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Biomedical subjects

M Schluchter

Publications and source records attributed to M Schluchter.

At least 19 recordsLinked to original sources
PubMed2001

Relation of measures of sleep-disordered breathing to neuropsychological functioning.

Sleep-disordered breathing (SDB) has been associated with neuropsychological (NP) deficits. The extent to which such effects are attributable to unmeasured confounders or selection biases, or are manifest across a range of SDB is unclear. The relationship of SDB with a broad range of NP functions was examined in 100 volunteers with a spectrum of SDB and without underlying comorbidity. Factor analysis suggested that the NP tests could be summarized as four constructs: declarative memory, signal discrimination, working memory, and set shifting. These factors plus vigilance were dependent variables. Independent variables were age, the respiratory disturbance index (RDI), a sleepiness score, the arousal index, and sleep-associated hypoxemia. Factors "declarative memory" (measuring 25% of the common variance, alpha = 0.95), "signal discrimination" (10% variance, alpha = 0.70), and "working memory" (9% variance, alpha = 0.52) were each significantly, linearly predicted by hypoxemia and/or the RDI, with no evidence for significant threshold effects. SDB measures accounted for 4-6% of the variance in NP constructs. In contrast, sleepiness best predicted vigilance. Thus, adverse exposures (hypoxemia or RDI) during sleep may negatively influence NP functions in a dose-response relationship, and, other than vigilance, these effects may not be directly attributable to sleepiness.

Attention↗
PubMed2000

Neurodevelopment and predictors of outcomes of children with birth weights of less than 1000 g: 1992-1995.

OBJECTIVE: To examine the neurosensory and cognitive status of extremely low-birth-weight (ELBW; < 1,000 g) children born from January 1, 1992, through December 31, 1995, and to identify the significant predictors of outcome. DESIGN: An inception cohort of ELBW infants admitted to the neonatal intensive care unit (NICU) and observed to 20 months' corrected age. SETTING: A tertiary level urban NICU and follow-up clinic at a university hospital. POPULATION: Of 333 ELBW infants without major congenital malformations admitted to the NICU, 241 (72%) survived to 20 months' corrected age. We studied 221 children (92%) at a mean of 20 months' corrected age. The mean birth weight was 813 g; mean gestational age, 26.4 weeks. MAIN OUTCOME MEASURES: Assessments of cognitive and neurosensory development. RESULTS: Major neurosensory abnormality was present in 54 children (24%), including 33 (15%) with cerebral palsy, 20 (9%) with deafness, and 2 (1%) with blindness. The mean (+/- SD) Bayley-Mental Developmental Index (MDI) score was 74.7 +/- 17. Ninety-two children (42%) had a subnormal MDI score (<70). Neurodevelopmental impairment (neurosensory abnormality and/or MDI score <70) was present in 105 children (48%). Multiple stepwise logistic regression analysis that considered sex, social risk, birth weight, and neonatal risk factors revealed significant predictors of a subnormal MDI score to be male sex (odds ratio [OR], 2.73; 95% confidence interval [CI], 1.52-4.92), social risk (OR, 1.48; 95% CI, 1.09-2.00), and chronic lung disease (OR, 2.18; 95% CI, 1.20-3.94). Predictors of neurologic abnormality were a severely abnormal finding on cerebral ultrasound (OR, 8.09; 95% CI, 3.69-17.71) and chronic lung disease (OR, 2.46; 95% CI, 1.12-5.40); predictors of deafness were male sex (OR, 2.79; 95% CI, 1.02-7.62), sepsis (OR, 3.15; 95% CI, 1.05-9.48), and jaundice (maximal bilirubin level, >171 micromol/L [>10 mg/dL]) (OR, 4.80; 95% CI, 1.46-15.73). CONCLUSION: There is an urgent need for research into the etiology and prevention of neonatal morbidity.

Brain Damage, Chronic↗
PubMed2000

Imaging evaluation of suspected appendicitis in a pediatric population: effectiveness of sonography versus CT.

OBJECTIVE: The purpose of this study was to compare the diagnostic accuracy of graded compression sonography with that of helical CT for the diagnosis of appendicitis in a pediatric and young adult population. SUBJECTS AND METHODS: Between June 1996 and April 1999, 386 pediatric and young adult patients with suspected appendicitis were examined using sonography, CT, or both: 233 underwent sonography only, 71 underwent CT only, and 82 underwent sonography and CT. All sonograms and CT scans were prospectively interpreted as showing positive or negative findings for appendicitis by one of six pediatric radiologists. CT and sonographic findings were correlated with surgical and histopathologic findings or findings at clinical follow-up. RESULTS: Helical CT had a significantly higher sensitivity (95% versus 78%, p = 0.009) and accuracy (94% versus 89%, p = 0.05) than graded compression sonography for the diagnosis of appendicitis in children, adolescents, and young adults. The specificity of both techniques was 93%. Twenty of 82 patients who underwent both sonography and CT had discordance between the findings of the two examinations. The CT results were correct in a significantly greater number of patients with discordant examinations (17/20 patients [85%]). CONCLUSION: Helical CT has a significantly higher sensitivity and accuracy than graded compression sonography for the diagnosis of appendicitis in a pediatric and young adult population, particularly in children more than 10 years old.

Adolescent↗
PubMed1999

Cytomegalovirus infection and HIV-1 disease progression in infants born to HIV-1-infected women. Pediatric Pulmonary and Cardiovascular Complications of Vertically Transmitted HIV Infection Study Group.

BACKGROUND AND METHODS: Cytomegalovirus (CMV) has been implicated as a cofactor in the progression of human immunodeficiency virus type 1 (HIV-1) disease. We assessed 440 infants (75 of whom were HIV-1-infected and 365 of whom were not) who had known CMV status and were born to HIV-1-infected women and who were followed prospectively. HIV-1 disease progression was defined as the presence of class C symptoms (according to the criteria of the Centers for Disease Control and Prevention [CDC]) or CD4 counts of less than 750 cells per cubic millimeter by 1 year of age and less than 500 cells per cubic millimeter by 18 months of age. RESULTS: At birth the frequency of CMV infection was similar in the HIV-1-infected and HIV-1-uninfected infants (4.3 percent and 4.5 percent, respectively), but the HIV-1-infected infants had a higher rate of CMV infection at six months of age (39.9 percent vs. 15.3 percent, P=0.001) and continued to have a higher rate of CMV infection through four years of age (P=0.04). By 18 months of age, the infants with both infections had higher rates of HIV-1 disease progression (70.0 percent vs. 30.4 percent, P=0.001), CDC class C symptoms or death (52.5 percent vs. 21.7 percent, P=0.008), and impaired brain growth or progressive motor deficits (35.6 percent vs. 8.7 percent, P=0.005) than infants infected only with HIV-1. In a Cox regression analysis, CMV infection was associated with an increased risk of HIV-1 disease progression (relative risk, 2.59; 95 percent confidence interval, 1.13 to 5.95). Among children infected with HIV-1 alone, but not among those infected with both viruses, children with rapid progression of HIV-1 disease had higher mean levels of HIV-1 RNA than those with slower or no progression of disease. CONCLUSIONS: HIV-1-infected infants who acquire CMV infection in the first 18 months of life have a significantly higher rate of disease progression and central nervous system disease than those infected with HIV-1 alone.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Risk factors for sleep-disordered breathing in children. Associations with obesity, race, and respiratory problems.

This study examined risk factors for sleep-disordered breathing (SDB) in children and adolescents; specifically, quantifying risk associated with obesity, race, and upper and lower respiratory problems. Subjects were participants in a genetic-epidemiologic study of SDB and included 399 children and adolescents 2 to 18 yr of age, recruited as members of families with a member (a proband) with known sleep apnea (31 index families) or as members of neighborhood control families (30 families). SDB was assessed with home overnight multichannel monitoring and SDB was defined based on an apneahypopnea index >/= 10 (moderately affected) or < 5 (unaffected). SDB of moderate level was significantly associated with obesity (odds ratio, 4.59; 95% confidence interval [CI], 1.58 to 13.33) and African-American race (odds ratio, 3.49; 95% CI, 1.56 to 8.32) but not with sex or age. After adjusting for obesity, proband sampling, race and familial clustering, sinus problems and persistent wheeze each independently (of the other) predicted SDB. These data suggest the importance of upper and lower respiratory problems and obesity as risk factors for SDB in children and adolescents. Increased risk in African Americans appears to be independent of the effects of obesity or respiratory problems.

Adolescent↗
PubMed1998

Maternal and perinatal factors related to maternal-infant transmission of HIV-1 in the P2C2 HIV study: the role of EBV shedding. Pediatric Pulmonary and Cardiovascular Complications of Vertically Transmitted HIV-1 Infection (P2C2 HIV) Study Group.

The association of maternal and perinatal factors with mother-infant transmission of HIV-1 was examined in a prospective multicenter cohort of singleton live births to 508 HIV-1-infected women with children of known HIV-1 infection status (91 [18%] HIV-1-infected, 417 [82%] uninfected). From multivariate logistic regression, independent predictors of HIV-1 transmission included maternal CD4 percentage (CD4%) (odds ratio [OR] per 10% increase in CD4% = 0.70; p = .003), ruptured membranes <24 hours (OR = 3.15; p = .02), and maternal bleeding (OR = 2.90; p = .03), whereas maternal zidovudine (ZDV) use was marginally associated (OR = 0.60; p = .08). The associations of maternal urinary cytomegalovirus (CMV) shedding, oropharyngeal Epstein-Barr virus (EBV) shedding, and serology profiles during pregnancy with HIV-1 transmission were examined in the subset of mothers in whom the CMV and EBV measurements were available. Maternal EBV seropositivity, CMV shedding, and CMV seropositivity were 100% (279 of 279), 7% (16 of 229), and 92% (270 of 274), respectively. These rates did not differ between transmitting and nontransmitting mothers. In univariate analyses, maternal EBV shedding was higher among transmitting than nontransmitting mothers (40 of 49 [82%] compared with 154 of 226 [68%]; p = .06) and was independently associated with transmission in multivariate logistic analyses adjusting for CD4%, ruptured membranes, and ZDV use, with an OR of 2.45 (95% confidence interval (CI), 1.03-5.84; p = .04). This permits the conclusion that EBV shedding is associated with maternal-infant HIV-1 transmission, independent of CD4%.

Anti-HIV Agents↗
PubMed1998

HIV vertical transmission rate determinations are subject to differing definitions and therefore different rates. The Pediatric Pulmonary and Cardiovascular Complications of Vertically Transmitted HIV Infection Study Group.

The HIV infection status of a cohort of 600 prospectively followed children born to HIV infected mothers was determined using HIV peripheral blood culture tests at 0, 3, and 6 months of age, HIV serology at > or = 15 months, and CDC AIDS criteria. We estimated transmission rates using five methods which differed in how HIV indeterminates are handled. These methods were applied at two points in time to illustrate effects of length of follow-up of the cohort on results. In January 1997, 30 months after the last birth, transmission rate estimates ranged from 15.5% (known positives/known positives x known negatives) to 18.1% (known positives x those with one positive culture x deaths/entire cohort minus those lacking negative cultures at age > or = 5 months). Estimates ranged from 14.8% to 20.7% using the subcohort of 284 children followed > or = 12 months as of May 1993. These results indicate that methods for assigning HIV infection status and for handling HIV indeterminates should be carefully defined when estimating transmission rates.

Adult↗
PubMed1997

Chest radiographic data acquisition and quality assurance in multicenter studies.

BACKGROUND: Multicenter studies rely on data derived from different institutions. Forms can be designed to standardize the reporting process allowing reliable comparison of data. OBJECTIVE: The purpose of the report is to provide a standardized method, developed as a part of a multicenter study of vertically transmitted HIV, for assessing chest radiographic results. MATERIALS AND METHODS: Eight hundred and five infants and children were studied at five centers; 3057 chest radiographs were scored. Data were entered using a forced-choice, graded response for 12 findings. Quality assurance measures and inter-rater agreement statistics are reported. RESULTS: The form used for reporting chest radiographic results is presented. Inter-rater agreement was moderate to high for most findings, with the best correlation reported for the presence of bronchovascular markings and/or reticular densities addressed as a composite question (kappa = 0.71). The presence of nodular densities (kappa = 0.56) and parenchymal consolidation (kappa = 0.57) had moderate agreement. Agreement for lung volume was low. CONCLUSION: The current tool, developed for use in the pediatric population, is applicable to any study involving the assessment of pediatric chest radiographs for a large population, whether at one or many centers.

Child↗
PubMed1993

Sensitivity and specificity of the tilt table test in young patients with unexplained syncope.

UNLABELLED: The usefulness of the head-up tilt testing (HUT) has been previously addressed in diagnosing vasovagal neuroregulatory syncope in the teenage population. However, data concerning sensitivity and specificity is deficient due to the lack of control groups. We compared the response to HUT in young patients referred because of syncope or near syncope (n = 44, mean age 16 +/- 3 years SD) to healthy young volunteers with a normal physical examination and no previous history of syncope (n = 18, mean age 16 +/- 2 years) and to determine the sensitivity and specificity of HUT. The graded tilt protocol was performed at 15 degrees, 30 degrees, and 45 degrees (each for 2 min), and then 60 degrees for 20 minutes. Cuff blood pressure was measured every minute and lead II ECG was continuously monitored. RESULTS: 25 of the 44 patients (57%) developed a vasovagal response or became symptomatic after 13.8 +/- 5.7 minutes of HUT. Three of the 18 volunteers (17%) had a vasovagal response and became symptomatic after 9 +/- 3 minutes of HUT. There was no statistical difference among the four groups (with and without tilt induced vasovagal response) in terms of age and baseline hemodynamic data. The sensitivity of 20 minutes HUT was 57% and its specificity was 83%. The presyncopal hemodynamic response in patients with history of syncope that was characterized by a significant decrease in systolic blood pressure and lack of increase of diastolic blood pressure as compared with baseline and with other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Radiology image interpretation system: modified observer performance study of an image interpretation expert system.

Application of computer-based expert systems to diagnostic medical problems has been described in many areas including clinical diagnosis and radiology. Expert systems are computer programs that contain encoded expert knowledge to provide expert advice. A modified observer-performance study was done comparing the efficacy of the Radiology Image Interpretation System (RIIS), an expert system that diagnoses focal bone abnormalities, and radiology residents on a known set of 44 abnormal and 10 normal cases. Modified receiver operating characteristic curves for four inexperienced residents, five experienced residents, and RIIS were generated using the set of known radiographs. The true-positive rates of RIIS and the residents at false-positive rates of 0.05, 0.15, and 0.20 were estimated using the modified receiver operating characteristics curve and were compared using a paired t test. On the average, the RIIS system was less accurate when compared with experienced and inexperienced residents but the difference was only significant for experienced residents at a false-positive rate of 0.05. RIIS performed better than inexperienced residents when RIIS was used by experienced residents but this difference was not significant.

Bone Diseases↗
PubMed1990

Remodelling of left ventricular after banding of ascending aorta in the rat.

STUDY OBJECTIVE: The aim was to study sequential changes of cardiac performance and structure after banding of ascending aorta. DESIGN: Cardiac performance and structure were examined at days 1 and 3, and weeks 1, 2, and 4 postoperatively (aortic banding or sham). Cardiac function indices were measured before and during volume overload. Passive pressure-volume relationship and cardiac morphology were examined at the end of the experiment. EXPERIMENTAL MATERIAL: 30 aortic banded and 33 age matched, sham operated rats were used for the studies. The animals were anaesthetised, then instrumented for haemodynamic measurements. MEASUREMENTS AND RESULTS: The left ventricular weight and calculated left ventricular wall thickness of banded rats increased significantly as early as one day postoperation, compared with the age matched shams. This increase persisted throughout the follow up period, except at day 3, when the increase in left ventricular weight did not reach statistical significance. Left ventricular wall mass/cavitary volume ratio increased significantly in banded rats at all follow up periods except at day 3. Cardiac index of banded rats at rest was not different from that of shams but showed a transient significant reduction at 3 d postoperative. However, maximum cardiac index produced by acute volume overload was not different between the two groups throughout the follow up period. Simultaneous end diastolic pressure was significantly higher in banded rats on the first postoperative day but not in later follow up. The passive pressure-volume curve at 1 d postoperative revealed that left ventricular volumes were significantly smaller in banded rats than in shams, whereas chamber stiffness constant and volume elasticity (chamber stiffness constant normalised for left ventricular volume) were not different between the two groups throughout the follow up period. CONCLUSIONS: Taken together, these findings suggest that structural change of the left ventricle may play a role in maintaining left ventricular function by shifting the pressure-volume curve leftward in the early period of aortic banding.

Animals↗
PubMed1983

Clinical trial of an emergency resuscitation algorithm.

Clinical trials of a resuscitation algorithm for patients entering the Surgical Emergency Department (ED) with acute hypotension were conducted for a 30-month period. The intent was not to compare good management with bad, but rather university-run county hospital services with and without an algorithm. The study group was comprised of 603 hypotensive patients out of 6833 consecutive admissions. The effects of the policy of using a resuscitation algorithm were evaluated by the outcomes of the patients who were treated by residents given the algorithm (protocol group) versus those treated by residents not given the algorithm (control group). The efficacy of the algorithm, per se, was evaluated by outcomes of patients whose management was in satisfactory compliance with the algorithm as compared with those whose management deviated from the algorithm. The patients were also evaluated by the primary cause of their hypotension and the presence of severe associated illnesses. Outcomes of patients treated by residents given the algorithm were as good and in a number of respects better than those of patients treated by residents without the algorithm. The mean resuscitation time of the protocol group was markedly and significantly less than that of the control group indicating that the policy of using the algorithm facilitated resuscitation even though it was not always properly followed. Patients with trauma, hemorrhage, and sepsis, whose care was in satisfactory compliance with the algorithm had shorter resuscitation times, lower MAP-time deficits, and less shock-related complications. The algorithm which is primarily directed toward fluid resuscitation did not appear to be efficacious for patients whose trauma was primarily head injury, where fluid restriction may be the therapy of choice.

Adolescent↗
PubMed1981

Comparison of the relative effectiveness of colloids and crystalloids in emergency resuscitation.

Over a 2.5 year period, the fluid management of 600 hypotensive patients entering our surgical emergency department was evaluated during a prospective clinical trial of a resuscitation algorithm. The major clinical determinants (low mean arterial pressure, age, severity of illness, primary illness or injury, amount of blood loss, volume of fluids given, use of a protocol or clinical algorithm and satisfactory compliance with the algorithm) were controlled by grouping the patients into specific strata; the resuscitation times were almost always shorter with a regimen of about one-fourth colloids than with crystalloids only. This is consistent with the observations of greater increases in hemodynamic and oxygen transport variables after albumin than after lactated Ringer's solution when the latter was given in either 2 or 4 times the volume.

Adult↗
PubMed1980

Selenium concentrations and glutathione peroxidase activities in a population exposed to selenium via drinking water.

Selenium concentrations in blood, urine, hair, and tap water were determined in samples obtained from individuals exposed to varying amounts of the element in water form home wells. Glutathione peroxidase activities were also determined on the blood samples. Correlations of blood Se with the enzyme activity were not statistically significant. Correlations of water Se, urine Se, and hair Se with glutathione peroxidase activity were also not statistically significant. It is concluded that a relationship between Se and glutathione peroxidase activity does not exist when Se status is adequate.

Glutathione Peroxidase↗
PubMed1979

An assay system for factors involved in mammalian DNA replication.

An assay for cellular factors stimulating DNA synthesis by partially lysed CHO cells is presented. The assay is based on the observation that in highly lysed cells, DNA synthesis, as determined by [3H]dTTP incorporation, was only 2-5% of that in gently lysed cells, and that this low level of DNA synthesis could be increased by a factor of approx. 50 by the addition of CHO cell extract (i.e. supernatant of a cell homogenate subjected to high-speed centrifugation). Highly lysed cells were obtained by treatment with 0.1% Brij-58 and 240 mM KCl, while for the preparation of gently lysed cells, 0.01% Brij-58 and 80 mM KCl were used. Incorporation of [3H]dTTP reflected DNA synthesis qualitatively similar to that in intact cells. It was semiconservative, and no repair synthesis was detected unless cells were irradiated with ultraviolet light prior to parital lysis. DNA molecules of 4 S were synthesized and converted to DNA of more than 25 S via 6-12-S intermediates. DNA synthesis was restricted to nuclei from cells in S phase, and cell extract did not induce DNA synthesis in nuclei from cells in G1 phase. Stimulation of DNA synthesis by cell extract was concentration-dependent. Cell extract activity was recovered to more than 50% after (NH4)2SO4 precipitation. Heat-inactivation experiments suggested that cell extract contained at least tow factors timulating DNA replication. This system may, therefore, be used for the purification and characterization of factors participating in DNA replication of mammalian cells.

Animals↗
PubMedDate not supplied

Placental lesions associated with abnormal growth in twins.

Abnormal growth in one or both twins may contribute to the increased morbidity and mortality observed in twin gestation. Our objective in this retrospective study of all twin pregnancies delivered at our hospital (n = 240) over a 2-year period was to study the relationship between placental lesions and abnormal growth. Standardized placental examinations were performed in 192 cases (80%), which constituted the study population. Two growth abnormalities were studied: discordant growth as defined by > 15% difference in birth weight and small-for-gestational-age (SGA) birth as defined by birth weight less-than the 10th percentile for gestational age. The majority of twin pregnancies with either discordant growth (41/57 cases) or SGA birth (26/35 cases) had dichorionic placentas. In monochorionic placentas studied by injection there was no significant relationship between vascular anastomoses and discordant growth. Placental weight for small discordant and SGA twins was equivalent or increased relative to infant weight, a pattern not suggestive of maternal vascular underperfusion. Eight lesions, five considered to represent chronic placental disease and three considered to represent intrauterine adaptation, were studied as possible predictors of abnormal growth. The overall prevalence of these lesions in twin placentas was less than that seen in singleton births. Concordance between twin placentas for most lesions was higher than would be expected, based on their prevalence in singleton placentas. Two lesions were associated with discordant growth in both univariate and multivariate analyses: peripheral cord insertion (OR 3.6, 95% CI 1.7-7.6) and avascular villi (AV; OR 3.2, 95% CI 1.0-10.3). Three placental lesions were associated with SGA infants at the univariate level: peripheral cord insertion, avascular villi, and maternal vascular underperfusion. Only peripheral cord insertion (OR 9.8, 95% CI 4.1-23.4) and AV (OR 3.7, CI 1.0-13.7) were significant in the multivariate analysis. The relative increase in peripheral cord insertion and AV with abnormal growth was observed for both monochorionic and dichorionic placentas. Subgroups of discordant infants with and without SGA were both associated with peripheral cord insertion while only those with SGA had an increase in AV. Both peripheral cord insertion and AV were increased in the subgroup with SGA but no discordancy. In summary, two placental lesions, peripheral cord insertion indicating a spatially limited intrauterine compartment and AV indicating occlusion of fetal vessels in the placenta, were associated with abnormal growth in twins.

Adult↗