. Author manuscript; available in PMC: 2010 Aug 1.

Published in final edited form as: Anesth Analg. 2009 Oct 9;111(2):387–394. doi: 10.1213/ANE.0b013e3181afe31c

Table 2.

Sevoflurane-remifentanil interaction model parameters fit to responses recorded in volunteers. Models include probability of unresponsiveness and lack of response to 30 PSI of anterior tibial pressure. Two sets of models are presented: one using sevoflurane effect-site concentrations and the other using end-tidal concentrations.

	Probability of unresponsiveness (OAA/S = 1)		Lack of response to Anterior Tibial Pressure (30 PSI)
Model Parameters	Effect-site	End-tidal	Effect-site	End-tidal
C₅₀ Sevoflurane (vol %)	0.74 (8%)	0.78 (10%)	0.83 (12%)	0.89 (12%)
C₅₀ Remifentanil (ng/mL)	50.9 (28%)	50.2 (30%)	1.3 (23%)	1.2 (24%)
Alpha (interaction)	9.4 (56%)	12.4 (61%)	0.9 (89%)	0.8 (94%)
N (slope)	5.2 (66%)	4.4 (93%)	2.7 (94%)	3.1 (149%)

Model Fit
% of Predictions >0.5 that matched observed responses	92%	93%	90%	90%
Spearman’s rho & P value	0.83 < 0.001	0.83 < 0.001	0.61 < 0.001	0.61 < 0.001

OAA/S indicates Observers Assessment of Alertness and Sedation(3). Model parameters were estimated using a Greco model structure. Numbers in parentheses represent coefficients of variation.