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Biomedical subjects

B A Stanton

Publications and source records attributed to B A Stanton.

90 records · Page 5Linked to original sources
PubMed1984

Influence of ADH on renal potassium handling: a micropuncture and microperfusion study.

To study the effects of ADH on the transport of potassium by the distal tubule and collecting duct system, we performed simultaneous clearance and micropuncture experiments in homozygous Brattleboro rats (with hereditary hypothalamic diabetes insipidus), before and after intravenous infusion of the hormone. Final urinary flow rate was reduced by a factor of 7 after ADH, but fractional potassium excretion increased by 77% for the group as a whole. During free-flow micropuncture, there was no significant difference in fractional delivery of potassium up to the late distal tubule between control (water diuresis) and ADH conditions; thus, the increase in final urinary potassium excretion was mediated beyond this tubular site. However, flow rate of tubular fluid was decreased significantly after ADH in late distal tubular segments, where potassium secretion is a flow-dependent process. To evaluate the possibility of a direct effect of ADH on distal tubular potassium secretion, independent of changes in flow rate, we studied another group of animals by continuous microperfusion, in vivo, of single distal tubules, using an isotonic perfusion fluid so that water reabsorption would be minimal after as well as before the addition of ADH. Under these conditions, a significant stimulation of distal tubular potassium secretion by ADH could be demonstrated. We suggest that this property of ADH may serve to prevent potassium retention during periods of antidiuresis.

Animals↗
PubMed1984

Differential acute effects of aldosterone, dexamethasone, and hyperkalemia on distal tubular potassium secretion in the rat kidney.

To determine the specific effects on renal potassium transport of acute elevations in plasma aldosterone, dexamethasone, and potassium concentrations, we studied adrenalectomized rats prepared such that each factor could be varied independently. Clearance data alone could not be used to deduce the underlying tubular transport effects, however, since infusion of each of these agents was associated with a marked change in urinary flow rate, which may itself have influenced potassium excretion. We therefore used a technique of continuous microperfusion, in vivo, of single superficial distal tubules to evaluate potassium secretion at constant luminal flow rate during each experimental maneuver. Acute aldosterone infusion was associated with a 90% stimulation of potassium secretion by microperfused tubules. However, total kidney sodium excretion and urinary flow rate were markedly reduced, and these factors opposed the direct tubular action of aldosterone, resulting in no net change in the amount of potassium excreted into the final urine. Conversely, dexamethasone had no direct effect on potassium secretion by single microperfused tubules, but it caused a sharp increase in urinary flow and sodium excretion, and secondarily enhanced urinary potassium excretion by 50%. Hyperkalemia per se stimulated renal potassium excretion both via a direct tubular effect and by increasing urinary flow rate. We conclude that urinary potassium excretion after infusion of each of these agents represents the net result of direct tubular effects and secondary flow-mediated changes.

Aldosterone↗
PubMed1983

Coronary artery bypass surgery. Physical, psychological, social, and economic outcomes six months later.

To evaluate the benefits of coronary artery bypass graft (CABG) surgery, we interviewed and tested 318 patients (268 men and 50 women) younger than age 70 before and six months after elective CABG at four university medical centers. Biomedical, psychoneurological, physical function, role function, occupational, social, family, sexual, emotional, and attitudinal variables were assessed. Quantitative comparisons showed improvement on many factors. Angina was completely relieved for 69% to 85% of persons, depending on whether it had been induced by exertion or other events. Disability days were reduced more than 80%. Seventy-five percent of employed persons had returned to work. Anxiety, depression, fatigue, and sleep problems declined. Vigor and well-being scores rose significantly. When losses were expected (eg, psychoneurological function, marital adjustment), they generally were not found. For none of the more than 60 outcome variables was widespread serious worsening found. The findings suggest that the great majority of patients are able to resume normal economic and social functioning within six months after CABG.

Adult↗
PubMed1983

Predictors of employment status after cardiac surgery.

Preoperative predictors of postoperative employment status were studied in 228 patients (aged 25 to 64 years) who underwent cardiac surgery. Of the 150 patients working in the year before surgery, 73% returned within six months. Of those not so employed, 18% started working. Patients who expected preoperatively to return to work did so at an 82% rate compared with 39% of the others. This was a strong predictor in the multiple regression analysis. Educational level and family income were stronger predictors than occupation or level of physical exertion required. Rates of return were higher in patients with less severe angina and less fatigue preoperatively, but did not differ significantly by sex, surgical procedure, or duration of illness. Seven variables predicted work status correctly for 86% of persons. These results suggest that determinants of return to work are largely present before surgery and that patients' attitudes and expectations play an important role.

Adult↗
PubMed1983

Correlates of angina pectoris among men awaiting coronary by-pass surgery.

Biomedical, behavioral, and psychological correlates of angina pectoris were identified in 204 men awaiting coronary artery by-pass graft surgery. Angina was rated by use of a precoded series of interview questions. Four circumstances of anginal symptoms were investigated: exertional, emotional, post-prandial, and while resting or sleeping. These were uncorrelated with one another, except for exertional and post-prandial. Two-thirds of these patients experienced angina less often than daily in the most recent unrestricted month. Severity of coronary artery obstruction was not positively associated with frequency or severity of any type of angina, and were primarily behavioral and psychological. Disturbances of sleep, physical inactivity, history of cigarette smoking, distressed response to life crises, life dissatisfactions, hostility, use of propranolol, duration of cardiac illness, and age were among the predictors in the multiple regression equations. These results from selected by-pass candidates may apply more directly to such persons than to unselected community residents reporting angina symptoms. The findings suggest the need for greater focus on sources of variability in myocardial oxygen supply and demand in understanding the dynamics of angina episodes.

Adult↗
PubMed1983

Physical, psychologic, social, and economic outcomes after cardiac valve surgery.

Eighty-nine patients receiving cardiac valve replacement or surgery consisting of valve replacement and coronary artery bypass grafts in four teaching hospitals were studied before surgery and again six months after surgery. More than 60 indicators of the quality of life were assessed. The majority of persons showed improvement in physical function, emotional states, and social activity. Of those with exertional angina or dyspnea before surgery, about two thirds were completely relieved at six months after surgery. There was a substantial reduction in number (from 31 to seven) of persons with five or more days of disability per month due to cardiac symptoms. The majority remained the same in their usual level of physical activity, most psychological traits, and attitudes and social support networks. Most previously employed persons returned to work. Improvements in the conditions of patients who had valve surgery closely paralleled those of patients who had undergone coronary artery bypass surgery in the same hospitals.

Activities of Daily Living↗
PubMed1982

Effects of pH on potassium transport by renal distal tubule.

To determine the relative importance of plasma and luminal pH changes as factors regulating potassium secretion by rat distal tubule, superficial tubules were continuously microperfused in vivo. The effects of changes in plasma pH were examined by producing acute systemic metabolic acidosis or alkalosis and holding luminal flow rate, solute composition, and pH constant by microperfusion. Alternatively, the effect of luminal solution pH was evaluated by microperfusing tubules with solutions buffered to either pH 6.5 or 8.0 at constant systemic acid-base balance. Net transport of Na and K and the pH of the luminal fluid were measured. Results showed that metabolic acidosis inhibited and metabolic alkalosis stimulated potassium secretion. Increased luminal fluid pH, in contrast, did not stimulate potassium transport. In experiments in which metabolic acidosis produced a diuresis, urinary potassium excretion was enhanced compared with hydropenic controls. Free-flow micropuncture studies revealed that the rate of fluid delivery to the distal tubule was 45% greater during acidosis compared with control and that potassium secretion increased in both the distal and collecting tubule. Since the rate of fluid delivery is a potent stimulus of potassium secretion in the distal tubule, it is concluded that the stimulus of increased delivery of fluid, observed in free-flow conditions, masked the inhibitory effect of acidosis on potassium transport. Potassium transport by the distal tubule, during acid-base disorders, is regulated by plasma pH and the rate of delivery of fluid but is not stimulated by alkalinization of the luminal fluid.

Acidosis, Renal Tubular↗
PubMed1982

Potassium transport by the renal distal tubule: effects of potassium loading.

Microperfusion studies were performed on superficial distal tubules to determine the relationship between potassium secretion by the distal tubule and plasma potassium concentrations in rats on a control and a high potassium diet. Potassium was infused in graded doses into animals on a control diet and into animals receiving a high potassium diet. Since potassium loading in rats is known to inhibit proximal tubular sodium and fluid reabsorption and thereby could lead to nonspecific flow-related stimulation of potassium secretion by the distal tubule, continuous microperfusion techniques at constant flow rate were used to measure the rate of potassium secretion. Additionally, plasma aldosterone levels were measured and renal clearance experiments carried out. The results show that potassium secretion, restricted to cells of the late distal tubule, reaches a maximal rate at a plasma potassium concentration of about 6 meq/liter. Potassium adaptation significantly enhances potassium secretion compared with animals on a control diet over a range of plasma potassium from 3.8 to 7.4 meq/liter. Enhanced potassium secretion by the distal tubule, in both control and potassium-adapted animals, is associated with increased aldosterone levels.

Aldosterone↗
PubMed1982

Neuropsychological dysfunction following elective cardiac operation. I. Early assessment.

Two neuropsychological tests were administered to 227 men and women, ages 25 to 69 years, before and after coronary bypass and cardiac valve operations to provide current information regarding the incidence of postoperative decrements in neuropsychological dysfunction and the factors associated with them. Biographical, psychological, and medical-surgical data were studied together with changes in scores on the Trail Making Tests and the Visual Reproduction (VR) Test of the Wechsler Memory Scale (WMS). Postoperative decrements greater than one standard deviation were observed in each of the four scores derived from these testings for 11% to 17% of the patients. Yet 70% of all patients remained within one standard deviation of original performance on all four scores. Among the preoperative correlates of significantly reduced test performance were age greater than 60 years, end-diastolic pressure greater than 30 mm Hg, moderate to severely enlarged heart size on preoperative x-ray film, and use of propranolol or chlordiazepoxide hydrochloride. Significant perioperative correlates included measure of duration of operation (such as total time of operation greater than 7 hours, time on the pump greater than 2 hours, and aortic cross-clamp time greater than 2 hours), total estimate of blood loss greater than 2,000 ml, hypotension, difficult intubation, and insertion of an intra-aortic balloon. Postoperative factors significantly associated with declines in test scores included electrolyte (Na+, K+, Cl-) abnormalities, longer stay in the intensive care unit, bizarre behavior or disorientation, and depression score. These findings suggest that those patients with more precarious heart function, a more protracted operation, and/or increased metabolic disturbances are especially prone to neuropsychological dysfunction following cardiac operations.

Adult↗
PubMed1982

Neuropsychological dysfunction following elective cardiac operation. II. A six-month reassessment.

Three neuropsychological tests were administered to 245 men and women, ages 25 to 69 years, before and 6 months after coronary bypass and cardiac valve operations to provide current information regarding the incidence of long-term postoperative decrements in neuropsychological function and the factors associated with them. Biographical, psychological and medical-surgical data were studied together with changes on the Trail Making Test from the Halstead-Reitan Battery, and Visual Reproduction (VR) and Logical Memory tests, both from the Wechsler Memory Scale (WMS). Although 28% of this group showed a deterioration in one or more test scores at a 9 day postoperative examination as compared to their preoperative scores, over 80% of these patients had returned to normal range by 6 months. Similarly, the majority of the 19% of patients showing a significant decrease in one or more of four scores at 6 months had incurred their performance decrements subsequent to the 9 day examination. Hence it seems inappropriate to attribute these latter dysfunctions to the surgical epidose per se, as others have reported. Only 5% of patients showed consistent postoperative test score deterioration both at 9 days and 6 months. Decrements of function at 6 months appear to be associated with total estimated blood loss greater than 3,000 ml and administration of propranolol during the operation plus several postoperative factors including higher levels of fatigue, depression, and worries related to the operation and the recovery process. These findings underscore the need for clinicians and investigators studying neuropsychological dysfunction following cardiac operations to take concurrent emotional and physical states into account, and to make repeated measures well separated in time, before interpreting the presence or absence of residual neuropsychological problems.

Coronary Artery Bypass↗
PubMed1981

Structural and functional study of the rat distal nephron: effects of potassium adaptation and depletion.

To examine the relationship between tubular transport of potassium and cell structure in segments of the superficial distal nephron, we performed potassium transport and quantitative electron microscopic studies in rats after potassium adaptation and potassium depletion. In distal nephrons continuously microperfused in vivo, potassium adaptation stimulated potassium secretion by 200%. Microperfused distal convoluted tubules (earliest portion of accessible distal nephron) did not, however, secrete potassium in potassium adapted animals. Morphometric analysis of the distal convoluted tubule also revealed no detectable effect of potassium diet on the structure of the distal cell type. In contrast, examination of the connecting tubule and the initial collecting tubule of the distal nephron demonstrated a striking increase in basolateral membrane in potassium-adapted animals. This change was limited to the connecting tubule cell and the principal cell type. No structural change of the intercalated cell type in either segment was associated with altered potassium transport. We conclude that cells of the distal convoluted tubule do not secrete potassium. Functional and morphologic evidence suggests that potassium is secreted by the connecting tubule cell and the principal cell of the connecting tubule and the initial collecting tubule, respectively.

Animals↗
PubMed1975

Data for peer review: acquisition and use. Results in the experimental medical care review organization program.

Nine Experimental Medical Care Review Organizations (EMCROs) review the process and outcome of medical care, using insurance billing claims or medical record abstracts as the data source. The cost of EMCRO insurance billing claims processing in 1972, including peer review, ranged from $0.47 to $2.50 per claim. Three EMCROs reviewed the necessity for elective hospital admission prospectively for $2.50, $8.50, and $10.02 per case. The EMCROs developed innovative methods for abstracting hospital, nursing home, and ambulatory medical records at a cost of $0.40 to $4.00 per abstract. These EMCRO cost estimates were not derived from uniform accounting methods. Problems of accuracy and comparability of data for peer review are discussed. The EMCRO experience may aid local implementation of Professional Standards Review Organizations (PSROs).

Abstracting and Indexing↗
PubMedDate not supplied

Quantifying and predicting recovery after heart surgery.

The validity of the biopsychosocial approach to the study of health and illness is reaffirmed by the prospective findings of the Recovery Study. This is a multidisciplinary examination, conducted in four teaching hospitals, of the predictors of symptoms of cardiac illness in 463 patients 6 months after coronary artery bypass or cardiac valve surgery. We found that the following preoperative measures predict freedom from cardiac symptoms 6 months after surgery: low levels of all of the following: angina pain, shortness of breath, fatigue and sleep problems, lifetime cigarette usage, and preoperative hospitalization for cardiac treatment; low levels of anxiety, depression, and hostility, and few life change events; high levels of all of the following: self-esteem, well-being, vigor; prevalence of activities and hobbies, social participation, and social support. The six variables in bold print contributed independently in a multiple regression equation that accounted for 21% of the variance of the symptoms score and was associated with an estimated 45% difference in success of recovery. The statistical strength and general nature of many of the predictors indicate that the predictors may also be important in recovery from other health crises. Psychosocial and biomedical factors correlate across time (predictively), as well as cross-sectionally, indicating that psychological, social, and biological mechanisms may be parts of a single general multifaceted process influencing recovery of health. A clinical trial could determine if psychological, social, or behavioral interventions will hasten and improve recovery from physical illness or trauma.

Activities of Daily Living↗
PubMedDate not supplied

Employment changes among patients following coronary bypass surgery: social, medical, and psychological correlates.

The relations of socioeconomic and psychological factors to resumption of employment following coronary artery bypass surgery were studied using a questionnaire returned by a sample of 426 men and 70 women. The sample was drawn from the membership of Mended Hearts, Inc., a nationwide voluntary organization of persons who have had heart surgery. Preoperatively, more men (92 percent) than women (59 percent) were employed. Return to work rates were high for men (81 percent) and much lower for women (58 percent). The 395 men tended to return to work an average of 3.7 months after surgery whereas the 41 women took an average of 4.8 months. Return to work following surgery was most clearly related to socioeconomic level for both sexes. In addition, for men, those most likely to return had less postoperative morbidity and held jobs requiring little physical exertion. Patients who reported that they were forced into an early retirement represent a particularly vulnerable group in that they were more likely to experience the most postoperative morbidity. As a group, they believed that their physicians had least prepared them to return to work, and they experienced the poorest emotional adjustment. Thus, women and those forced into early retirement represent two potentially high-risk groups of patients who would seem to require additional clinical and psychological management following surgery.

Adult↗