Sitting position does not alter minimum alveolar concentration for desflurane

Chun Ming Lin, Chieh Tsai Wu, Shih Tseng Lee, Tai Ngar Lui, Chia Chun Huang, Allen Hon Lun Li, Anthony G. Doufas

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Purpose: Hypotension is a common complication of the sitting position during anesthesia, and is often counteracted by decreasing anesthetic depth, thereby exposing patients to the risk of being inadequately anesthetized. Baroreceptor unloading and the consequent sympathoexcitation, as during head up tilt, decreases pain threshold and arouses the central nervous system (CNS), whereas hypotension exerts a direct CNS depressant effect. We estimated the minimal alveolar concentration (MAC) of desflurane for immobility in patients undergoing surgery in the sitting position, in comparison to MAC desflurane for patients having a similar type of surgery in the supine position. Methods: The Dixon up-and-down method was used to evaluate the MAC for desflurane in patients undergoing cervical spine laminoplasty (n = 24) or discectomy (n = 24) in the sitting and supine positions, respectively. Logistic regression with co-variate adjustment was employed to examine if the two positions (sitting and supine) have different or share the same concentration vs response relationship for immobility. Monte Carlo simulation was used to calculate 95% confidence intervals (CI) for the MAC in each position, and to estimate the difference in MAC (delta MAC) between the sitting and supine positions. Results: Modeling both sitting [6.54% (6.50-6.66, 95% CI)] and supine [6.70 (6.55-6.81)] patients as having different MAC concentrations did not significantly improve our simplified model, which treats the two patient groups as one [6.61 (6.52-6.70), delta -2 log likelihood = 2.735, P = 0.098]. Mean delta MAC (95% CI) was -0.14 (-0.30, 0.03). Conclusion: The sitting position does not change desflurane anesthetic requirements for immobility.

Original languageEnglish
Pages (from-to)523-530
Number of pages8
JournalCanadian Journal of Anesthesia
Volume54
Issue number7
Publication statusPublished - Jul 2007
Externally publishedYes

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine

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  • Cite this

    Lin, C. M., Wu, C. T., Lee, S. T., Lui, T. N., Huang, C. C., Li, A. H. L., & Doufas, A. G. (2007). Sitting position does not alter minimum alveolar concentration for desflurane. Canadian Journal of Anesthesia, 54(7), 523-530.