Association between intraoperative electroencephalographic suppression and postoperative mortality.
BACKGROUND
Low bispectral index values frequently reflect EEG suppression and have been associated with postoperative mortality. This study investigated whether intraoperative EEG suppression was an independent predictor of 90 day postoperative mortality and explored risk factors for EEG suppression.


METHODS
This observational study included 2662 adults enrolled in the B-Unaware or BAG-RECALL trials. A cohort was defined with >5 cumulative minutes of EEG suppression, and 1:2 propensity-matched to a non-suppressed cohort (≤5 min suppression). We evaluated the association between EEG suppression and mortality using multivariable logistic regression, and examined risk factors for EEG suppression using zero-inflated mixed effects analysis.


RESULTS
Ninety day postoperative mortality was 3.9% overall, 6.3% in the suppressed cohort, and 3.0% in the non-suppressed cohort {odds ratio (OR) [95% confidence interval (CI)]=2.19 (1.48-3.26)}. After matching and multivariable adjustment, EEG suppression was not associated with mortality [OR (95% CI)=0.83 (0.55-1.25)]; however, the interaction between EEG suppression and mean arterial pressure (MAP) <55 mm Hg was [OR (95% CI)=2.96 (1.34-6.52)]. Risk factors for EEG suppression were older age, number of comorbidities, chronic obstructive pulmonary disease, and higher intraoperative doses of benzodiazepines, opioids, or volatile anaesthetics. EEG suppression was less likely in patients with cancer, preoperative alcohol, opioid or benzodiazepine consumption, and intraoperative nitrous oxide exposure.


CONCLUSIONS
Although EEG suppression was associated with increasing anaesthetic administration and comorbidities, the hypothesis that intraoperative EEG suppression is a predictor of postoperative mortality was only supported if it was coincident with low MAP.


BACKGROUND
NCT00281489 and NCT00682825.
Department of Anesthesiology, Washington University in St Louis School of Medicine, Campus Box 8054, 660 S. Euclid Ave., St Louis, MO 63110, USA.
M
M
Willingham
Department of Anesthesiology, Washington University in St Louis School of Medicine, Campus Box 8054, 660 S. Euclid Ave., St Louis, MO 63110, USA.
A
A
Ben Abdallah
Department of Anesthesiology, Washington University in St Louis School of Medicine, Campus Box 8054, 660 S. Euclid Ave., St Louis, MO 63110, USA.
S
S
Gradwohl
Department of Anesthesiology, Washington University in St Louis School of Medicine, Campus Box 8054, 660 S. Euclid Ave., St Louis, MO 63110, USA.
D
D
Helsten
Department of Mathematics, Washington University in St Louis, Campus Box 1146, One Brookings Drive, St Louis, MO 63130, USA.
N
N
Lin
Department of Anesthesia and Perioperative Medicine, University of Manitoba, 2nd Floor, Harry Medovy House, 671 William Ave., Winnipeg, Canada MB R3E 0Z2.
A
A
Villafranca
Department of Anesthesia and Perioperative Medicine, University of Manitoba, 2nd Floor, Harry Medovy House, 671 William Ave., Winnipeg, Canada MB R3E 0Z2.
E
E
Jacobsohn
Department of Anesthesiology, Washington University in St Louis School of Medicine, Campus Box 8054, 660 S. Euclid Ave., St Louis, MO 63110, USA.
M
M
Avidan
Department of Anesthesiology, Washington University in St Louis School of Medicine, Campus Box 8054, 660 S. Euclid Ave., St Louis, MO 63110, USA heikokaiser@me.com.
H
H
Kaiser
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018681:Anesthetics, General / Q000494:pharmacology; D001794:Blood Pressure / Q000502:physiology; D015897:Comorbidity; D003243:Consciousness / Q000187:drug effects / Q000502:physiology; D004569:Electroencephalography / Q000187:drug effects / Q000379:methods; D008350:Manitoba / Q000453:epidemiology; D016343:Monitoring, Intraoperative / Q000379:methods; D011183:Postoperative Complications / Q000401:mortality; D011379:Prognosis; D018570:Risk Assessment / Q000379:methods; D014481:United States / Q000453:epidemiology; D015337:Multicenter Studies as Topic; D016032:Randomized Controlled Trials as Topic
D018681:Anesthetics, General
anaesthesia, general; comorbidity; deep sedation; electroencephalography; risk assessment