Altered Level of Consciousness: Evidence-Based Management in the Emergency Department (Pharmacology CME)

Download Calculated Decisions PDF

Glasgow Coma Scale

• Introduction
• Points & Pearls
• Why and When to Use, and Next Steps
• Calculator Review Author
• Critical Actions
• Evidence Appraisal
• Calculator Creator
• References
• Related Calculator

Introduction

The Glasgow Coma Scale (GCS) estimates coma severity based on eye, verbal, and motor criteria.

Access Calculator

Points & Pearls

• The Glasgow Coma Scale (GCS) allows providers in multiple settings and with varying levels of training to communicate succinctly about a patient’s mental status.
• The GCS has been shown to have a statistical correlation with a broad array of adverse neurologic outcomes, including brain injury, need for neurosurgery, and mortality.
• The GCS score has been incorporated into numerous guidelines and assessment scores (eg, Advanced Cardiac Life Support, Advanced Trauma Life Support, Acute Physiology and Chronic Health Evaluation I-III, the Trauma and Injury Severity Score, and the World Federation of Neurologic Surgeons Subarachnoid Hemorrhage Grading Scale).

Points to keep in mind:

• Correlation with outcome and severity is most accurate when applied to an individual patient over time; the patient’s trend is important.
• A GCS score of 8 should not be used in isolation to determine whether or not to intubate a patient but does suggest a level of obtundation that should be evaluated carefully.
• Reproducibility of the GCS score can be low; if individual institutions have concerns about an agreement between providers, training and education are available online from the GCS creators at www.glasgowcomascale.org.
• Simpler scores that have been shown to perform as well as the GCS in the prehospital and emergency department setting (for initial evaluation); these are often contracted versions of the GCS itself. For example, the Simplified Motor Score (SMS) uses the motor portion of the GCS only. THE SMS and other contracted scores are less well studied than the GCS for outcomes like long-term mortality, and the GCS has been studied as trended over time, while the SMS has not.

Why and When to Use, and Next Steps

Calculator Review Author

Daniel Runde, MD

Critical Actions

Although it has been adopted widely and in a variety of settings, the GCS score is not intended for quantitative use. Clinical management decisions should not be based solely on the GCS score in the acute setting.

Evidence Appraisal

The Modified Glasgow Coma Scale (the 15-point scale that has been widely adopted, including by the original unit in Glasgow, as opposed to the 14-point original GCS Scale score) was developed to be used in a repeated manner in the inpatient setting to assess and communicate changes in mental status and to measure the duration of coma (Teasdale 1974).

In the acute care setting, the GCS has been shown to have highly variable reproducibility and inter-rater reliability (ie, 56% among neurosurgeons in 1 study, 38% among emergency department physicians in another). In its most common usage, the 3 sections of the scale are often combined to provide a summary of severity. The authors themselves have explicitly objected to the score being used in this way, and analysis has shown that patients with the same total score can have huge variations in outcomes, specifically mortality. A GCS score of 4 predicts a mortality rate of 48% if calculated 1 + 1 + 2 for eye, verbal, and motor components, and a mortality rate of 27% if calculated 1 + 2 + 1, but a mortality rate of only 19% if calculated 2 + 1 + 1 (Healey 2014).

In summary, the Modified Glasgow Coma Scale provides an almost universally accepted method of assessing patients with acute brain damage. Summation of its components into a single overall score results in information loss and provides only a rough guide to severity. In some circumstances, such as early triage of severe injuries, assessment of only a contracted version of the motor component of the scale, as in the SMS, can perform as well as the GCS and is significantly less complicated. However, the SMS may be less informative in patients with lesser injuries.

Calculator Creator

Sir Graham Teasdale, MBBS, FRCP

References

Original/Primary Reference

• Teasdale G, Jennett B. Assessment of coma and impaired consciousness. A practical scale. Lancet. 1974;2(7872):81-84.

Validation

• Moore L, Lavoie A, Camden S, et al. Statistical validation of the Glasgow Coma Score. J Trauma. 2006;60(6):1238-1243; discussion 1243-1244.

Other References

• Teasdale G, Jennett B. Assessment of coma and severity of brain damage. Anesthesiology. 1978;49(3):225-226.
• Teasdale G, Jennett B, Murray L, et al. Glasgow coma scale: to sum or not to sum. Lancet. 1983;2(8351):678.
• Healey C, Osler TM, Rogers FB, et al. Improving the Glasgow Coma Scale score: motor score alone is a better predictor. J Trauma. 2003;54(4):671-678; discussion 678- 680.
• Green SM. Cheerio, laddie! Bidding farewell to the Glasgow Coma Scale. Ann Emerg Med. 2011;58(5):427-430.
• Middleton PM. Practical use of the Glasgow Coma Scale; a comprehensive narrative review of GCS methodology. Australas Emerg Nurs J. 2012;15(3):170-183.
• Yeh DD. Glasgow Coma Scale 40 years later: in need of recalibration? JAMA Surg. 2014;149(7):734.
• Teasdale G. Forty years on: updating the Glasgow Coma Scale. Nurs Times. 2014;110(42):12-16.
• Gill M, Windemuth R, Steele R, et al. A comparison of the Glasgow Coma Scale score to simplified alternative scores for the prediction of traumatic brain injury outcomes. Ann Emerg Med. 2005;45(1):37-42.
• Haukoos JS, Gill MR, Rabon RE, et al. Validation of the Simplified Motor Score for the prediction of brain injury outcomes after trauma. Ann Emerg Med. 2007;50(1):18-24.
• Thompson DO, Hurtado TR, Liao MM, et al. Validation of the Simplified Motor Score in the out-of-hospital setting for the prediction of outcomes after traumatic brain injury. Ann Emerg Med. 2011;58(5):417-425.