控制性降压对切皮时丙泊酚EC50及术中相同BIS条件下靶控浓度的影响

The effect of controlled hypotension on EC50 of propofol for skin incision and intraoperative BIS value

目的探讨控制性降压对切皮时丙泊酚EC50及术中镇静深度的影响。方法择期行髋部手术全麻患者例40例,ASAI～Ⅱ级,随机分为降压组(L组)和对照组(C组),应用AspectA-2000Tm BIS麻醉深度监护仪监测BIS,诱导时设定丙泊酚血浆靶浓度4.5μg/L,雷米芬太尼血浆靶浓度4ng/L;意识消失后置入喉罩,机械控制呼吸,监测呼气末二氧化碳分压使CO2CP在35～40mmHg之间。L组降压采用硝普钠复合艾司洛尔,至目标血压(使MAP降至55～60mmHg)5min后开始手术切皮,对照组泵入等量生理盐水。切皮时两组丙泊酚给药按序贯法TCI血浆靶控输注,靶浓度的间隔为0.5μg/ml。切皮完成后术中通过调节丙泊酚靶控血浆浓度维持BIS维持在45～55之间。并记录控制性降压前即刻(T0)、降压后15min(T1)、30min(T2)、90min(T3)、术毕10min(T4)5个时间点的丙泊酚靶控浓度、血液动力学指标。结果L组与C组切皮后5min丙泊酚的EC50和95%置信区间(mcg/ml)差异无统计学意义,术中L组MAP、HR低于C组(P<0.05)。与T0时刻相比,C组T1时刻心率加快,T2～5心率与T0相比无统计学差异;L组术中HR低于降压前(P<0.05)。维持相同BIS值情况下,两组丙泊酚TCI浓度随时间延长均降低,T4时刻C组丙泊酚浓度高于L组(P<0.05)。结论短时间控制性降压不改变丙泊酚切皮时的EC50,较长时间控制性降压后可增加丙泊酚的镇静深度,需减少临床丙泊酚用量。

Objective The aim of the study is to evaluate the influence of controlled hypotension on EC50 of propofol for skin incision and intraoperative anaesthesia depth. Methods Forty ASA Ⅰ - Ⅱ adult patients scheduled for hip arthroplasty were randomly allocated into hypotension group and control group. TCI propofol with target plasma concentration of 4.5 μg/L and remifentanil 4 ng/L were started for induction. LMA classic was inserted and mechanical ventilation was applied in all patients. Ventilator parameter was set to maintain end - tidal CO2 between 35 - 40 mm Hg. In the hypotension group, sodium nitroprusside and esmolol were infused and skin incision commenced after MAP decreased to 55 -60 mmHg and remained stable for at least 5 min. normal saline was infused in the control group before skin incision. The target plasma concentratin of propofol was adjusted using up and down method with 0.5μg/ml. Then the plasma concentration of propofol was adjusted to maintain BIS between 45 - 55 during operation. Hemody- namic variables and plasma concentration of propofol were recorded at time points of immediately before controlled hypotension, 15, 30 ,90 min after controlled hypotension and 10 min after the end of operation. Results The EC50 of propofol for skin incision were not different between the two groups. MAP and HR were significantly lower in the hypotension group during operation. In the control group, HR increased at T1 and decreased to T0 level at T2 - T5 ; while in the hypotension group, HR was lower than T0 at all other time points. TCI concentration of propofol decreased with time in both groups to maintain similar anaesthesia depth indicated by BIS and were similar at most of time points except for T4, at which the hypotension group had a lower concentration. Conclusions Short time of controlled hypotension would not cause change in EC50 of propofol for skin incision. However, long time hypotension might enhance the sedative effect of propofol.