The Observational Scale of Level of Arousal: a brief tool for assessing and monitoring level of arousal in patients with delirium outside the ICU

Objectives
Altered level of arousal, encompassing drowsiness and hypervigilance, affects at least 10% of acutely unwell patients. Existing scales provide limited coverage of milder changes in level of arousal. We devised the Observational Scale of Level of Arousal (OSLA) to enable more detailed arousal assessment. Here we provide a preliminary case-control study of performance of the OSLA in assessing abnormal level of arousal associated with delirium outside the ICU.MethodsHip fracture patients (N=108, median age=82y) were assessed for delirium pre-and postoperatively using the Confusion Assessment Method and the Delirium Rating Scale-Revised-98. The OSLA has four graded items assessing eye opening, eye contact, posture, and movement (score range 0 [normal arousal] - 15). We assessed the psychometric and diagnostic characteristics of the OSLA. Adjusted linear mixed-effects models were used to explore responsiveness of the OSLA to within-patient change in delirium status.ResultsForty-four patients (40.7%) were diagnosed with delirium. OSLA scores were higher in delirium (pooled median=3, Inter-Quartile Range (IQR)=2-5) compared to no delirium (pooled median=1, IQR=1-2; p-values <0.05 to <0.001). The Area under the Receiver Operating Characteristic curve was 0.82 (95% Confidence Interval (CI)=0.77-0.86). OSLA scores were responsive to change in delirium status (ß=-3.09. S.E.=1.41, p<0.03).ConclusionsThis study provides preliminary evidence supporting use of the OSLA as an instrument for identifying abnormal level of arousal associated with delirium and monitoring this longitudinally. Further validation in larger cohorts with blinded raters is required.