Brian M. Fabri

Risk factors for sternal wound infection and mid-term survival following coronary artery bypass surgery

OBJECTIVE To identify risk factors for sternal wound infection following coronary artery bypass surgery (CABG), and to compare early and mid-term survival outcome. METHODS Data were prospectively collected for 4228 patients who underwent CABG surgery between April 1997 and March 2001. One hundred and nine (2.6%) patients developed sternal wound infection. We used logistic regression to identify independent risk factors associated with post-operative sternal wound infection. Patient records were linked to the National Strategic Tracing Service, which records all deaths in the UK, to establish current vital status. Deaths occurring over time were described using Kaplan-Meier techniques. To control for differences in patient characteristics, we used Cox proportional hazards analysis to calculate adjusted hazard ratios (HR) and 95% confidence intervals (CI). RESULTS The results of the logistic regression analysis found that the independent predictors of sternal wound infection were obesity (odds ratio (OR) 2.0; P<0.001), New York Heart Association class >/=3 (OR 1.6; P=0.022), use of bilateral internal mammary arteries (OR 3.2; P<0.001), increasing number of grafts (OR 1.5; P<0.001), re-exploration for bleeding (OR 3.1; P=0.011), and increased duration of mechanical ventilation (for every 10 h (OR 1.12; P<0.001)). Three hundred and forty one (8.1%) deaths occurred during the study period with mean follow up of 3.2+/-1.3 years. The crude HR of mid-term mortality for sternal wound infection patients was 2.51 (95% CI 1.59-3.94, P<0.001). After adjustment for pre, intra and post-operative factors, the adjusted HR of mid-term mortality for sternal wound infection patients was 1.64 (95% CI 1.03-2.61, P=0.037). The adjusted freedom from death for sternal wound infections at 30 days, and 1, 2 and 4 years was 96.8, 93.7, 91.4 and 86.7%, respectively, compared with 98.1, 96.1, 94.7 and 91.7% for patients without sternal wound infections. CONCLUSIONS In conclusion, we have identified risk factors for sternal wound infection, many of which are modifiable. We have also shown that there is a significant increase in mortality in patients with sternal wound infection during a 4-year follow-up period after CABG.

The logistic EuroSCORE in cardiac surgery: How well does it predict operative risk?

Objectives: To study the ability of the logistic EuroSCORE to predict operative risk in contemporary cardiac surgery. Design: Retrospective analysis of prospectively collected data. Setting: All National Health Service centres undertaking adult cardiac surgery in northwest England. Patients: All patients undergoing cardiac surgery between April 2002 and March 2004. Main outcome measures: The predictive ability of the logistic EuroSCORE was assessed by analysing how well it discriminates between patients with differing observed risk by using the area under the receiver operating characteristic (ROC) curve and studying how well it is calibrated against observed in-hospital mortality. The performance of the EuroSCORE was examined in the following surgical subgroups: all cardiac surgery, isolated coronary artery surgery, isolated valve surgery, combined valve and coronary surgery, mitral valve surgery, aortic valve surgery and other surgery. Results: 9995 patients underwent surgery. The discrimination of the logistic EuroSCORE was good with a ROC curve area of 0.79 for all cardiac surgery (range 0.71–0.79 in the subgroups). For all operations, the predicted mortality was 5.7% and observed mortality was 3.3%. The logistic EuroSCORE overpredicted observed mortality for all subgroups but by differing degrees (p  =  0.02) Conclusions: The logistic EuroSCORE is a reasonable overall predictor for contemporary cardiac surgery but overestimates observed mortality. Its accuracy at predicting risk in different surgical subgroups varies. The logistic EuroSCORE should be recalibrated before it is used to gain reassurance about outcomes. Caution should be exercised when using it to compare hospitals or surgeons with a different operative case mix.

Has the publication of cardiac surgery outcome data been associated with changes in practice in northwest England: an analysis of 25 730 patients undergoing CABG surgery under 30 surgeons over eight years

Objectives: To study changes in coronary artery surgery practice in the years spanning publication of cardiac surgery mortality data in the UK. Methods: A retrospective analysis of prospectively collected data from all National Health Service centres undertaking adult cardiac surgery in northwest England was carried out. Patients undergoing coronary artery surgery for the first time between April 1997 and March 2005 were included. Changes in observed, predicted and risk adjusted mortality (EuroSCORE) were studied. Evidence of risk-averse behaviour was looked for by examining the number of patients at low risk (EuroSCORE 0–5), high risk (6–10), and very high risk (11 or more), before and after public disclosure. Results: 25 730 patients underwent coronary artery surgery during the study period. The observed mortality decreased from 2.4% in 1997–8 to 1.8% in 2004–5 (p = 0.014). The expected mortality (EuroSCORE) increased from 3.0 to 3.5 (p<0.001). The observed to expected mortality ratio decreased from 0.8 to 0.51 (p<0.05). The total number and percentage of patients who were at low risk, high risk and very high risk was 2694 (84.6%), 449 (14.1%) and 41 (1.3%) before and 2654 (81.7%), 547 (16.8%) and 47 (1.4%) after public disclosure, respectively, demonstrating a significant increase in the number and proportion of high risk patients undergoing surgery (p<0.001). Conclusions: Publication of cardiac surgery mortality data in the UK has been associated with decreased risk adjusted mortality on retrospective analysis of a large patient database. There is no evidence that fewer high risk patients are undergoing surgery because mortality rates are published.

Neurological outcomes in coronary surgery: independent effect of avoiding cardiopulmonary bypass.

BACKGROUND Recent studies examining neuroprotective effects of off-pump coronary artery bypass grafting (CABG) have shown inconsistent results. We examined our database to quantify the independent effects of avoidance of cardiopulmonary bypass (CPB) and aortic manipulation on neurologic outcomes after CABG. METHODS A total of 2,327 consecutive cases undergoing isolated CABG between April 1997 and May 2001 were identified at our two institutions. Patients were divided into three groups: on CPB, off-pump with aortic manipulation, and off-pump without aortic manipulation. To control for the confounding effects of other risk factors, we performed a multivariate logistic regression analysis. Potential covariates considered in the logistic model included age, sex, redo operations, diabetes, chronic obstructive pulmonary disease, neurologic disease, peripheral vascular disease, ejection fraction, and priority of operation. RESULTS A total of 1,210 cases were performed on CPB, compared with 520 off-pump with aortic manipulation, and 597 off-pump without aortic manipulation. The incidence of focal neurologic deficit was 1.6% (n = 19) in the on-pump group, 0.4% (n = 2) in the off-pump with aortic manipulation group, and 0.5% (n = 3) for the off-pump without aortic manipulation group (p for trend = 0.027). The results of the multivariate logistic regression analysis demonstrated that use of CPB was a risk factor for focal neurologic deficit, with an odds ratio of 3.82 (95% confidence interval, 1.41 to 10.34; p = 0.005). Aortic manipulation did not significantly influence neurologic outcome in off-pump patients. CONCLUSIONS Off-pump operation, with or without aortic manipulation, reduces adverse neurologic outcomes compared with on-pump procedures.

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.

Selective decontamination of the digestive tract in cardiac surgical patients.

ObjectiveTo test the hypothesis that selective decontamination of the digestive tract improves outcome in cardiac surgical patients. DesignProspective, consecutive, controlled trial over two 4-month periods. SettingEight-bed, open-plan postcardiac surgery ICU. PatientsAll patients undergoing cardiac bypass surgery were eligible. Patients requiring endotracheal intubation for >4 days were included in the analysis. In the initial 4 months, 12 (8.5%) of 141 patients required >4 days of intubation. These 12 patients were not treated with selective decontamination of the digestive tract. We therefore used these patients as the control group. In the second 4-month period, 12 (6.6%) of 180 patients were treated with selective decontamination of the digestive tract and formed the study group. Main Outcome MeasuresThe primary measure was mortality. Secondary measures included oropharyngeal decontamination and the presence of lower airway infection. InterventionsCephradine prophylaxis. The study group received every 6 hrs 4 mL orally and 20 mL intragastrically a suspension of antimicrobial agents (tobramycin 80 mg, polymyxin E 100 mg, amphotericin B 500 mg), starting on postoperative day 1. The control group did not receive any oral antimicrobial agents. ResultsMortality rate was significantly (p < .05) reduced from eight (66%) of 12 patients in the control group to two (16.7%) of 12 patients in the selective decontamination of the digestive tract group. No differences in oropharyngeal decontamination or lower airway infection rates between the two groups were found. ConclusionsThere is a reduced mortality rate in patients receiving selective decontamination of the digestive tract. However, the reader should recognize the small sample size studied. A simple suspension of the antimicrobial agents failed to rid the oropharynx of bacteria.

Validation of EuroSCORE II in a modern cohort of patients undergoing cardiac surgery.

OBJECTIVE We aimed to validate the new EuroSCORE II risk model in a contemporary cardiac surgery practice in the United Kingdom (UK). METHODS The original logistic EuroSCORE was compared to EuroSCORE II with regard to accuracy of predicting in-hospital mortality. Analysis was performed on isolated coronary artery bypass grafts (CABG; n = 2913), aortic valve replacement (AVR; n = 814), mitral valve surgery (MVR; n = 340), combined AVR and CABG (n = 517), aortic (n = 350) and miscellaneous procedures (n = 642), and the above cases combined (n = 5576). RESULTS In a single-institution experience, EuroSCORE II is a reasonable risk model for in-hospital mortality from isolated CABG (C-statistic 0.79, Hosmer-Lemeshow P = 0.052) and aortic procedures (C-statistic 0.81, Hosmer-Lemeshow P = 0.43), and excellent for mitral valve surgery (C-statistic 0.87, Hosmer-Lemeshow P = 0.6). EuroSCORE II is better than the original EuroSCORE, using contemporaneous data for combined AVR and CABG operations (C-statistic 0.74, Hosmer-Lemeshow P = 0.38). However, EuroSCORE II failed to improve on the original EuroSCORE model for isolated AVR (C-statistic 0.69, Hosmer-Lemeshow P = 0.07) and miscellaneous procedures (C-statistic 0.70, Hosmer-Lemeshow P = 0.99). EuroSCORE II has better calibration than the original EuroSCORE or the Society of Cardiothoracic Surgeons of Great Britain and Ireland (SCTS) modified EuroSCORE for cumulative sum survival (CUSUM) curves. CONCLUSIONS EuroSCORE II improves on the original logistic EuroSCORE, though mainly for combined AVR and CABG cases. Concerns still exist, however, over its use for isolated AVR procedures, aortic surgery and miscellaneous procedures. There is still room for improvement in risk modelling.

Preoperative calculation of risk for prolonged intensive care unit stay following coronary artery bypass grafting

ObjectivePatients who have prolonged stay in intensive care unit (ICU) are associated with adverse outcomes. Such patients have cost implications and can lead to shortage of ICU beds. We aimed to develop a preoperative risk prediction tool for prolonged ICU stay following coronary artery surgery (CABG).Methods5,186 patients who underwent CABG between 1st April 1997 and 31st March 2002 were analysed in a development dataset. Logistic regression was used with forward stepwise technique to identify preoperative risk factors for prolonged ICU stay; defined as patients staying longer than 3 days on ICU. Variables examined included presentation history, co-morbidities, catheter and demographic details. The use of cardiopulmonary bypass (CPB) was also recorded. The prediction tool was tested on validation dataset (1197 CABG patients between 1st April 2003 and 31st March 2004). The area under the receiver operating characteristic (ROC) curve was calculated to assess the performance of the prediction tool.Results475(9.2%) patients had a prolonged ICU stay in the development dataset. Variables identified as risk factors for a prolonged ICU stay included renal dysfunction, unstable angina, poor ejection fraction, peripheral vascular disease, obesity, increasing age, smoking, diabetes, priority, hypercholesterolaemia, hypertension, and use of CPB. In the validation dataset, 8.1% patients had a prolonged ICU stay compared to 8.7% expected. The ROC curve for the development and validation datasets was 0.72 and 0.74 respectively.ConclusionA prediction tool has been developed which is reliable and valid. The tool is being piloted at our institution to aid resource management.

Repair of post-infarct ventricular septal defect with or without coronary artery bypass grafting in the northwest of England: a 5-year multi-institutional experience.

OBJECTIVE To present the 5-year experience of the northwest of Englands surgical repair of post myocardial infarction (MI) ventricular septal defects (VSD). Our primary aim was to evaluate the effect of concomitant coronary artery bypass grafting (CABG) on mid-term survival and also to identify prognostic indicators. METHODS A multi-centre regional observational study involving clinical data from 65 consecutive patients who underwent post MI VSD repair in the northwest of England between April 1997 and March 2002. Both prospective and retrospective collection of preoperative, operative and postoperative information was performed. Patient follow-up was performed by linking their records to the National Strategic Tracing Service database. Multivariate logistic regression and Cox proportional hazards analyses were used to identify independent risk factors for poor prognosis. RESULTS Of the 65 patients included in the study, 42 (64.6%) underwent concomitant CABG with a median of two grafts. The majority of patients who had their coronary arteries grafted had multivessel disease (92.9%). Overall 30-day mortality was 23.1%. Predictors of poor prognosis included preoperative inotropes (P<0.001) and total occlusion of infarct related artery (P=0.03). The crude hazard ratio (HR) of mid-term mortality for concomitant CABG patients was 0.82 [95% confidence interval (CI) 0.38-1.78; P=0.62]. After adjustment for differences in patient and disease characteristics, the adjusted HR of mid-term mortality for concomitant CABG patients was 0.17 (95% CI 0.04-0.74; P=0.019). The adjusted freedom from death in the concomitant CABG patients at 30 days, 1, 2, and 4 years was 96.2%, 91.6%, 88.8%, and 82.8%, respectively, compared with 79.1%, 58.8%, 49.1%, and 32.2% for the non-concomitant CABG patients. CONCLUSION These data provide evidence that concomitant CABG is significantly beneficial to mid-term mortality rates. We recommend that patients who present with post MI VSD who have multivessel disease should be routinely revascularised.

The effect off-pump coronary artery bypass surgery on in-hospital mortality and morbidity.

OBJECTIVE Off-pump coronary artery bypass (OPCAB) surgery is being increasingly reported to show better outcomes compared to conventional on bypass grafting. We examined the effect of OPCAB on in-hospital mortality and morbidity, while adjusting for patient and disease characteristics, in four institutions in the North West of England. METHODS Between April 1997 and March 2001, 10,941 consecutive patients underwent isolated coronary artery bypass surgery at these four institutions. Of these, 7.7% were performed off-pump. We used logistic regression to examine the effect of OPCAB on in-hospital mortality and morbidity after adjusting for potentially confounding variables. RESULTS The crude odds ratio (OR) for death (off-pump versus on-pump coronary bypass grafting) was 0.48 (95% confidence interval, CI 0.26-0.92; P=0.023). After adjustment for all major risk factors, the OR for death was 0.59 (95% CI 0.31-1.12; P=0.105). Off-pump patients had a substantially reduced risk of post-operative stroke (0.6 versus 2.3%, respectively; adjusted OR 0.26 (95% CI 0.09-0.70; P=0.008) and a significant reduction in post-operative hospital stay. Other morbidity outcomes were similar in both groups. CONCLUSIONS Off-pump coronary artery bypass incurs no increased risk of in-hospital mortality. In contrast, there is a significant reduction in morbidity in patients undergoing off-pump coronary bypass grafting when compared to that performed on cardiopulmonary bypass.