The study investigated whether intraoperative administration of remifentanil leads to acute opioid tolerance, characterized by increased postoperative pain and morphine requirement. Fifty adult patients undergoing major abdominal surgery were randomly assigned to two anesthetic regimens: one group received a constant desflurane concentration with titrated remifentanil infusion, while the other group received a constant remifentanil infusion with titrated desflurane. Both groups received a preoperative morphine bolus. Postoperative pain scores and morphine consumption were recorded for 24 hours. The results showed that the remifentanil group had significantly higher remifentanil infusion rates and postoperative pain scores compared to the desflurane group. They also required morphine earlier and needed nearly twice as much morphine in the first 24 hours postoperatively. The study concluded that large-dose intraoperative remifentanil increases postoperative pain and morphine consumption, suggesting that remifentanil causes acute opioid tolerance and hyperalgesia.The study investigated whether intraoperative administration of remifentanil leads to acute opioid tolerance, characterized by increased postoperative pain and morphine requirement. Fifty adult patients undergoing major abdominal surgery were randomly assigned to two anesthetic regimens: one group received a constant desflurane concentration with titrated remifentanil infusion, while the other group received a constant remifentanil infusion with titrated desflurane. Both groups received a preoperative morphine bolus. Postoperative pain scores and morphine consumption were recorded for 24 hours. The results showed that the remifentanil group had significantly higher remifentanil infusion rates and postoperative pain scores compared to the desflurane group. They also required morphine earlier and needed nearly twice as much morphine in the first 24 hours postoperatively. The study concluded that large-dose intraoperative remifentanil increases postoperative pain and morphine consumption, suggesting that remifentanil causes acute opioid tolerance and hyperalgesia.