Pediatric Critical Care Pediatric illness severity measures predict delirium in a pediatric intensive care unit Jan N. M. Schieveld, MD, PhD; Richel Lousberg, MSc, PhD; Eline Berghmans, MD; Inge Smeets, MSc; Piet L. J. M. Leroy, MD; Gijs D. Vos, MD, PhD; Joost Nicolai, MD; Albert F. G. Leentjens, MD, PhD; Jim van Os, MD, PhD, MRCPsych D elirium is a serious neuro- psychiatric disorder caused by a general medical condi- tion or its treatment and characterized by an acute onset, fluctuat- ing disturbances of consciousness, and cognitive disturbances (1). It is fre- quently seen in critically ill adult pa- tients, associated with a poorer prognosis of the primary disorder, longer hospital stay, higher mortality rate, and a worse functional outcome, especially in patients who are also mechanically ventilated (2, 3). In critically ill adult patients, inci- dences have been reported ranging from 10 – 30% in a general hospital setting, to 50% in postoperative patients, and up to 80% in the terminally ill. The systematic screening for delirium and its appropriate treatment in critical illness were recently included in the clinical practice guide- lines for sedatives and analgesia of the Society of Critical Care Medicine (4). The search for risk factors is therefore a key concern. Known risk factors in adult and elderly patients are: severe illness, any medical procedure, exposure to medica- tion, notably polypharmacy, malnutri- tion, and dehydration (5, 6). There is emerging literature on pedi- atric delirium (PD), as evidenced by, for example, the papers from Sikich and Le- rhman (7) regarding the PAED (Pediatric Anesthesia Emerging Delirium) scale and of Kain, Caldwell–Andrews and col- leagues (8) regarding treatment of peri- operative discomfort in children. These last authors reported a reduction of post- operative emerging delirium in children from 24% in the control group to just 10% in the intervention group. However, PD in critical illness in a PICU (pediatric intensive care unit) context is an under- studied area. Two papers reported PD in- cidences of at least 4% (9) and 4.5% (10). However, little is known about risk fac- tors for this condition. Given the fact that many routine illness severity measures are used in pediatrics, an efficient way to expand the possibilities to make a quan- titative judgment about the risk of PD is to focus on such existing measures in the first instance. The aim of the current study, therefore, was to assess whether two routinely used illness severity indica- tors, the Pediatric Index of Mortality (PIM) and the Pediatric Risk of Mortality (PRISM II), are of value in the risk assess- From the Department of Psychiatry (JNMS, RL, EB, IS, AFGL, JvO); Department of Pediatrics (PLJML, GDV), Division of Pediatric Intensive Care; Department of Neu- rology (JN), University Hospital Maastricht, Maastricht, The Netherlands; Division of Psychological Medicine (JvO), Institute of Psychiatry, London, UK. Dr. van Os is a speaker with or has received grant support from Eli Lilly, Lundbeck, Organon, BMS, GSK, Janssen-Cilag, and Astra Zeneca. Dr. Leentjens par- ticipated in research for and is on the advisory board of a study from Boehringer Ingelheim. The remaining authors have not disclosed any potential conflicts of interest. For information regarding this article, E-mail: jan.schieveld@mumc.nl Copyright © 2008 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins DOI: 10.1097/CCM.0b013e31817cee5d Context: Delirium in children is a serious but understudied neuropsychiatric disorder. So there is little to guide the clinician in terms of identifying those at risk. Objective: To study, in a pediatric intensive care unit (PICU), the predictive power of widely used generic pediatric mortality scoring systems in relation to the occurrence of pediatric delirium (PD). Design and Methods: Four-year prospective observational study, 2002–2005. Predictors used were the Pediatric Index of Mortality (PIM) and Pediatric Risk of Mortality (PRISM II). Setting: A tertiary 8-bed PICU in the Netherlands. Patients: 877 critically ill children who were acutely, nonelec- tively, and consecutively admitted. Main Outcome Measure: Pediatric delirium. Main Results: Out of 877 children with mean age 4.4 yrs, 40 were diagnosed with PD (Cumulative incidence: 4.5%), 85% of whom (versus 40% with nondelirium) were mechanically venti- lated. The area under the curve was 0.74 for PRISM II and 0.71 for the PIM, with optimal cut-off points at the 60th centile (PRISM: sensitivity: 76%; specificity: 62%; PIM: sensitivity: 82%; specific- ity: 62%). A PRISM II or PIM score above the 60th centile was strongly associated with later PD in terms of relative risk (PRISM II: risk ratio  4.9; 95% confidence interval: 2.3–10.1; PIM: RR  6.7; 95% confidence interval: 3.0 –15.0). Given the low incidence of PD, values for positive predictive value were lower (PRISM II: 8.3%; PIM: 8.9%, rising to, respectively, 10.1% and 10.6% in mechanically ventilated patients) and values for negative predic- tive value were higher (PRISM II: 98.3%; PIM: 98.7%). Limitations: Given the relatively low incidence of delirium, a low detection rate biased toward the most severe cases cannot be excluded. Conclusions: Given the fact that PIM and PRISM II are widely used mortality scoring instruments, prospective associations with PD suggest additional value for ruling in, or out, patients at risk of PD. (Crit Care Med 2008; 36:1933–1936) KEY WORDS: Pediatric delirium; risk factors; predicting delirium; Pediatric Index of Mortality and Pediatric Risk of Mortality II scores; receiving operating characteristics curves and areas un- der the curve; positive predictive value; negative predictive value; operating room; pediatric intensive care unit 1933 Crit Care Med 2008 Vol. 36, No. 6