Depth of sedation in children undergoing computed tomography: validity and reliability of the University of Michigan Sedation Scale (UMSS)

Background. Safe care of sedated children requires ongoing assessment of the depth of sedation to permit early recognition of progression to over-sedation. This study evaluated the validity and reliability of the University of Michigan Sedation Scale (UMSS) as a measure of sedation during procedures. The UMSS is a simple observational tool that assesses the level of alertness on a five-point scale ranging from 1 (wide awake) to 5 (unarousable with deep stimulation). Methods. Thirty-two children aged 4 months to 5 yr (mean 1.5 yr), sedated for computed tomography (CT), were studied prospectively. The CT nurse assessed sedation using the UMSS before sedative administration and every 10 min thereafter. The child was video-taped during each assessment, and segments were edited and their order was randomized. Four nurses blinded to sedative administration viewed the segments and scored sedation using the UMSS. One of these nurses also scored sedation using a visual analogue scale (VAS) and another using the Observer's Assessment of Alertness/Sedation Scale (OAAS). To examine the test-retest reliability, 75 randomly selected video segments were viewed and scored on a second occasion. Results. Changes in scores from baseline to discharge supported construct validity (P<0.0001). Criterion validity was demonstrated by significant correlations between the UMSS and the VAS and OAAS. There was good interobserver agreement between blinded observers' scores for each level of sedation and at discharge, and between blinded observers and the CT nurse for scores of 0 and 1 (lighter levels of sedation), but less agreement for scores 2 and 3 (deeper sedation) and discharge scores. Test-retest reliability was supported by agreement in the observers' UMSS scores. Conclusion. The UMSS is a simple, valid and reliable tool that facilitates rapid and frequent assessment and documentation of depth of sedation in children.