Fluid resuscitation: Colloids vs crystalloids

The choice of fluid to be used in the resuscitation of critically-ill patients remains a matter of debate. All fluid types have their drawbacks and no studies have demonstrated a beneficial effect on survival of one type of fluid over another in critically-ill patients. Generally speaking, most patients will receive some crystalloid and some colloid solution. Of the crystalloid solutions, balanced fluids, such as Ringer's lactate, may be preferable to normal saline as they reduce the risk of hyperchloraemic acidosis which has been associated with impaired renal function. Of the colloid solutions, dextrans are used less often than in the past due to problems with anaphylaxis and may increase the risk of renal failure, gelatin is of limited effectiveness, and albumin is effective but expensive. Hydroxyethyl starch solutions have also been associated with detrimental effects on renal function. Further studies are needed to provide clearer data on the benefits and harms of specific fluid regimens in the critically-ill patient population as a whole and in patients with or at risk of acute renal failure. Until the results from such studies are available, physicians should probably be more concerned with ensuring that enough fluid is given to maintain perfusion than with which fluid they use to achieve it.