Evidence-based medicine in intensive care.

The life-threatening nature of critical illness, requiring simultaneous, multiple interventions, makes it difficult, if not impossible, to study the effects of any one treatment. It is often not possible to conduct trials in critically ill patients, as they can not give informed consent. Some high quality, prospective studies have influenced clinical practice in intensive care, but others with lower grades of evidence have led to some controversy. In intensive care, clinical practice is still influenced by a combination of theory, experience and evidence.