Fig. 4. Individual relations between spectral edge frequency (SEF) and effect site isoflurane concentration (Ce) in each state. Open circles are EC50values with 95% confidence intervals. The EC50values (with 95% confidence intervals) were 1.2 (1.1–1.3) under control conditions, 1.2 (1.1–1.3) with 20% bleeding, and 1.1 (1.0–1.2) with 30% bleeding, respectively. R 2values are correlation coefficients between SEF and Ce.