摘要
体外循环(CPB)术后并发昏迷、谵妄、消化道出血及肾功能衰竭等将严重影响患者的顺利康复和术后生活质量。其原因是多方面因素的综合结果,诸多因素中组织灌注不足及氧代谢障碍是其重要原因。体外循环心脏手术期间如何监测组织灌注不足及其防治成为目前研究热点。当机体微环境发生改变时,其重要调节机制是首先保证心、脑、肾等重要脏器的血供,因血流重新分布导致内脏器官的血流减少。所以胃肠道被称为预测机体缺血缺氧的“前哨器官”。大量研究表明胃肠张力计能敏感、可靠的评估内脏组织灌注及氧合状态。本实验采用空气胃张力计连续监测CPB期间胃肠组织的灌注情况。尼卡地平是二氢吡啶类钙离子拮抗剂,具有扩张冠脉和小动脉,降低外周阻力的作用,并对心肌、脑及肾缺血性损害有保护作用。本实验拟观察CPB期间全身和胃肠组织灌注及氧合情况,并将尼卡地平应用于体外循环手术中,观察其对血流动力学,全身和组织灌注及氧合的影响,为临床降低心脏手术患者并发症,改善预后提供一种新的措施。
目的:动态观察体外循环心脏手术期间患者血流动力学、全身和胃肠黏膜血流灌注及氧合的变化;比较尼卡地平在术中对全身和胃肠组织血流灌注及氧合的影响,并探讨其机制。
方法:选择26例择期行体外循环下瓣膜置换术的风心病成年患者,随机分为常规麻醉组(C组)和尼卡地平组(N组),每组13例。两组患者均在常规麻醉诱导完成后,明视下经鼻置入空气胃张力计,连续监测胃黏膜内二氧化碳分压(PgCO_2);经右颈内静脉穿刺置入Swan-Ganz导管,用于测定血流动力学参数。C组:采用常规麻醉及体外循环方法,术中需要降压时不用尼卡地平,可应用硝酸甘油等;N组:麻醉诱导结束血流动力学指标平稳后,将尼卡地平以约0.5μg/kg/min速度持续泵入,维持转机前后平均动脉压(MAP)不低于70mmHg,转机中MAP不低于50mmHg至手术结束。持续监测一般指标和血流动力学指标;在体外循环前(T1),转流开始后30min(T2),停机后20min(T3)和术毕(T4)四个时点,采集Swan-Ganz导管远端肺小动脉血进行混合静脉血氧饱和度(SvO_2)测定,抽取动脉血作血气分析并计算氧供(DO_2),氧耗(VO_2)和摄氧率(ERO_2)反映全身氧合情况;同时在以上各个时点记录PgCO_2,并计算胃黏膜内—动脉血CO_2分压差(Pg-aCO_2)和胃黏膜内pH(pHi),作为评价胃肠组织灌注及氧合的指标。
结果:①血流动力学指标:停机后两组患者心脏指数(CI)均明显高于术前(P<0.01),组间比较在T3、T4时点N组CI高于C组(P<0.05,P<0.01);在T2、T3时点C组全身血管阻力指数(SVRI)较T1明显下降(P<0.01),N组在T2、T3和T4三时点均较T1明显下降(P<0.01),且在T4时点N组SVRI与C组相比明显降低(P<0.01);②全身氧合指标:T2时点两组SvO_2均较转机前明显增高,C组在T3和T4时点较T1明显下降(P<0.01),N组无明显变化且在T4时点与C组相比有统计学差异(P<0.05);在T2时点两组DO_2、VO_2、ERO_2均下降(P<0.05),在T3、T4时点C组DO_2较基础值无明显变化, N组DO_2与T1相比升高(P<0.05)且明显高于C组(P<0.01);在T3时点两组VO_2较T1升高(P<0.05),在T4时点与T1相比无明显差异,停机后C组ERO_2与N组相比增高(P<0.05);③胃肠灌注指标:在T2时点两组PgCO_2和Pg-aCO_2均较转机前降低(P<0.01),pHi较转机前升高(P<0.01);在T3、T4时点C组PgCO_2和Pg-aCO_2较转流前明显升高,且明显高于N组(P<0.01);C组pHi在T3和T4两时点低于7.35,而N组高于7.35。
结论:体外循环下心脏手术期间存在胃肠组织低灌注及氧合障碍。尼卡地平能明显改善体外循环中的全身和胃肠组织血流灌注及氧合。空气胃张力计是监测组织血流灌注敏感的无创指标,在临床麻醉工作中值得推广使用。
Complications such as coma, delirium, gastrointestinal hemorrhage and renal failure after cardiopulmonary bypass (CPB) affect rehabilitation and postoperative quality of life seriously. Many factors contribute to it comprehensively. Tissue perfusion inadequacy and oxygen metabolism disturbance are the most important reasons. During cardiopulmonary bypass, how to monitor the tissue perfusion and prevent hypoperfusion has become a hotspot recently. When the microenvironment of the body changes, circulation blood flow redistributes away from visceral regions to vital organs to guarantee the perfusion of myocardium, brain and kidney as a regulatory mechanism. So gastrointestinal tract is called as“sentinel organ”of predicting systemic hypoxia-ischemia. Many research reported that gastrointestinal tonometry could assess the perfusion and oxygenation of visceral organs reliably and sensitively. In our study, air-tonometry was adopted to monitor gastrointestinal mucosa perfusion continuously during cardiopulmonary bypass. As one of the dihydropyridine calcium antagonists, Nicardipine not only has the effect of expansion of arterioles and coronary artery to decrease peripheral vascular resistance but also prevents ischemia of myocardium, brain and kidney. This study was carried out to investigate the effect of CPB on hemodynamics, systematic and gastrointestinal perfusion. At the same time we observed whether nicardipine has the function of improving gastrointestinal perfusion and oxygenation during cardiopulmonary bypass, and provide a new method for reducing patients, postoperative complications and improving prognosis.
Objective: This study was carried out to investigate the effect of cardiopulmonary bypass on hemodynamics, systematic and gastrointestinal perfusion by using gastric tonometry. And with the use of nicardipine during CPB, we can also observe whether nicardipine has the function of improving gastrointestinal perfusion and oxygenation. We also discuss its mechanisms.
Methods: Twenty-six adult patients scheduled for cardiac valve replacement were divided randomly into two groups: conventional anesthetic group (group C) and nicardipine group (group N) with 13 patients each. After the completion of induction of anesthesia, all patients were inserted the Tonometry Catheters nasogastrically and its position confirmed by auscultation over the epigastrium. Gastric intramucosal partial pressure of carbon dioxide (PgCO_2) is measured by infrared spectroscopy every 10 minutes internals using the Tonocap. A Swan-Ganz catheter was inserted into the pulmonary artery via the right internal jugular vein to perform cardiac output by the thermodilution. The patients were mechanically ventilated after tracheal intubation and PET CO_2 was maintained at 35-45mmHg. Conventional methods of anesthesia and cardiopulmonary bypass were adopted, in group C such as nitroglycerin was given instead of nicardipine if the arterial blood pressure need to lower; while in group N nicardipine was titrated at the rate of 0.5μg/kg/min to maintain mean arterial blood pressure not below 70mmHg before or after CPB and not below 50mmHg during CPB. General indicators and hemodynamic parameters were monitored continuously. Pulmonary arteriole blood were extracted from Swan-Ganz catheter to measure mixed venous oxygen saturation (SvO_2) and arterial blood from radial artery to determine blood-gas analysis at the following time points: before CPB (T1), 30min after beginning of CPB (T2), 20min after weaning from CPB (T3) and the end of operation (T4). The delivery of oxygen (DO_2), consumption of oxygen (VO_2) and oxygen extraction ratio (ERO_2) were calculated. SvO_2, DO_2, VO_2 and ERO_2 were to reflect systematic oxygenation. At the above each time point PgCO_2 was recorded by Tonocap, gastric luminal PCO_2-arterial PCO_2 (Pg-aCO_2) and gastric intramucosal pH (pHi) were calculated to evaluate gastrointestinal perfusion and oxygenation.
Results: In both two groups significant increase in cardiac index(CI) at T3、T4 compared with T1(P<0.01) and CI in group N was notably increased compared with group C after weaning from CPB(P<0.01); At T2、T3 systemic vascular resistance index (SVRI) in group C was obviously decreased with T1(P<0.01), while SVRI in group N was decreased at T2、T3、T4 with T1(P<0.01). At T4 SVRI was significantly decreased in group N compared with group C (P<0.01). In both two groups increase in SvO_2 at T2 compared with T1(P<0.01), at T3、T4 SvO_2 in group C gradually descent but that in group N hasn’t so change. In both two groups decrease in DO_2、VO_2and ERO_2 at T2 compared with T1(P<0.05). DO_2 of T3、T4 in group N was significantly higher than that in group C(P<0.01) while VO_2 in two groups was increased at T3 compared with T1(P<0.05) and at T4 remained unchanged. And ERO_2 in group C was higher than that in group N after completion of CPB(P<0.05). In group C significant increase in PgCO_2 and decrease in pHi at T3、T4 compared with T1 and contrary result was seen at T2 compared with T1(P<0.01). In group N only pHi decreased at T4 compared with T1(P<0.01). The tendency of Pg-aCO_2 was the same as PgCO_2. At T3、T4 pHi in group C was below of 7.35, but group N was properly opposite.
Conclusions: There were gastric mucosal hypoperfusion and disorder of oxygenation during hypothermic CPB, as shown by reduced pHi and increased PgCO_2. Nicardipine can maintain systematic and gastrointestinal tissue perfusion and oxygenation. Nicardipine has the effect of gastrointestinal protection. Gastrointestinal air-tonometry is a sensitive and noninvasive method that monitors gastrointestinal tissue perfusion continuously. Tonometry should be applied extensively in clinical anesthesia performance.
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