Optimization Of Propofol Step-by-Step Target Control Induction On Consciousness Loss And Hemodynamics In Elderly Patients

Objective To screen out the best drug delivery scheme of propofol step-by-step target controlled infusion combined with remifentanil of different plasma concentrations suitable for elderly patients during induction of general anesthesia.Methods Eighty ASAⅠ-Ⅲelderly patients,aged 65 to 79 years undergoing elective general anesthesia surgery were randomly divided into groups A,B,C and D.The initial plasma concentrations of propofol in groups A and B were 1.5μg/ml and 2.0μg/ml respectively,and the plasma concentrations of remifentanil were 2.0ng/ml.The initial plasma concentrations of propofol in groups C and D were 1.5μg/ml and 2.0μg/ml respectively,and remifentanil were 3.0ng/ml.The propofol plasma target concentration was then increased by 1.0μg/ml every 60s until the patients lost their consciousness.The time of loss of consciousness was recorded;MAP and HR were recorded before induction（T₀）,LOC（T₁）,before tracheal intubation（T₂）and after intubation（T₃）,1（T₄）,2（T₅）,3（T₆）,4（T₇）and 5（T₈）minutes afterwards.The propofol plasma,effect-site concentrations were recorded in T₁,T₂;BIS was recorded inT₀-T₄ and BIS minimum was recorded during induction Period.Results Compared with T₀,MAP and HR in group A,B and D increased significantly at T₃ and T₄ after intubation（p<0.05）,while MAP in group C decreased significantly（p<0.05）with no significant difference in heart rate（p>0.05）.Compared with T₂,there was no significant difference in BIS values after intubation in group A,B and C（p>0.05）,but there was a difference in group D（p<0.05）.The time of loss of consciousness in group D was shortest,which was 1.7±0.45 min.Propofol effect-site concentrations in groups A and C were significantly higher than those in groups B and D（LOC:2.41±0.3μg/ml,2.45±0.2μg/ml vs 1.35±0.0μg/ml,1.41±0.2μg/ml;before intubation:3.41±0.4μg/ml,3.45±0.2μg/ml vs 2.50±0.3μg/ml,2.26±0.2μg/ml p<0.05）Conclusion Propofol step-by-step target control induction combined with remifentanil can be safely used for induction of general anesthesia in elderly patients.When the initial target plasma concentration of propofol was 1.5ug/ml and remifentanil was3.0ng/ml,the hemodynamics during induction was the most stable.At this time,the consciousness loss time was 2.73±0.2 min;BIS value was 50.3±2.2,propofol plasma and effect-site concentrations were 3.5±0.0μg/ml and 3.41±0.4μg/ml respectively before tracheal intubation.