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Biomedical subjects

A Hillis

Publications and source records attributed to A Hillis.

At least 19 recordsLinked to original sources
PubMed2001

Diffusion- and perfusion-weighted brain magnetic resonance imaging in patients with neurologic complications after cardiac surgery.

BACKGROUND: Neurologic complications after cardiac surgery include stroke, encephalopathy, and persistent cognitive impairments. More precise neuroimaging of patients with these complications may lead to a better understanding of the etiology and treatment of these disorders. OBJECTIVE: To study the pattern of ischemic changes on diffusion- and perfusion-weighted magnetic resonance imaging (DWI, and MRPI, respectively) in patients with neurologic complications after cardiac surgery. METHODS: All records were reviewed of our patients undergoing cardiac surgery in the previous year who also underwent postoperative DWI or MRPI. Neurologic symptoms, vascular studies, and the pattern of ischemic changes were recorded. Acute ischemic lesions were classified as having a territorial, watershed, or lacunar pattern of infarction. Patients with multiple territorial infarcts in differing vascular distributions that were not explained by occlusive vascular lesions were classified as having multiple emboli. RESULTS: Fourteen patients underwent DWI and 4 underwent MRPI. Acute infarcts were found in 10 of 14 patients by DWI as compared with 5 of 12 patients by computed tomography. Eight patients presented with encephalopathy (associated with focal neurologic deficits in 4), 4 with focal deficits alone, and 2 with either fluctuating symptoms or transient ischemic attacks. Among patients with encephalopathy, 7 of 8 had patterns of infarction suggestive of multiple emboli, including 3 of 4 patients with no focal neurologic deficits. Several patients had combined watershed and multiple embolic patterns of ischemia. Findings of MRPI studies were abnormal in 2 of 4 patients, showing diffusion-perfusion mismatch; both patients had either fluctuating deficits or transient ischemic attacks, and their conditions improved with blood pressure manipulation. CONCLUSIONS: In patients with neurologic symptoms after cardiac surgery, DWI is more sensitive to ischemic change than computed tomographic scanning and can demonstrate patterns of infarction that may help us understand etiology. The most common pattern was multiple embolic infarcts. Preliminary experience with MRPI suggests that some patients have persistent diffusion-perfusion mismatch after surgery and may benefit from therapeutic intervention.

Adult↗
PubMed2000

Patient Tan revisited: a case of atypical global aphasia?

Broca's first patient presented in support of a relationship between a lesion of the frontal lobe and aphasia was patient Tan. Although Pierre Marie refers to this case as "indisputably aphasia of Broca," the clinical diagnosis of Tan's aphasia has not been re-examined in light of current clinical criteria. Superficially, the patient's extremely limited verbal output and intact comprehension appear to fit with the diagnosis of Broca's aphasia, but a more thorough examination of the onset, evolution and nature of the patient's speech symptoms suggests alternate interpretations. Contemporary evidence in support of a robust relationship between stereotypical utterances and Global aphasia suggests that patient Tan may have suffered from a Global rather than Broca's aphasia.

Aphasia↗
PubMed1998

Three years of experience with prospective randomized effectiveness studies.

We developed methodology for prospective randomized effectiveness studies using a demonstration project at a multispecialty practice, health maintenance organization, and hospital in academic medical center. An operational unit called the effectiveness registry was developed to design and support comparisons of potential practice improvements with standard care. The studies differ from observational effectiveness studies in that they provide long-term follow-up of randomized comparison groups. Physician involvement in data collection is limited. No tests or observations are made other than those required for clinical care. Follow-up and data collection are modeled after tumor registry procedures. Patients who refuse randomization enter the study in whichever treatment arm they choose. The protocol for each study is approved by the institutional review board (IRB) before recruitment begins, and all patients, randomized and nonrandomized, sign an informed consent document. Between its beginning on October 7, 1993 and April 7, 1997, the IRB approved 14 trials. Four were terminated after entering at most a few patients. Recruitment is complete in four trials and continues in six. Randomization was accepted by 74% (596/804) of the patients. Over 800 patients in 10 studies are being followed at least annually. Major peer-reviewed journals have accepted reports of initial findings for two studies. Prospective randomized effectiveness studies are feasible in the multipractice setting and have potential to provide useful and reliable assessment of treatment outcomes. Collaborative arrangements between several institutions are needed to provide larger sample sizes.

Academic Medical Centers↗
PubMed1997

Forced-air warming is no more effective than conventional methods for raising postoperative core temperature after cardiac surgery.

OBJECTIVE: To determine whether postoperative forced-air warming of cardiac bypass patients in the intensive care unit (ICU) results in faster rate of warming and improved outcomes compared with more conventional ICU warming methods. DESIGN: Prospective randomized effectiveness study. SETTING: Three hundred fifty-bed university-affiliated hospital. PARTICIPANTS: Sixty consenting randomized patients from a consecutive series of 84 patients undergoing routine adult cardiac surgery. INTERVENTIONS: One group of patients received usual patient care, which includes warm blankets and overhead heat lamps. Patients in the other group were placed under forced-air warming devices on arrival in the ICU. Sixty consenting patients (30 in each group) were randomly assigned to one or the other method of warming. The remaining 24 patients refused randomization and self-selected a treatment group. MEASUREMENTS AND MAIN RESULTS: Results are presented for the randomized groups. Core temperature, measured by pulmonary artery catheter thermistor, increased in both groups at the rate of 0.25 degree C per hour. No statistically or clinically significant differences were found between the group for whom the warming device was used and the standard care group in the incidence of postoperative cardiac arrhythmia, duration of time in the ICU, or any other clinical variable. CONCLUSIONS: There is no evidence from this study to warrant use of forced-air warming devices for the care of postoperative cardiac surgical patients in the ICU.

Aged↗
PubMed1994

Computer-aided mammographic screening for spiculated lesions.

PURPOSE: To study the use of a computer vision method as a second reader for the detection of spiculated lesions on screening mammograms. MATERIALS AND METHODS: An algorithmic computer process for the detection of spiculated lesions on digitized screen-film mammograms was applied to 85 four-view clinical cases: 36 cases with cancer proved by means of biopsy and 49 cases with negative findings at examination and follow-up. The computer detections were printed as film with added outlines that indicated the suspected cancers. Four radiologists screened the 85 cases twice, once without and once with the computer reports as ancillary films. RESULTS: The algorithm alone achieved 100% sensitivity, with a specificity of 82%. The computer reports increased the average radiologist sensitivity by 9.7% (P = .005), moving from 80.6% to 90.3%, with no decrease in average specificity. CONCLUSION: The study demonstrated that computer analysis of mammograms can provide a substantial and statistically significant increase in radiologist screening efficacy.

Algorithms↗
PubMed1992

Resident research in obstetrics and gynecology: development of a program with comparison to a national survey of residency programs.

OBJECTIVE: The objective of this report is to describe our recently established resident research program and to compare this program with those of other obstetrics and gynecology residency training programs in the United States. STUDY DESIGN: The components of our program are described. Data for comparison from other programs were obtained from questionnaires, phone follow-up and the Directory of Obstetrics and Gynecology Residency Programs of the Council on Resident Education in Obstetrics and Gynecology. RESULTS: We initiated a residency research program in 1987 with acceptable projects defined, a time for completion of manuscripts established, and a Resident Research Day organized with presentation of articles, critique by a guest speaker, and an awards banquet. Nationally, less than 60% of residency programs have research requirements. Of the 208 programs responding to the written questionnaire 86% of programs associated with a university required research compared with 10% of community-based residency programs. CONCLUSION: While more than a third of residency programs in obstetrics and gynecology do not have resident research programs, the trend is for programs to establish research as a required portion of training. An outline of a recently established program is provided.

Data Collection↗
PubMed1990

Lexical morphology and its role in the writing process: evidence from a case of acquired dysgraphia.

A case of acquired dysgraphia is presented in which the deficit is attributed to an impairment at the level of the Graphemic Output Buffer. It is argued that this patient's performance can be used to identify the representational character of the processing units that are stored in the Orthographic Output Lexicon. In particular, it is argued that the distribution of spelling errors and the types of lexical items which affect error rates indicate that the lexical representations passed from the lexical output system to the Graphemic Output Buffer correspond to the productive morphemes of the language.

Agraphia↗
PubMed1989

Surrogate endpoints in clinical trials: ophthalmologic disorders.

We examined three examples of surrogate observations in ophthalmology. The first represents a simple case: the status of one eye is used as a surrogate for the (unobservable) status of the opposite eye in the same individual. The second and third examples represent possible extrapolation of long term results on the basis of early changes. These examples are used to illustrate the assumptions intrinsic in the use of surrogate variables.

Clinical Trials as Topic↗
PubMed1989

Renal transplantation: cyclosporin A and antibody development after donor-specific transfusion.

The survival of a one haplotype, mismatched living-related renal allograft is improved by donor specific transfusion (DST) before transplantation although the mechanism is unclear. The major risk of DST is sensitization of the recipient to donor lymphocytes precluding transplantation. Fifty prospective recipients of a living related transplant received either DST with cyclosporin A (group I) or DST alone (group II). Persistent donor sensitization precluding transplantation occurred in no patients in group I but in six in group II (P less than 0.05). Ten of 14 of those who developed donor cytotoxicity had previously been pregnant or received greater than or equal to 10 third party transfusions compared with 11 of 36 without such a history (P less than 0.05). Alloantibodies detected by a cellular ELISA developed following DST in 29% patients and antiidiotypic antibodies detected by the short antiidiotypic assay (SAA) in 36%; antiidiotypic activity occurred more frequently in those given cyclosporin A (P less than 0.02). Potentiating activity in the SAA which occurred in sera from six patients after DST had no influence on transplant outcome. Persistent sensitization, particularly in potential transplant recipients who have been pregnant or received many transfusions, can be prevented by giving cyclosporin A with DST; the mechanisms of this effect may be the induction of antiidiotypic antibodies. Both alloantibodies and antiidiotypic antibodies are induced by DST and may protect a subsequent renal allograft from the specific donor.

Antibodies↗
PubMed1987

Locative inferences in medical texts.

Medical research relies on epidemiological studies conducted on a large set of clinical records that have been collected from physicians recording individual patient observations. These clinical records are recorded for the purpose of individual care of the patient with little consideration for their use by a biostatistician interested in studying a disease over a large population. Natural language processing of clinical records for epidemiological studies must deal with temporal, locative, and conceptual issues. This makes text understanding and data extraction of clinical records an excellent area for applied research. While much has been done in making temporal or conceptual inferences in medical texts, parallel work in locative inferences has not been done. This paper examines the locative inferences as well as the integration of temporal, locative, and conceptual issues in the clinical record understanding domain by presenting an application that utilizes two key concepts in its parsing strategy--a knowledge-based parsing strategy and a minimal lexicon.

Artificial Intelligence↗