Aung Oo

Risk of morbidity and in-hospital mortality in obese patients undergoing coronary artery bypass surgery

OBJECTIVES Obesity is often perceived to be a risk factor for adverse outcomes following coronary artery bypass graft (CABG) surgery. Several studies have been unclear about the relationship between obesity and the risk of adverse outcomes. The aim of this study was to examine the relationship between obesity and in-hospital outcomes following CABG, while adjusting for confounding factors. METHODS A total of 4713 consecutive patients undergoing isolated CABG between April 1997 and September 2001 were retrospectively analyzed. Body mass index (BMI) was used as the measure of obesity and was grouped as non-obese (BMI <30), obese (BMI 30-35), and severely obese (BMI > or =35). Associations between obesity and in-hospital outcomes were assessed by use of logistic regression to adjust for differences in patient characteristics. RESULTS A total of 3429 patients were defined as non-obese, compared to 1041 obese and 243 severely obese. There was no association between obesity and in-hospital mortality, stroke, myocardial infarction, re-exploration for bleeding and renal failure. Obesity was significantly associated with atrial arrhythmia (adjusted odds ratio (OR) 1.19, P = 0.037 for the obese; adjusted OR 1.52, P = 0.008 for the severely obese) and sternal wound infections (adjusted OR 1.82, P = 0.002 for the obese; adjusted OR 2.10, P = 0.038 for the severely obese). The severely obese patients were 4.17 (P < 0.001) times more likely to develop harvest site infections. Severely obese patients were also more likely to have prolonged mechanical ventilation and post-operative stays, compared to non-obese patients. CONCLUSIONS Obese patients are not associated with an increased risk of in-hospital mortality following coronary artery bypass surgery. In contrast, there is a significant increased risk of morbidities and post-operative length of stay in obese patients compared to non-obese patients.

A meta-analysis of deep hypothermic circulatory arrest versus moderate hypothermic circulatory arrest with selective antegrade cerebral perfusion

INTRODUCTION A recent concern of deep hypothermic circulatory arrest (DHCA) in aortic arch surgery has been its potential association with increased risk of coagulopathy, elevated inflammatory response and end-organ dysfunction. Recently, moderate hypothermic circulatory arrest (MHCA) with selective antegrade circulatory arrest (SACP) seeks to negate potential hypothermia-related morbidities, while maintaining adequate neuroprotection. The present meta-analysis aims to compare postoperative outcomes in arch surgery using DHCA or MHCA+SACP as neuroprotective strategies. METHODS Electronic searches were performed using six databases from their inception to January 2013. Two reviewers independently identified all relevant studies comparing DHCA with MHCA+SACP, as defined by a recent hypothermia temperature consensus. Data were extracted and meta-analyzed according to pre-defined clinical endpoints. RESULTS Nine comparative studies were identified for inclusion in the present meta-analysis. Stroke rates were significantly lower in patients undergoing MHCA+SACP (P=0.0007, I(2)=0%), while comparable results were observed with temporary neurological deficit, mortality, renal failure or bleeding. Infrequent and inconsistent reporting of systemic outcomes precluded analysis of other systemic outcomes. CONCLUSIONS The present meta-analysis indicated the superiority of MHCA+SACP in terms of stroke risk.

Intravenous hydration versus naso-jejunal enteral feeding after esophagectomy: a randomised study

OBJECTIVE Patients undergoing esophagectomy are typically nutritionally depleted and cannot establish oral feeding for up to a week after surgery. We have investigated the routine use of enteral feeding via a naso-jejunal tube. METHODS Forty consecutive patients undergoing a transthoracic esophagectomy for cancer were randomised to receive enteral feeding or intravenous crystalloid fluids after surgery. Nutritional indices were obtained prior to surgery and on the 7th post-operative day. RESULTS There were no post-operative deaths. Non-fatal complications occurred in 10 patients, without difference in morbidity between the two groups. Lean body mass did not change in either group over the study period. No differences in any other parameters were identified between the two groups. CONCLUSION Enteral feeding via a naso-jejunal tube is safe and well tolerated after esophagectomy. It is a simple method of providing nutritional support prior to the re-introduction of oral feeding. However it provides no measurable benefit over intravenous hydration only for patients undergoing routine esophagectomy.

Ascending aortic curvature as an independent risk factor for type a dissection, and ascending aortic aneurysm formation: a mathematical model

OBJECTIVE To develop a mathematical model to demonstrate that ascending aortic curvature is an independent risk factor for type A dissections, in addition to hypertension, bicuspid aortic valve, aneurysm of ascending aorta, and intrinsic aortic tissue abnormalities, like Marfans syndrome. METHODS A steady state one-dimensional flow analysis was performed, utilising Newtons third law of motion. Five different clinical scenarios were evaluated: (1) effect of aortic curvature; (2) effect of beta-blockers, (3) effect of patient size, (4) forces on a Marfans aorta, and (5) site of entry flap in aortic dissection. RESULTS Aortic curvature increases the forces exerted on the ascending aorta by a factor of over 10-fold. Aortic curvature can cause patients with a systolic blood pressure of 8 0mmHg to have greater forces exerted on their aorta despite smaller diameters and lower cardiac outputs, than patients with systolic blood pressures of 120 mmHg. In normal diameter aortas, beta-blockers have minimal effect compared with aortic curvature. Aortic curvature may help to explain why normal diameter aortas can dissect, and also that the point of the entry tear may be potentially predictable. Aortic curvature has major effects on the forces exerted on the aorta in patients with Marfans syndrome. CONCLUSIONS Aortic curvature is relatively more important that aortic diameter, blood pressure, cardiac output, beta-blocker use, and patient size with regard to the force acting on the aortic wall. This may explain why some patients with normal diameter ascending aortas with or without Marfans syndrome develop type A dissections and aneurysms. Aortic curvature may also help to explain the site of entry tear in acute type A dissection. Further clinical study is needed to validate this studys finding.

Phenoxybenzamine treatment is insufficient to prevent spasm in the radial artery: the effect of other vasodilators

OBJECTIVES After its reintroduction as an arterial graft in coronary artery surgery, the radial artery is now established as an alternative arterial conduit, with good early and midterm patency. However, because of the concern about its vasospasticity, numerous vasodilator strategies have been used. Recently the use of the irreversible alpha-adrenergic antagonist phenoxybenzamine has been proposed. Although this treatment is effective in eliminating the vasoconstriction mediated by noradrenaline, the contribution of other circulating vasoconstrictors to vasospasm could be as important. This study investigates the response of radial arteries treated with phenoxybenzamine to vasoconstrictor stimuli and possible preventative strategies. METHODS In vitro, sections of radial artery, pretreated with phenoxybenzamine after harvesting, were stimulated with maximal concentrations of the vasoconstrictors noradrenaline, vasopressin, angiotensin II, KCl, and endothelin-1. In matched segments of artery, vasoconstrictor responses were recorded in the presence of diltiazem, glyceryl trinitrate, and papaverine and compared with phenoxybenzamine-treated samples. RESULTS Phenoxybenzamine-treated radial artery failed to respond to noradrenaline but did respond to vasopressin, angiotensin II, endothelin-1, and KCl. Diltiazem was largely ineffective against contractile stimuli apart from KCl. Glyceryl trinitrate and papaverine significantly reduced responses to all of the vasoconstrictors tested. CONCLUSION In phenoxybenzamine-treated sections of radial artery, circulating vasoconstrictor agonists may still contribute to the induction of spasm. Additional vasodilator strategies may be required to completely prevent vasospasm.

A meta-analysis of deep hypothermic circulatory arrest alone versus with adjunctive selective antegrade cerebral perfusion.

INTRODUCTION Recognizing the importance of neuroprotection in aortic arch surgery, deep hypothermic circulatory arrest (DHCA) now underpins operative practice as it minimizes cerebral metabolic activity. When prolonged periods of circulatory arrest are required, selective antegrade cerebral perfusion (SACP) is supplemented as an adjunct. However, concerns exist over the risks of SACP in introducing embolism and hypo- and hyper-perfusing the brain. The present meta-analysis aims to compare postoperative outcomes in arch surgery using DHCA alone or DHCA + SACP as neuroprotection strategies. METHODS Electronic searches were performed using six databases from their inception to January 2013. Two reviewers independently identified all relevant studies comparing DHCA alone with DHCA + SACP. Data were extracted and meta-analyzed according to pre-defined clinical endpoints. RESULTS Nine comparative studies were identified in the present meta-analysis, with 648 patients employing DHCA alone and 370 utilizing DHCA + SACP. No significant differences in temporary or permanent neurological outcomes were identified. DHCA + SACP was associated with significantly better survival outcomes (P=0.008, I(2)=0%), despite longer cardiopulmonary bypass time. Infrequent and inconsistent reporting of other clinical results precluded analysis of systemic outcomes. CONCLUSIONS The present meta-analysis indicate the superiority of DHCA + SACP in terms of mortality outcomes.

Standardizing Clinical End Points in Aortic Arch Surgery A Consensus Statement From the International Aortic Arch Surgery Study Group

Since the introduction of hypothermic circulatory arrest for aortic arch surgery in 1975,1 there has been considerable progress in addressing this complex surgical pathology.2–4 However, the rapidity with which operative techniques have evolved has outpaced methodical appraisal of their clinical merit, leaving behind a wealth of perfunctory data. In particular, existing emphasis on neurological outcomes has neglected other critical end points, whereas inconsistent definitions and reporting formats limit the applicability of the results of some studies. Robust comparisons between institutional reports are therefore difficult, restricting critical appraisal and summary of existing surgical approaches. The International Aortic Arch Surgery Study Group (IAASSG) has been formed to enable multi-institutional collaboration to better explore the impact of surgical techniques on patient outcomes, using uniform definitions of events and clinical end points. A key endeavor is to standardize reporting formats to facilitate effective comparisons. Such a concerted effort, with the combined expertise of leading academic surgeons, paves the way for a unified language specific for aortic arch surgery that promotes closer cooperation and systematic evaluation and is essential in forming a framework of existing knowledge and guiding progress and research for the future.5,6 The IAASSG has devised a management-orientated classification system for significant clinical end points specific for aortic arch surgery and has undertaken a consensus survey of leading arch surgeons. The following report describes this classification scheme and reports the results of the consensus. ### Rationales of the Grading System A management-oriented classification system for complications, which grades adverse events by severity on the basis of the management required, is simple, reproducible, and comprehensive.7 It avoids duplication of overlapping results and limits the fluctuating ratings of negative outcomes between institutions by providing standardized definitions.7,8 Stratifying the severity of relevant complications into grades allows more thorough analysis to be …

The ARCH Projects: design and rationale (IAASSG 001)

OBJECTIVE A number of factors limit the effectiveness of current aortic arch studies in assessing optimal neuroprotection strategies, including insufficient patient numbers, heterogenous definitions of clinical variables, multiple technical strategies, inadequate reporting of surgical outcomes and a lack of collaborative effort. We have formed an international coalition of centres to provide more robust investigations into this topic. METHODS High-volume aortic arch centres were identified from the literature and contacted for recruitment. A Research Steering Committee of expert arch surgeons was convened to oversee the direction of the research. RESULTS The International Aortic Arch Surgery Study Group has been formed by 41 arch surgeons from 10 countries to better evaluate patient outcomes after aortic arch surgery. Several projects, including the establishment of a multi-institutional retrospective database, randomized controlled trials and a prospectively collected database, are currently underway. CONCLUSIONS Such a collaborative effort will herald a turning point in the surgical management of aortic arch pathologies and will provide better powered analyses to assess the impact of varying surgical techniques on mortality and morbidity, identify predictors for neurological and operative risk, formulate and validate risk predictor models and review long-term survival outcomes and quality-of-life after arch surgery.

Does prophylactic sotalol and magnesium decrease the incidence of atrial fibrillation following coronary artery bypass surgery: a propensity-matched analysis

BackgroundAtrial fibrillation can occur in up to 40% of patients undergoing coronary surgery.MethodsWe retrospectively analysed 103 consecutive coronary surgery patients under the care of one surgeon between April 2003 and September 2003. These patients received 40 mg of sotalol orally twice daily from the first post-operative day for 6 weeks and 2 g of magnesium intravenously immediately post surgery and on the first post-operative day. We developed a propensity score for the probability of receiving sotalol and magnesium after coronary surgery. 89 patients from the sotalol and magnesium group were successfully matched with 89 unique coronary surgery patients who did not receive either sotalol or magnesium with an identical propensity score.ResultsPreoperative characteristics were well matched between groups. There was no significant difference with respect to in-hospital mortality between groups (sotalol and magnesium 1.1% versus control 4.5%; p = 0.17). The incidence of atrial fibrillation in the sotalol and magnesium group was 13.5% compared to 27.0% in the controls (p = 0.025).ConclusionThe combination of sotalol and magnesium can significantly reduce the incidence of post-operative atrial fibrillation following coronary surgery.

The effect of patient sex on survival in patients undergoing isolated coronary artery bypass surgery receiving a radial artery

OBJECTIVES To determine whether patient sex makes a difference to in-hospital mortality and survival in patients undergoing isolated coronary artery bypass graft surgery (CABG) receiving a radial artery graft. METHODS Analysis of consecutive patients on a validated prospective cardiac surgery database was performed for patients undergoing isolated CABG. Uni- and multivariate analyses were performed for in-hospital mortality and long-term survival. A propensity analysis was also performed. RESULTS Overall mortality was 2.1% (n = 284) for all cases, n = 13 369. Median follow-up was 7.0 (interquartile range 4.1-10.1) years. Of the cases 28.2% of males (n = 384) and 29.7% of females (n = 764) had a radial artery utilized. Univariate analysis demonstrated that in-hospital mortality was significantly lower in male patients, P < 0.001, and radial artery use was associated with increased survival in males, P < 0.0001, but not in females, P = 0.82. In male patients, multivariate analysis failed to identify the radial artery as a risk factor for in-hospital death. The radial artery was identified as a significant prognostic factor, associated with improved long-term survival (hazard ratio [HR] 0.78, 95% confidence interval [CI] 0.69-0.88, P = 0.0001). Propensity analysis confirmed this finding (HR 0.76, 95% CI 0.67-0.86, P < 0.0001). In female patients, multivariate analysis failed to identify the radial artery as a significant factor determining in-hospital mortality or long-term survival. Propensity analysis confirmed these findings. CONCLUSION Males derive a significant survival advantage if they receive a radial artery graft when undergoing isolated CABG. The radial artery makes no difference to long-term survival in female patients. Radial artery use does not affect in-hospital mortality regardless of patient sex.