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Paradox of age: older patients receive higher age-adjusted minimum alveolar concentration fractions of volatile anaesthetics yet display higher bispectral index values.

Publication ,  Journal Article
Ni, K; Cooter, M; Gupta, DK; Thomas, J; Hopkins, TJ; Miller, TE; James, ML; Kertai, MD; Berger, M
Published in: Br J Anaesth
September 2019

BACKGROUND: Minimum alveolar concentration (MAC) and MAC-awake decrease with age. We hypothesised that, in clinical practice, (i) end-tidal MAC fraction in older patients would decline by less than the predicted age-dependent MAC decrease (i.e. older patients would receive relatively excessive anaesthetic concentrations), and (ii) bispectral index (BIS) values would therefore be lower in older patients. METHODS: We examined the relationship between end-tidal MAC fraction, BIS values, and age in 4699 patients > 30 yr in age at a single centre using unadjusted local regression (locally estimated scatterplot smoothing), Spearman's correlation, stratification, and robust univariable and multivariable linear regression. RESULTS: The end-tidal MAC fraction in older patients declined by 3.01% per decade (95% confidence interval [CI]: 2.56-3.45; P<0.001), less than the 6.47% MAC decrease per decade that we found in a meta-regression analysis of published studies of age-dependent changes in MAC (P<0.001), and less than the age-dependent decrease in MAC-awake. The BIS values correlated positively with age (ρ=0.15; 95% CI: 0.12-0.17; P<0.001), and inversely with the age-adjusted end-tidal MAC (aaMAC) fraction (ρ= -0.13; 95% CI: -0.16, -0.11; P<0.001). CONCLUSIONS: The age-dependent decline in end-tidal MAC fraction delivered in clinical practice at our institution was less than the age-dependent percentage decrease in MAC and MAC-awake determined from published studies. Despite receiving higher aaMAC fractions, older patients paradoxically showed higher BIS values. This most likely suggests that the BIS algorithm is inaccurate in older adults.

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Published In

Br J Anaesth

DOI

EISSN

1471-6771

Publication Date

September 2019

Volume

123

Issue

3

Start / End Page

288 / 297

Location

England

Related Subject Headings

  • Retrospective Studies
  • Pulmonary Alveoli
  • Monitoring, Intraoperative
  • Middle Aged
  • Male
  • Humans
  • Female
  • Electroencephalography
  • Drug Administration Schedule
  • Dose-Response Relationship, Drug
 

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Ni, K., Cooter, M., Gupta, D. K., Thomas, J., Hopkins, T. J., Miller, T. E., … Berger, M. (2019). Paradox of age: older patients receive higher age-adjusted minimum alveolar concentration fractions of volatile anaesthetics yet display higher bispectral index values. Br J Anaesth, 123(3), 288–297. https://doi.org/10.1016/j.bja.2019.05.040
Ni, Katherine, Mary Cooter, Dhanesh K. Gupta, Jake Thomas, Thomas J. Hopkins, Timothy E. Miller, Michael L. James, Miklos D. Kertai, and Miles Berger. “Paradox of age: older patients receive higher age-adjusted minimum alveolar concentration fractions of volatile anaesthetics yet display higher bispectral index values.Br J Anaesth 123, no. 3 (September 2019): 288–97. https://doi.org/10.1016/j.bja.2019.05.040.
Ni, Katherine, et al. “Paradox of age: older patients receive higher age-adjusted minimum alveolar concentration fractions of volatile anaesthetics yet display higher bispectral index values.Br J Anaesth, vol. 123, no. 3, Sept. 2019, pp. 288–97. Pubmed, doi:10.1016/j.bja.2019.05.040.
Ni K, Cooter M, Gupta DK, Thomas J, Hopkins TJ, Miller TE, James ML, Kertai MD, Berger M. Paradox of age: older patients receive higher age-adjusted minimum alveolar concentration fractions of volatile anaesthetics yet display higher bispectral index values. Br J Anaesth. 2019 Sep;123(3):288–297.
Journal cover image

Published In

Br J Anaesth

DOI

EISSN

1471-6771

Publication Date

September 2019

Volume

123

Issue

3

Start / End Page

288 / 297

Location

England

Related Subject Headings

  • Retrospective Studies
  • Pulmonary Alveoli
  • Monitoring, Intraoperative
  • Middle Aged
  • Male
  • Humans
  • Female
  • Electroencephalography
  • Drug Administration Schedule
  • Dose-Response Relationship, Drug