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Biomedical subjects

R Simon

Publications and source records attributed to R Simon.

At least 325 records · Page 18Linked to original sources
PubMed1989

Young chronic patients and substance abuse.

The prevalence of substance abuse was investigated in 100 young chronic patients consecutively admitted to a long-term private psychiatric hospital. Data were obtained from diagnostic research interviews with each subject at admission. Half of the subjects had concurrent diagnoses of psychiatric disorder and substance abuse. One-third of the dual-diagnosis patients began using substances before the onset of a diagnosable psychiatric disorder, and they more often had a diagnosis of schizophrenia. Half of the dual-diagnosis patients abused three or more drugs. Implications of the findings for treatment and community management of dual-diagnosis patients are discussed.

Adolescent↗
PubMed1989

[Lack of tolerance development with low dose nitrate administration in acute myocardial infarct].

Reports on the development of tolerance have modified the use of nitrates in the treatment of coronary heart disease. Dosage limitations and nitrate-free intervals are frequently recommended to solve this problem (4, 5). In the clinical setting of acute myocardial infarction continuous application of glyceryl trinitrate (GTN) is still a widely used therapy (1). In this study we investigated whether a low-dose intravenous GTN administration leads to a rapid development of tolerance. During the observation period of 60 h, no attenuation of drug effects on the pulmonary pressures could be detected. Subsequent oral medication also showed an undiminished nitrate response.

Aged↗
PubMed1989

[Videometry and videodensitometry: possibilities within the scope of clinical angiocardiography].

Videometry and videodensitometry was developed more than 20 years ago by the groups of E. H. Wood in Rochester, New York, USA and P. H. Heintzen in Kiel, West Germany. These techniques allow the extraction of quantitative parameters such as dimensions and volumes (videometry) and the concentration and distribution of contrast material (videodensitometry) from videoangiograms. Whereas videometric techniques have, in between, been implemented world-wide into clinical practice (e.g., for geometric measurement of heart chamber volume or the quantitative assessment of coronary morphology), videodensitometry has still been restricted to a small number of laboratories, mainly due to the technical requirements. Videodensitometry, however, offers an on-line frame-to-frame analysis of left and right ventricular volumes throughout the cardiac cycle, the measurement of valvular regurgitant fraction, the estimation of intracardiac shunts, as well as the measurement of blood flow and velocity in coronary arteries and the assessment of changes in myocardial perfusion due to interventions form clinical videoangiograms. Since the basic principles of these techniques can easily be applied to digital image processing, videodensitometry has gained new interest in a time of increasing distribution of digital cardiac imaging.

Angiocardiography↗
PubMed1989

Designs for efficient clinical trials.

This article reviews statistical designs for the conduct of efficient Phase II and Phase III clinical trials. Two stage designs for Phase II trials are tabulated which minimize the number of patients entered when the experimental treatment is inactive or not promising. Randomized Phase II trials for selecting the most promising of several experimental regimens are also described. Phase III designs are presented with simple early stopping rules for dropping experimental regimens. Inappropriate sequential analysis of interim data is a likely cause of many spurious claims of treatment effectiveness. General methods for the valid calculation of confidence limits for differences in treatment effectiveness based on sequentially accumulating data are described. Factorial designs for answering "two questions for the price of one" are also discussed.

Clinical Trials as Topic↗
PubMed1989

[Simulated tachyarrhythmia. A case report].

In this case report, the hospitalization of a 34-year-old woman with a history of heart disease is described. Arrhythmias and precordial chest pain led to her admission to the coronary care unit. Different therapeutic trials failed. Finally it became obvious that all tachycardias documented by the arrhythmia monitoring system were artifacts, produced by manipulation at the ECG electrodes. After disclosure and confrontation, a psychic misdevelopment in combination with an abuse of analgetics was found.

Adult↗
PubMed1989

A two-stage design for choosing among several experimental treatments and a control in clinical trials.

In clinical trials where several experimental treatments are of interest, the goal may be viewed as identification of the best of these and comparison of that treatment to a standard control therapy. However, it is undesirable to commit patients to a large-scale comparative trial of a new regimen without evidence that its therapeutic success rate is acceptably high. We propose a two-stage design in which patients are first randomized among the experimental treatments, and the single treatment having the highest observed success rate is identified. If this highest rate falls below a fixed cutoff then the trial is terminated. Otherwise, the "best" new treatment is compared to the control at a second stage. Locally optimal values of the cutoff and the stage-1 and stage-2 sample sizes are derived by minimizing expected total sample size. The design has both high power and high probability of terminating early when no experimental treatment is superior to the control. Numerical results for implementing the design are presented, and comparison to Dunnett's (1984, in Design of Experiments: Ranking and Selection, T. J. Santner and A. C. Tamhane (eds), 47-66; New York: Marcel Dekker) optimal one-stage procedure is made.

Biometry↗
PubMed1988

The Non-Hodgkin Lymphoma Pathologic Classification Project. Long-term follow-up of 1153 patients with non-Hodgkin lymphomas.

STUDY OBJECTIVE: To document the long-term prognosis of patients with non-Hodgkin lymphoma treated between 1971 and 1975 and to determine how the prognosis varies by histologic subtype and stage. SETTING: Three cancer referral centers in the United States and one center in Italy. PATIENTS: A consecutive sample of 1153 previously untreated patients with non-Hodgkin lymphoma. At the time of analysis, 71% of the patients had died and the median follow-up for patients still alive was 11.2 years. MEASUREMENTS AND MAIN RESULTS: The 10-year survival proportions were 45% (CI, 40% to 50%); 26% (CI, 22% to 30%); and 23% (CI, 18% to 30%) for patients with low-, intermediate-, and high-grade lymphomas, respectively. Patients with intermediate- and high-grade lymphomas were curable, but this was not apparent for patients with advanced stage low-grade lymphomas. For the low-grade follicular small cleaved and follicular mixed lymphomas, the Ann Arbor staging system distinguished the prognosis of patients with stage I disease from those with more extensive involvement. For the diffuse large cell and immunoblastic lymphomas, the Ann Arbor staging system distinguished long-term prognosis for patients with stage I disease from patients with stage II disease and those with more disseminated involvement. CONCLUSIONS: The probability of long-term survival for unselected patients with non-Hodgkin lymphoma can be substantial. Long-term prognosis depends on the histologic subtype of the tumor and the extent of dissemination. The Working Formulation for non-Hodgkin lymphomas is a simple and useful nomenclature for selecting treatment and reporting results. The Ann Arbor staging system is a useful but imperfect prognostic indicator.

Bone Marrow↗
PubMed1988

Type IV collagen immunoreactivity in colorectal cancer. Prognostic value of basement membrane deposition.

Using antibodies to type IV collagen, basement membrane (BM) deposition at the tumor-stromal border was studied in 163 cases of colorectal carcinomas. Immunoreactivity was scored semiquantitatively as moderate/extensive versus limited BM deposition and correlated with Dukes' stages and survival data. Cases with limited BM deposition showed an overall significant shorter survival and were overrepresented in Dukes' Stages C/D. Stratification of the cases, for limited versus moderate/extensive BM deposition and Dukes' Stages A/B and C/D, showed that in Dukes' Stages C/D, cases with moderate/extensive BM deposition reached a plateau phase in the survival curve after 2 years. Cases with limited BM deposition showed a continuous downward course on the survival curve. The results suggest that immunostaining of BM in cases in Dukes' C differentiates tumors with relatively high invasive and metastatic capacity from tumors with low invasive and metastatic capacity.

Basement Membrane↗
PubMed1988

Optimal two-stage designs for clinical trials with binary response.

We present a simple two-stage design for a randomized clinical trial with dichotomous outcomes. It is based on a design of Ellenberg and Eisenberger which permits early acceptance of the null hypothesis after the first stage. We have optimized the design by minimizing the average expected sample size subject to constraints on the type 1 and type 2 errors. The resulting designs have maximum sample size only slightly larger than that of single stage trial, with 40-45 per cent of this maximum allocated to the first stage, and null hypothesis probability of early acceptance in excess of 0.60.

Clinical Trials as Topic↗
PubMed1988

Effects of intravenous verapamil on left ventricular systolic function and diastolic filling dynamics in patients with coronary artery disease: analysis of intramyocardial markers.

Left ventricular (LV) intramyocardial markers (MM) were used to study the effects of intravenous verapamil on LV pump function and diastolic filling dynamics. Verapamil (0.1 mg/kg bolus followed by 0.005 mg/kg/min) was administered to 10 patients with severe coronary artery disease 4 years after coronary bypass grafting and implantation of 7 tantalum markers into the LV. MM were filmed at 100 frames/sec (biplane 30 degrees RAO/60 degrees LAO). The digitized biplane MM coordinates were transformed into 3-dimensional coordinates and maximal projection area was defined. LV volumes were calculated frame-by-frame and ejection fraction and peak filling rate derived. Pressure-volume relations were calculated in early-, mid-, and end-diastole. Verapamil caused a slight rise in end-diastolic pressure (12 to 14 mmHg, p less than 0.001) and end-diastolic volume (142 to 152 ml; p less than 0.005) and a fall in max dP/dt (1732 to 1570 mmHg/s; p less than 0.01) reflecting the drug's negative inotropic action. Verapamil reduced LV systolic pressure (136 to 126 mmHg; p less than 0.01), diastolic aortic pressure (74 to 68 mmHg; p less than 0.001) and peripheral resistance (1496 to 1348 dynes.s.cm-5; p less than 0.025); cardiac index was increased (2.7 to 2.9 l/min/m2; p less than 0.05), as were ejection fraction (47 to 49%; p less than 0.02) and stroke volume (67 to 75 ml; p less than 0.001). Great cardiac vein flow increased as well (88 to 102 ml/min; p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Sample size considerations for studies comparing survival curves using historical controls.

Formulas are derived for determination of the number of patients needed in a prospective comparison of survival curves, when the control group patients have already been followed for some period. Although an explicit formula for the required sample size is not available, the computing is straightforward, and tables of examples are presented. Situations are described when one might need to allocate some new patients to the control group, rather than exclusively to the experimental group.

Clinical Trials as Topic↗
PubMed1988

Effects of intracoronary nitroglycerin on coronary vascular volume in man, assessed by a double-indicator dilution technique.

The effects of 0.2 mg nitroglycerin administered directly into the left coronary artery were studied in 7 patients with coronary artery disease. A multipurpose catheter designed for simultaneous measurement of coronary sinus flow and great cardiac vein flow by thermodilution and for addition recording of dye dilution curves by a fiberoptic method was introduced from a right antecubital vein into the coronary sinus and advanced with its tip to the great cardiac vein/anterior cardiac vein juncture. Coronary sinus flow and great cardiac vein flow were measured using the constant infusion technique. Selective bolus injections of indocyanine green dye were measured using the constant infusion technique. Selective bolus injections of indocyanine green dye were performed into the left coronary system via a 8 French Judkins catheter and dye dilution curves were recorded in the upper great cardiac vein. From these curves, coronary transit time was assessed and coronary vascular volume was calculated as great cardiac vein flow times coronary transit time. Intracoronary nitroglycerin led to a transient drop in regional coronary resistance that was associated with an almost parallel increase in intravascular volume. Since this increase in coronary vascular volume exceeded the well-known dilatory effect on the epicardial arteries, and lasted slightly longer than the drop in regional resistance, these data imply that the vasodilatory action of nitroglycerin is different in magnitude as well as in time course in different parts of the coronary circulation.

Blood Volume↗