Figure 5. 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 6 micro gram/ml. The mean measured blood propofol concentrations were 6.3, 8.4, 11.9, 7.7, 8.4, 10.6, and 11.4 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.
