Fig. 3. Plot of net drug flux (J^net) per flow for fentanyl, sufentanil, and alfentanil under the assumption that cerebral blood flow is not quantitated but remains constant. Under these conditions, J^netcorresponds to the difference in mass per unit time of drug respectively entering and leaving the brain via  the arterial and venous blood vessels. Data are presented as the median (solid lines) and fifth and ninety-fifth percentiles (dotted lines) from individual patients