Measuring quality of sedation in adult mechanically ventilated critically ill patients: the Vancouver Interaction and Calmness Scale

There are no reliable, valid, and responsive scales to measure the quality of sedation in adult critically ill patients. Our objective was to develop a summated rating scale with these properties and to define the minimal cli nically important difference (MCID). We developed and tested the scale in a n 18-bed medical-surgical intensive care unit (ICU) (12-bed acute and 6-bed subacute unit). Following identification of relevant domains and item deri vation, 116 observations were made on 38 patients, psychometric properties and interrater reliability were assessed to allow item reduction. The final scale consisted of two five-item subscales quantifying calmness and intera ction along a continuum from 5 to 30 points. Interrater reliability was 0.8 9 and 0.90: internal consistency was 0.95 for both subscales. To test const ruct validity, MCID, and responsiveness 302 observations were made on 54 pa tients. Construct validity: calmness score vs. need for further interventio n to make the patient calm (R = -0.82, P < 0.001); interaction score discri minated between acute vs. subacute units, mean scores 15.28 +/- 8.26 vs. 23 .54 +/- 7.42, mean difference 8.27 (95% CI - 10.32 to -6.22); MCID - 2.2 an d 2.5 for the calmness and interaction subscales; Guyatt's responsiveness s tatistics - 1.4 and 2.3. The Vancouver Interaction and Calmness Scale (VICS ) is reliable, valid, and responsive. (C) 2000 Elsevier Science Inc. All ri ghts reserved.