Objective: To find the minimum effective concentration required by remifentanil to inhibit circulatory response due to pneumoperitoneum during laparoscopic surgery in elderly patients.
Methods: ASA grade I/II patients aged 65-80 years old who received elective laparoscopic colon surgery were selected. All patients received Target-Controlled Infusion (TCI) of propofol, with a target plasma concentration of 3.5 μg/ml. They were administrated with 0.9 mg/kg rocuronium after loss of consciousness, inserted with laryngeal mask 2 minutes later and given plasma TCI with remifentanil before the start of surgery to determine its concentration using the sequential method. If mean arterial pressure and/or heart rate of a previous patient increased by >20% within five minutes after pneumoperitoneum compared with before pneumoperitoneum, the current patient was administered with remifentanil at a higher concentration. If the values increased by <20% within five minutes, the current patient was a lower concentration of remifentanil. The target concentration ratio of adjacent effect-site compartments was 1.2. The TCI target plasma concentration (EC50) of remifentanil for inhibiting the hemodynamic fluctuations of 50% of elderly patients after pneumoperitoneum was calculated using the sequential method.
Results: With the sequential method, EC50 of remifentanil for suppressing the hemodynamic response to laparoscopic pneumoperitoneum was 2.67 ng/ml and the 95% confidence interval was 2.61-2.72 ng/ml.
Conclusion: In combination with propofol during TCI, remifentanil at the target plasma concentration of 2.67 ng/ml can inhibit 50% of elderly patients from circulatory fluctuations caused by laparoscopic pneumoperitoneum.