Assessment and Diagnostic Tools

Although a thorough review of the patient's chart is important, a retrospective review of the medical record is an imprecise way of establishing the diagnosis of delirium (Johnson et al. 1992). The consultant also needs to review the patient's history and pertinent laboratory and radiographic studies and obtain information from the patient's family about baseline behavior, mood, and cognitive function. An astute history and physical examination, review of medications, and targeted laboratory tests should be adequate to assess for most potential causes of delirium. Further testing should be tailored to the specific clinical situation. A thorough review of a patient's current and recent medications is mandatory. Patients often receive a variety of psychotropic medications before psychiatric consultation is requested, and these medications can precipitate or exacerbate delirium. Attention should be given to the type, dosage, and recent addition or discontinuation of medications, with emphasis on sedative-hypnotic, opioid, and psychotropic drugs (Maldonado 2008a). Lumbar puncture and examination of the cerebro-

spinal fluid should be done whenever CNS infection is suspected. Brain imaging may be most useful with new focal neurological signs or a history of head trauma (Inouye 1994). In patients with no focal neurological signs, neuroimaging is unlikely to be helpful. Serious medical disease is a better predictor of the development of delirium than is the presence of abnormal brain imaging (Kishi et al. 1995).

In an early clinical study of delirium in children and adolescents, patients with acute CNS disorders of toxic, metabolic, traumatic, and other types of conditions considered associated with delirium were compared with other hospitalized children who were not suspected of having a CNS disorder (Prugh et al. 1980). The patients and controls were administered a battery of tests of neuropsychological function, including double simultaneous stimulation, synkinesia, astereognosis, graphesthesia, right-left orientation, examiner transposition orientation, identification of common objects, drawing of geometric shapes, modified Bender test, drawing of concentric circles, and subtraction of serial 7s. These tests were done during the acute episode of delirium and again after recovery. Bedside EEG was performed on all the patients. At the end of the study, patients with delirium could be distinguished from the controls by abnormalities on electroen-cephalographic and neuropsychological parameters (Prugh et al. 1980).

Generalized slowing of background activity on EEG was once considered characteristic of delirium, but it is nonspecific and not useful in distinguishing subjects with and without delirium (Inouye 1994). Occasionally, abnormal occipital delta waves that are blocked by eye opening are seen in patients with more benign conditions, which may be useful in differentiating delirium associated with acute but benign febrile illness from more serious encephalitis and encephalopathy (Onoe et al. 2003).

Various published instruments are used to diagnose delirium and assess symptom severity in adults. They are usually structured to distinguish delirium from dementia, depression, or schizophrenia. Most consist of operationalized diagnostic criteria from DSM-IV-TR or the International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10; World Health Organization 1992), usually in the form of a checklist, and incorporate information from patient observation and the medical record. Their breadth of symptom coverage varies, as does their applicability. No unique diagnostic criteria or rating instruments have been developed specifically to aid in diagnosing delirium in the pediatric population.

Using a standardized scale is of value in the diagnostic process, evaluation of treatment, and assessment of outcome. Some scales are designed for nursing or other nonphysician staff to administer when only a brief screening instrument is needed. Education of ICU staff about delirium and the use of the screening instrument is required for any instrument to be useful (Devlin et al. 2007). More quantifiable instruments for diagnosis and treatment evaluation are usually longer and more detailed and typically require the expertise of a psychiatrist.

For many years, brief cognitive tests, such as the Mini-Mental State Examination (Folstein et al. 1975), were used to diagnose delirium. Although these tests documented cognitive abnormalities, they could not distinguish between delirium and dementia (Robertsson 1999) and they are not suitable for younger children. The Children's Orientation and Amnesia Test (COAT) is designed to assess cognition in pediatric patients but has not been used to assess for delirium (Ruijs et al. 1992).

The Confusion Assessment Method (CAM) is based on DSM-III-R criteria for delirium. Three of four criteria—acute onset, fluctuating course, inattention, and disorganized thinking—are required to make the diagnosis of delirium (Ely et al. 2001). The CAM is the basis of the CAM-ICU method for adults in the ICU (Ely et al. 2001). The CAM-ICU and the Intensive Care Delirium Screening Checklist (ICDSC; Bergeron et al. 2001) were both designed to be applicable for intubated patients in the ICU (Polderman 2007). Using these two instruments, delirium was found to be an independent risk factor for adverse outcome and increased length of stay in the ICU (Polderman 2007). A pCAM-ICU version for assessing delirium in pediatric patients is under development (Bartoo 2009).

The Delirium Rating Scale (DRS), the most widely used scale for diagnosing delirium, has been translated into many languages (Trzepacz et al. 1988) and has been studied in children and adolescents (Turkel et al. 2003). Individual item scores and the total DRS scores are the same in adult and pediatric patients (Turkel et al. 2003). The DRS was revised in 1998 (DRS-R-98) (Trzepacz et al. 2001). The DRS appears to be more useful in patients younger than age 3, whereas the DRS-R-98 is preferable for older children and adolescents.

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