Factors influencing preoperative stress response in coronary artery bypass graft patients

BACKGROUND: In many studies investigating measures to attenuate the hemodynamic and humoral stress response during induction of anaesthesia, primary attention was paid to the period of endotracheal intubation since it has been shown that even short-lasting sympathetic cardiovascular stimulation may have detrimental effects on patients with coronary artery disease. The aim of this analysis was, however, to identify the influencing factors on high catecholamine levels before induction of anaesthesia. METHODS: Various potential risk factors that could impact the humoral stress response before induction of anaesthesia were recorded in 84 males undergoing coronary aortic bypass surgery, and were entered into a stepwise linear regression analysis. The plasma level of norepinephrine measured immediately after radial artery canulation was chosen as a surrogate marker for the humoral stress response, and it was used as the dependent variable in the regression model. Accordingly, the mean arterial blood pressure, heart rate and the calculated pressure-rate product were taken as parameters of the hemodynamic situation. RESULTS: Stepwise regression analysis revealed that the oral administration of low-dose clonidine (mean dose 1.75 μg.kg-1) on the morning of surgery was the only significant predictor (p = 0.004) of the high variation in preoperative norepinephrine plasma levels. This intervention decreased norepinephrine levels by more than 40% compared to no clonidine administration, from 1.26 to 0.75 nmol.l-1. There was no evidence for dose-responsiveness of clonidine. All other potential predictors were removed from the model as insignificant (p > 0.05). The use of beta-blocker, ace-inhibitors, ejection fraction, and body mass index were significant determinants for the hemodynamic situation (heart rate, mean arterial pressure, pressure rate product) of the patient during the pre-induction period. CONCLUSION: The oral administration of clonidine is the only significant predictor for the observed variation of norepinephrine levels during the preoperative period. Lack of significant dose responsiveness suggests that even a low dose of the drug can attenuate the preoperative stress response and thus is recommended in cardiovascular high risk patients.     

The sheep as a model for coronary artery bypass surgery

The sheep is considered to be a suitable model for cardiovascular surgery because of its ease of handling, size, and vascular anatomy which bears close resemblance to the human. Several difficulties, however, have limited the use of the sheep for such a purpose-mainly the high infection rate resulting from median sternotomy incision and its susceptibility to intractable ventricular fibrillation (VF) with the slightest manipulation of the heart, and even the risk of short periods of myocardial ischaemia. We have used the sheep model extensively to perform coronary artery bypass surgery and were successful in overcoming these difficulties. Fifty-seven adult female sheep were used to test a new anastomotic device for the creation of a sutureless connection between venous and arterial grafts and the coronary arteries. The study required full access to the heart and great vessels and mobilization of one of the internal mammary arteries. Changing to the left lateral thoracotomy (LLT) approach solved the initial fatal problems of postoperative infected median sternotomy incisions. Aggressive prophylactic treatment with anti-arrhythmic drugs, maintenance of normothermia and myocardial preconditioning rendered the heart much less vulnerable to manipulations and ischaemia. These measures have reduced the mortality rate from 45% to 0% (P <0.0001). With specific operative techniques and pharmaceutical interventions, the sheep can be effectively and safely used as a model for coronary artery surgery.     

The current status of anastomotic devices for coronary artery bypass surgery

The purpose of this article is to briefly review the history of proximal and distal anastomotic devices and to discuss presently available devices. Clinical outcome data from the EPIC Trial of the Cardica PAS-Port Proximal Anastomosis System will also be presented.     

Predictors of postoperative atrial fibrillation after coronary artery bypass graft surgery

Objectives

The present study was aimed to identify the preoperative, intraoperative, and postoperative predictors of AF in a pure cohort of the patients with coronary artery disease who underwent CABG surgery.

Methods

Between November 2005 and May 2006, 302 consecutive patients were included in this prospective study. All the relevant clinical, electrocardiographic, echocardiographic, and laboratory data were gathered in the included patients and they were also monitored for development of post-CABG AF.

Results

Postoperative AF occurred in 46 (15%) of patients. By univariate analysis, older age, P-wave abnormality in ECG, presence of mitral regurgitation, larger left atrium (LA), left main coronary artery involvement, failure to graft right coronary artery (RCA), and adrenergic use in ICU were significantly associated with occurrence of post-CABG AF (all P< 0.05). However, in the logistic regression model, age (OR: 1.067, 95%CI: 1.02-1.116, P=0.005), LA dimension (OR: 1.102, 95%CI: 1.017-1.1936, P=0.017), P-wave morphology (OR: 12.07, 95%CI: 3.35-48.22, P=0.0001), failure to graft RCA (OR: 3.57, 95%CI: 1.20-10.64, P=0.022), and postoperative adrenergic use (OR: 0.35, 95%CI: 0.13-0.93, P=0.036) remained independently predictive of postoperative AF.

Conclusion

The present study suggested that age, P-wave morphology, LA dimension, failure to graft right coronary artery, and postoperative adrenergic use were independent predictors of post-CABG AF. Therefore, clinical data, ECG and echocardiography may be useful in preoperative risk stratification of the surgical patients for the occurrence of post-CABG AF.     

Tetraplegia after coronary artery bypass surgery in a patient with cervical herniation

Tetraplegia is a rare complication after coronary artery bypass surgery. The authors present a case of tetraplegia after uncomplicated coronary artery bypass surgery because of cervical disc herniation. No distinct abnormality was found in the preoperative neurologic examination although the postoperative cervical magnetic resonance imaging revealed a huge hernia at C5-C6 level presenting with tetraplegia. Surgical decompression was performed on the second postoperative day of bypass surgery, and neurologic deficits gradually improved.     

B-mode and color Doppler ultrasound of the forearm arteries in the preoperative screening prior to coronary artery bypass grafting

The objective of this paper was to establish the normal findings of B-mode and color Doppler ultrasound of the forearm arteries in candidates for coronary artery bypass grafting with radial artery graft. Examination of radial and ulnar arteries was performed in 127 patients. The vessel diameters and peak systolic velocities were measured and the presence of atherosclerotic changes, calcifications and anatomical variants was assessed. Radial artery proved to be dominant forearm artery with non-significant side-to-side asymmetry. The luminal changes were present in 30% of the patients. Ulnar arteries were more prone to these changes than radial arteries (28.4% vs. 24.4%). The anatomical variants found included ulnar artery hypoplasia in 3.9% of patients and high brachial artery bifurcation in 2.4% of patients. No cases of high-grade stenosis or occlusion were found. The results of the present study indicate that B-mode and color Doppler are valuable methods for preoperative screening as they enable morphological and functional evaluation of the forearm circulation.     

80岁以上老年人冠状动脉旁路移植术合并瓣膜置换手术的临床分析

目的：总结老年患者行冠状动脉旁路移植术（CABG）合并瓣膜置换（VR）手术的特点及经验。方法：上海交通大学附属第一人民医院心血管外科2001年11月至2010年3月对60例年龄大于80的患者施行冠状动脉搭桥＋瓣膜置换手术,男33例,女27例。年龄80-87岁,平均年龄（83.77±2.45）岁。均为冠心病合并瓣膜病变患者。其中36例患者行冠状动脉旁路移植＋二尖瓣置换手术,15例患者行冠状动脉旁路移植＋主动脉瓣置换手术,9例患者行冠状动脉旁路移植＋双瓣置换手术,同时8例患者行三尖瓣成形手术,3例患者行射频消融手术,1例升主动开成形术。置换生物瓣膜者51例,置换机械瓣膜者9例。CABG平均搭桥（2.13±0.75）根,搭桥材料为左乳内动脉与大隐静脉。结果：全组早期死亡9例（15%）,1例死于术后出血,1例死于多器官功能衰竭,7例死于术后心衰。早期生存51例（85%）,出现术后并发症10例,其中2例发生胸腔积液,1例心包填塞,3例肺部感染,1例心房扑动后发生室颤,3例二次开胸止血。给予相应对症治疗后痊愈出院。门诊随访49例,随访时间1～60个月,心功能I级2例、Ⅱ级29例、Ⅲ级18例、Ⅳ级0例（NYHA分级）。结论：对老年患者行冠脉搭桥＋瓣膜置换手术,只要掌握手术适应证,充分作好术前准备、术中及术后处理,手术治疗可以取得良好效果。     

Measurement of the flow in coronary artery bypass grafts

The aim of our study was to measure the flow in coronary artery bypass grafts and to compare the flow between two groups of patients. In group A the arterial revascularization was performed with both internal thoracic arteries using as a Y graft and in group B conventional revascularization using left internal thoracic artery (ITA) attached to the left anterior descending artery (LAD) and venous grafts to the other branches of the left coronary artery was performed. The flow in all grafts was measured at six time points during the operation. The cumulative flow at the end of the operation in the group A (arterial Y graft) was 51.8 +/- 24.5 ml/min and in group B (conventional technique) it was 96.8 +/- 41.1 ml/min (p < 0.05). The flow in left ITA to LAD was similar in both groups (27.3 +/- 15.9 ml/min and 26.3 +/- 16.1 ml/min in group A and B). The flow in right ITA (25.2 +/- 18.4 ml/min) was significantly lower than in venous grafts (72.5 +/- 45.5 ml/min). The calculated flow reserve was 2.2 in group A and 2.1 in group B. We found that the cumulative flow in arterial Y graft was lower in comparison with conventional revascularization. This is due to the lower flow in the right ITA branch of the Y graft compared to venous grafts. However based on clinical results, we can postulate that the flow in the Y graft is sufficient to meet the demand of the myocardium originally supplied by the left coronary artery.