Introduction

Imagine you are caring for a critically ill patient admitted with severe community-acquired pneumonia. Unfortunately, this evolves rapidly with severe sepsis that results in both cardiovascular and respiratory failure. You know the patient has haemodynamic failure because you are monitoring the blood pressure and heart rate. You know the patient has respiratory failure because you are monitoring the respiratory rate and the oxygen saturation. You treat the patient with antibiotics, ventilatory support, fluids and inotropes.

He gets better, a job well done.

But what about the brain?

Just like the other organs, the brain can acutely fail in critical illness. An acute episode of brain failure is recognized as delirium. Delirium is an acute organ failure, and can happen in critical care, the general ward or the community at large. It is common; it is dangerous, even life-threatening. It is all the more dangerous because we know little about it. Its importance has been underestimated in the critically ill patient. The delirious patient is in an acute confusional state with a fluctuating altered mental status, inattention, an altered level of consciousness, disorganized thinking and often will have hallucinations. The delirium is triggered by an acute medical event, related to drugs or illness.