体外循环下低温对靶控输注丙泊酚血浆药物浓度的影响

Effect of cardiopulmonary bypass-induced acute hypothermia on plasma concentration of propofol target controlled infusion

目的观察低温体外循环时丙泊酚实监测浓度与靶浓度比值(Cm/Cp)的变化,为降温时丙泊酚靶浓度的调整提供临床参考数据。方法13例ASAⅡ-Ⅳ级、择期行双瓣置换术的患者,术中静脉靶控输注(TCI)丙泊酚,设定靶浓度为2μg/ml,于34、32、30、28℃(肛温)时采集2ml桡动脉血,采用高效液相色谱荧光法测定药物浓度,同时测定血红蛋白(Hb)、血细胞比容(Hct)、AST、ALT、血肌酐(Cr)及血尿素氮(BUN)。结果所有采样点之间的Hct及Hb比较,差异无统计学意义(P>0.05);随着肛温的降低,Cm/Cp逐渐升高,于28℃达到峰值。在此期间,AST、ALT、Cr及BUN随着肛温降低而逐渐降低,于28℃时达到最低(P<0.05)。结论CPB后的低温通过降低肝肾的代谢率而导致丙泊酚Cm/Cp明显上升,为防止麻醉过深,应该按比例下调丙泊酚TCI时的靶浓度。

Objective To investigate the effect of cardiopulmonary bypass （CPB）-induced hypothermia on plasma concentration of propofol target controlled infusion （TCI） for optimizing the dosage of propofol, Method Thirteen ASA Ⅱ-Ⅳ patients, aged 48.2±12.0 years and weighed 40-75kg, were subjected to bicuspid valve and aortic valve replacement. The vital signs of the patients, including MAP, HR, P, CVP, ECG, ETCO2, SPO2, NT （temperature of nasal cavity） and RT （rectal temperature）, were continuously monitored before and during anesthesia. The radial artery and right internal jugular vein were canulated before induction of anesthesia for MAP and CVP monitoring. TCI of propofol was performed in all the patients after induction of anesthesia. The target plasma concentration （Cp） of propofol was set at 2μg/ml by Diprifusor TCI system Then the temperature was reduced by CPB, ice cap and cooling the operating room.The core temperature was lowered to 34℃ in 20min after CPB. Arterial blood samples were obtained at 34℃, 32℃, 30℃ and 28℃ for determining the plasma concentration of propofol（measured concentration, Cm） by HPLC. Hot, Hb, AST, ALT, Cr and BUN were also determined at the same time Results After hypothemaia in the course of CPB, no difference was found in Hb and Hct at 34℃ and down to 28℃ （P〉0. 05）, the ratio of Crn/Cps rose gradually with lowering of rectal temperature and it reached the top value at 28℃; during this period AST, ALT, Cr and BUN decreased with dropping of rectal temperature （ P〈0.05） and reached the peak-valley at 28℃. Conclusion Hypothermia induced by CPB increases the Cm/Cps of propofol obviously. It is better to down-regulate the target concentration of propofol proportionally for safety when TCI is practised.