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Ann Thorac Surg 2000;69:146-150
© 2000 The Society of Thoracic Surgeons
a Heartland Regional Medical Center, St. Joseph, Missouri, USA
Address reprint requests to Dr Early, 9125 SE Hillyard Rd, Easton, MO 64443
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Abstract |
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Methods. Using The Society of Thoracic Surgeons Cardiac Database, we examined the data for all coronary artery bypass graft-only patients (n = 615) operated on by us from July 1991 to June 1997.
Results. The observed mortality was 0.33% and the observed-to-expected ratio was 0.12 (p < 0.005). Morbidity was low as well.
Conclusions. Excellent results can be obtained for patients undergoing coronary artery bypass grafting in the presence of both low surgeon and low hospital case volume.
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Introduction |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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The Ad Hoc Committee on Cardiac Surgery Credentialing of The Society of Thoracic Surgeons has found no meaningful differences in CABG results except in groups with less than 100 patients per group per year or more than 600 [5]. We have found that excellent results can be obtained in spite of low surgeon and hospital volumes.
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Material and methods |
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The first patient was operated on July 16, 1991, and the last on June 19, 1997, when the practice was sold to the hospital. Each patient was entered into The Society of Thoracic Surgeons (STS) national database [6]. The primary surgeon completed the database form and each form was reviewed by a clinical nurse and by office staff. The data were again reviewed in the final week of July 1997, and no in-hospital or 30-day mortalities were excluded for any reasons. Unless otherwise noted, the STS database definition of terms was used [7].
Techniques
Preoperative evaluation and preparation was commonly performed by the surgical team. This included the diagnosis and treatment of hematologic, oncologic, endocrine, gastrointestinal, vascular, pulmonary, and cardiac diseases. An attempt was made to convert emergent and urgent cases to an elective status by medical stabilization, which was sometimes directed by the consulting surgeon. Screening for carotid artery disease was done by history and physical examination, and noninvasive studies and angiography were selectively applied. Staged surgical repair of significant carotid stenosis and cardiac disease was used when possible, with no adverse consequences. A combined carotid endarterectomy/CABG procedure was sometimes required and both procedures were done by the cardiac surgeons. When possible aspirin and other antiplatelet drugs were stopped 1 week before operation, but the administration of antiplatelet drugs did not preclude operation. Preoperative allopurinol and vitamin E were used routinely when possible and antianginal medication and intravenous heparin and nitroglycerin were continued up to and including the day of operation. Issues of spiritual and psychological health were routinely addressed and intercessory prayer was solicited.
Operating room techniques
All patients had a peripheral arterial line and venous line plus a pulmonary artery catheter with venous oxygen saturation (SVO2) monitoring capabilities.
The operations were performed through a median sternotomy. Arterial cannulization was done at the ascending aorta and a two-stage venous cannula was placed in the right atrium for venous return. A combination vent/cardioplegia needle was placed in the ascending aorta and a retrograde cardioplegia cannula with a self-inflating balloon was positioned in the coronary sinus without direct visualization. Cardiopulmonary bypass was performed using a roller pump device with a centrifugal pump for arterial inflow. A membrane oxygenator was used with systemic cooling to 26°C as measured by a urinary bladder temperature probe. Flow was maintained at 2.4 L · min-1 · m-2 and the mean pressure was kept between 50 and 90 mm Hg by the use of phenylephrine or in-line isoflurane as indicated. Mean pressures in the upper range were selectively applied in the presence of known carotid stenosis and alpha-stat blood gas management was practiced.
A review of the cardiac catheterization film was done immediately before the procedure and the films remained loaded on a projector in the operating room for review during the operation. Two cardiac surgeons participated in each operation and headlamp illumination and optical magnification were used.
Cold blood-to-crystalloid cardioplegia in a 4:1 mix at 4°C was given in both an antegrade and a retrograde fashion and repeated every 20 minutes. An insulation pad was placed in the pericarduim and iced electrolyte solution was applied to the epicardium. Myocardial temperature was monitored and adjusted as warranted. Warm (37°C) cardioplegia was given both antegrade and retrograde before removal of the cross-clamp.
The distal anastomoses were done during a single period of aortic cross-clamping. Proximal anastomoses were done after removal of the cross-clamp, while still on cardiopulmonary bypass with a partial occlusion clamp placed on the aorta. An attempt was made to graft the left anterior descending artery with the left internal mammary artery in those patients with appropriate lesions. The exceptions were patients with subclavian artery stenosis or very severe chronic obstructive lung disease. Complete revascularization was always the goal.
Patients were rewarmed to 36°C and given 30 minutes or more of perfusion time after removal of the aortic cross-clamp. Magnesium and triiodothyronine were given before removal of the cross-clamp and low-dose dopamine was infused before termination of cardiopulmonary bypass. Meticulous hemostasis was obtained before closure.
Overnight ventilation was used in a cardiovascular intensive care unit and postoperative care was provided by the cardiac surgical team. Discharge was targeted for postoperative day 8 early in the series and gradually decreased to day 4 in the latter part. Home health services were routinely used and outpatient care was managed by the surgeons with clinical nurses and designated home health nurses.
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Results |
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Patients’ risk factors are not dissimilar from other reports and included smoking, 402 patients (65%); cardiomegaly, 188 patients (31%); morbid obesity, 161 patients (26%); diabetes mellitus, 144 patients (23%); chronic obstructive lung disease, 125 patients (20%); pulmonary hypertension, 35 patients (6%); cerebrovascular accident, 25 patients (4%); and renal failure, 18 patients (3%).
Three hundred sixty-three (59%) of the patients had a previous myocardial infarction. This occurred less than 21 days before operation in 150 (24%) and more than 21 days in 213 (35%). The mean recorded ejection fraction was 52% (±12%) with a range of 20% to 80%. Many of these were measured in the first beat after a ventricular premature contraction. The mean left ventricular end-diastolic pressure was 19 (±8) with a range of 1 to 45 mm Hg (Table 1).
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An intraaortic balloon pump was used in 21 (3.4%) patients. Of those who received an intraaortic balloon pump, 4 (19%) had it placed preoperatively, 16 (76%) during the operation (usually to assist in weaning from bypass), and 1 patient had an intraaortic balloon pump placed postoperatively.
Reoperation for bleeding was required in 9 (1.5%) patients and deep sternal infection occurred in 2 (0.33%). Nineteen (3%) required more than 1 day of mechanical ventilation, renal failure developed in 5 (0.8%), none of whom required dialysis and permanent stroke or coma occurred in 1 patient (0.16%).
Operative mortality included those patients who died during the same admission as their operation, those patients discharged and readmitted within 30 days of their operation who died during that subsequent admission, plus those who died out of the hospital within 30 days of their operation. Two patients (0.33%) died. The predicted (expected) mortality for the entire group was 16.6 (2.70%) with a range of 0.23% to 33.7%. The observed/expected ratio (O/E) was 0.12 and 
2 analysis yielded a p value of less than 0.005 (Table 2).
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Comment |
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In Philadelphia, a study of the results from five teaching hospitals reported that surgeon volume was not predictive of patient mortality [10] and the Ad Hoc Committee on Cardiac Surgery Credentialing of the STS has concluded that "There are no data to conclusively indicate that outcomes of cardiac operations are related to a specific minimum number of cases performed annually by a cardiac surgeon" [11]. Our results show that low surgeon volume does not preclude good CABG results.
The annual volume of CABG cases for a given hospital has also been reported to be a determinant of patient mortality [3]. The number of "excess deaths" that purportedly occur in hospitals performing 200 or fewer CABGs per year has been published [12] and it has been stated that the "greatest improvement in average outcomes for CABG surgery would result from the closure of low-volume surgery units" [13]. However, the Veterans Affairs Hospital system report noted that there was not a continuous relationship between surgical volume and mortality but that there was a higher O/E ratio in Veterans Affairs hospitals performing 100 or fewer cases per year [14]. In 1982 and 1984 crude mortality rates of 3.3% [15] and 1.7% [16] were reported in two separate low-volume cardiac surgery programs. We found that we were able to obtain a very low crude mortality rate of 0.33% with an O/E of 0.12 in a hospital that averaged only 117 CABG cases per year, showing that good results can be obtained in the presence of low hospital CABG case loads even when the surgeon volume is also low.
We were extensively involved in the preoperative preparation of the CABG patients, sometimes to an extent greater than we desired. This included completion of history and physical examinations, addressing laboratory abnormalities, ordering diagnostic tests, treatment of infections, and changes in medications including antianginal medications and intraaortic balloon pump therapy. We tried to maximize patient stability and were frequently able to downgrade patient status (and risk) from emergent to urgent or elective. This aggressive approach to preoperative involvement was time consuming and not always well received (popular), but it appeared to minimize the impact of associated comorbidities and known risk factors. When possible, we avoided operation within 7 days of an acute myocardial infarction and preferentially allowed 21 days of recovery after an acute myocardial infarction. This could be safely accomplished in many patients with the generous use of ß-blockers and nitrates, careful patient monitoring including cardiac rehabilitation after acute myocardial infarction, plus good patient education and follow-up.
Intercessory prayer has been noted to be of value in some acute care patients [17] and was applied to all of our patients. Attention to the patients’ spiritual and psychological health was part of the preoperative care and input from a chaplain and a psychiatric clinical nurse was routinely obtained.
Preoperative aspirin has been noted to increase operative blood loss [18] and we endeavored to stop aspirin as well as other platelet-affecting drugs 7 days before operation when possible. This assisted us in avoiding some of the morbidity associated with postoperative bleeding and transfusion. The antioxidants allopurinol and vitamin E have been reported to have positive effects on patients undergoing CABG [19–21] and we routinely administered them preoperatively as has been suggested. Aware that cold agglutinins can cause hemolysis and intravascular occlusive crises, we followed published guidelines for testing and management of this entity [22].
The intraoperative care was as outlined. It represented attention to detail using known techniques and procedures. Postoperative care was directed by the surgeons and orders were seldom written by other physicians. Frequent and complete review of the patients status occurred among the surgeons and with the clinical and bedside nursing staff. Physician/nurse collaboration was promoted and a team atmosphere was present. In addition, we adhered to the manufacturing credo that "decreasing variance increases quality" and used standardized approaches and pathways to deal with repetitive events in patient care. We conclude that a high degree of surgeon involvement in patient care, attention to detail, and application of known principles and guidelines allowed us to obtain good outcomes. Noting that neither of us is an unusually "gifted" surgeon, we believe that similar results are obtainable by other surgeons.
The STS Ad Hoc Committee on Physician-Specific Mortality Rates for Cardiac Surgery notes that "Not uncommonly, poor outcomes were found to be associated with problems in the overall system rather than with individual surgeons" [23]. It may be that small volume programs tend toward outcome problems because of lack of maintenance of standards and support from the institution. We suspect that quality results may be more difficult to maintain in a low-volume program.
In our situation we found that each patient required a great deal of personal effort and our time investment per case seemed high. We have also found that a diminution in committment to quality on the part of an institution can imperil good results.
This report should not be construed as an argument that every institution can or should do cardiac surgery. What we have shown is that a surgical team can develop a system that yields good CABG results in the presence of low case volumes. We are convinced that surgeon leadership is vitally important in the development and maintenance of a successful system, that institutional support of that leadership is critical, and that painstaking application of known processes of patient care can yield excellent CABG results in a low-volume practice. Although continued monitoring is warranted, in situations such as this volume-based credentialing is erroneous.
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References |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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This article has been cited by other articles:
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  D. M. Shahian, G. J. Heatley, and G. A. Westcott Relationship of hospital size, case volume, and cost for coronary artery bypass surgery: Analysis of 12,774 patients operated on in Massachusetts during fiscal years 1995 and 1996 J. Thorac. Cardiovasc. Surg., July 1, 2001; 122(1): 53 - 64. [Abstract] [Full Text] [PDF]
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 A. Chandra Excellence and low case volume Ann. Thorac. Surg., April 1, 2001; 71(4): 1399 - 1399. [Full Text] [PDF]
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J. D. Urschel and D. M. Urschel Volume-outcome relationship in thoracic surgery Ann. Thorac. Surg., September 1, 2000; 70(3): 1001 - 1001. [Full Text] [PDF]
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G. L. Early and S. R. Roberts Reply Ann. Thorac. Surg., September 1, 2000; 70(3): 1001 - 1001. [Full Text] [PDF]
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