Fig. 4. Remifentanil concentration–effect relations in the individual patients for the intraabdominal part of surgery when remifentanil was given as a supplement to a target propofol concentration of 2 μg/ml. The mean measured blood propofol concentrations were 2.1, 2.3, 2.8, 2.0, 1.9, 2.2, 1.9, and 2.9 μg/ml in patients 1–8, respectively (table 5). The curves were determined by logistic regression of response–no response data versus  the corresponding measured blood remifentanil concentrations of remifentanil, as shown beneath the curves. Dots = blood remifentanil concentrations associated with a 50% probability of no response.