Utility of the Richmond Agitation-Sedation Scale in evaluation of acute neurologic dysfunction in the intensive care unit
Multiorgan failure is common in the intensive care unit (ICU) setting with increasing mortality with greater number of dysfunctional organs. An objective assessment of the severity of individual organ dysfunction is essential for clinical care and research. Severity of illness scoring systems in the ICU have been developed over the past 30 years and are currently used widely to risk stratify patients, predict hospital mortality, perform outcome based research, assess resource utilization and measure performance improvement in patient care (1,2). The Sequential Organ Failure Assessment (SOFA) was initially devised in 1994 by an expert panel to describe severity of organ dysfunction in patients with sepsis, and has subsequently been validated as a useful marker for predicting outcomes in medical and surgical ICUs (1). Each of the six organ systems (respiratory, cardiovascular, renal, hepatic, neurologic, coagulation) are assigned values between 0 (normal function) and 4 (significant dysfunction), total scores can range from 0 to 24 (1). In the recent Third International Consensus Definition for Sepsis and Septic shock (Sepsis-3), organ dysfunction due to infection is identified as an acute change in the total SOFA score by ≥2 points. The task force has also developed quick SOFA (qSOFA) model consisting of clinical criteria (systolic blood pressure of 100 mmHg or less, respiratory rate of 22/min or greater, altered mental status) for rapid bedside identification of patients at risk of worse outcomes (3). Serial SOFA score assessments in the first 48 hours after ICU admission correlate well with mortality (4). When compared to other organ dysfunction scores, SOFA has been shown to be consistent and an accurate predictor of mortality (1). Neurologic component of the SOFA score is derived from the Glasgow Coma Scale (GCS). GCS was first developed in 1974 by Teasdale and Jennett as a tool to objectively assess consciousness in patients with head injuries and offer a standardized approach that providers could utilize to monitor neurologic exam (5). Verbal, motor and eye response in the GCS define level of consciousness. Currently, the GCS is used in a broad spectrum of medical and surgical ICU patients and is an integral part of severity of illness and prognostic scoring systems such as the Acute Physiology and Chronic Health Evaluation (APACHE), Simplified Acute Physiology Score (SAPS), SOFA, Multiple Organ Dysfunction Score (MODS) and Logistic Organ Dysfunction Score (LODS) (1). However, several limitations of using the GCS in the critically ill population have been identified; including low interobserver reliability, inability to assess verbal component in tracheally intubated patients, weak prognostic value and erroneous estimation by providers due to lack of standardized assessments (6,7). The Richmond Agitation-Sedation Scale (RASS) is used for routine neurological assessments in the ICU, especially in patients without traumatic brain injury. RASS is a 10 point scale with discrete criteria, with four levels of agitation (+1 to +4), one level for calm and alert state (0), and 5 levels of sedation (−1 to −5) (8). It was initially devised to assist with administration and titration of sedation and analgesia in the ICU and has been shown to have high interobserver reliability, and consistency in estimating the patient’s level of consciousness. It is easy to recall and can be administered in less than a minute with a simple three step sequence (observation, response to verbal stimulation and response to physical stimulation) (8-10). Sedation assessments based on the RASS are recommended by critical care consensus guidelines (10).