Effect of propofol on the efficacy of remifentanil by TCI in elderly patients

Objective To evaluate the effect of continuous infusion of propofol on the efficacy of remifentanil administered by TCI in elderly patients. Methods Thirty ASA Ⅰ or Ⅱ patients aged 65-75 yrs, weighing 50-71 kg undergoing elective surgery were randomly allocated into 2 groups ( n = 15 each) : remifentanil group (R) and propofol-remifentanil group (R-P group) . The patients were unpremedicated. Radial artery was cannulated for blood pressure monitoring and blood sampling. Subclavian vein was cannulated for drug and fluid administration. MAP, HR, SpO2 and BIS were continuously monitored during the study. Remifentanil was given with TCI system (using pharmacokinetic parameters reported by Minto) at target plasma concentration of 5 μg·ml-1 for 30 min in both groups. In R-P group propofol was infused at a rate of 5 mg ·kg-1 ·h-1 for 30 min simultaneously. The target plasma remifentanil concentration and infusion rate of propofol were maintained constant during the study. Arterial blood samples were obtained at 1, 3, 5, 10, 15, 20, 25 and 30 min after target plasma remifentanil concentration had been reached for determination of actual blood remifentanil concentration. The performance error (PE) was calculated for each measured blood remifentanil concentration. The median performance error (MDPE), the median absolute performance error (MDAPE) and Wobble (the median absolute deviation of each PE from MDPE) were also calculated.Results The MDPE, MDAPE and Wobble of remifentanil by TCI system in the elderly patients were - 16.8% , 23.9% and 8.3% in group R and - 15.5% , 21.7% and 10.7% in R-P group. There was no significant difference between the two groups. The measured remifentanil concentrations were significantly lower than the target concentration set by TCI system (P 0.05). There was no significant difference in the measured remifentanil concentrations between the two groups. Conclusion The efficacy of remifentanil administered by TCI system using Minto pharmacokinetic parameters is acceptable clinically in elderly patients and is not affected by simultaneous propofol infusion (at 5 mg·kg-1·h-1).