Intravenous fluid therapy in critically ill adults

Intravenous fluid therapy is one of the most common interventions in acutely ill patients. Each day, over 20% of patients in intensive care units (ICUs) receive intravenous fluid resuscitation, and more than 30% receive fluid resuscitation during their first day in the ICU. Virtually all hospitalized patients receive intravenous fluid to maintain hydration and as diluents for drug administration. Until recently, the amount and type of fluids administered were based on a theory described over 100 years ago, much of which is inconsistent with current physiological data and emerging knowledge. Despite their widespread use, various fluids for intravenous administration have entered clinical practice without a robust evaluation of their safety and efficacy. High-quality, investigator-initiated studies have revealed that some of these fluids have unacceptable toxicity; as a result, several have been withdrawn from the market (while others, controversially, are still in use). The belief that dehydration and hypovolaemia can cause or worsen kidney and other vital organ injury has resulted in liberal approaches to fluid therapy and the view that fluid overload and tissue oedema are ‘normal’ during critical illness; this is quite possibly harming patients. Increasing evidence indicates that restrictive fluid strategies might improve outcomes.This Review updates the evidence base for the administration of intravenous fluids to critically ill patients. Finfer and colleagues also discuss unresolved questions, such as whether buffered solutions are better than normal saline, and the benefits and harms of restrictive approaches to fluid administration.Key pointsIntravenous fluid administration is one of the most common interventions in acute and critical care medicine, but much of the physiological theory on which practice has been based is flawed.Intravenous fluids were established in clinical practice and licensed for use without robust investigation of their efficacy or safety, although large, high-quality, investigator-initiated trials have now provided such data.Crystalloid fluids should be used for first-line therapy; in most patients, buffered salt solutions seem to offer benefits over normal saline.Albumin administration might be beneficial in patients with sepsis, cirrhosis or infections, but albumin in hypotonic carrier fluid is contraindicated in patients with acute traumatic brain injury.Synthetic colloids, notably hydroxyethyl starch and gelatins, should not be used owing to their unacceptable safety profiles and lack of proven benefits over crystalloids.Strategies that restrict fluid administration might reduce morbidity and mortality, but larger trials are still needed to confirm these promising initial data.