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J Ross

Publications and source records attributed to J Ross.

At least 379 records · Page 21Linked to original sources
PubMed1991

Validity and generalizability of global ratings in an objective structured clinical examination.

The performance of foreign medical graduates on multistation standardized patient-based tests and used to determine the validity and generalizability of global ratings of their clinical competence made by expert examiners. Data were derived from the entrance examinations of the 1989 and 1990 applicants to the Ontario Pre-Internship Program and the exit examination of 24 participants from the 1989 cohort. For each candidate, the examiners completed a detailed checklist and two five-point global ratings dealing with the candidate's approach to the patients' problem and attitude toward the patient. Generalizability coefficients for both ratings were satisfactory and stable across cohorts. Construct validity of the global ratings was demonstrated by comparing entry and exit ratings and by evidence of significant and positive correlations between the global ratings and total test scores. Tentative evidence of criterion validity of the global ratings was demonstrated. These findings suggest that global ratings by expert examiners can be used as an effective form of assessment in multistation standardized patient examinations.

Attitude of Health Personnel↗
PubMed1990

Subgroups of patients with atypical circadian patterns of symptom onset in acute myocardial infarction.

Circadian variation of onset of acute myocardial infarction has been noted in many studies and may carry important implications. However, only a few previous studies have attempted subgroup analysis. In 4,796 patients with documented acute myocardial infarction, the time of symptom onset was recorded. As in other studies, a peak occurred in the morning hours from 6 A.M. to noon with 28% of the population (1.16 times the average percent for the other time periods) experiencing symptom onset in that period (p less than 0.001). There was a second lower peak (25%) in the evening hours between 6:01 P.M. and midnight, also observed in some previous studies. Whether the presence of subgroups with specific clinical characteristics would exhibit different patterns and thereby contribute to these peaks in the overall population was then determined. In patients with a history of congestive heart failure (n = 606) or with non-Q-wave infarction (n = 832), a pronounced peak (29%) occurred only in the evening hours. In patients greater than 70 years of age (n = 1,422), smokers (n = 2,057), diabetics (n = 767), women (n = 1,213) and patients taking beta blocking drugs (n = 847), 2 nearly equal peaks were observed. Finally, in patients with previous myocardial infarction (n = 1,104), no peaks were observed. In a subgroup of patients (n = 1,084) free from the most important modifying factors, there was a single very pronounced late morning peak (32%), 1.39 times the average percent for the other time periods (p less than 0.001), without evidence of a second evening peak.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1990

Formation and persistence of novel benzo(a)pyrene adducts in rat lung, liver, and peripheral blood lymphocyte DNA.

Male CD rats were injected with single i.p. doses of benzo(a)pyrene (B(a)P), and peripheral blood lymphocytes (PBLs), livers, and lungs were removed at various times after administration. DNA adducts were analyzed in each tissue by 32P postlabeling with nuclease P1 enhancement. Sister chromatid exchange frequencies were concomitantly measured in cultured whole blood. B(a)P-DNA adducts were observed in all three tissues from animals sacrificed between 1 and 56 days after injection. Maximal adduction levels occurred at about 4 days after administration, followed by a gradual loss of adducts over the period examined. The apparent half-lives of total DNA adducts were 15 days in liver, 17 days in PBLs, and 22 days in lung. Induced sister chromatid exchanges were linearly related to the amount of DNA adducts remaining in the PBLs at the time of harvest up to 56 days and were significantly elevated above concurrent controls up to 14 days. One of the major adducts found in each tissue was N2-(10 beta-[7 beta,8 alpha,9 alpha-trihydroxy-7,8,9,10-tetrahydrobenzo(a) pyrene]yl)deoxyguanosine. An additional novel major adduct was found in the liver DNA and is derived from the further metabolism of B(a)P-trans-7,8-dihydrodiol. A second major novel B(a)P adduct was found in the DNA of lung tissues and accounts for about 40% of the total adducts present. Experimental evidence suggests that this adduct is derived from a metabolic pathway that includes the formation of 9-hydroxy-B(a)P.

Adenosine Triphosphate↗
PubMed1990

[Coronary arteriography after acute myocardial infarction].

On the basis of a population of 1,848 patients with acute myocardial infarction (AMI), prognostic stratification has been developed for detection of patients with high risks of death and repeated AMI in the first year after admission for coronary arteriography (KA). Patients with ischaemia at rest during hospitalization (17% of the patients, 18% one-year mortality), with previous AMI and cardiac failure during hospitalization (8%, 25% mortality), with positive exercise ECG (6%, 11% mortality) and patients with left ventricular ejection fraction (LVEF) between 0.22 and 0.44 (12%, 12% mortality) are recommended for coronary arteriography. Patients over the age of 75 years (31% mortality), patients with very low LVEF (less than 0.20) (33% mortality), patients with negative exercise ECG (3% mortality) and patients with normal LVEF (greater than 0.45) (5% mortality) are not recommended for investigation by coronary arteriography. These guidelines for coronary arteriography after AMI, based on recommendations from abroad should be considered in Denmark in relation to the capacity for carrying out this examination.

Aged↗
PubMed1990

Effect of depressed left ventricular function on hemodynamics of normal St. Jude Medical prosthesis in the aortic valve position.

To evaluate the effect of left ventricular (LV) dysfunction on Doppler-derived transprosthetic hemodynamic indexes in patients with normally functioning St. Jude aortic valve prostheses, 74 consecutive patients were studied. LV ejection fraction was assessed by using Simpson's biplane rule. The 34 patients with normal ejection fraction (greater than or equal to 0.51) (group A) generally had the highest values of peak (31 +/- 13 mm Hg) and mean (16 +/- 6 mm Hg) gradients, whereas 19 patients with moderate to severe reduction of ejection fraction (less than or equal to 0.31) (group C) had the lowest values (17 +/- 6 and 9 +/- 3 mm Hg, respectively) (p less than 0.05). Significant decreases (p less than 0.05) for acceleration and corrected (for heart rate) velocity time integral in group C were noted compared to group A, and group B (21 patients with mild to moderately reduced ejection fraction [0.50 to 0.32]). A significant inverse correlation for Doppler-derived peak and mean gradients and corrected velocity time integral was demonstrated with increasing aortic valve prosthetic sizes from 19 to 29 mm in group A patients (r = -0.41 to -0.71) but less so in group B or C. Thus, in addition to valve size, LV function should be considered an important factor in detecting prosthetic valvular flow characteristics and dysfunction. A normal derived velocity and gradient in patients with moderately to severely depressed LV function may not rule out significant valvular stenosis.

Aortic Valve↗
PubMed1990

Influence of heart rate on mortality after acute myocardial infarction.

Elevated heart rate (HR) during hospitalization and after discharge has been predictive of death in patients with acute myocardial infarction (AMI), but whether this association is primarily due to associated cardiac failure is unknown. The major purpose of this study was to characterize in 1,807 patients with AMI admitted into a multicenter study the relation of HR to in-hospital, after discharge and total mortality from day 2 to 1 year in patients with and without heart failure. HR was examined on admission at maximum level in the coronary care unit, and at hospital discharge. Both in-hospital and postdischarge mortality increased with increasing admission HR, and total mortality (day 2 to 1 year) was 15% for patients with an admission HR between 50 and 60 beats/min, 41% for HR greater than 90 beats/min and 48% for HR greater than or equal to 110 beats/min. Mortality from hospital discharge to 1 year was similarly related to maximal HR in the coronary care unit and to HR at discharge. In patients with severe heart failure (grade 3 or 4 pulmonary congestion on chest x-ray, or shock), cumulative mortality was high regardless of the level of admission HR (range 61 to 68%). However, in patients with pulmonary venous congestion of grade 2, cumulative mortality for patients with admission HR greater than or equal to 90 beats/min was over twice as high as that in patients with admission HR less than 90 beats/min (39 vs 18%, respectively); the same trend was evident in patients with absent to mild heart failure (mortality 18 vs 10%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1990

Changes in mean concentration, phase shifts, and dissipation in a forced oscillatory reaction.

Experiments are presented that confirm earlier predictions that the mode of supply of reactants to a nonlinear (bio)chemical reaction determines or controls concentrations at steady states far from equilibrium. The oxidation of nicotinamide adenine dinucleotide (NADH) catalyzed by the enzyme horseradish peroxidase with continuous input of oxygen was studied; NAD+ is continuously recycled to NADH through a glucose-6-phosphate dehydrogenase system. A comparison of steady-state concentrations is made with an oscillatory oxygen input and a constant input at the same average oxygen input for both modes. By varying the frequency and amplitude of the perturbation (O2 influx), the following may be changed: the average concentration of NADH; the Gibbs free energy difference delta G of the reactants and products at steady state; the average rate of the reaction; the phase relation between the oscillatory rate and delta G; and the dissipation. These results confirm the possibility of an "alternating current chemistry," of control and optimization of thermodynamic efficiency and dissipation by means of external variation of constraints in classes of nonlinear reactions and biological pumps, and of improvements of the yield in such reactions (heterogeneous catalysis, for example).

Adenosine Triphosphate↗
PubMed1990

Alpha-adrenergic regulation of myocardial performance in the exercising dog: evidence for both presynaptic alpha 1- and alpha 2-adrenoceptors.

New evidence supporting both presynaptic alpha 1- and alpha 2-adrenoceptors playing a role in the regulation of myocardial contractile performance in the exercising dog is reviewed. Studies utilized chronically instrumented dogs having sonomicrometers for the measurement of regional wall thickening and transducers for the measurement of left ventricular and systemic hemodynamics. During steady state exercise, either the selective alpha 1-adrenoceptor blocker prazosin (80 micrograms/kg) or the selective alpha 2-adrenoceptor blocker idazoxan (80 micrograms/kg) was infused into the left atrium while exercise continued. Immediately following the administration of either alpha-adrenoceptor blocking agent, there were substantial increases in heart rate, left ventricular dP/dt and regional contractile function as assessed using sonomicrometers, and norepinephrine release by the myocardium increased substantially. beta-adrenergic blockade prevented the heart rate and contractile effects of either alpha 1- or alpha 2-adrenoceptor blocker whereas norepinephrine release was further enhanced. These effects could not be attributed to baroreceptor unloading. In dogs studied under resting conditions with norepinephrine infusion to produce an increase in dP/dt similar to that observed during treadmill exercise, no sympathetic augmentation was observed following either alpha-blocker. Together, these studies provide evidence that both alpha 1- and alpha 2-adrenoceptors participate in the modulation of sympathetic neuronal norepinephrine release in the canine myocardium.

Adrenergic alpha-Antagonists↗
PubMed1990

Mechanisms of benefit in the ischemic myocardium due to heart rate reduction.

The studies reviewed here examine the role of heart rate reduction in the beneficial effect observed following beta-adrenoceptor blockade during exercise-induced ischemia in conscious dogs. To further study the effects of heart rate reduction on regional blood flow in an ischemic bed without collateral circulation, anesthetized swine with controlled coronary perfusion were also studied. Measurements of regional myocardial blood flow (microspheres) and contractile function (sonomicrometers) during steady state exercise in dogs with chronic coronary artery stenosis indicated the existence of severe regional contractile dysfunction and subendocardial ischemia. The administration of beta-adrenoceptor blockade (1.0 mg/kg atenolol) improved regional contractile function when heart rate was reduced from 220 to 165 beats/min. Atrial pacing during exercise to prevent the bradycardia following beta-adrenoceptor blockade eliminated the improved regional function and blood flow. Thus, the beneficial effect of beta-blockade was only apparent when exercise heart rate was reduced. In anesthetized swine with constant inflow coronary perfusion, two levels of coronary hypoperfusion were examined at heart rates of 91 beats/min or 55 beats/min. Bradycardia was produced using the bradycardic agent UL-FS 49 (0.3 mg/kg). Regional contractile function and subendocardial blood flow were markedly improved at the lower heart rate for either level of reduced coronary perfusion, indicating a redistribution of blood flow towards the subendocardium. The improvement in contractile function was larger than predicted on the basis of the improvement in blood flow per min to the subendocardium. Independent relationships between regional contractile function and the subendocardial blood flow per min were observed for each heart rate. Thus, the studies in conscious exercising dogs indicated that heart rate reduction is an essential mechanism for the improvement of ischemic regional myocardial contractile function during exercise by beta-blockade. This is likely the result of the marked improvement in subendocardial blood flow per beat which accompanies the reduced heart rate; regional myocardial blood flow per beat appears to be a predictor of regional contractile function during ischemia both at rest and during exercise.

Animals↗
PubMed1990

Alpha 2-adrenergic coronary constriction in ischemic myocardium during exercise.

The effect of either selective alpha 1- or alpha 2-adrenoceptor blockade on ischemic myocardial blood flow and function was examined in beta-blocked dogs trained to run on a motor-driven treadmill. The animals were instrumented with sonomicrometers for the assessment of regional systolic wall thickening (%WTh) of the left ventricle. For drug infusion, an intracoronary catheter was implanted in the circumflex coronary artery and a hydraulic cuff was placed proximally around the artery. Following systemic beta-blockade with 0.8 mg/kg propranolol, an acute stenosis of the circumflex coronary artery inflated during exercise induced severe dysfunction in the posterior wall. Intracoronary infusion of 80 micrograms/kg of the selective alpha 2-adrenoceptor blocking agent idazoxan improved posterior wall (PW)-%WTh from 5.1 +/- 1.6 to 10.8 +/- 2.8% (p less than 0.06) and regional myocardial blood flow (radiolabelled microspheres) in the subendocardium of the posterior wall from 0.17 +/- 0.05 to 0.45 +/- 0.30 (ml/min)/g (p less than 0.05). No increases in regional blood flow and regional myocardial function were observed after infusion of the selective alpha 1-adrenoceptor blocking agent prazosin (20 micrograms/kg) under the same experimental conditions. It is concluded that during severe ischemia, significant postjunctional alpha 2-adrenoceptor mediated coronary vasoconstriction exists. Regional alpha 2-adrenoceptor blockade, but not alpha 1-adrenoceptor blockade is effective in reducing regional ischemia and dysfunction by attenuating sympathetic vasoconstriction in the conscious dog.

Adrenergic alpha-Antagonists↗
PubMed1990

Predicting 1-year outcome following acute myocardial infarction: physicians versus computers.

Whether decision rules derived statistically from patient data can produce better decisions than an expert clinician or a model of the expert clinician (expert system) is controversial. We examined this issue in the context of predicting cardiac death by 1 year for patients discharged from the hospital following acute myocardial infarction. Decision rules were derived from a base sample of 781 patients. These decision rules and three experienced cardiologists then estimated probability of death by 1 year for each patient in a separate test sample (n = 400). In our evaluation of the performance of the decision rules and physicians, we detected no differences, although the decision rules and physicians tended to classify the patients somewhat differently. Further multivariate analyses on the physicians' predictions showed that two of the physicians paid attention to somewhat different variables than the third physician. Lack of agreement among expert cardiologists would complicate modeling of a consensual decision-making process within the framework of an expert system.

Aged↗
PubMed1990

Nepal: integrating traditional and modern health services in the remote area of Bashkharka.

Within a framework of Primary Health Care (PHC) and Health Promotion (HP), the focus of this paper is on integrating traditional and modern health care in the remote area of Bashkharka, Nepal. The relevance to integrated health care of factors such as geography, ethnicity, religion, national infrastructure and international development agencies are discussed. Issues concerning the relationship between the theory and practice of PHC and HP are raised.

Health Policy↗
PubMed1990

Ethics in cardiovascular medicine. Task Force IV: Scientific responsibility and integrity in medical research.

Ethical standards are a set of affirmative responsibilities to which the investigator must subscribe; behavior that is incompatible with these responsibilities should be presumed unethical, whether or not it is explicitly proscribed. This Task Force sought to present these standards as principles or guidelines. In undertaking research an investigator must accept that publicly funded or supported research is intended to yield public benefit; personal gain should be only incidental to and not at the expense of the public benefit. The responsibilities of the investigator are summarized as follows: Design of Research To develop a research design that effectively and efficiently addresses the scientific question while minimizing the likelihood of incorrect or misleading results. To protect the rights and welfare of human subjects, assure the humane use of laboratory animals and protect the safety of laboratory workers and the environment. Conduct of Research To ensure that accepted laboratory and research practices are followed and that all data are accurately collected and properly recorded; the investigator must participate in the review of original data. To carry out research in accordance with that approved by the institutional review board and ensure that fully informed consent is obtained, that the welfare of human subjects is protected and that animal welfare and laboratory safety procedures are carried out. To provide effective ongoing supervision of research trainees and technicians. In multidisciplinary collaborative research, to have at least an overview familiarity with the work outside his or her areas of expertise. In fixed protocol, multicenter collaborative research the investigator must be satisfied with the adequacy of the collaborative activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomedical Research↗
PubMed1990

Prehospital data entry compliance by paramedics after institution of a comprehensive EMS data collection tool.

OBJECTIVE: To determine the completeness of data entry by paramedics after an extensive modification of the prehospital first-care form in an urban emergency medical services (EMS) system. DESIGN: Comprehensive medical information was added to the EMS data collection tool used by a metropolitan fire department. We evaluated the frequency of failure to enter data pertaining to medical assessment and/or treatment of victims of cardiac arrest after implementation of the system. RESULTS: Failure to enter data in the first month was compared with two subsequent two-month blocks. A high rate of noncompliance existed in the first month (all medical data were missing in 24.6%). However, the subsequent two months revealed a marked decline in noncompliance (4.4%, P less than .001). This decline was maintained after a three-month interim (5.0%, P less than .001). CONCLUSION: Data entry noncompliance can be a significant problem after implementation of a new prehospital data collection system. However, compliance can be markedly improved over a relatively short period. Because EMS system evaluation is based on data collected in the field. EMS researchers and administrators must be aware of the data entry compliance rate in their system when attempting to make conclusions from such information.

Adolescent↗
PubMed1990

Geriatric injury: an analysis of prehospital demographics, mechanisms, and patterns.

STUDY OBJECTIVE: To evaluate emergency medical services (EMS) system use, injury mechanisms, and prehospital assessments among elderly victims of trauma. DESIGN: We analyzed all prehospital data for injuries among patients 70 years old or older for whom 911 EMS dispatch was requested in a medium-sized metropolitan area during a 12-month period. RESULTS: A total of 1,154 cases occurred (women, 65.1%), which represented 30.3% of all 911 dispatches involving elderly patients. Injury mechanisms were fall (60.7%), motor vehicle accident (MVA; 21.5%), fight (2.4%), accidental poisoning (2.3%), and choking (2.1%). Persons in their 90s had a lower frequency of MVAs (3.4%) than did younger patients (23.0%) (P less than .005). The most frequent injuries determined by prehospital assessment were head or face (25.1%), upper extremity (17.2%), hip (14.5%), lower extremity (13.8%), back (9.8%), and chest or abdomen (5.0%). The frequency of serious neurologic injuries was less for falls or MVAs than for other mechanisms (P less than .005). Suspected hip (P less than .001) and pelvic (P less than .005) injuries occurred more frequently during falls than during other mechanisms of injury, whereas back injuries occurred most frequently in MVAs (P less than .001). Seventy-one fall victims (10.1%) had suspected medical causes of their fall. Twelve patients (1.0%) were in cardiac arrest. CONCLUSION: We report injury patterns and mechanisms among elderly victims of trauma presenting to an EMS system. A knowledge of these patterns will be useful to emergency physicians and EMS administrators.

Accidents↗