Figure 3. The alfentanil concentration-effect relations in the individual patients for the intraabdominal part of surgery when alfentanil was given as a supplement to a target propofol concentration of 2 micro gram/ml. The mean measured blood propofol concentrations were 2.5, 2.8, 2.0, 2.7, 2.6, 3.4, and 2.9 micro gram/ml in patients 1-7, respectively (see Table 4). The curves were determined by logistic regression of response-no-response data versus the corresponding measured plasma alfentanil concentrations, as shown beneath the curves. Filled circles = concentrations of alfentanil associated with a 50% probability (EC50s) of no response.
