Diagnosing delirium in critically ill children: Validity and reliability of the Pediatric Confusion Assessment Method for the Intensive Care Unit

Abstract

Objective: To validate a diagnostic instrument for pediatric delirium in critically ill children, both ventilated and nonventilated, that uses standardized, developmentally appropriate measurements.

Design and setting: A prospective observational cohort study investigating the Pediatric Confusion Assessment Method for Intensive Care Unit (pCAM-ICU) patients in the pediatric medical, surgical, and cardiac intensive care unit of a university-based medical center.

Patients: A total of 68 pediatric critically ill patients, at least 5 years of age, were enrolled from July 1, 2008, to March 30, 2009.

Interventions: None.

Measurements: Criterion validity including sensitivity and specificity and interrater reliability were determined using daily delirium assessments with the pCAM-ICU by two critical care clinicians compared with delirium diagnosis by pediatric psychiatrists using Diagnostic and Statistical Manual, 4th Edition, Text Revision criteria.

Results: A total of 146 paired assessments were completed among 68 enrolled patients with a mean age of 12.2 yrs. Compared with the reference standard for diagnosing delirium, the pCAM-ICU demonstrated a sensitivity of 83% (95% confidence interval, 66-93%), a specificity of 99% (95% confidence interval, 95-100%), and a high interrater reliability (κ = 0.96; 95% confidence interval, 0.74-1.0).

Conclusions: The pCAM-ICU is a highly valid reliable instrument for the diagnosis of pediatric delirium in critically ill children chronologically and developmentally at least 5 yrs of age. Use of the pCAM-ICU may expedite diagnosis and consultation with neuropsychiatry specialists for treatment of pediatric delirium. In addition, the pCAM-ICU may provide a means for delirium monitoring in future epidemiologic and interventional studies in critically ill children.

Figure 1

The Confusion Assessment Method for the Intensive Care Unit uses the four cardinal features for delirium diagnosis. The diagnosis of delirium requires acute change or fluctuation of mental status (feature 1) with inattention (feature 2) and either altered level of consciousness (feature 3) or disorganized thinking (feature 4). A similar framework was used for the Pediatric Confusion Assessment Method for the Intensive Care Unit. Adapted from Ely et al (31).

Figure 2

Pediatric Confusion Assessment Method for the Intensive Care Unit: a practical time-saving approach to bedside implementation. A, For this investigation, we performed all features with each patient evaluation. However, in the out-of-study setting, the arrows inserted onto this figure indicate the practical approach by which bedside nurses and physicians can streamline the clinical examination of a patient. For example, if a patient is feature 1-negative or feature 2-negative, then the assessment for delirium is complete, because the patient does not have delirium. B, Delirium diagnosis using the Pediatric Confusion Assessment Method for the Intensive Care Unit requires positive features 1 and 2 with either positive feature 3 or 4. ASE, attention screening examination; RASS, Richmond Agitation Sedation Scale.

Figure 3

Consciousness, as defined by Plum and Posner (39), is comprised of two components, including arousal and content. In this investigation, the assessment of these two components of consciousness was accomplished using 1) a sedation/arousal scale (Richmond Agitation Sedation Scale [RASS]) (37) and 2) a delirium assessment tool (Pediatric Confusion Assessment Method for the Intensive Care Unit [pCAM-ICU]). Other validated instruments are available for the arousal assessment, including the Motor Activity Assessment Scale (MMAAS)(59) and the State Behavioral Scale (SBS)(60). To date, there are no other validated instruments available for mechanically ventilated (ie, nonverbal) children by which intensive care unit personnel who do not have formal psychiatric training can complete the delirium assessment.

Figure 4

The Richmond Agitation Sedation Scale (RASS)(37, 61) was used to assess arousal state of patients before content assessment with the Pediatric Confusion Assessment Method for the Intensive Care Unit (pCAM-ICU). Patients who respond to verbal stimulation (RASS ≥−3) can be evaluated for delirium. Patients who are unable to respond to verbal stimulation are either RASS of −4 or −5 and are considered comatose and unable to undergo delirium diagnosis.

Figure 5

CONSORT figure showing patient flow of screening, exclusions, and inclusions for the investigation. One patient was determined on initial assessment by the Diagnostic and Statistical Manual of Mental Disorders reference rater to have cognition <5 yrs after consent was obtained. No further evaluation was completed and that patient was excluded. PICU, pediatric intensive care unit.

Figure 6

Positive Pediatric Confusion Assessment Method for the Intensive Care Unit (pCAM-ICU) features correlate to delirium diagnosis. This box plot demonstrates on the x-axis the category of delirium rating (no delirium, subsyndromal delirium, and full delirium) by the psychiatry (Diagnostic Statistical Manual of Mental Disorders [DSM]) reference standard rater. For each of these categories, the number of positive pCAM-ICU features (median in bold, interquartile ranges as the limits of the box, and fifth/95th percentiles by the whiskers) when assessed by the pCAM-ICU team is shown on the y-axis. Thus, patients diagnosed with no delirium by the DSM reference rater had a median of zero positive pCAM-ICU features; those diagnosed with subsyndromal had a median of two positive pCAM-ICU features; and those diagnosed with full delirium by the DSM reference rater had a median of three positive pCAM-ICU features.