The life-threatening nature of critical illness, requiring simultaneous, mu
ltiple interventions, makes it difficult, if not impossible, to study the e
ffects of any one treatment.
It is often not possible to conduct trials in critically ill patients, as t
hey 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 o
f theory, experience and evidence.