Delirium as defined by the DSM – V is a set of diagnostic criteria that includes a disturbance in attention, awareness and cognition that develops over a short period of time and tends to fluctuate in severity throughout the day (American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 2013.). The incidence of delirium in the ICU has been reported to range from 16% to-89% (Reade & Finfer. N Engl J Med. 2014;370[5]:444; Pun & Ely. Chest. 2007;132[2]:624). Delirium is now recognized as a product of our treatments for patients in the ICU and may, therefore, lend itself to methods of prevention. We have unknowingly increased the risk of cognitive and psychological decline in our patients. With this realization, preventing delirium in patients in the ICU has become an integral part of daily rounds.
It is well established that physicians are poor at diagnosing and recognizing delirium. There is a multitude of tests that has been validated as a screening tool to monitor for the presence of delirium in the ICU population. Two of the popular tools are the Confusion Assessment Method for the ICU (CAM-ICU) and the Intensive Care Unit Delirium Screening Checklist (ICDSC). The CAM-ICU can be used on nonverbal patients, translated in multiple languages, and takes an average of less than a minute to complete. It can be administered by any staff member with a high compliance and accuracy rate. It has a specificity and sensitivity of greater than 90%. The ICDSC is an eight item checklist with a specificity of 64% and sensitivity of 99% and with an interrater reliability of 0.94 (Pun & Ely). Choice of a screening tool is institution-dependent, but using the tool is imperative in order to recognize delirium and intervene early.
We have begun to observe the many adverse effects that our critically ill patients attain from being mechanically ventilated, deeply sedated, and even paralyzed at times. Patients identified as having delirium while in the ICU have more than a three-fold increased risk of reintubation and are more likely to have more than 10 days added to their length of stay (LOS) in the hospital. Each day of delirium correlates to an almost 20% increase risk of increased LOS and 10% increased risk of death. All of these factors together equate to an increased LOS, which is associated with an increased cost per admission (Pun & Ely).
Recent studies have shown that delirium causes further decline in not only the current hospitalization but also extends well beyond their discharge. With prolonged hospitalizations, we see patients physical abilities deteriorate and a higher incidence for posthospitalization rehabilitation. Pandharipande and colleagues showed that the cognitive impairments found in patients with ICU delirium were similar to those with mild Alzheimer disease or moderate traumatic brain injury (Pandharipande et al. N Engl J Med. 2013;369[14]:1306). These long-term cognitive defects involve difficulties in attention, memory, and executive function. These may affect each patient differently but can contribute to an inability to return to work or perform the normal activities of daily living, which overall will decrease their quality of life. They are also at an increased risk for requiring institutionalization (Pun & Ely).
Prevention is the only effective way to decrease the risk of delirium. There are some innate features that serve as risk factors for a higher frequency of delirium, but there are some aspects of care that we as physicians have control over. Examples of these baseline risk factors include advanced age, dementia, depression, hypertension, alcoholism, severity of illness, and APACHE II score (Pun & Ely; Ouimet et al. Intensive Care Med. 2007;33[1]:66). Any type of coma increases the likelihood of developing delirium, including those that are medically induced (Ouimet et al).
There is no level 1 evidence for pharmacologic intervention to prevent or treat delirium. In regards to pharmacologic intervention, most physicians consider avoidance of medication rather than giving a specific medication as a treatment. It has been well studied that benzodiazepines have a high incidence in causing delirium, especially when compared with other sedatives, including dexmedetomidine or propofol (Reade & Finfer; Jones & Pisani. Curr Opin Crit Care. 2012;18[2]:146). Dexmedetomidine is an alpha-2 receptor agonist that also inhibits the release of norepinephrine, and its actions resemble a normal sleep pattern. This may be the reason that patients have a lower incidence of delirium when it is used for both sedation and pain control (Reade & Finer, Pun & Ely). Treating pain has been a slightly controversial area in delirium. To simplify it, using opioids for a sedative purpose and not an analgesic one has been shown to increase the incidence of delirium. However, if it is used correctly to remove pain, then it has been shown to reduce the risk of delirium (Brummel & Girard. Crit Care Clin. 2013;29(1):51).