Randomized Trials in Cardiac Surgery: JACC Review Topic of the Week

Compared with randomized controlled trials (RCTs) in medical specialties, RCTs in cardiac surgery face specific issues. Individual and collective equipoise, rapid evolution of the surgical techniques, as well as difficulties in obtaining funding, and limited education in clinical epidemiology in the surgical community are among the most important challenges in the design phase of the trial. Use of complex interventions and learning curve effect, differences in individual operators' expertise, difficulties in blinding, and slow recruitment make the successful completion of cardiac surgery RCTs particularly challenging. In fact, over the course of the last 20 years, the number of cardiac surgery RCTs has declined significantly. In this review, a team of surgeons, trialists, and epidemiologists discusses the most important challenges faced by RCTs in cardiac surgery and provides a list of suggestions for the successful design and completion of cardiac surgery RCTs.

Training and Management of a Multisite Neuropsychological Testing Protocol for the Department of Veterans Affairs Cooperative Study Evaluating on- and Off-pump Coronary Artery Bypass Graft Procedures

Research study coordinators from 17 sites participating in a cardiac surgery study were trained to administer and score a brief neuropsychological test battery. Results were sent to the study's centralized laboratory for review and feedback. The average examiner errors on the first six protocols were compared with the average errors on the last six protocols over 12 months for each site. Overall, errors for the first six protocols were 4.42, and errors for the last six protocols were 1.83, representing a significant overall decline. Errors for instruction, administration, and recording showed a significant decrease over time. Despite ongoing feedback to examiners, scoring errors did not decline significantly overall; this suggests that a review of all protocols is necessary to achieve reliable scoring. However, when examiners' number of protocols completed was compared with number of scoring errors per protocol, there was a trend for examiners who had completed more protocols to show more improvement in scoring.

Patency outcomes of aortic connectors

OBJECTIVE

: Controlled outcome analysis of mechanical aortic connectors for proximal saphenous vein bypass graft anastomosis is lacking. We report the clinical and angiographic outcome of patients receiving the Symmetry aortic connector (St. Jude Medical, Inc St. Paul, MN, US) within a multicenter, prospective, randomized study.

METHODS

: Twenty-five patients at 3 study sites received aortic connectors at the time of coronary artery bypass surgery. Protocol-defined angiographic follow-up was completed in 19 of 25 patients (76%) at time-points up to 14 months postoperatively; 32 connector anastomoses were evaluated in these 19 patients. Beating heart surgery was performed in 17 patients, and 2 were performed with cardiopulmonary bypass. Age was 69.7 ± 8.1 year; all patients were males.

RESULTS

: The connector anastomosis patency rate was 15.6% (5/32). There were no deaths during the follow-up period. Four patients (21%) suffered myocardial infarction and 2 additional patients (10.5%) required percutaneous coronary interventions; one of who required 3 percutaneous coronary interventions, the other received one percutaneous coronary intervention.

CONCLUSIONS

: In this nonrandomized cohort of patients, occlusion rate with Symmetry connectors was significantly greater than anticipated. Patients who have received these connectors during coronary artery bypass surgery may require closer follow-up and evaluation. While the manufacturer has stopped producing this device, there has been no recall of the product, clinical support remains ongoing, and next generation connectors have now been marketed. Consideration should be given to discontinuation of the clinical use of Symmetry connectors.

Percutaneous coronary intervention versus repeat bypass surgery for patients with medically refractory myocardial ischemia: AWESOME randomized trial and registry experience with post-CABG patients

OBJECTIVES

This report compares long-term percutaneous coronary intervention (PCI) and coronary artery bypass graft (CABG) survival among post-CABG patients included in the Angina With Extremely Serious Operative Mortality Evaluation (AWESOME) randomized trial and prospective registry.

BACKGROUND

Repeat CABG surgery is associated with a higher risk of mortality than first-time CABG. The AWESOME is the first randomized trial comparing CABG with PCI to include post-CABG patients.

METHODS

Over a five-year period (1995 to 2000), patients at 16 hospitals were screened to identify a cohort of 2,431 individuals who had medically refractory myocardial ischemia and at least one of five high-risk factors. There were 454 patients in the randomized trial, of whom 142 had prior CABG. In the physician-directed registry of 1,650 patients, 719 had prior CABG. Of the 327 patient-choice registry patients, 119 had at least one prior CABG. The CABG and PCI survivals for the three groups were compared using Kaplan-Meier curves and log-rank tests.

RESULTS

The CABG and PCI three-year survival rates were 73% and 76% respectively for the 142 randomized patients (75 and 67 patients) (log-rank = NS). In the physician-directed registry, 155 patients were assigned to reoperation and 357 to PCI (207 received medical therapy); 36-month survivals were 71% and 77% respectively (log-rank = NS). In the patient-choice registry, 32 patients chose reoperation and 74 chose PCI (13 received medical therapy); 36-month survivals were 65% and 86% respectively (log-rank test p = 0.01).

CONCLUSIONS

Percutaneous coronary intervention is preferable to CABG for many post-CABG patients.

Percutaneous coronary intervention versus coronary bypass graft surgery for diabetic patients with unstable angina and risk factors for adverse outcomes with bypass: outcome of diabetic patients in the AWESOME randomized trial and registry

OBJECTIVES

This study compared survival after percutaneous coronary intervention (PCI) with survival after coronary artery bypass graft surgery (CABG) among diabetics in the Veterans Affairs AWESOME (Angina With Extremely Serious Operative Mortality Evaluation) study randomized trial and registry of high-risk patients.

BACKGROUND

Previous studies indicate that CABG may be superior to PCI for diabetics, but no comparisons have been made for diabetics at high risk for surgery.

METHODS

Over five years (1995 to 2000), 2,431 patients with medically refractory myocardial ischemia and at least one of five risk factors (prior CABG, myocardial infarction within seven days, left ventricular ejection fraction <0.35, age >70 years, or an intra-aortic balloon being required to stabilize) were identified. A total of 781 were acceptable for CABG and PCI, and 454 consented to be randomized. The 1,650 patients not acceptable for both CABG and PCI constitute the physician-directed registry, and the 327 who were acceptable but refused to be randomized constitute the patient-choice registry. Diabetes prevalence was 32% (144) among randomized patients, 27% (89) in the patient-choice registry, and 32% (525) in the physician-directed registry. The CABG and PCI survival rates were compared using Kaplan-Meier curves and log-rank tests.

RESULTS

The respective CABG and PCI 36-month survival rates for diabetic patients were 72% and 81% for randomized patients, 85% and 89% for patient-choice registry patients, and 73% and 71% for the physician-directed registry patients. None of the differences was statistically significant.

CONCLUSIONS

We conclude that PCI is a relatively safe alternative to CABG for diabetic patients with medically refractory unstable angina who are at high risk for CABG.

Percutaneous coronary intervention versus coronary bypass graft surgery for patients with medically refractory myocardial ischemia and risk factors for adverse outcomes with bypass: The VA AWESOME multicenter registry: comparison with the randomized clinical trial

OBJECTIVES

This study was designed to compare the three-year survival after percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery (CABG) in physician-directed and patient-choice registries with the Angina With Extremely Serious Operative Mortality Evaluation (AWESOME) randomized trial results.

BACKGROUND

The AWESOME multicenter randomized trial and registry compared the long-term survival after PCI and CABG for the treatment of patients with medically refractory myocardial ischemia and at least one additional risk factor for adverse outcome with CABG. The randomized trial demonstrated comparable three-year survival.

METHODS

Over a five-year period (1995 to 2000), 2,431 patients with medically refractory myocardial ischemia and at least one of five risk factors (prior heart surgery, myocardial infarction within seven days, left ventricular ejection fraction <0.35, age >70 years, intra-aortic balloon required to stabilize) were identified. By physician consensus, 1,650 patients formed a physician-directed registry assigned to CABG (692), PCI (651) or further medical therapy (307), and 781 were angiographically eligible for random allocation; 454 of these patients constitute the randomized trial, and the remaining 327 constitute a patient choice registry. Survival for CABG and PCI was compared using Kaplan-Meier curves and log-rank tests.

RESULTS

The CABG and PCI 36-month survival rates for randomized patients were 79% and 80%, respectively. The CABG and PCI 36-month survival rates were both 76% for the physician-directed subgroup; comparable survival rates for the patient-choice subgroup were 80% and 89%, respectively. None of the global log-rank tests for survival demonstrated significant differences.

CONCLUSIONS

Both registries support the randomized trial conclusion: PCI is an alternative to CABG for some medically refractory high-risk patients.

Comparison of surgical outcomes between teaching and nonteaching hospitals in the Department of Veterans Affairs

OBJECTIVE

To determine whether the investment in postgraduate education and training places patients at risk for worse outcomes and higher costs than if medical and surgical care was delivered in nonteaching settings.

SUMMARY BACKGROUND DATA

The Veterans Health Administration (VA) plays a major role in the training of medical students, residents, and fellows.

METHODS

The database of the VA National Surgical Quality Improvement Program was analyzed for all major noncardiac operations performed during fiscal years 1997, 1998, and 1999. Teaching status of a hospital was determined on the basis of a background and structure questionnaire that was independently verified by a research fellow. Stepwise logistic regression was used to construct separate models predictive of 30-day mortality and morbidity for each of seven surgical specialties and eight operations. Based on these models, a severity index for each patient was calculated. Hierarchical logistic regression models were then created to examine the relationship between teaching versus nonteaching hospitals and 30-day postoperative mortality and morbidity, after adjusting for patient severity.

RESULTS

Teaching hospitals performed 81% of the total surgical workload and 90% of the major surgery workload. In most specialties in teaching hospitals, the residents were the primary surgeons in more than 90% of the operations. Compared with nonteaching hospitals, the patient populations in teaching hospitals had a higher prevalence of risk factors, underwent more complex operations, and had longer operation times. Risk-adjusted mortality rates were not different between the teaching and nonteaching hospitals in the specialties and operations studied. The unadjusted complication rate was higher in teaching hospitals in six of seven specialties and four of eight operations. Risk adjustment did not eliminate completely these differences, probably reflecting the relatively poor predictive validity of some of the risk adjustment models for morbidity. Length of stay after major operations was not consistently different between teaching and nonteaching hospitals.

CONCLUSION

Compared with nonteaching hospitals, teaching hospitals in the VA perform the majority of complex and high-risk major procedures, with comparable risk-adjusted 30-day mortality rates. Risk-adjusted 30-day morbidity rates in teaching hospitals are higher in some specialties and operations than in nonteaching hospitals. Although this may reflect the weak predictive validity of some of the risk adjustment models for morbidity, it may also represent suboptimal processes and structures of care that are unique to teaching hospitals. Despite good quality of care in teaching hospitals, as evidenced by the 30-day mortality data, efforts should be made to examine further the structures and processes of surgical care prevailing in these hospitals.

Percutaneous coronary intervention versus coronary artery bypass graft surgery for patients with medically refractory myocardial ischemia and risk factors for adverse outcomes with bypass: a multicenter, randomized trial. Investigators of the Department of Veterans Affairs Cooperative Study #385, the Angina With Extremely Serious Operative Mortality Evaluation (AWESOME)

BACKGROUND

Percutaneous coronary intervention (PCI) and coronary artery bypass graft surgery (CABG) are being applied to high-risk populations, but previous randomized trials comparing revascularization methods have excluded a number of important high-risk groups.

OBJECTIVES

This five-year, multicenter, randomized clinical trial was designed to compare long-term survival among patients with medically refractory myocardial ischemia and a high risk of adverse outcomes assigned to either a CABG or a PCI strategy, which could include stents.

METHODS

Patients from 16 Veterans Affairs Medical Centers were screened to identify myocardial ischemia refractory to medical management and the presence of one or more risk factors for adverse outcome with CABG, including prior open-heart surgery, age >70 years, left ventricular ejection fraction <0.35, myocardial infarction within seven days or intraaortic balloon pump required. Clinically eligible patients (n = 2,431) underwent coronary angiography; 781 were angiographically acceptable; 454 (58% of eligible) patients consented to random assignment between CABG and PCI.

RESULTS

A total of 232 patients was randomized to CABG and 222 to PCI. The 30-day survivals for CABG and PCI were 95% and 97%, respectively. Survival rates for CABG and PCI were 90% versus 94% at six months and 79% versus 80% at 36 months (log-rank test, p = 0.46).

CONCLUSIONS

Percutaneous coronary intervention is an alternative to CABG for patients with medically refractory myocardial ischemia and a high risk of adverse outcomes with CABG.

A simple method for fume cupboard performance assessment

The performance of a fume cupboard is determined by a complex interaction of factors which are time consuming and expensive to determine. This paper describes a simple and practical means of ranking, and assessing fume cupboard installations that can help to discharge managerial responsibility for a 'safe' environment. The method also gives an economically viable and technically defensible system for assessing fume cupboard performance as part of upgrading exercises or performance audits. The assessment strategy uses flow visualisation techniques and measurements of inflow air velocity as well as overall condition evaluation to rank performance and identify poor performing cupboards. The method has been used to carry out a condition and performance survey of 199 fume cupboards, both aerodynamic and box-type designs, in an academic institution. The results of this survey are presented which not only highlight performance characteristics but also provide insights into user attitudes and knowledge of fume cupboard operation and performance. It is suggested that surveys such as this could be helpful in training programmes for laboratory workers to enable them to optimise the use of fume cupboards.

A multicenter, randomized trial of percutaneous coronary intervention versus bypass surgery in high-risk unstable angina patients. The AWESOME (Veterans Affairs Cooperative Study #385, angina with extremely serious operative mortality evaluation) investigators from the Cooperative Studies Program of the Department of Veterans Affairs

This multicenter, prospective randomized trial was designed to test the hypotheses that percutaneous coronary intervention (PCI) is a safe and effective alternative to coronary artery bypass grafting (CABG) for patients with refractory ischemia and high risk of adverse outcomes. As a comparison of revascularization strategies, the trial specifically allows surgeons and interventionists to use new techniques as they become clinically available. After 42 months of this 72-month trial, 17,624 patients have been screened and 2022 met eligibility requirements: 341 have been randomized to either CABG or PCI, and the remaining 1681 are being prospectively followed in a registry. The 3-year overall survival of patients in the registry and randomized trial is comparable. To enhance accrual into the randomized trial, site visits were conducted, a few low-accruing hospitals were put on probation and/or replaced, eligibility criteria were reviewed at annual meetings of investigators, and the accrual period was extended by 1 year. These data demonstrate that a prospective randomized trial and registry of coronary revascularization for medically refractory high-risk patients is feasible.

Relation of surgical volume to outcome in eight common operations: results from the VA National Surgical Quality Improvement Program

OBJECTIVE

To examine, in the Veterans Health Administration (VHA), the relation between surgical volume and outcome in eight commonly performed operations of intermediate complexity.

SUMMARY BACKGROUND DATA

In multihospital health care systems such as VHA, consideration is often given to closing low-volume surgical services, with the assumption that better surgical outcomes are achieved in hospitals with larger surgical volumes. Literature data to support this assumption in intermediate-complexity operations are either limited or controversial.

METHODS

The VHA National Surgical Quality Improvement Program data on nonruptured abdominal aortic aneurysmectomy, vascular infrainguinal reconstruction, carotid endarterectomy (CEA), lung lobectomy/pneumonectomy, open and laparoscopic cholecystectomy, partial colectomy, and total hip arthroplasty were used. Pearson correlation, analysis of variance, mixed effects hierarchical logistic regression, and automatic interaction detection analysis were used to assess the association of annual procedure/specialty volume with risk-adjusted 30-day death (and stroke in CEA).

RESULTS

Eight major surgical procedures (68,631 operations) were analyzed. No statistically significant associations between procedure or specialty volume and 30-day mortality rate (or 30-day stroke rate in CEA) were found.

CONCLUSIONS

In VHA hospitals, the procedure and surgical specialty volume in eight prevalent operations of intermediate complexity are not associated with risk-adjusted 30-day mortality rate from these operations, or with the risk-adjusted 30-day stroke rate from CEA. Volume of surgery in these operations should not be used as a surrogate for quality of surgical care.

The Department of Veterans Affairs' NSQIP: the first national, validated, outcome-based, risk-adjusted, and peer-controlled program for the measurement and enhancement of the quality of surgical care. National VA Surgical Quality Improvement Program

OBJECTIVE

To provide reliable risk-adjusted morbidity and mortality rates after major surgery to the 123 Veterans Affairs Medical Centers (VAMCs) performing major surgery, and to use risk-adjusted outcomes in the monitoring and improvement of the quality of surgical care to all veterans.

SUMMARY BACKGROUND DATA

Outcome-based comparative measures of the quality of surgical care among surgical services and surgical subspecialties have been elusive.

METHODS

This study included prospective assessment of presurgical risk factors, process of care during surgery, and outcomes 30 days after surgery on veterans undergoing major surgery in 123 medical centers; development of multivariable risk-adjustment models; identification of high and low outlier facilities by observed-to-expected outcome ratios; and generation of annual reports of comparative outcomes to all surgical services in the Veterans Health Administration (VHA).

RESULTS

The National VA Surgical Quality Improvement Program (NSQIP) data base includes 417,944 major surgical procedures performed between October 1, 1991, and September 30, 1997. In FY97, 11 VAMCs were low outliers for risk-adjusted observed-to-expected mortality ratios; 13 VAMCs were high outliers for risk-adjusted observed-to-expected mortality ratios. Identification of high and low outliers by unadjusted mortality rates would have ascribed an outlier status incorrectly to 25 of 39 hospitals, an error rate of 64%. Since 1994, the 30-day mortality and morbidity rates for major surgery have fallen 9% and 30%, respectively.

CONCLUSIONS

Reliable, valid information on patient presurgical risk factors, process of care during surgery, and 30-day morbidity and mortality rates is available for all major surgical procedures in the 123 VAMCs performing surgery in the VHA. With this information, the VHA has established the first prospective outcome-based program for comparative assessment and enhancement of the quality of surgical care among multiple institutions for several surgical subspecialties. Key features to the success of the NSQIP are the support of the surgeons who practice in the VHA, consistent clinical definitions and data collection by dedicated nurses, a uniform nationwide informatics system, and the support of VHA administration and managerial staff.

Pulmonary capillaritis: a possible histologic form of acute pulmonary allograft rejection

Acute rejection after lung transplantation occurs commonly and is usually characterized histologically by a perivascular mononuclear infiltrate. We report five cases of pulmonary capillaritis with a histologic appearance distinct from typical rejection, occurring in patients ranging in age from 18 to 45 years, with a variety of underlying diseases including alpha1 antitrypsin deficiency, pulmonary hypertension, cystic fibrosis, and rheumatoid arthritis. Four of the five patients had alveolar hemorrhage histologically, and two had frank hemoptysis. Time of onset ranged from 3 weeks to many months after transplantation. Three cases were fulminant, and there were two deaths. In only one case, with methicillin-resistant Staphylococcus aureus bronchitis, could infection be established. All were treated with intensification of immunosuppressive therapy. Plasmapheresis was carried out in two cases and coincided with temporary improvement, but its efficacy was questionable because of concurrent immunosuppressive therapy. Two had recurrent biopsy-proven acute rejection within 6 weeks of treatment, and one had recurrent severe pulmonary hemorrhage that abated with total lymphoid irradiation. Our experience suggests that pulmonary capillaritis in lung transplant recipients can be an acute, fatal illness with the potential for recurrence in the survivors. We speculate that it represents a form of acute vascular rejection. Early pathologic diagnosis and aggressive immunosuppressive therapy are recommended. Although a humoral component was not documented, the possible response to plasmapheresis requires continued evaluation.

Independent association between acute renal failure and mortality following cardiac surgery

PURPOSE

To determine whether there is an independent association of acute renal failure requiring dialysis with operative mortality after cardiac surgery.

PATIENTS AND METHODS

The 42,773 patients who underwent coronary artery bypass or valvular heart surgery at 43 Department of Veterans Affairs Medical Centers between 1987 and 1994 were evaluated to determine the association between acute renal failure sufficient to require dialysis and operative mortality, with and without adjustment for comorbidity and postoperative complications. Crude and adjusted odds ratios (OR) and 95% confidence intervals (95% CI) were derived from logistic regression analysis.

RESULTS

Acute renal failure occurred in 460 (1.1%) patients. Overall operative mortality was 63.7% in these patients, compared with 4.3% in patients without this complication. The unadjusted OR for death was 39 (95% CI 32 to 48). After adjustment for comorbid factors related to the development of acute renal failure (surgery type, baseline renal function, preoperative intraaortic balloon pump, prior heart surgery, NYHA class IV status, peripheral vascular disease, pulmonary rales, left ventricular ejection fraction below 35%, chronic obstructive pulmonary disease, systolic blood pressure, and the cross-product of systolic blood pressure and surgery type), the OR was 27 (95% CI 22 to 34). Further adjustment was made for seven postoperative complications (low cardiac output, cardiac arrest, perioperative myocardial infarction, prolonged mechanical ventilation, reoperation for bleeding or repeat cardiopulmonary bypass, stroke or coma, and mediastinitis), that were independently associated with operative mortality. The OR adjusted for comorbidity and postoperative complications associated with acute renal failure was 7.9 (95% CI 6 to 10).

CONCLUSIONS

Acute renal failure was independently associated with early mortality following cardiac surgery, even after adjustment for comorbidity and postoperative complications. Interventions to prevent or improve treatment of this condition are urgently needed.

Risk adjustment of the postoperative morbidity rate for the comparative assessment of the quality of surgical care: results of the National Veterans Affairs Surgical Risk Study

BACKGROUND

The National Veterans Affairs Surgical Risk Study was designed to collect reliable, valid data on patient risk and outcomes for major surgery in the Veterans Health Administration and to report comparative risk-adjusted postoperative mortality and morbidity rates for surgical services in the Veterans Health Administration.

STUDY DESIGN

This was a cohort study conducted at 44 Veterans Affairs Medical Centers closely affiliated with university medical centers. Included were 87,078 major noncardiac operations performed under general, spinal, or epidural anesthesia between October 1, 1991, and December 31, 1993. The main outcomes measures in this report are 21 postoperative adverse events (morbidities) occurring within 30 days after the index procedure. Multivariable logistic regression risk-adjustment models for all operations and for eight surgical subspecialties were developed.

RESULTS

Patient risk factors predictive of postoperative morbidity included serum albumin level, American Society of Anesthesia class, the complexity of the operation, and 17 other preoperative risk variables. Wide variation in the unadjusted rates of one or more postoperative morbidities for all operations was observed across the 44 hospitals (7.4-28.4%). Risk-adjusted observed-to-expected ratios ranged from 0.49 to 1.46. The Spearman rank order correlation between the ranking of the hospitals based on unadjusted morbidity rates and risk-adjusted observed-to-expected ratios for all operations was 0.87. There was little or no correlation between the rank order of the hospitals by risk-adjusted morbidity and risk-adjusted mortality.

CONCLUSIONS

The Department of Veterans Affairs has successfully implemented a system for the prospective collection and comparative reporting of postoperative mortality and morbidity rates after major noncardiac operations. Risk adjustment had only a modest effect on the rank order of the hospitals.

Risk adjustment of the postoperative mortality rate for the comparative assessment of the quality of surgical care: results of the National Veterans Affairs Surgical Risk Study

BACKGROUND

The National Veterans Affairs Surgical Risk Study was designed to collect reliable, valid data on patient risk and outcomes for major surgery in the Veterans Health Administration and to report comparative risk-adjusted postoperative mortality rates for surgical services in Veterans Health Administration.

STUDY DESIGN

This cohort study was conducted in 44 Veterans Affairs Medical Centers. Included were 87,078 major noncardiac operations performed under general, spinal, or epidural anesthesia between October 1, 1991, and December 31, 1993. The main outcomes measure was all-cause mortality within 30 days after the index procedure. Multivariable logistic regression risk-adjustment models for all operations and for eight surgical subspecialties were developed. Risk-adjusted surgical mortality rates were expressed as observed-to-expected ratios and were compared with unadjusted 30-day postoperative mortality rates.

RESULTS

Patient risk factors predictive of postoperative mortality included serum albumin level, American Society of Anesthesia class, emergency operation, and 31 additional preoperative variables. Considerable variability in unadjusted mortality rates for all operations was observed across the 44 hospitals (1.2-5.4%). After risk adjustment, observed-to-expected ratios ranged from 0.49 to 1.53. Rank order correlation of the hospitals by unadjusted and risk-adjusted mortality rates for all operations was 0.64. Ninety-three percent of the hospitals changed rank after risk adjustment, 50% by more than 5 and 25% by more than 10.

CONCLUSIONS

The Department of Veterans Affairs has successfully implemented a system for the prospective collection and comparative reporting of risk-adjusted postoperative mortality rates after major noncardiac operations. Risk adjustment had an appreciable impact on the rank ordering of the hospitals and provided a means for monitoring and potentially improving the quality of surgical care.

Preoperative renal risk stratification

BACKGROUND

After cardiac surgery, acute renal failure (ARF) requiring dialysis develops in 1% to 5% of patients and is strongly associated with perioperative morbidity and mortality. Prior studies have attempted to identify predictors of ARF but have had insufficient power to perform multivariable analyses or to develop risk stratification algorithms.

METHODS AND RESULTS

We conducted a prospective cohort study of 43 642 patients who underwent coronary artery bypass or valvular heart surgery in 43 Department of Veterans Affairs medical centers between April 1987 and March 1994. Logistic regression analysis was used to identify independent predictors of ARF requiring dialysis. A risk stratification algorithm derived from recursive partitioning was constructed and was validated on an independent sample of 3795 patients operated on between April and December 1994. The overall risk of ARF requiring dialysis was 1.1%. Thirty-day mortality in patients with ARF was 63.7%, compared with 4.3% in patients without ARF. Ten clinical variables related to baseline cardiovascular disease and renal function were independently associated with the risk of ARF. A risk stratification algorithm partitioned patients into low-risk (0.4%), medium-risk (0.9% to 2.8%), and high-risk (> or = 5.0%) groups on the basis of several of these factors and their interactions.

CONCLUSIONS

The risk of ARF after cardiac surgery can be accurately quantified on the basis of readily available preoperative data. These findings may be used by physicians and surgeons to provide patients with improved risk estimates and to target high-risk subgroups for interventions aimed at reducing the risk and ameliorating the consequences of this serious complication.

Donor-to-host transmission of Mycoplasma hominis in lung allograft recipients

Mycoplasma hominis is a significant pathogen in immunocompromised hosts, particularly organ transplant recipients. We describe two recipients of lung allografts from the same donor who had M. hominis pleuropulmonary infection during the immediate postoperative period. The most likely source of infection in these cases was the donor's respiratory tract. The slow-growing pinpoint colonies formed by M. hominis on routine bacterial culture medium may be easily overlooked and should be subcultured to mycoplasmal medium for definitive identification. The recommended management of this infection consists of drainage and antimicrobial therapy with tetracycline, clindamycin, or a fluoroquinolone. This report highlights the potential for M. hominis to be transmitted from donor to recipient during organ transplantation.

The National Veterans Administration Surgical Risk Study: risk adjustment for the comparative assessment of the quality of surgical care

BACKGROUND

The use of surgical outcome in the comparative assessment of the quality of surgical care is predicted on the development of proper models that adjust for the severity of the preoperative risk factors of the patient. The National Veterans Administration Surgical Risk Study was designed to collect reliable, valid data about patient risk and outcome for major surgery in the Veterans Health Administration (VHA) and to report comparative risk-adjusted surgical morbidity and mortality rates for surgical services in VHA. This study describes the rationale and methods used in the Risk Study and reports on the frequency distribution of the data elements that will be used in the development of risk-adjusted reporting of surgical outcome.

STUDY DESIGN

This study was a prospective observational study in which dedicated nurses collected preoperative, intraoperative, and outcome data on patients undergoing noncardiac operations using general, spinal, and epidural anesthesia in 44 Veterans Administration Medical Centers. Outcome measures included all cause mortality within the 30 days after the index procedure and 21 major morbidities.

RESULTS

Eighty-three thousand nine hundred fifty-eight cases meeting inclusion criteria were entered in the study between October 1, 1991 and December 31, 1993. Ninety-seven percent of patients were men, with a mean age of 60.1 +/- 13.6 (standard deviation) years. The most common preoperative risk factors were smoking (40.7 percent) and hypertension (36.1 percent). Of the patients, 84.6 percent had one or more risk factors. The most common procedures were transurethral resection of the prostate gland (6.7 percent), total knee replacement (3.1 percent), thromboendarterectomy (2.4 percent), partial colectomy (2.2 percent), and total hip replacement (2 percent). The unadjusted mortality rate was 3.1 percent at 30 days. The most common postoperative morbidities were pneumonia (3.6 percent), urinary tract infection (3.5 percent), and failure to wean from the ventilator at 48 hours postoperatively (3.2 percent). Seventeen percent of the patients have one or more major complications.

CONCLUSIONS

The Veterans Health Administration has successfully implemented an outcome reporting system for major surgery that prospectively collects patient risk and outcome information reliably and validly. Risk adjustment models and comparative hospital-specific rates of risk-adjusted outcomes are currently being developed.

Effectiveness of percutaneous transluminal coronary angioplasty for patients with medically refractory rest angina pectoris and high risk of adverse outcomes with coronary artery bypass grafting

This study was undertaken to test the hypothesis that percutaneous transluminal coronary angioplasty (PTCA) is a reasonable alternative to coronary artery bypass grafting (CABG) for some high-risk patients with medically refractory rest angina. Over a 5-year period, 1 operator at a tertiary Veterans Affairs Medical Center performed angioplasty on 624 patients, of whom 441 had unstable angina. Of these 441 patients, 288 had rest angina and 225 had medically refractory rest angina. Medically refractory unstable angina was defined as reversible myocardial ischemia occurring at rest in an intensive care unit setting with low flow oxygen despite the following medications: (1) oral aspirin, intravenous heparin, or both; (2) some combination of beta blocker, calcium blocker, and/or nitrate so that resting heart rate is < 70 beats/min or resting blood pressure < 140 mm Hg, or both. There were 207 patients with medically refractory rest angina who had > or = 1 of the following characteristics predictive of a more than twofold increased risk of operative death at CABG: age > 70 years, prior CABG, recent myocardial infarct, need for intravenous nitroglycerin, need for intraaortic balloon pump, and left ventricular ejection fraction < 0.35. Of these 207 patients, 11 died (5%) during index hospitalization, 196 (95%) were discharged, and 186 (90%) went home angina free. There were 2 emergency CABGs and 9 acute myocardial infarctions. At follow-up (3 to 60 months, average 24), there were 27 late deaths (for a total of 38 [18%]), 8 (4%) late CABGs, and 44 (21%) late PTCAs (with 17 [8%] late myocardial infarctions). The 2-year mortality of 18% for this cohort is comparable to a 21% 2-year mortality observed in a group of 1,073 "high-risk" patients who underwent CABG in the Veterans Affairs Medical Center from 1987 to 1988. These data support the hypothesis that PTCA provides an alternative to CABG in some high-risk patients with medically refractory rest angina.

Percutaneous transluminal angioplasty of saphenous vein grafts for medically refractory unstable angina

OBJECTIVES

We attempted to answer the question, Is balloon angioplasty a reasonable alternative to repeat coronary artery bypass graft surgery in patients with previous coronary bypass graft surgery, medically refractory unstable angina and vein graft lesions?

BACKGROUND

Patients with medically refractory unstable angina need revascularization. Patients with previous coronary artery bypass graft surgery and medically refractory angina are at "high risk" for adverse outcomes with repeat coronary bypass graft surgery. Conversely, patients with angioplasty of old vein grafts are also at "high risk" for adverse outcomes.

METHODS

Balloon angioplasty of 89 lesions in saphenous vein grafts was performed in 75 consecutive patients with medically refractory unstable angina. Of these 75 patients, 24 (32%) had myocardial infarct within 30 days, 23 (31%) had left ventricular ejection fraction < 0.35, and 50 (67%) had major comorbidity. Patients underwent standard balloon angioplasty with aggressive use of intravenous and intracoronary heparin, urokinase, nitroglycerin, oral aspirin, calcium channel blocking agents and coumadin.

RESULTS

Angiographic success (reduction of stenosis < or = 50% without major complication) was seen in 84 of 89 lesions. Clinical success (angiographic success plus hospital discharge without major complication) was seen in 70 of 75 patients. During index hospitalization, two patients (3%) died, two (3%) had nonfatal infarcts, and one (1%) had emergency reoperation (coronary bypass graft surgery). In late follow up (3 to 66 months), 14 (20%) patients were lost to follow-up, 17 (23%) had repeat percutaneous transluminal coronary angioplasty, 2 (3%) had late bypass graft reoperation, 18 (25%) had late death, and 1 (< 1%) had a heart transplant. Of the 41 patients alive after one or more angioplasties, 25 have little or no angina, and 16 have occasional or more angina. We compared long-term survival rate in these 75 patients with a cohort of patients with high risk, unstable angina from the Veterans Affairs Surgical Registry (2,570 patients). The 30-day survival rate was better in patients with coronary angioplasty (97% vs. 92%, p < 0.05), but by 6 months there was no difference, and by 5 years a trend toward a higher survival rate with coronary artery bypass graft surgery was seen.

CONCLUSIONS

Balloon angioplasty of saphenous vein grafts with aggressive adjunctive pharmacotherapy is a reasonable alternative to repeat coronary bypass graft surgery in patients with medically refractory unstable angina, previous coronary bypass graft surgery and saphenous vein narrowing.

Open fronted safety cabinets in ventilated laboratories

Open fronted Class I and II microbiological safety cabinets (MSCs) are required by the British Standard 5726 to provide similar levels of operator protection (viz. 10(5). In laboratories that are naturally ventilated large numbers of both types of cabinets have been shown to exceed this requirement consistently over a number of years. The designs of some mechanically ventilated laboratories, however, produce excessive turbulence and draughts that can prejudice containment at the front aperture. On-site commissioning tests to determine operator protection factor are now well established and are recognized as being essential to the setting up of all open fronted cabinets in both ventilated and unventilated laboratories. This paper shows that where environmental conditions induce unsatisfactory cabinet containment, adjustments to air supply and exhaust systems can be made which will enable both Class I and II cabinets to produce operator protection factors in excess of 10(5). When compatibility is achieved between the local environment and the cabinets it is demonstrated that disturbances at the front aperture, caused by operator working procedures or by disturbances due to personnel movement within the room, have similar effects on both Class I and II cabinets. Once performance levels have been satisfactorily achieved, regular containment testing has shown that consistent performance can be maintained. These aspects of open fronted safety cabinet performance are discussed in relation to ventilated laboratories suitable for work with the human immunodeficiency virus (HIV). Of paramount importance in the future is the necessity to design laboratory air systems that will be compatible with satisfactory safety cabinet performance--a relatively new requirement in ventilation system specifications.