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Biomedical subjects

N Sanchez

Publications and source records attributed to N Sanchez.

At least 19 recordsLinked to original sources
PubMed2001

Silent infarction as a risk factor for overt stroke in children with sickle cell anemia: a report from the Cooperative Study of Sickle Cell Disease.

OBJECTIVE: To determine whether children with homozygous sickle cell anemia (SCD) who have silent infarcts on magnetic resonance imaging (MRI) of the brain are at increased risk for overt stroke. METHODS: We selected patients with homozygous SCD who (1) enrolled in the Cooperative Study of Sickle Cell Disease (CSSCD) before age 6 months, (2) had at least 1 study-mandated brain MRI at age 6 years or older, and (3) had no overt stroke before a first MRI. MRI results and clinical and laboratory parameters were tested as predictors of stroke. RESULTS: Among 248 eligible patients, mean age at first MRI was 8.3 +/- 1.9 years, and mean follow-up after baseline MRI was 5.2 +/- 2.2 years. Five (8.1%) of 62 patients with silent infarct had strokes compared with 1 (0.5%) of 186 patients without prior silent infarct; incidence per 100 patient-years of follow-up was increased 14-fold (1.45 per 100 patient-years vs 0.11 per 100 patient-years, P =.006). Of several clinical and laboratory parameters examined, silent infarct was the strongest independent predictor of stroke (hazard ratio = 7.2, P =.027). CONCLUSIONS: Silent infarct identified at age 6 years or older is associated with increased stroke risk.

Anemia, Sickle Cell↗
PubMed2000

Detection of epileptogenic focal cortical dysplasia by depth, not subdural electrodes.

Centers that perform presurgical epilepsy evaluations disagree on whether depth or subdural electrodes represent the optimal technique for invasive recording, especially in seizures originating outside the temporal lobe. A 13-year-old girl with a normal magnetic resonance imaging scan had unlocalized partial onset seizures, despite scalp and subdural grid ictal video/EEG recordings. Repeat video/EEG with depth electrodes showed a discrete site of continuous interictal spiking and seizure onset that was located 2-2.5 cm beneath the surface of the sensory cortex. The resected region showed focal cortical dysplasia and the patient had greater than 95% seizure frequency reduction at 3-year follow-up. We conclude that although subdural electrodes have many advantages when recording seizures outside the temporal lobes, depth electrodes may provide superior recordings when the epileptogenic region is beneath the cortical surface.

Cerebral Cortex↗
PubMed1997

Gaucher disease: enzyme therapy in the acute neuronopathic variant.

The responses to regular intravenous enzyme infusions were compared in two sibs with Gaucher disease type 2, the acute neuronopathic variant. Enzyme administration was begun at 7 months in patient 1 who had severe progressive visceral and neuronopathic disease. No significant effect of enzyme infusions was noted. Death occurred at 9 months. Patient 2 was prenatally diagnosed and enzyme infusions were initiated at age 4 days. Overall development progressed at a rate similar to her unaffected full sib until her death at 15.1 months. Slowly progressive esotropia, ocular paresis and dysphagia began at 8 months as did infiltrative pulmonary disease. Comparison of these clinical courses show significant visceral and neurologic effects of anticipatory enzyme therapy, but with unaltered outcome, for Gaucher disease type 2.

Gaucher Disease↗
PubMed1997

Evaluation of two competing methods for calculating Charlson's comorbidity index when analyzing short-term mortality using administrative data.

The performance and predictive power of the Deyo-Charlson and the Romano-Charlson comorbidity indices were compared when short-term mortality after hospitalization was the outcome of interest. These indices are commonly used to adjust for the effect of comorbidities when using administrative data in comparative studies. In hospital Medicare clam data for patients admitted to one of six medical categories (back pain, stroke, pneumonia, hip replacement, transurethral radical prostatectomy, or lysis of peritoneal adhesion), were selected for analyses. Logistic regression models were employed to evaluate the relative importance and the explanatory power of these indices for predicting mortality 30, 90, and 180 days after admission. The contribution of each index to mortality was assessed via the likelihood ratio chi-square statistic (G2), and the area under the receiver operator characteristic (ROC) curve was used to assess predictive power. Indices were evaluated using weights suggested by Charlson et al. and using empirically derived weights. Both indices improved the base model equally, although the predictive power of both indices was poor with values of the C statistic ranging from 0.60 to 0.78. Our results suggest limited applicability of these approaches when examining short-term mortality. A slight increase in predictive power was observed when indices were calculated using empirical weights derived from our data.

Chi-Square Distribution↗
PubMed1997

The effects of perceived stigma and psychological over-control on the behavioural problems of children with epilepsy.

This pilot study finds that parents who think that their child will be stigmatized and who perceive that epilepsy limits their child, report higher levels of four child behavioural problems than reported by other parents of children with epilepsy. Those children with epilepsy who report that their parents use an over-controlling psychological approach to parenting report higher levels of four behavioural problems than those children with epilepsy who do not report over-controlling behaviour from their parents. The effects of simple partial seizures and of seizure severity on children's behavioural problems are completely mediated by perceived stigma, perceived limitations, and perceived parenting. Seizure frequency, absence seizures, and treatment with ethosuximide have direct effects on three children's behavioural problems; the effects of these medical variables are generally unaffected by control for parent's and children's perceptions.

Adolescent↗
PubMed1997

The effect of accommodative hysteresis on apparent stationarity.

The potential contribution of accommodation to the ability to perceive whether an object is moving in space during lateral movement of the head was examined in 16 visually-normal young adults. The target, which provided a highly effective accommodation stimulus, was viewed monocularly in an otherwise completely darkened room. Self-generated head movements of controlled amplitude and frequency were used to produce lateral target motion of continuously variable amplitude either in-phase or counter-phase to the lateral translation of the head. Tonic accommodation and the target/head displacement ratio needed for apparent target stationarity were measured before and after sustained focus at either the nearpoint or farpoint. Tonic accommodation shifted inward under the nearpoint condition and outward under the farpoint condition. The tonic aftereffects induced under the nearpoint and farpoint conditions were accompanied by increases and decreases, respectively, in the degree of positive (same direction as the head) concomitant motion required for apparent target stationarity. These results suggest that the altered accommodative effort required to compensate for the tonic aftereffects influenced the magnitude of the absolute visual parallax ascribed to self-motion. The accommodative system therefore appears to contribute to position constancy, at least in a relatively impoverished visual environment.

Accommodation, Ocular↗
PubMed1996

The relationship of episiotomy to third and fourth degree lacerations.

Third and fourth degree lacerations can produce significant long term morbidity to women undergoing childbirth. The incidence of third and fourth degree lacerations is variable depending on the institution and the obstetrical provider. While episiotomy remains a valuable intervention in selected cases, an improvement program directed at lowering the use of episiotomy can reduce the incidence of this clinical event. Hospitals and physicians with higher rates of third and fourth degree tears should examine the use of episiotomy, and midline episiotomy in particular, which is associated with an increased incidence of third and fourth degree tears.

Adolescent↗
PubMed1996

The cooperative cardiovascular project an AFMC special report.

Patients who suffer myocardial infarction can have improved outcomes if the following elements are part of their treatment plans: 1. Rapid diagnosis of the condition. 2. Use of thrombolytics or angioplasty early in the presentation, if appropriate. 3. Use of aspirin early in the course of care. 4. Discharge medications of aspirin and beta blockade, in appropriately selected patients. 5. Documentation of efforts to counsel the patient to quit smoking. The above material outlines the key indicators in the national project to improve care for heart attack victims. Hospitals should assess the diagnosis, immediate care, and long-term management of patients with this condition. Patients have a variety of comorbidities and do not always fit into a simplified therapeutic scheme. Nevertheless, the care of myocardial infarction victims in the pilot CCP states demonstrated that a sizable number of these patients could benefit from a more focused approach to the above therapeutic interventions.

Adrenergic beta-Antagonists↗
PubMed1994

Gallbladder surgery for Medicare patients in Mississippi.

Mississippi Foundation for Medical Care (MFMC) conducted a review of gallbladder surgery performed on Mississippi Medicare Patients using hospital claims files and limited record review for verification of claims file data. Significant error rates in the surgeon identification number were found in the claims files. It should also be noted that the current ICD-9-CM coding system does not allow for identification of laparoscopic cholecystectomies converted to open procedures. Past studies have attempted to use claims data alone for these types of analyses. These findings demonstrate the importance of using caution by those attempting to use claims data (without verification) to define patterns of hospital utilization, clinical outcomes and/or physician profiling. Claims data must be tested for validity for reliable pattern analysis. In addition, considerable variation was found among providers in elements such as conversion rates, complication and readmission rates. A few surgeons showed patterns for critical variables that were quite different from the universe. There was however, no statistically significant differences associated between volume of cases performed and outcomes. Time frame comparisons over several years show significant (> 80%) increase in gallbladder surgery since the introduction of the laparoscopic procedure.

Cholecystectomy↗
PubMed1993

Chromatic aberration and ocular focus: Fincham revisited.

Longitudinal chromatic aberration of the eye (LCA) produces "color fringes" at edges that specify focus. Fincham [(1951) British Journal of Ophthalmology, 35, 381-393] concluded that these chromatic effects were important for accommodation, but most investigators disagree. We monitored accommodation in 25 subjects while they viewed a sinusoidally moving target (1.5-2.5 D at 0.2 Hz) in a Badal optometer. The target was monochromatic (590 nm with 10 nm bandwidth), or white (3000 K) with LCA normal, neutralized or reversed. Sensitivity to the effects of LCA is profound and widespread. Gain decreases substantially and phase-lag increases when LCA is eliminated, and reversing the aberration severely disrupts accommodation. The ordered arrangement of spectral foci produced by LCA seems to be a fundamental aspect of the stimulus for "reflex" accommodation.

Accommodation, Ocular↗