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

doi:10.1016/S0895-4356(00)00208-0

Journal of Clinical Epidemiology

Volume 53, Issue 9, September 2000, Pages 908-919

https://doi.org/10.1016/S0895-4356(00)00208-0 Get rights and content

Abstract

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 clinically important difference (MCID). We developed and tested the scale in an 18-bed medical–surgical intensive care unit (ICU) (12-bed acute and 6-bed subacute unit). Following identification of relevant domains and item derivation, 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 interaction along a continuum from 5 to 30 points. Interrater reliability was 0.89 and 0.90; internal consistency was 0.95 for both subscales. To test construct validity, MCID, and responsiveness 302 observations were made on 54 patients. Construct validity: calmness score vs. need for further intervention to make the patient calm (R = −0.82, P < 0.001); interaction score discriminated 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 and 2.5 for the calmness and interaction subscales; Guyatt's responsiveness statistics - 1.4 and 2.3. The Vancouver Interaction and Calmness Scale (VICS) is reliable, valid, and responsive.

Introduction

Ensuring a calm state is an integral part of caring for critically ill patients, and sedative agents are routinely used to achieve this goal. Although sedation scales for use in the critically ill have been published, these have not been shown to be reliable, valid, or responsive [1]. However, without such a measurement tool one cannot assess the need for sedation, set goals for therapy, evaluate outcomes, or consistently communicate this information to others. Therefore, our objective was to develop a scale to meet these needs for adult, critically ill, mechanically ventilated patients. The specific objective for scale development and testing was to derive a scale that would 1) capture and measure the intended goals or unwanted effects of sedation in this population, 2) be able to measure differences between individual (i.e., be discriminative) and measure change in an individual over time (i.e., be evaluative), 3) be short enough in length to allow routine clinical use at the bedside (minimal respondent burden), and 4) provide interval level measurement to allow parametric analysis of derived data. As well, we wished to identify the minimal clinically important difference (MCID) of the scale. The Vancouver Interaction and Calmness Scale (VICS), which was finally developed, consists of two subscales measuring calmness and interaction, respectively.

Section snippets

Study organization

The VICS was developed and tested in four phases. Phase 1 involved identifying relevant domains, deriving an item pool, developing a questionnaire, and testing its face and content validity. Phase 2 involved testing the reliability of the questionnaire items retained from Phase 1 together with item, factor, and multitrait scaling analyses followed by item reduction to produce the final VICS scale. Phase 3 involved testing the VICS for validity, responsiveness, and MCID. The questionnaire items

Identification of domains and item pool, face and content validity

We hypothesized that the quality of sedation may be measured within two domains describing patient appearance (calmness) and the quality of patient function in relation to their caregiver (interaction). Fifteen items were initially derived from these two domains. Face and content validity were endorsed for 14 items by informal assessment and preliminary clinical testing. The remaining item (“wakes up easily”) was removed prior to starting Phase 2. Thus, at the end of Phase 1 the questionnaire

Discussion

The VICS is the first published scale to be documented as a reliable, valid, and responsive tool with which to measure the quality of sedation in mechanically ventilated adult critically ill patients. The VICS meets the minimum psychometric standards for a summated rating scale with high internal consistency and interrater reliability. Construct validity was demonstrated in three ways. First, the calmness score correlated with the need for intervention. Second, the interaction score

Acknowledgements

We would like to thank the nursing staff of the Intensive Care Unit at Vancouver General Hospital for their support of this study.

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

Abstract

Introduction

Section snippets

Study organization

Identification of domains and item pool, face and content validity

Discussion

Acknowledgements

J Clin Epidemiol

J Chron Dis

Lancer

Br J Anaesth

Intensive Crit Care Nurs

J Pediatr Surg

J Clin Epidemiol

J Chron Dis

J Clin Epidemiol

Beyond the Ramsay scaleneed for a validated measure of sedating drug efficacy in the intensive care unit

Crit Care Med.

Methods of constructing health measures

Psychometric Theory

Factor analysis

Coefficient alpha and the internal structure of tests

Psychometrika

Intraclass correlationsuses in assessing rater reliability

Psychol Bull

Measurement of health status. Ascertaining the minimally clinically important difference

Controlled Clin Trials

Comparative measurement sensitivity of short and longer health status instruments

Med Care

Health Measurement Scales. A Practical Guide to Their Development and Use

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