Sedation Assessment with Subjective Methods

Individual assessments of sedation, performed at the bedside by nurses or physicians, can be hampered by a lack of objectivity. Guidelines recommend establishing a sedation target and regularly redefining it for each patient, using a validated sedation assessment scale. The use of such a scale is a key component of sedation algorithms [1, 4-6]. It helps in managing agitation and establishing a target level of sedation for medication titration, in order to promptly detect oversedation when the target level is exceeded. All sedation algorithms recommend to use a sedation scale, such as Ramsay Sedation Scale (RSS), Richmond Agitation-Sedation Scale (RASS), and Riker Sedation-Agitation Scale (SAS) [56].

The use of a scale to assess level of consciousness dates to the introduction of a six-point scale by Ramsay et al. (RSS) more than 40 years ago [57]. Nowadays, it continues to be a widely used scale for monitoring sedation in daily practice [58]. Some experts consider that it is more a scale of consciousness than a tool for the measurement of sedation. RSS has been extensively tested but it has never been validated. Moreover, it does not grade agitation. Consequently, this scale is excessively subjective and has poor validity. Many other scales have been proposed [59]; some of them are not validated. They are not recommended for clinical use.

The ideal scoring system should be easy, reliable, sensitive, and with minimal interobserver variability. Moreover, it should give no or minimal additional discomfort to the patient. Even though a complex scoring system is not suitable for the ICU, oversimplification brings risk of neglecting important information. Most of the proposed tools are a compromise between accuracy and time required for evaluation of sedation [60].

Recently developed scales often combine the sedation/arousal domain with an assessment of agitation, like the SAS, the RASS, the Motor Activity Assessment Scale (MAAS), the Observer’s Assessment of Alertness and Sedation (OAAS), the Nursing Instrument for the Communication of Sedation (NICS) [61], and the Bloomsbury Sedation Score (Fig. 18.3).

Unlike other validated instruments, the RASS separates verbal from physical stimulation so that the patient’s level of arousal may be graded according to the potency of the stimulus. Interestingly, RASS is validated also to assess patients’ sedation over time, both in spontaneously breathing/mechanically ventilated and in sedated/nonsedated critically ill patients.

Fig. 18.3 Among the different validated tools for agitation and sedation assessment, each ICU should collegially choose the one to use

Other multiple-item sedation scales are described in literature. The Adaptation to the Intensive Care Environment scale (ATICE) consists of five items [62]: awareness and comprehension combined in a “Conscious” domain; calmness, ventilator synchrony, and facial relaxation are combined in a “Tolerance” domain. As for ATICE, the Minnesota Sedation Assessment Tool (MSAT) evaluates the level of consciousness of patients receiving invasive mechanical ventilation. It measures arousability, spontaneous muscle activity, and global sedation quality. The Vancouver Interaction and Calmness Scale (VICS) consists of two five-item subscales quantifying separately calmness and interaction with operators. These more complex scoring systems are usually adopted in clinical trials to evaluate a new drug or a new objective tool for sedation assessment, whereas in daily practice, easily applied scores are usually preferred.