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Biomedical subjects

F H Edwards

Publications and source records attributed to F H Edwards.

At least 55 records · Page 3Linked to original sources
PubMed1990

True emergency coronary artery bypass surgery.

Previous reports of emergency coronary artery bypass grafting often included cases that were not true surgical emergencies, thereby creating inappropriately favorable results. To accurately investigate this important subgroup of patients, we analyzed our recent experience with truly emergent coronary artery bypass grafting. From January 1984 to January 1989, 117 patients underwent true emergency bypass grafting for acute refractory coronary artery ischemia. Clinical deterioration was associated with failure of percutaneous angioplasty in 37 patients and instability during diagnostic catheterization in 13 patients. Refractory ischemia developed in the remaining patients while on the ward or in the intensive care unit. All operations were performed within four hours of surgical consultation, most within one hour. Overall in-hospital operative mortality was 14.5% (17/117), and 76.5% of deaths (13/17) were due to cardiac-related causes. Major morbidity occurred in 35.9% (42/117). Univariate analysis isolated ejection fraction, extent of coronary artery disease, previous myocardial infarction, hypertension, need for inotropic support, use of an intraaortic balloon pump, and cardiopulmonary resuscitation as risk factors for operative mortality. Stepwise multivariate analysis confirmed that previous myocardial infarction, hypertension, cardiopulmonary resuscitation, and reoperation were independently significant risk factors. Age, sex, diabetes, left main disease, and peripheral vascular disease had no significant impact on the prognosis. The 4% operative mortality (2/50) for patients taken directly to the operating room from the catheterization suite was significantly lower than the 22.4% mortality (15/67) associated with emergencies arising on the ward or intensive care unit (p less than 0.01). A logistic risk equation developed from this population accurately modeled operative mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Computerized tomography in the evaluation of myasthenia gravis.

Thymomas occur in 10% to 15% of patients with myasthenia gravis. Since not all patients are referred for thymectomy, a test that could reliably predict the presence or absence of a thymoma would be of great assistance in the management of these patients. We studied all patients referred for thymectomy at Walter Reed Army Medical Center from 1983 to 1989. Complete records were available for 13 patients. Computerized tomography (CT) correctly predicted the presence of a thymoma in one patient and falsely predicted a thymoma in a patient with a thymic cyst; it accurately predicted the absence of a thymoma in the remaining 11 patients. The sensitivity of CT scanning was 100%, the specificity was 92%, and the accuracy was 92%, results that are in agreement with previously published data. Compared to conventional chest roentgenography, CT scanning provided a more precise anatomic localization, and accurately predicted local invasion. We recommend a CT scan of the mediastinum in all patients with myasthenia gravis to avoid delayed diagnosis of thymoma in patients who normally would not be referred for thymectomy.

Adult↗
PubMed1990

Risk assessment in urgent/emergent coronary artery surgery.

A statistical model has been developed to allow for prediction of individual patient prognosis following urgent/emergent coronary artery bypass grafting (CABG). None of the models previously described for use in coronary artery surgery has been tested with a prospective patient series that confirms the true predictive capacity of the model. Ideally, the predictive ability of such models should be validated with prospective trials. To examine the feasibility of statistical modeling in this clinical context, a computerized model based on the theorem of Bayes was developed to predict operative mortality for urgent coronary artery surgery. The presence or absence of 20 risk factors was determined for each of 405 consecutive patients undergoing urgent coronary artery surgery from January 1984 to January 1989. The first 100 patients were used to develop a database for the model, which was then used to prospectively evaluate the remaining 305 patients. There was good agreement between predicted and observed results. Models of this kind are particularly advantageous because of the ability to (1) accommodate multiple risk factors, (2) become tailored to a specific practice, and (3) determine individual rather than group prognosis. Validation with a prospective trial confirms the practical utility of this approach. This model has reliably predicted the risk associated with urgent coronary artery surgery and may provide important clinical information for the management of patients being evaluated for urgent revascularization.

Algorithms↗
PubMed1990

A comparative evaluation of pulmonary artery balloon counterpulsation and a centrifugal flow pump in an experimental model of right ventricular infarction.

To compare the efficiency of pulmonary artery balloon counterpulsation and a centrifugal flow pump in reversing the hemodynamic consequences of acute right-sided heart failure, we employed both devices in 14 Yorkshire pigs in which right ventricular infarction was created via surgical ligation of branches of the right coronary artery. Pulmonary artery balloon counterpulsation improved some of the indicators of right heart failure, as manifested by significantly decreased right atrial pressure and increased mean systemic blood pressure. In contrast, the centrifugal flow pump consistently and significantly reversed all of the hemodynamic consequences of right ventricular infarction. In comparison to pulmonary artery balloon counterpulsation, the centrifugal flow pump resulted in lower right atrial pressures (p=0.020), lower mean pulmonary pressures (p less than 0.0001), increased left atrial pressures (p=0.026), increased cardiac output (p less than 0.0001), and increased mean systemic blood pressures (p less than 0.0001). Possible mechanisms to explain the superiority of the centrifugal flow pump include better hemodynamic unloading of the failing myocardium and independence from right ventricular output.

Animals↗
PubMed1989

A quality assurance model of operative mortality in coronary artery surgery.

Quality assurance in coronary artery bypass grafting (CABG) surgery requires a comparison of operative mortality against an accepted standard of care. Raw mortality statistics are unacceptable in this context, and risk factor analysis is essential. However, this principle has not been adequately demonstrated in previous reports. Our goal in this study was to develop a risk model of accepted CABG mortality and illustrate its proper use in coronary artery surgery. The model was derived from a Bayesian analysis of 6,630 patients undergoing CABG in the Coronary Artery Surgery Study (CASS) registry. Age, sex, ventricular function, previous myocardial infarction, extent of coronary artery disease, unstable angina, and surgical priority were used by the model to sort patients into risk categories. From January 1984 through December 1987, 840 patients underwent isolated CABG at our hospital. With raw mortality data, the 3.9% (33/840) mortality of our patients was significantly different from the 2.3% (153/6,630) CASS mortality (p less than 0.001). When our patients were entered into the CASS model for risk stratification, however, our CABG mortality conformed to the CASS experience. These results illustrate the fallacy of using raw mortality statistics for interinstitutional comparisons. This type of risk model is a fundamental element of CABG quality assurance.

Aged↗
PubMed1989

Coronary artery bypass in idiopathic thrombocytopenia without splenectomy.

A patient with coronary artery disease and idiopathic thrombocytopenia purpura underwent coronary artery bypass grafting without splenectomy. Our experience indicates that use of cardiopulmonary bypass in patients with idiopathic thrombocytopenic purpura does not invariably mandate splenectomy.

Coronary Artery Bypass↗
PubMed1989

Use of artificial intelligence for the preoperative diagnosis of pulmonary lesions.

The relatively new field of artificial intelligence has spawned a variety of techniques associated with computer-assisted diagnosis. These techniques have been applied to the diagnosis of pulmonary lesions, but previous reports have focused on medical rather than surgical populations and the results have been evaluated using only retrospective patient surveys. We used a Bayesian algorithm to develop a diagnostic computer model for prospectively evaluating patients undergoing thoracotomy for suspected pulmonary malignancy. Patients who had a preoperative diagnosis were not included. Preoperative clinical and radiographic parameters for 100 consecutive patients were prospectively entered into the diagnostic model, which then categorized the lesion as benign or malignant. The computer predictions agreed with the final histological diagnosis in 95 of the 100 patients. The sensitivity was 96% and the specificity was 89% for this prospective series. These results indicate that the computer-assisted diagnosis of pulmonary lesions may have a role in this clinical setting.

Adult↗
PubMed1988

Use of a Bayesian statistical model for risk assessment in coronary artery surgery.

A computerized statistical model based on the theorem of Bayes was developed to predict mortality after coronary artery bypass grafting. From January, 1984, to April, 1987, at our hospital, 700 patients underwent isolated coronary artery bypass grafting. The presence or absence of 20 risk factors was determined for each patient. The first 300 patients formed the initial database of the Bayesian predictive model, and the remaining 400 patients were prospectively evaluated in four groups of 100 each. Each group was prospectively evaluated and then incorporated into the database to update the model. There was good agreement between predicted and observed results. Bayesian theory is particularly suited to this task because it (1) accommodates multiple risk factors, (2) is tailored to one's specific practice, (3) determines individual, rather than group, prognosis, and (4) can be updated with time to compensate for a changing patient population. These flexible attributes are especially valuable in light of recent changes in the coronary artery bypass graft patient profile.

Aged↗
PubMed1987

Bayesian diagnostic theory using a programmable pocket calculator.

A programmable pocket calculator program has been written to serve as an aid in diagnosis. The program uses a Bayesian statistical algorithm to calculate the relative probability of two diagnostic alternatives. The ability to carry out Bayesian statistical calculations at the bedside should make the use of such techniques more attractive to clinical practitioners.

Algorithms↗
PubMed1987

Bayesian statistical theory in the preoperative diagnosis of pulmonary lesions.

We used a computerized Bayesian algorithm to assist in the preoperative diagnosis of pulmonary lesions. One hundred consecutive patients who were undergoing exploratory thoracotomy for newly discovered pulmonary lesions were prospectively evaluated. The Bayesian model used a total of 44 preoperative clinical and roentgenographic factors to categorize the lesions as benign or malignant. The Bayesian algorithm correctly categorized 96 of the 100 lesions, thereby providing an accuracy of 96 percent. The sensitivity of the model was 98 percent and the specificity was 87 percent. All but two of the 85 malignant lesions were correctly categorized and 13 of the 15 benign lesions were correctly analyzed by the model. These results indicate that computer-assisted diagnosis using the Theorem of Bayes may provide valuable preoperative information for the management of selected patients.

Adolescent↗
PubMed1987

The theorem of Bayes as a clinical research tool.

The theorem of Bayes is a powerful research tool that has a multitude of clinical applications. Its use has been somewhat restricted because of the intrinsic complexity of Bayesian theory and the need for computer support. We explain herein the Theorem of Bayes in practical terms that specifically apply to clinical research.

Bayes Theorem↗
PubMed1986

Surgical implications of intraoperative postinfarction ventricular rupture.

This case report documents that ventricular myocardial rupture after acute infarction may seal with clot, only to rupture again with potentially lethal consequences. At exploration, the clot over a fresh rupture was intact. As closure was started, the clot disrupted, causing severe hemorrhage. Rupture was successfully repaired and the patient survived.

Cardiopulmonary Bypass↗
PubMed1986

The handheld computer in critical care medicine.

The wealth of information that can be generated from programmable pocket calculators is not widely appreciated. These inexpensive devices have evolved into "user-friendly" microcomputers with impressive memory capacity and mathematic sophistication. A series of critical care programs is presented to illustrate the degree of computer support that is available from the newest generation of programmable pocket calculators. These programs constitute the most comprehensive microcomputer software package reported in the literature. They demonstrate that high-level mathematic capability is available not only in large medical centers, but in virtually any small community hospital as well.

Aminoglycosides↗
PubMed1984

Use of a Bayesian algorithm in the computer-assisted diagnosis of appendicitis.

One hundred consecutive patients with acute right lower quadrant abdominal pain were prospectively evaluated with a computerized Bayesian diagnostic algorithm. An accuracy rate of 92 per cent was obtained. Computer recommendations would have resulted in a negative exploration rate of 9 per cent, as compared with the rate of 19 per cent which was actually obtained. Even though our clinical management of these patients was in keeping with accepted standards, the Bayesian program would have avoided eight unnecessary operations. In all instances in which the patient presented with appendicitis, the computer correctly predicted that appendicitis was present. Computer-assisted diagnostic programs using a Bayesian approach may have some role in the evaluation of right lower quadrant abdominal pain. The technique presented herein describes a means of developing a database of conditional probabilities without reliance on large patient surveys. Even with this refinement, the Bayesian approach to diagnosis remains complex. The development of this type of program requires close interaction between computer scientists and surgeons. Nevertheless, the approach does appear promising and it may well be worth the considerable effort required to initiate such a system. The exact role for Bayesian diagnostic analysis cannot be predicted at this point. Certainly it should have no greater importance than a routine laboratory test. Perhaps the results of Bayesian analysis in this setting might assume a diagnostic significance similar to that of the white blood cell count. The work of DeDombal has done much to eliminate the physician reluctance seen with earlier programs. It has become increasingly apparent that computers may perform many clinically useful functions without infringing upon the art of medicine. The computer assisted diagnosis of acute abdominal pain may well constitute one such function.

Acute Disease↗
PubMed1983

Bedside determination of aminoglycoside therapy in the patient with renal insufficiency.

A computer program has been written to assist the clinician in making dosage adjustments for the patient with renal insufficiency. The entire program can be run in less than one minute and requires no previous computer experience. Large memory storage requirements are averted by the introduction of analytic equations to model tabular data. The easy access and friendly alphanumeric capability should make the calculator sufficiently convenient to overcome the physician reluctance noted with earlier programs. Even though the accuracy of these techniques is well established, it should be emphasized that aminoglycoside concentrations can, occasionally, be unpredictable, and therefore, peak and trough levels should be drawn for all patients in this setting. Used in this context, the program described herein should prove to be a useful addition to the physician's armamentarium of clinical software.

Aminoglycosides↗
PubMed1982

Computer assisted planning of parenteral hyperalimentation therapy.

A computer program has been written to assist the physician in the planning of nutritional support. The program is divided into individual segments dealing with nutritional assessment, caloric requirements, hyperalimentation planning, and evaluation of nutritional therapy. Tables of anthropometric data have been fitted to exponential and polynomial equations in order to minimize data storage requirements and eliminate the need for interpolation schemes. Operation of the program does not require any form of reference material and prior computer training is not a prerequisite for program users. The program may be run on either a large desktop computer or a hand-held programmable pocket calculator with continuous memory and optional printer.

Anthropometry↗
PubMed1982

Late post-traumatic obstructive jaundice secondary to a biliary tract foreign body.

Post-traumatic biliary obstruction caused by a penetrating foreign body is rare. Our patient appears to be the first case in which the diagnosis was established by endoscopic retrograde cholangiopancreatography. Even though this entity is uncommon, it should be considered in patients presenting with jaundice and abdominal pain years after penetrating abdominal trauma.

Adult↗