Validating the Sedation-Agitation Scale with the Bispectral Index and Visual Analog Scale in adult ICU patients after cardiac surgery

Intensive Care Med. 2001 May;27(5):853-8. doi: 10.1007/s001340100912.


Objective: To validate the Sedation-Agitation Scale (SAS) with the Visual Analog Scale (VAS) and Bispectral Index (BIS) in adult ICU patients after cardiac surgery.

Design: Prospective study comparing blinded evaluations of the SAS, VAS and BIS.

Setting: Forty-two-bed multidisciplinary ICU.

Patients and participants: Convenience sample of 39 adults after cardiac surgery.

Measurements and results: Bispectral Index 3.2 was continuously recorded using the Aspect A-1000 and evaluators were blinded to this value. The bedside nurse and a trained researcher independently rated wakefulness using a 100 mm VAS upon patient arrival on the ICU, at first awakening, when ventilator weaning was started and after extubation; the researcher also evaluated patients using SAS. Upon arrival on the ICU, the median SAS score was 2 (interquartile range = 1-3), the mean VAS was 26+/-30 and the mean BIS was 70+/-16. Twenty-four patients underwent a trial of weaning from mechanical ventilation with a SAS of 4 (IQR = 4), VAS of 86+/-12 and BIS of 87+/-10. SAS correlated well with VAS performed by one researcher (r = 0.91, p < 0.001) or by 19 different bedside nurses (r = 0.43, p < 0.001) and with BIS 3.2 (r = 0.60, p < 0.001). The correlation between SAS and BIS was reduced in patients with above average electromyogram (EMG) power. As a measure of construct validity, significant differences were noted for the BIS, SAS, VAS and EMG between ICU arrival and extubation (all p < 0.001).

Conclusions: Sedation-Agitation Scale and BIS are valid measures of wakefulness after cardiac surgery, but EMG interference may affect the accuracy of BIS for a small percentage of patients not receiving neuromuscular blockade.

Publication types

  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Aged
  • Conscious Sedation*
  • Critical Care / methods
  • Electroencephalography
  • Female
  • Heart Diseases / surgery
  • Humans
  • Male
  • Pain Measurement / standards*
  • Pain, Postoperative*
  • Prospective Studies
  • Severity of Illness Index
  • Ventilator Weaning*