Effect Of Different Ages On EC₅₀ Of Propofol And BIS With TCI During Induction Of Anesthesia

Background and objectivePropofol is an intravenous anesthesia, which is rapid onset, short-acting, waking up quickly and completely, with a continuous infusion of no accumulation phenomenon.It has gained wide acceptance since its introduction in the late 80s, not only in operating rooms and maintenance but also widely used in patients local anesthesia and ICU for sedation.With the deepening study of the pharmacodynamics and pharmacokinetic of propofol, a variety of computer innovation infusion system to regulate depth of sedation, maintain hemodynamic stability,inhibit the stress response and promote the development of total intravenous anesthesia.In recent years, many studies have shown that the age can affect the pharmacokinetics and pharmacodynamics of many anesthetic drugs, and the drug dose must be adjusted appropriately according to age during the clinical anesthesia and sedation aiming to increase the effectiveness and safety of anesthesia drugs at most.However, there are many and quite difference on the study of the impact of age on pharmacodynamics of propofol.This study was designed to observe the change of EC50 and BIS value of propofol with target-controlled infusion during induction of anesthesia in different ages,and the aim is to define the safety dosage range in different ages and provide reasonable reference for safety of the clinical anesthesia drugs.Materials and methodsNinety patients were selected as subjects who will undergo general anesthesia, male 33 cases and female 57 cases, Anesthesiologists(ASA)physical status of I orⅡ,BMI 18.5～30kg/m2,divided equally into three groups by age, (youth group 18～44 years, middle age group 45～64 years, elderly group 65～75 years)(n=30 each).Each group undergone physical examination preoperatively showed no abnormality. Every subject has no long-term using of opium or sedative hypnotic drugs, no mental or nervous system diseases, no hearing impairment, and were given upper extremity venous access when entering the operating room, pre-infusion of lactated Ringer 10ml/kg/h, oxygen to nitrogen in full, after 5min of anesthesia Application of TCI-Ⅰinduced by target-controlled infusion pump sufentanil target controlled effect site concentration of 0.3ng/ml, when the plasma drug concentration and effect compartment to reach equilibrium of drug, propofol Graseby3500 pump by sequential application of plasma TCI, the initial concentration was 2.5μg/ml (youth group),2.0μg/ml (middle age group),1.5μg/ml (elderly group), to achieve target plasma concentration, as the current patients lost consciousness, then The next level of patients with low concentrations of the target interval of the concentration of 0.5μg/ml, such as the awareness has not disappeared, then the next higher level of concentration of patients, adjusting the target concentration of propofol infusion until BIS value to 60 patients the following, given vecuronium 0.1mg/kg,2min underwent laryngeal mask airway insertion. TCI patients were recorded before (baseline)(t1),TCI sufentanil after the concentration and effect compartment concentration of plasma equilibrium(t2) TCI of propofol after the plasma concentration reached(t3),TCI after the loss of consciousness(t4), laryngeal mask airway insertion immediately (t5) at each time point HR, BP, MAP, SpO2, and BIS values. Plasma concentrations reached after the eyelash reflex, no response to verbal commands, no response to tapping the shoulder that loss of consciousness. Loss of consciousness, the subjects were recorded when each target concentration, the use of regression analysis to calculate the loss of consciousness in patients with different ages of propofol EC50 values.Statistical analysis:statistical Package (SPSS16.0) was used for statistical analysis, parametric varibles were expressed as mean±standard deviation (SD), and were compared using One-way analysis of variance in the intergroup and using. t-test in the intragroup.χ2 test was used to Count data.The significance level was a 0.05.Results1 General state of patientsThere was no significant difference in height,weight,body mass index, and F/M(P>0.05).2 Comparison of hemodynamics conditionsThe differences of HR, SBP, and DBP in the intragroup were statistically significant (P<0.05). compared to the groupⅠ, SBP and MAP values decreased significantly (P<0.05).3 Comparison of BIS value in each time pointsBIS values of the three groups decreased after induction in each time, compared to baseline values, the difference was statistically significant (P<0.05). Compared to groupⅠ,Ⅱ, BIS values of the groupⅢon the time of t2, t3, t4, t5 decrease, the difference was statistically significant (P<0.05) no difference.4 The EC50 and 95% confidengce interval of propofol at loss of consciousness in each groupYouth age group, loss of consciousness EC50 of propofol for the 2.34μg/ml,95% confidence interval 2.15～2.56μg/ml; middle age group, loss of consciousness EC50 of propofol for the 2.29μg/ml,95% confidence range of 2.12～2.48μg/ml; senile group, loss of consciousness EC50 of propofol for the 1.70μg/ml,95% confidence interval 1.55～1.86μg/ml.Conclusion1. With the increacing of age, there was a tendency to decrease of EC50 values when the patients unconsciousness, and there was no geometric relationship between elderly patients and youth-middle patients.2. When the target-controlled plasma drug concentrations balanced, there was significant decrease of BIS values.