The lack of consensus or accepted definition for light sedation presents challenges to critical care practitioners seeking to follow guidelines related to pain, agitation and delirium.
Comfort and sedation are central components of patient care in an intensive care unit (ICU), and the most recent guidelines recommend avoiding oversedation and targeting light sedation for critically ill adult patients receiving mechanical ventilation.
Light sedation is associated with better patient outcomes, but the degree of wakefulness needed to accurately report pain or identify delirium remains unclear. Patients receiving intermittent or too little sedation may experience discomfort, pain or agitation, while those who are deeply sedated are unable to participate in their care and are at greater risk for delirium and other negative outcomes.
Researchers at Maine Medical Center in Portland conducted a pilot study seeking to address some of the uncertainties related to accurately describing sedation levels.
"Prospective Validation of Sedation Scale Scores That Identify Light Sedation: A Pilot Study" sought to determine the scores on the Sedation-Agitation Scale (SAS) and the Richmond Agitation-Sedation Scale (RASS) that best describe patients' ability to follow voice commands. The study is published in American Journal of Critical Care.
They found that scores best associated with the ability to follow at least three commands were a SAS score of 4 and a RASS score of -1, which are higher than the commonly recommended thresholds for each assessment tool.
The degree of wakefulness, and the potential implications of our pilot study reach beyond the depth of sedation titration to the level of wakefulness needed for accurate assessments and important discussions with patients. A consistent and better understanding of what light sedation really means may help us reliably target sedation levels associated with improved patient outcomes."
Richard Riker, MD, co-author, director of medical critical care
To gather the data, pairs of trained investigators evaluated a patient's SAS and RASS scores and the ability to follow commands before and up to two hours after sedation was lightened. They conducted assessments of 25 patients, with 50 assessments before sedation was lightened and 46 after sedation was lightened.
Patients were asked to comply with four simple voice commands, such as showing two fingers and wiggling toes. They were also asked to open or close their eyes for three seconds and to squeeze and release the evaluator's hand. While one evaluator conducted the assessment, a second evaluator observed patient responses and timed eye contact.
Patients exhibiting SAS and RASS scores at or above the thresholds associated with light sedation may better cooperate with their caregivers, participate in their care and respond accurately when pain, delirium or patient preferences are being assessed.
The authors call for further research in different settings with larger patient populations. If validated, their findings could have major implications, leading to a shift in titration targets that use these sedation scales and affecting how delirium and pain are assessed.
Brown, C., et al. (2022) Prospective Validation of Sedation Scale Scores That Identify Light Sedation: A Pilot Study. American Journal of Critical Care. doi.org/10.4037/ajcc2022437.