Biomedical subjects
Publications and source records attributed to R K White.
Cardiac surgery continues to evolve in response to advances in technology, patient demands, and healthcare reimbursement. The development of minimally invasive operative techniques and laser technology has enhanced the therapeutic armamentarium available to the cardiac surgeon. Advances in biomaterial development will see the artificial heart in clinical trials by the millennium.
Employee assistance programs have developed from alcoholism assessment and referral centers to specialized behavioral health programs. Comprehensive employee assistance programs are defined by six major components: identification of problems based on job performance, consultation with supervisors, constructive confrontation, evaluation and referral, liaison with treatment providers, and substance abuse expertise. Other services have been added as enhancements to the basic model and include managed behavioral health activities and professional assistance committees, which provide services for impaired professionals and executives. Recent developments in the field are illustrated through examples from the experience of the employee assistance program at the University of Maryland Medical System in Baltimore.
Physician impairment contributes to patient morbidity, malpractice claims, physician license loss and suicide. This paper describes four years of experience of the University of Maryland's Professional Assistance Committee. The committee is composed of medical staff members. Its mission is to help impaired physicians obtain assessment, treatment and monitoring, and to protect patients from harm. The committee has evaluated 23 cases over the past four years. Ten were credential checks, and 13 investigations of active problems. Eight of the 23 cases were for alcohol, eight for drug, and seven for behavioral problems. Only one person lost medical staff privileges. The committee has been well accepted by the medical staff and hospital administration and can be easily reproduced in other hospitals.
Esophageal perforation remains a difficult diagnostic and management problem. Recommendations regarding treatment remain controversial. A 15-year experience with perforation of the esophagus from all causes was reviewed at Louisiana State University and Veterans Administration, Medical Centers (Shreveport, LA). The majority of the injuries involved the thoracic esophagus (28 or 54%), followed by the cervical (21 or 40%), and the intraabdominal esophagus (3 or 6%). Iatrogenic causes constituted most of the injuries (52%), followed by external trauma (23%), barogenic rupture (15%), and ingested foreign bodies (10%). Diatrizoate methylglucamine 66 per cent, sodium diatrizoate 10 per cent (Gastrografin; Squibb, Princeton, NJ) contrast studies and flexible esophagoscopy were performed in 44 and 22 patients, respectively. In the cervical esophagus, contrast studies were more sensitive and specific than endoscopy (P less than .01), but both studies were equally effective as diagnostic methods in thoracic perforations. Cervical perforations were treated with either drainage alone (7 patients) or primary repair with drainage (14 patients) with an operative mortality of 4.8 per cent. Several procedures were used in thoracic perforations, which carried a mortality of 36 per cent and were more lethal than cervical tears (P less than 0.2). Any thoracic esophageal perforation treated more than 24 hours after the onset of symptoms, irrespective of what procedure was used, was associated with a significantly higher mortality than if operated on earlier (P less than .001). Five patients with perforated carcinomas were treated by esophageal resection with no mortality. Significantly higher mortality was seen with a delay in diagnosis, thoracic perforations, and Boerhaave's Syndrome. A subset of patients with perforated carcinomas may benefit from esophageal resection with delayed reconstruction.
This paper presents a review of the current literature on hospital professional assistance committees, a discussion of key issues, and a set of guidelines for the design and operation of these committees. The employee assistance program is suggested as a resource to these committees.
Methods to predict and control cardiac output (CO) accurately in total artificial heart (TAH) recipients have varied significantly in the last few decades. Early models exhibited minimal control mechanisms and involved fixed pumping parameters. Elaborate electromechanical systems that have recently evolved require intricate communication between the circulating blood volume and the electric pump to maintain blood flow to critical organs. Attempts to quantitate specific end-organ blood flow, metabolic alterations, and oxygen delivery and, finally, to link these functions to the control of the TAH have not succeeded. Current devices seek to predict the needed CO by monitoring preload, afterload, or a combination of both. No consensus has developed concerning the appropriate physiologic parameters that should be surveyed in vivo and then used to regulate the output of the TAH.
Pharmacological therapy for congestive heart failure includes drugs that have both inotropic and vasoactive effects, although it is sometimes difficult to differentiate between the two effects. An animal with an implanted total artificial heart (TAH) allows the investigation of the vascular effect of these drugs in the absence of the effect on the myocardium. An advantage of the TAH model is its sensitivity to changes in right and left ventricular preload and afterload. Four instrumented TAH calves were given vasoactive drugs and the response was compared to control. Epinephrine, dopamine, isoproterenol, and nitroprusside were selected because of the predictability of their responses. Epinephrine caused a significant increase in systemic vascular resistance (SVR), and dopamine caused a significant increase in Pulmonary vascular resistance (PVR) and Isoproterenol caused a significant decrease in PVR. TAH implanted calves can thus serve as a pharmacological model to study the vascular response, which may be useful in investigation of new agents with inotropic and vascular effects.
Pneumatically powered artificial hearts readily accommodated the higher net stroke volumes by the right ventricle than from the left ventricle. We published that this discrepancy was approximately 8% of the left ventricular cardiac output. A variety of methods have been used to achieve balance between the right and left atrial pressures. Relatively large volume-displacement chambers (VDC) present potential problems, but do provide balance. The VDC in volumetrically coupled right-left stroke volumes was eliminated by using a small-diameter interatrial shunt (IAS). Preliminary studies demonstrated excellent balance in contracted and expanded blood volume (preload) and by hypotension and hypertension created with vasoactive drugs (afterload). At a mean aortic pressure of 120 mmHg, heart rate of 120 BPM, cardiac output of 8 L/minute and right atrial pressure of 13 mmHg, the peak IAS flow was 3.2 ml/beat in a right to left direction and 8.0 ml/beat in a left to right direction. The net left to right flow was 4.8 ml/beat. Over a wide range of preload (2 to 20 mmHg) and afterload (45 to 180 mmHg), the left atrial pressure was routinely 5 mm Hg more than the right atrial pressure. Elimination of the VDC reduces the number of components, volume, and weight of the totally implantable artificial heart. The IAS offers a simple solution to a very complex problem and provides a device that is simpler to implant and is possible to explant.
The purpose of this paper is to use physiologically based pharmacokinetic models to demonstrate that if toxic response is a function of the time profile in physiological time of the concentration of the toxic moiety in the target tissue, then the appropriate interspecies scaling law for toxic compounds which are metabolically deactivated is mg kg-1 per unit of physiological time (mg kg-1 pt-1). At low dose rates this metric is approximately equivalent to mg kg-0.75 day-1. For reactive metabolites which are spontaneously deactivated, an approximate interspecies scaling law is mg kg-1 day-1.
This paper reexamines the scaling approaches used in cancer risk assessment and proposes a more precise body weight scaling factor. Two approaches are conventionally used in scaling exposure and dose from experimental animals to man: body weight scaling (used by FDA) and surface area scaling (BW0.67--used by EPA). This paper reanalyzes the Freireich et al. (1966) study of the maximum tolerated dose (MTD) of 14 anticancer agents in mice, rats, dogs, monkeys, and humans, the dataset most commonly cited as justification for surface area extrapolation. This examination was augmented with an analysis of a similar dataset by Schein et al. (1970) of the MTD of 13 additional chemotherapy agents. The reanalysis shows that BW0.75 is a more appropriate scaling factor for the 27 direct-acting compounds in this dataset.
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Freshly extracted human third molars with completely formed roots were sectioned and placed in Karnovsky's fixative. The specimens were decalcified in ethylenediaminetetraacetic acid (EDTA) for 91 days, followed by digestion in collagenase. They were then fixed in a solution of buffered osmium tetroxide or ruthenium red and buffered osmium tetroxide, embedded in Spurr's plastic mixture, and sectioned for transmission electron microscopy. Each section was stained with uranyl acetate and lead citrate and viewed with a transmission electron microscope. No odontoblast processes could be identified at the cemental third of the dentin with the described technique.
This article reviews a group of inflammatory mediators called leukotrienes. It includes their historical background, chemical pathway of formation, presence in cells and fluids, and biologic activity. These potent substances may be involved in pulpal and periradicular disease, but such involvement has not yet been reported.
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To assess community awareness of a community mental health center, a telephone survey was conducted, using a random stratified sample. In order to provide comparative analyses, two other mental health agencies were included in the study. Five specific issues were addressed: (a) the percentage of the population that was aware of the agencies, (b) inter-agency comparisons, (c) heterogeneity of awareness levels among geographic areas, (d) the relative merit of different sources of information, and (e) the relationship between awareness and demographic factors. The results indicated relatively high levels of awareness for the three agencies (X = 57%). There were, however, significant differences in awareness levels between agencies and between geographic areas. The source of information cited most often by respondents was the newspaper; in addition, there was an effect for the primary agency's storefront office. Sex, education, and family size had significant but weak correlations with the amount of accurate information a respondent possessed. The results provided substantive answers to the agency's concerns as well as methodological guidelines for future evaluations of community awareness.
A small exhaust hood was designed and constructed of clear acrylic plastic for use within a biological research environment. The hood's primary function was to draw irritating vapors away from the user's breathing zone and into an exhaust system. The hood was of simple construction.