Biomedical subjects

MA Topinka

Publications and source records attributed to MA Topinka.

4 recordsLinked to original sources

PubMed2000

Imaging coherent electron flow from a quantum point contact

Scanning a charged tip above the two-dimensional electron gas inside a gallium arsenide/aluminum gallium arsenide nanostructure allows the coherent electron flow from the lowest quantized modes of a quantum point contact at liquid helium temperatures to be imaged. As the width of the quantum point contact is increased, its electrical conductance increases in quantized steps of 2 e(2)/h, where e is the electron charge and h is Planck's constant. The angular dependence of the electron flow on each step agrees with theory, and fringes separated by half the electron wavelength are observed. Placing the tip so that it interrupts the flow from particular modes of the quantum point contact causes a reduction in the conductance of those particular conduction channels below 2 e(2)/h without affecting other channels.

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PubMed2000

The accuracy of the emergency physician at diagnosing CVA/TIA in the acute care setting

OBJECTIVE: To determine the accuracy of the ED physician at diagnosing CVA/TIA in the acute setting. METHODS: We reviewed 246 patients admitted for acute CVA/TIA during 1997. We reviewed admitting and discharge diagnoses, CT, MRI, and MRA results. We also reviewed the medical histories of the patients. Patients with tumors and ICH diagnosed on the initial CT scan were excluded. RESULTS: A total of 241 patients were included for analysis. Of the patients admitted for CVA, 67% were discharged with the same diagnosis. Of the patients admitted for TIA, 82% were discharged with the same diagnosis. 10% of TIAs diagnosed at admission received the diagnoses at discharge. 22% of CVAs at admission were diagnosed as TIAs. 11% of CVA/TIAs at admission were given other diagnoses at discharge. Some of these diagnoses included hemiplegic migraines, Bell's palsy, lumbosacral spondylosis, giant cell arteritis, basilar artery aneurysm, and viral meningitis. In considering thrombolysis for CVA, one may then overtreat approximately 30% of patients and miss approximately 10% of patients who could be candidates for treatment. The NNT for CVA and thrombolysis is approximately 10. If 30% overtreatment rate is accurate, then the NNH is approximately 333 assuming an ICH rate of 1%. For 1,000 patients treated, 100 may benefit (improved function) and 3 would die who did not have the disease. CONCLUSIONS: The accuracy rate of the diagnosis of CVA at initial presentation is 67%. This is due to many initial neurologic changes being TIAs and some other diagnoses which can mask as CVA. Choosing thrombolysis for CVA treatment will involve treatment of many patients who do not have disease.

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PubMed2000

Blood cultures in pyelonephritis: Do results change therapy?

OBJECTIVE: To determine how often blood culture results are instrumental in directing the therapy of patients with pyelonephritis. METHODS: Retrospective chart review of all patients admitted to Doctors Hospital with a diagnosis of pyelonephritis to ascertain whether the results of blood cultures were instrumental in the management of those patients. For study purposes, results of blood cultures were considered instrumental if the treatment regimen or diagnostic procedures were changed because of those results. RESULTS: 212 patients were admitted during the study period with a diagnosis of pyelonephritis. Of these, 105 (49.5%) had blood cultures ordered as part of their workup. Adult patients had at least 2 blood cultures ordered and some had as many as 4 or 6 sets ordered during hospitalization. Most pediatric patients had only a single blood culture ordered for diagnosis. Of the 105 patients, 88 (83.5%) had no growth on any of the tubes drawn. 17 patients had positive growth in at least one tube; however, 6 out of these 17 patients were judged by the treating physician to have contaminated cultures that were not diagnostically useful. Of the 105 patients, only 11 (10.4%) were considered to have positive culture results by their treating physician. The organism identified by blood culture was compared to that present in the patient's urine culture, and in only 2 patients did the results differ and were found to have a secondary site of infection. Only in these 2 cases were the antibiotic regimens changed because of the blood culture results. No patient without a second site of infection had a change in therapy based on the blood culture results. CONCLUSIONS: In patients admitted for pyelonephritis, blood cultures may not be needed.

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PubMed2000

The incidence of positive cultures in women suspected of having PID/Salpingitis

OBJECTIVES: To determine the incidence of GC and chlamydia in women with suspected acute pelvic inflammatory disease. A secondary objective was to investigate the clinical usefulness of physical exam findings of vaginal discharge, cervical motion, and adnexal tenderness. METHODS: This was a retrospective chart review of patients seen in the ED. Patients were entered into the study if they had PID/salpingitis as their discharge diagnosis and cultures performed for GC and chlamydia. RESULTS: A total of 133 charts were reviewed. 13 patients were excluded due to incomplete charting of history and physical exam or inability to obtain culture results. Of the remaining 120 patients, 70 cultures were negative for any growth. 10 cultures were positive for GC and 10 cultures were positive for chlamydia. In reviewing the physical exam findings in women with negative cultures, 74% had discharge, 93% had cmt, and 66% had adnexal tenderness. For women with cultures positive for GC and chlamydia, 90% had discharge, 80% had cmt, and 75% had adnexal tenderness. For vaginal discharge the sens, spec, ppv, npv were 0.90, 0.26, 0.35, 0.90. For cmt the sens, spec, ppv, npv were 0.80, 0.07, 0.20, 0.55. For adnexal tenderness the sens, spec, ppv, npv were 0. 75, 0.34, 0.25, 0.83. No combination of the three physical exam findings increased the ppv. CONCLUSIONS: The incidence of positive cultures in women suspected of having PID/salpingitis is 16%. The physical exam findings were not predictive of disease secondary to the high number of false positives. Although 16% positives may warrant empiric treatment, patients should not be told they have PID/salpingitis until the cultures are available.

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