyethyl starches (e.g. Voluven®)
Gelatins (e.g. Gelofusine®)


Although colloids provide rapid fluid resuscitation, there is little evidence of improved overall mortality. Studies conducted among patients with severe sepsis demonstrate increased mortality and incidence of kidney injury with hydroxyethyl starch (HES) compared to Ringer’s solution. Anaphylactic reactions are also a concern with colloids. Modern HES (e.g. Voluven®) and albumin have the lowest incidence of anaphylactic reactions while dextrans have the highest.

Colloid preparations differ widely in their pharmacokinetic and pharmacodynamic properties. Their safety and efficacy profiles are therefore also quite varied. Overall, colloids are associated with significant side effects and may not always offer clinical benefit over the less expensive crystalloid solutions.


  1. Annane D, Siami S, Jaber S, Martin C, Elatrous S, Descorps Declere A, et al. Effects of fluid resuscitation with colloids vs crystalloids on mortality in critically ill patients presenting with hypovolemic shock: the CRISTAL randomized trial. JAMA. 2013; 310(17): 1809-17.
  2. Myburgh JA, Finfer S, Bellomo R, Billot L, Cass A, Gattas D, et al. Hydroxyethyl starch or saline for fluid resuscitation in intensive care. NEJM. 2012; 367: 1901-11.

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