Gavin Elster: She’ll be talking to me about something. Suddenly the words fade into silence. A cloud comes into her eyes and they go blank. She’s somewhere else, away from me, someone I don’t know. I call her, she doesn’t even hear me. Then, with a long sigh, she’s back. Looks at me brightly, doesn’t even know she’s been away, can’t tell me where or when.
Scottie: How often does this happen?
Gavin Elster: More and more in the past few weeks.
Common Risk Factors
Just as delirium has myriad causes, it also has many risk factors and predisposing conditions. As we’ll see later in the course, reducing or preventing many of these factors can have a very beneficial effect.
Individuals are differently susceptible to delirium. Despite the exposing to the same causative factor, individuals are not equally prone to develop delirium. Predisposing and risk factors appear to play a role in the susceptibility to delirium. There have been numerous studies on predisposing and risk factors of delirium. For instance, Inouye and Charpentier (1996) demonstrated the five independent precipitating factors for delirium, including use of physical restraints, malnutrition, more than three medications taken, use of bladder catheter, and any iatrogenic event. Recently, risk factors for delirium have been established in four domains, including patient characteristics, chronic pathology, acute illness, and environmental factors (Van Rompaey et al., 2009). Another study in elderly patients receiving hip surgery found that early symptoms of memory impairment, incoherence, disorientation, and underlying somatic illness were predictors of delirium (De Jonghe et al., 2007).
- Age > 60 years
- Acute brain condition (eg, stroke)
- Chronic brain condition (eg, Alzheimer-type dementia)
- HIV infection (Maneeton & Maneeton, 2013
- Vision impairment
- Physical restraint use
- Bladder catheter use
- Adding more than three drugs
- Sudden withdrawal of regular medications or alcohol use
- Hip fractures (Inouye, 2000; Ahmed, et al., 2014)
Gender, however, does not appear to be a strong risk factor for delirium, according to several studies (Van Rompaey et al., 2009; Dyer et al., 1995; Korevaar et al., 2005; Ahmed et al., 2014).
Risk Factors in the ICU
Because the prevalence of delirium is so high in the ICU—as much as 80%—several studies focused on this population of patients (van Rompaey et al., 2009, Brummel et al., 2013; Ely et al., 2001).
An in-depth study by Van Rompaey and colleagues grouped delirium risk factors for ICU patients into four domains depending on their ability to be mitigated: patient characteristics, chronic pathology, environment, and acute illness (van Rompaey et al., 2009).
Patient characteristics included age, gender, and daily smoking or chronic alcohol habits. Chronic pathology indicated primarily a pre-existing cognitive impairment. Environmental characteristics included whether visible daylight could be observed by the patient, a private or shared room, the presence of a clock, the use of restraints, and whether relatives visited the patient. Acute illness factors were those relating to the patient’s “current diagnosis or treatment,” and included such factors as temperature, nutrition, and the use of tubes, drains, and catheters (van Rompaey et al., 2009).
The domains were scored to see if “an intervention on relevant factors could influence the incidence of delirium in the intensive care unit. To prevent delirium, precipitating factors are more modifiable than predisposing factors” (van Rompaey et al., 2009).
Results in the van Rompaey study revealed that patient characteristics of smoking and alcohol use were significant risk factors for developing delirium in the ICU. In the chronic pathology domain, only an established diagnosis of dementia appeared to be a risk factor. In the acute illness domain, the longer a patient stayed in the ICU, the greater the risk of developing delirium.
Patients admitted because of a medical diagnosis as opposed to a surgical diagnosis also seemed to have a greater risk of developing delirium. The use of multiple psychoactive medications, tubes, bladder catheters, multiple infusions, and those who could not have a regular meal were also factors in the acute illness domain that were correlated with a higher risk of the onset of delirium. Environmental factors such as no visible daylight, no visits from relatives, and a transfer from another ward were significant risk factors (van Rompaey et al., 2009).