Sensitivity to volatile anesthetics in patients with dementia: a case-control analysis.
BACKGROUND
Patients with dementia are thought to be more sensitive to anesthesia, although volatile anesthetic requirement has not specifically been evaluated in this population. We tested the hypothesis that patients with dementia having non-cardiac surgery have a lower ratio of bispectral index (BIS) to minimal alveolar concentration (MAC) during the five minutes immediately preceding incision, thus exhibiting deeper hypnotic levels at a given MAC fraction.


METHODS
We obtained records from our database registry on patients who had volatile general anesthesia during their most recent operation. We excluded patients premedicated with midazolam. Patients with dementia were identified and their diagnosis was confirmed by chart review. Each patient with dementia was successfully matched with a maximum of five patients without dementia using a multivariate nearest-neighbor distance-matching algorithm restricted to the following criteria: American Society of Anesthesiologists physical status, age, five-minute pre-incision time-weighted average (TWA) estimated effect-site concentration of propofol and fentanyl, and use of remifentanil. Our primary outcome was the TWA BIS-to-MAC ratio during the five minutes immediately preceding incision.


RESULTS
We analyzed 31 patients with dementia matched with 151 patients without dementia. Median [quartiles] TWA BIS-to-MAC ratios for the matched patients were 85 [73, 100] for the patients with dementia and 78 [73, 84] for the patients without dementia. The percent difference in mean BIS-to-MAC ratios between patients with dementia and patients without dementia was 9% (95% confidence interval: -9% to 29%) (P = 0.35, Wald test).


CONCLUSIONS
Our results do not support the hypothesis that patients with dementia are more sensitive to volatile anesthetics than patients without dementia.
Anesthesiology Institute, Cleveland Clinic Foundation, Cleveland, OH, USA.
Silvia
S
Perez-Protto
Mariya
M
Geube
Daniel
D
Ontaneda
Jarrod E
JE
Dalton
Andrea
A
Kurz
Daniel I
DI
Sessler
D000368:Aged; D000369:Aged, 80 and over; D000768:Anesthesia, General / Q000379:methods*; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000494:pharmacology*; D016022:Case-Control Studies; D056805:Consciousness Monitors; D003704:Dementia / Q000150:complications*; D005283:Fentanyl / Q000008:administration & dosage; D006801:Humans; D008875:Middle Aged; D015999:Multivariate Analysis; D010880:Piperidines / Q000008:administration & dosage; D015742:Propofol / Q000008:administration & dosage; D000077208:Remifentanil; D012189:Retrospective Studies
D018685:Anesthetics, Inhalation; D010880:Piperidines; D000077208:Remifentanil; D005283:Fentanyl; D015742:Propofol