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 ASA?-?elderly 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 1.5?g/ml and 2.0?g/ml respectively,and the plasma concentrations of remifentanil were 2.0ng/ml.The initial plasma concentrations of propofol in groups C and D were 1.5?g/ml and 2.0?g/ml respectively,and remifentanil were 3.0ng/ml.The propofol plasma target concentration was then increased by 1.0?g/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±0.3?g/ml,2.45±0.2?g/ml vs 1.35±0.0?g/ml,1.41±0.2?g/ml;before intubation:3.41±0.4?g/ml,3.45±0.2?g/ml vs 2.50±0.3?g/ml,2.26±0.2?g/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±0.0?g/ml and 3.41±0.4?g/ml respectively before tracheal intubation.