Remifentanil, a short-acting opioid, is commonly used in cardiac anesthesia. In this study we sought to demonstrate the feasibility of pain treatment and to determine the remifentanil dose necessary for adequate analgesia in tracheally extubated patients after cardiac surgery. Thirty patients undergoing elective cardiac surgery were included in this study. After surgery, the intraoperatively administered remifentanil was initially continued at 0.05 microg . kg(-1) . min(-1). Before tracheal extubation, a nonsteroidal antiinflammatory drug was administered and remifentanil was reduced to 0.035 microg . kg(-1) . min(-1). Pain assessment using a visual analog scale (VAS) was performed after tracheal extubation, in 2-min intervals for 10 min, every 10 min until the end of the first hour and every 30 min during the ensuing 5 h. A VAS score > or =30 or a respiratory rate <10 breaths/min was followed by an increase or decrease in the remifentanil dose by 0.005 microg . kg(-1) . min(-1), respectively. For rapid dose adaptation during the first 10 min, remifentanil was increased twice by 0.005 microg. kg(-1) . min(-1) and then 3 times by 0.01 microg . kg(-1) . min(-1). With a mean remifentanil dose of 0.051 microg . kg(-1) . min(-1) VAS decreased to 26 +/- 14 after 30 min. Sufficient analgesia was achieved with remifentanil doses ranging from 0.03 to 0.09 microg. kg(-1) . min(-1). A maximum mean remifentanil dose of 0.057microg. kg(-1) . min(-1) was reached after 4 h. The combination of remifentanil with a nonsteroidal antiinflammatory drug provided adequate analgesia in 73% of patients 30 min after tracheal extubation. Rapid dose titration was necessary during the first 10 min in 50% of patients. Increasing the initial remifentanil dose could shorten the titration period but may be associated with respiratory complications.