Delirium is a common problem in patients admitted to the intensive care unit and is associated with increased length of hospital stay, high mortality and long term cognitive impairment. Delayed diagnosis can often make things worse. Delirium is known to fluctuate in its presentation and its severity can also vary. Delirium is generally classified into one of three subtypes- hypoactive (inattentiveness, lethargy, and motor slowness), hyperactive (restlessness, aggression, and hallucinations) and mixed (fluctuating between the hypoactive and hyperactive subtypes)
However, several clinical studies suggest that there may be important differences in risk factors and outcomes among the different subtypes of delirium. Two recent systematic reviews and meta-analysis identified risk factors of delirium such as dementia, advanced age, pre ICU emergency trauma or surgery, hypertension, APACHE II score, metabolic acidosis, mechanical ventilation, delirium one day prior, duration of mechanical ventilation and long length of ICU stay. It is possible that increased knowledge about the risk factors could help develop effective interventions to prevent delirium in high-risk individuals.
This particular systematic review was conducted to summarise, compare and evaluate risk factors and outcomes for delirium subtypes in an adult ICU setting.The researchers looked at 20 studies on delirium.
The results showed that:
1) Advanced age was not associated with any subtype of delirium in 57% of the studies.
2) The gender of the patient was not linked with any subtype of delirium in all studies.
3) Mortality was consistently associated with hypoactive delirium in 57% of the studies.
The researchers also looked at other confounding risk factors like the need for mechanical ventilation, APACHE-II score, length of ICU stay, removal of any tubes and duration of delirium. They did not find any strong association to any subtype of delirium across all these studies.
Delirium is a common problem in the intensive care unit and if not recognised, is associated with high morbidity and mortality. Despite the huge number of publications (these authors identified over 9500 abstracts on the topic), there is no consensus on the risk factors for the different subtypes of delirium. In fact, in many studies, the subtypes have not been differentiated but all grouped into one generalised category. Overall, researchers found too much heterogeneity in the reporting, problems with methodology, differing outcome goals, and no universal criteria for inclusion or exclusion of patients into the studies.
Image Credit: iStock