主动脉夹层手术中Del Nido与传统心脏停搏液心肌保护效果的比较

目的 比较主动脉夹层手术中应用del Nido心脏停搏液和传统心脏停搏液的心肌保护效果。方法 回顾性总结分析2017年7月至2019年12月上海交通大学医学院附属新华医院63例主动脉夹层手术的临床资料,根据应用的心脏停搏液不同分两组,应用del Nido心脏停搏液（DN组）33例,应用传统心脏停搏液（传统组）30例。DN组用del Nido晶体液与氧合血按4：1混合（4份晶体1份血）,灌注量 20ml/kg,最大不超过 1 L。主动脉阻断时间超过90min再次灌注300ml。传统组应用4：1含血冷晶体改良St. Thomas液（4份血1份晶体）,灌注量 15ml/kg。每隔20-30min灌注一次（7.5ml/kg）。结果 两组术前一般资料无差异。术中体外循环时间、主动脉阻断时间传统组较长,但无统计学差异。停搏液灌注次数和灌注耗时传统组显著高于DN组。自动复跳率两组相近,DN组94%,传统组97%。术后早期（30天内）死亡率DN组（6.1%）与传统组（6.7%）无差异。术后第1天血清肌钙蛋白I DN组 (4.10±0.65ng/ml)与传统组（4.25±0.61 ng/ml）无差异。术后低心排发生率、术后1天和出院前LVEF两组之间均无统计学差异。结论 主动脉夹层术中应用del Nido心脏停搏液可以达到满意的心肌保护效果。     

Del Nido心脏停搏液在成人心脏外科中的应用效果分析

目的：评价Del Nido心脏停搏液在成人心脏外科手术中的安全性及有效性，为成人心脏手术选择合适心肌保护液提供参考。方法：回顾性分析2018年1月至2019年1月我科95例应用Del Nido心脏停搏液的临床资料。结果：本研究中男47例（49.5%），年龄55.0±17.6岁，病因以心脏瓣膜病（64例，67.4%）为主，术前合并房颤26例（27.4%）。体外循环时间138.6±65.4 min，主动脉阻断时间75.8±32.0 min，灌注次数1.14±0.43次，顺灌94例（98.9%），自动复跳86例（90.5%）。转流最低肛温33.3±2.7℃，转流结束时乳酸值1.7（1.4-2.3）mmol/L。术后第2天 cTnI浓度3.3（1.8-5.7）ng/ml。呼吸机辅助时间24（18-67）h，ICU停留时间4（3-7）天，术后住院13（9-16）天。术后无脑卒中和新发心肌梗死，新发房颤26例（37.7%），胸腔积液14例（14.7%），二次开胸2例（2.1%），急性肾衰2例（2.1%），感染3例（3.2%）。出院前最后一次LVEF较术前稍降低（59.6±9.0% vs. 62.4±8.7%，P＜0.01），围手术期死亡2例，与心脏停搏液无关。结论：Del Nido心脏停搏液灌注次数少，未发现其对心肌的额外损伤，适合多种疾病的心肌保护。近期安全性、有效性良好，提高了手术操作的简便性。     

del Nido停搏液在急性Stanford A型主动脉夹层外科手术中心肌保护的临床效果研究

目的 观察del Nido停搏液在急性Stanford A型主动脉夹层外科手术中的心肌保护临床效果,探讨del Nido停搏液在成人大血管手术中应用的安全性和有效性。方法 回顾性分析2018年5月至2019年5月因急性Stanford A型主动脉夹层在本院行心脏外科手术的50例病例,按照术中心肌保护灌注液的不同分为两组：del Nido停搏液组（del Nido组,即DN组,24例）和高钾全血停搏液组（whole blood组,即WB组,26例）。对两组患者术前一般资料、体外循环时间、主动脉阻断时间、停循环时间、停搏液用量、体外循环最低血红蛋白浓度、自动复跳率、术前术后血清肌钙蛋白I（troponin I,cTnI）浓度、机械通气时间、监护室停留时间、术后并发症及预后情况等进行比较。结果 两组患者术前资料无统计学差异。两组术后各1例患者出现死亡,其中1例死于多器官功能衰竭,1例死于神经系统并发症。DN组患者术中停搏液晶体总量显著高于WB组［（1568±230）ml比（43±12）ml,P<0.05］,DN组停搏液灌注次数显著低于WB组［（1.80±0.72）次比（5.23±0.81）次,P<0.05］,DN组总灌注时间显著低于WB组［（6.23±0.39）min比（12.49±1.02）min,P<0.05］,其余各项术中、术后指标两组比较未见统计学差异。结论 del Nido停搏液在急性Stanford A型主动脉夹层外科手术中可以提供较好的心肌保护作用,临床效果良好。     

HTK液与含血停搏液心肌保护效果比较

目的 比较HTK液和含血停搏液在复杂心脏手术中的心肌保护效果。方法40例重症复杂心脏手术患者分为两组。HTK液组（16例）手术中采用HTK液保护心肌；对照组（24例）术中采用常规1：4含血停搏液保护心肌。测定术前、主动脉开放后8h、24h、48h血中肌钙蛋白I（cTnI）和磷酸激酶同工酶（CK-MB）浓度，并比较两组患者术后心脏自动复跳率、正性肌力药物使用率、机械通气支持时间、ICU监护时间等临床指标。结果HTK组和对照组平均体外循环转流时间和主动脉阻断时间无明显差异，术后心脏自动复跳率分别为87．5％、64．6％（P〈0．05）。主动脉开放后8h、24h对照组cTnI和CK-MB均明显高于HTK组（P〈0．05）。两组其余观察指标无明显差异。结论HTK心脏停搏液对复杂重症心脏手术患者的心肌保护作用略优于1：4含血停搏液。     

HTK液与del Nido液在心脏瓣膜手术中心肌保护效果对比分析

目的 回顾性分析比较在心脏瓣膜手术中HTK停搏液与del Nido停搏液的心肌保护效果。方法收集选取2019年1月至2021年12月在阜外华中心血管病医院行体外循环（CPB）下心脏直视手术的153例成人心脏瓣膜患者纳入研究。依据使用心脏停搏液不同而分为两组,HTK停搏液组（71例）和del Nido停搏液（冷D组,82例）。采集血液中心肌损伤标志物数据及愈后情况作临床比较。结果 两组在CPB时间、升主动脉阻断时间、术后机械通气时间、ICU停留时间、术后出院时间、电击复跳率、术后并发症的发生率及病死率等方面均无统计学差异（P>0.05）;两组在术后24 h血液指标中超敏肌钙蛋白（P=0.08）、肌酸激酶（P=0.68）、心肌肌酸激酶同工酶（P=0.06）、N端-BNP（P=0.05）无统计学差异（P>0.05）。在停搏液灌注用量方面冷D组较少（P=0.001）,HTK组所需灌注次数更少（P<0.001）。出院后1月门诊复查,两组患者左心室射血分数值、左心室收缩末内径,左心室舒张末内径无显著性差异（P>0.05）。结论 在心脏瓣膜手术中,应用HTK停搏液及del N...     

Del Nido停搏液在急性主动脉夹层手术中的心肌保护作用及对肾功能的影响

目的:比较Del Nido停搏液与含血停搏液在急性主动脉夹层外科手术中的心肌保护效果及对肾功能的影响.方法:回顾性分析2019年6月至2020年6月因急性主动脉夹层Stanford A型在海军军医大学附属第一医院手术的69例患者,根据术中使用的心脏停搏液分为Del Nido停搏液组(DN组,n=35)和含血停搏液组(C...     

氨基酸在长时间心脏停搏中对心肌的保护作用

目的：探讨谷氨酸盐（Ｇ）和天门冬氨酸盐（Ａ）在长时间心脏缺血的心肌保护作用。方法：离体大鼠工作心模型。心脏在１５°Ｃ缺血１５０分钟。４８只Ｗｉｓｔａｒ大鼠分为３组：１组，即对照组（ｎ＝１６），心脏用多剂量４°ＣＳｔ．Ｔｈｏｍａｓ冷晶体心脏停搏液结合温血停搏液诱导及终末再灌注进行心肌保护；２组（ｎ＝１６）同１组，但温血停搏液含Ｇ和Ａ各１３ｍｍｏｌ／Ｌ；３组（ｎ＝１６）同１组，但Ｓｔ．Ｔｈｏｍａｓ冷晶体心脏停搏液和温血停搏液中均含相同浓度的Ｇ和Ａ。结果：温血停搏液中应用Ｇ和Ａ能增加心肌的收缩性和心输出量，使缺血后心肌耗氧量恢复较好（Ｐ＜０．０５）。Ｓｔ．Ｔｈｏｍａｓ冷晶体心脏停搏液和温血停搏液中应用Ｇ和Ａ均明显增加心肌保护，使心功能和心肌耗氧量几乎完全恢复。缺血后心肌酶漏出少，缺血前后心肌高能磷酸盐含量和含水量无明显变化，超微结构改变也不明显。结论：含Ｇ和Ａ温血停搏液诱导及终末再灌注增加冷晶体心脏停搏液对长时间心脏停搏的心肌保护效果，冷晶体心脏停搏液中也应用Ｇ和Ａ能提高心肌对长时间缺血的耐受性     

del Nido停搏液在常温体外循环下心脏手术中的应用：一项回顾性观察研究

目的 回顾性分析常温体外循环（cardiopulmonary bypass,CPB）与低温CPB使用del Nido停搏液在成人心脏瓣膜手术中的应用效果。方法 回顾性分析2019年1月至2020年12月在广东省人民医院行心肺转流下心脏直视手术的77例成人患者的临床资料。入选患者均在CPB中使用del Nido停搏液进行心肌保护,按照CPB温度管理分成两组,常温组（≥35℃）39例,低温组（31～32℃）38例。观察两组患者手术时间、CPB时间及主动脉阻断时间;同时收集患者心肌损伤标志物及患者预后情况进行比较。结果 常温组患者的手术时间、CPB时间及主动脉阻断时间明显低于低温组,差异有统计学意义（P<0.001）。与低温组患者相比,常温组患者在手术方式、除颤情况、术后机械通气时间、重症监护时间、术后正性肌力药物评分（vasoactive inotropic score,VIS）、术后24 h的左心室射血分数（left ventricular ejection fraction,LVEF）、术后住院时间、围术期死亡、术后恶性心律失常、术后低心排血量综合征等均差异无统计学意义（P>...     

血液心脏停搏后不良反应少于晶体停搏

已有不少小样本随机对照试验比较了血液或晶体停搏液在心脏手术中的心肌保护作用。由于血液的成分比晶体停搏液更接近于正常生理状态，因此在心脏手术中可带来显著的临床益处。为明确血液是否能降低术后不良反应，加拿大多伦多Surmybrook和女子学院Guru等检索了MEDLINE、EMBASE和Cochrane对照试验登记数据库，对相关数据进行荟萃分析，并将分析结果在Circulation[2006，114（1 Suppl）：I331]上发表。     

心脏手术中温血心脏停搏液微流量连灌心肌保护效果的研究

为提高心脏手术中心保护的效果，将20例风湿性心瓣膜病手术患者随机分为温血组与冷血组。温血组术中采用温血心脏停搏液微流量连续灌注，冷血采用冷血心脏停搏液间断灌注行心肌保护。检测两组体外循环主动脉开放后即刻，主动脉开放后6、12、24、72小时血清心肌肌钙蛋白Ⅰ（cTnI）值；术中切取心房肌肉标本，电镜下观察超微结构变化，对比评价心肌保护效果。结果术前及主动脉开放即刻两组血清cTnI无显著性差异（P＞0．05）；主动脉开放后6、12、24、72小时温血组cTnI均显著低于冷血组，P＜0．01；超微结构检测示温血组心肌纤维及线粒体损伤显著轻于冷血组。认为温血心脏停搏液微流量连灌的心肌保护效果优于冷血心脏停搏液间断灌注。     

The application of del Nido cardioplegia for myocardial protection in adult coronary artery bypass grafting: a cohort study

BackgroundDel Nido cardioplegia is widely used in adult cardiopulmonary bypass surgery and has a satisfying cardioprotective effect for about 90 minutes by single dose, but the effect in patients with coronary heart disease remains confused. The purpose of this study was to examine the cardioprotective effect of del Nido cardioplegia in adult multivessel coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB).MethodsThis retrospective comparative analysis included 124 consecutive patients undergoing isolated on-pump CABG performed by a single surgeon between January 2017 and December 2020. The demographic characteristics and medical history of the included patients were collected. The included patients were divided into two groups: a del Nido cardioplegia (DN) group and a conventional multidose blood cardioplegia (BC) group. Perioperative, intraoperative, and postoperative indicators and complications were compared.ResultsCompared with the BC group, CPB and aortic cross-clamp time were significantly shorter in the DN group. In the early postoperative period, the hemoglobin concentration in the DN group was significantly higher than that in the BC group (P<0.05).ConclusionsThis study demonstrated that the application of del Nido cardioplegia in adult on-pump CABG could lead to a significantly shorter aortic cross-clamp and CPB time, as well as a higher hemoglobin concentration in the early postoperative period. The myocardial protective effect of del Nido cardioplegia is not inferior to that of conventional blood perfusion in adult on-pump CABG.     

三种停搏液心肌保护实验研究中心肌结构观察

目的　观察三种方法对体外循环犬心肌在缺血前、缺血中及再灌注后的心肌结构变化,以评价其心肌保护效果。方法　１５ 只犬随机分成３ 组（ ｎ＝ ５） 分别灌注三种停搏液。在心肌缺血前,缺血后１２０ ｍｉｎ 及再灌注３０ ｍｉｎ 于右心室相同部位取心肌作光镜及电镜观察。电镜采用线粒体计数作半定量分析。结果　３ 组在缺血前、中及再灌注后光镜结构无明显改变。电镜结构线粒体半定量分析显示在缺血１２０ ｍｉｎ 及再灌注３０ ｍｉｎ 冷血停搏液间断顺灌组及血利钾停搏液及双向性灌注组心肌线粒体损伤轻于冷晶体停搏液组（Ｐ＜０－０５）。前两组之间无显著差异（ Ｐ＞ ０－０５）。结论三种方法均能提供较好的心肌保护,血利钾停搏液及双向性灌注组心肌保护效果同等于冷血停搏液间断顺灌组,优于冷晶体停搏液间断顺灌组。     

Antegrade and retrograde cardioplegia with different reperfusion techniques in patients with multiple coronary artery lesions.

To evaluate the effectiveness of retrograde cardioplegia and reperfusion, a total of 266 patients undergoing coronary bypass surgery between Nov 1987 to Dec 1989 were divided into three groups depending on the method of cardioplegic fluid delivery and reperfusion. In group I (80 patients) antegrade cardioplegia and reperfusion was used. In group II (98 patients) antegrade and retrograde cardioplegia and antegrade reperfusion was used while in group III antegrade and retrograde cardioplegia and retrograde reperfusion was used. Myocardial functions were studied with the help of an on-line computer on the basis of mathematical model of heart before and after cardiopulmonary bypass. Biopsy specimens were collected before, during and after cardiopulmonary bypass in order to study myocardial structural changes. In group I patients there was decrease in myocardial function in the immediate post perfusion period while group II patients had considerable improvement in their myocardial function and groups III patients showed further improvement in it. Ultrastructural myocardial study revealed considerable detrimental changes in group I, minimal changes in group II and no change in group III patients. Thus in our experience retrograde cardioplegia and retrograde reperfusion with warm oxygenated blood provide maximum myocardial protection in patients with multiple coronary artery lesions.     

The effect of glutamate and aspartate on myocardial protection at cardiopulmonary bypass]

OBJECTIVE: To determine whether glutamat and aspartat enriched cold crystalloid cardioplegia which was given in antegrade way has any effect on the myocardial protection during cardiopulmonary bypass. METHODS: Thirty-four patients who were electively undergone open heart surgery at Osmangazi University Faculty of Medicine, thoracic and cardiovascular surgery department, between March 2001 and May 2001 were included in this study. The patients were divided in two groups, each consisting of 17 patients. In group 1 coronary artery bypass surgery (CABG) was performed in 11 patients, mitral valve replacement (MVR) in 3 patients, aortic valve replacement (AVR) in 1 patient and AVR and MVR in 2 patients. While in group 2 CABG was performed in 13 patients and MVR was done in 4 patients. Group 1 patients received antegrade glutamat and aspartat (15 mmol/L) enriched cold crystalloid cardioplegia and group 2 patients were given cold crystalloid cardioplegia by antegrade route. Age, gender, diabetes mellitus, hypertension, preoperative myocardial infarction, smoking, ejection fraction, aortic cross-clamp time, need to defibrillation, inotropic support, and intraaortic balloon pump were recorded. The levels of cardiac troponin I (cTI) and creatine kinase myocardial band fraction (CK-MB) were measured in arterial blood samples at five different times. Statistical analysis was performed using Student's t-test and Chi-square test. RESULTS: There were no statistically significant differences in cTI and CK-MB values in blood samples taken at 5 different times pre and postoperatively between group 1 and group 2. CONCLUSION: It is concluded that glutamat and aspartat enriched cold crystalloid cardioplegia does not have any effect on myocardial protection.     

晶体停跳液和含血停跳液的临床应用研究

目的：观察晶体停跳液和含血停跳液对心肌的保护作用。方法：２０例择期性心脏瓣膜替换术患者分别用晶体停跳液（１０例）和含血停跳液（１０例）灌注的结果进行分析。结果：两组在直视手术中心脏停跳良好。围术期血液动力学指标，平均动脉压、中心静脉压、心率无明显差异。心肌摄氧率大致相同。但晶体停跳液组的冠状动脉乳酸摄取率明显低于含血停跳液组，而含血停跳液组的血浆肌酸激酶及其同功酶的水平明显低于晶体停跳液组。电子显微镜观察可见晶体停跳液组右心房心肌的超微结构（线粒体、肌丝）严重损坏，而含血停跳液组对其有明显保护效果。含血停跳液组自动复跳率（６０．５％）明显高于晶体停跳液组（４４．９％）。结论：含血停跳液有很多优点，如临床安全性、心肌酶释放减少、超微结构损伤轻等。     

Myocardium utilizes more oxygen and glucose during tepid blood cardioplegic infusion in arrested heart

The aims of this study were to evaluate myocardial metabolic activity during tepid blood cardioplegic infusion in the arrested heart in comparison with cold blood cardioplegia and to assess the early clinical outcomes of these patients. Thirty patients undergoing first elective coronary artery bypass grafting surgery were included and randomized to two groups (T for tepid and C for cold), 15 patients in each. Myocardial protection was similar in both groups except for the reinfusion of blood cardioplegia, which was 6 degrees C in group C and 28 degrees C in group T (same temperature as the body perfusion). The route of cardioplegic reinfusion was antegrade during the first reinfusion and retrograde during the second reinfusion. In order to assess myocardial metabolic activity, myocardial oxygen consumption (MVO2), myocardial glucose uptake, and myocardial lactate and acid production were all calculated. Arterial and coronary venous blood samples were obtained from the aortic root cannula and coronary sinus. During cardioplegic re-infusions in the ischemic period, the calculated values of myocardial oxygen extraction, oxygen consumption, and glucose uptake were higher in group T than in group C (P < 0.05). This difference was observed during both antegrade and retrograde delivery of cardioplegic solution. Myocardial lactate production was greater in group C than in group T during cardioplegic reinfusion, both antegradely and retrogradely (P < 0.05). In all patients, cardiopulmonary bypass was terminated in the first attempt. The clinical outcome was similar in both groups. The results of this study indicate that globally ischemic myocardium is able to utilize more oxygen and glucose during cardioplegic re-infusions at a tepid temperature in comparison to cold. In addition, the data showed evidence of less myocardial injury and better left ventricular function throughout the critical period of recovery from global ischemia for the heart protected by tepid cardioplegia.     

Effect of Cardioplegia for Myocardial Protection in Pediatric Cardiac Surgery: A Network Meta-Analysis

Cardioplegia has been widely used to reduce myocardial injury during pediatric cardiac surgery; however, which cardioplegia solution has the best protective effect has not been established. Thus, we compared the myocardial protective effects of different cardioplegia solutions used in pediatric cardiac surgery. Seven databases were searched to identify the relevant randomized controlled trials. A network meta-analysis with a Bayesian framework was conducted. The outcomes included the following biochemical and clinical outcomes: serum concentrations of the creatine kinase-myocardial band at 6 h postoperatively; cardiac troponin I (cTnI) at 4, 12, and 24 h postoperatively; spontaneous beating after declamping; postoperative arrhythmias; inotropic support percentage and duration; mechanical ventilation hours; intensive care unit stay in days; hospital stay in days; and mortality. The group treated with cold crystalloid cardioplegia (cCCP) was chosen as the control group. The 22 studies involved 1529 patients. Six types of cardioplegia solutions were described in these studies, including cold blood cardioplegia, cCCP, del Nido, histidine-tryptophan-ketoglutarate (HTK), terminal warm blood cardioplegia, and warm blood cardioplegia (wBCP). The serum concentrations of the 24-h cTnI with wBCP (MD = −2.52, 95% CI: −4.74 to −0.27) was significantly lower than cCCP. The serum concentrations of the 24-h cTnI with HTK (MD = 4.91, 95%CI: 2.84–7.24) was significantly higher than cCCP. There was no significant difference in other biochemical and clinical outcomes when compared to cCCP. In conclusion, wBCP may have a superior myocardial protective effect with lower 24-h cTnI levels postoperatively and similar clinical outcomes after pediatric cardiac surgery.     

Continuous warm blood cardioplegia: A randomized prospective clinical comparison

Seventy-eight patients undergoing isolated coronary artery bypass grafting (CABG) were randomized to receive one of two myocardial preservation techniques. Control patients (C) (n=38) had myocardial protection by moderate systemic hypothermia, topical cold saline, and myocardial arrest with antegrade dilute blood/cold potassium cardioplegia with subsequent intermittent retrograde solution every 10–15 minutes during the period of aortic cross-clamping. The experimental group (warm blood, WB) (n=40) had myocardial protection at systemic normothermia, myocardial arrest with antegrade high potassium, and warm blood cardioplegia with subsequent continuous retrograde low potassium warm blood cardioplegia throughout aortic cross-clamping. The two groups were similar preoperatively. After aortic declamping, all WB patients developed a spontaneous rhythm. Only three (7.5%) required intraoperative defibrillation compared with 23 (61%) C patients,p<0.0001. The cross-clamp time per graft was greater with WB,p=0.003. The postoperative need for inotropes, cardiac pacing, incidence of ventricular dysrhythmia, chest tube drainage, and hospital stay did not differ between groups. Perioperative myocardial infarction occurred in 2 WB and 0 C patients (p=0.25). Mortality was not different between groups (WB=1, C=2,p=0.89). It is possible to perform CABG with continuous warm blood cardioplegia with low morbidity and mortality. However, no clear advantage was demonstrated over standard techniques that allow the technical ease of a bloodless field. The metabolic and physiologic significance of spontaneous resumption of sinus rhythm upon aortic declamping remains to be elucidated.     

磷酸肌酸含血心停搏液对联合瓣膜置换术心肌保护作用研究

目的观察含血圣.托马斯(STH2)液加入外源性磷酸肌酸(CP)后对重症瓣膜病患者联合瓣膜置换术心肌保护作用。方法40例同期行二尖瓣、主动脉瓣置换术患者随机分为两组,CP治疗组在含血STH2心灌注液中加入CP,对照组用等量含血STH2液,分别切开主动脉根部经冠状动脉窦直接灌注,观察心脏复搏情况、术后机械通气及监护室停留情况。两组分别于麻醉诱导前、诱导后、主动脉阻断开放后6h、16h,采集患者中心静脉血,测血细胞比积(HCT)、磷酸肌酸激酶同工酶(CK-MB)、心肌钙蛋白I(cTn-I)。结果CP治疗组心脏自动复搏率较对照组高,术后多巴胺用量较对照组少,两组术后CK-MB、cTn-I较术前高,CP治疗组较对照组高。结论CP加入心停搏液中能显著提高心肌保护作用。     

Myocardial protection in valvular surgery by retroperfusion of the coronary sinus with cardioplegic solution in valve surgery. Immediate results and technical considerations

Retrograde coronary sinus perfusion as a means of delivering cardioplegia was evaluated in 20 patients undergoing cardiac valve surgery. Other 10 patients, undergoing similar operation with antegrade coronary cardioplegic perfusion served as a control. Results showed no significant differences between the two groups of patients in terms of: myocardial cooling; pre-ischemic and post-perfusion myocardial lactate extraction; post-operative clinical findings (myocardial infarction occurrence, need for inotropic support, mortality). We conclude that retroperfusion through the coronary sinus is a safe and effective alternative of cardioplegic delivery. Since it simplifies the operative procedure (it allows the cardioplegia delivery at any desired time of the operation, without discontinuing the procedure), we recommended its use during valvular cardiac operations, especially on aortic valve replacement.