Biomedical subjects

Sarah J Ratcliffe

Publications and source records attributed to Sarah J Ratcliffe.

11 recordsLinked to original sources

PubMed2006

Aging: impact upon local cerebral oxygenation and blood flow with acute isovolemic hemodilution.

Data from the neurosurgical critical care arena demonstrate a correlation between cerebral oxygenation, survival, and cognitive function. Transfusion may increase and hemodilution decrease cerebral oxygenation. Both acute and chronic anemia have been associated with cognitive dysfunction. Aggressive blood conservation protocols have been instituted across all age groups without conclusive evidence for their impact upon outcome. Aged subjects are at the greatest risk of cognitive sequelae after major surgery associated with significant blood loss. We hypothesize that cerebral physiologic changes associated with "normal" aging may compromise cerebral oxygenation in the presence of severe anemia.Fischer 344 rats, the NIH National Institute of Aging normal aging rat model, underwent a stepwise isovolemic hemodilution protocol. Age groups (Age Grp) studied were as follows: Age Grp-A (3 months), n=14; Age Grp-B (9 to 12 months), n=14; and Age Grp-C (24 months), n=14. Brain oxygen tension (PBrO2), laser Doppler flow, and mean arterial pressure were measured. Final hemoglobin averaged 6.1+/-0.9 g/dL. PBrO2 levels decreased from a baseline of 18.1+/-4.1 to 17.5+/-6.8 mm Hg (P=0.49), and laser Doppler flow increased by 18+/-20% (P<0.0001) after hemodilution. Employing repeated measures multiple regression, Age Grp (P=0.30) was not a significant controlling covariate of PBrO2 in response to isovolemic hemodilution. PBrO2 levels were actually higher in Age Grp-C animals at all time points of the hemodilution protocol, although this was not statistically significant. Aged animals were also fully capable of mounting a robust local cerebral hyperemic response to the anemic challenge that was not separable from the response of younger animals.

Aging↗

PubMed2005

Maternal complications with vaginal birth after cesarean delivery: a multicenter study.

OBJECTIVE: This study was undertaken to determine incidence and risk factors for uterine rupture in women attempting vaginal birth after cesarean delivery (VBAC) in a wide range of hospital settings. STUDY DESIGN: We performed a case-control study nested within a cohort of women who have had a prior cesarean to determine the incidence and risk factors for uterine rupture in women attempting VBAC. RESULTS: The incidence rate of uterine rupture in those who attempt VBAC was 9.8 per 1000. A prior vaginal delivery was associated with a lower risk of uterine rupture (adjusted odds ratio [OR] = 0.40, 95% CI 0.20-0.81). Although prostaglandins alone were not associated with uterine rupture, sequential use of prostaglandin and pitocin was associated with uterine rupture (adjusted OR = 3.07, 95% CI 0.98-9.88). CONCLUSION: Women with a prior cesarean should be offered VBAC, and women with a prior cesarean and prior vaginal delivery should be encouraged to VBAC. Although other studies have suggested that prostaglandins should be avoided, we suggest that inductions requiring sequential agents be avoided.

Adult↗

PubMed2005

An exploratory study of depression among older African American users of an academic outpatient rehabilitation program.

Variation in the presentation of depressive illness among older African Americans may complicate assessment of depression, especially among those with multiple medical comorbidities and functional disabilities. The purpose of this study was to explore the prevalence of depression among older poor African Americans attending an academic outpatient rehabilitation program, using a depression measure with low somatic item content. Correlates of depression in this population also were explored. Health-care records of 150 older African Americans seen over a 2-year period were examined. Depression was assessed on admission using the 30-item Geriatric Depression Scale (GDS). Using a GDS cutoff score for depression of 11 or higher, 30% of the sample (age 75.5 +/- 7.16 years, range 65-95, 75% women) scored positive for depression. Nine percent also reported having suicidal thoughts within the previous week. Consistent with existing literature, depressed patients, as compared to nondepressed patients, were significantly younger, more suicidal, more likely to rate their general health as poor, had higher mean ratings of pain, and more often limited their social activities. Six GDS items were found to have little ability to discriminate between depressed and nondepressed patients: satisfaction with life, getting bored easily, prefer staying at home, find life exciting, getting started on new projects, and full of energy. The authors recommend further testing of the GDS with similar populations of older, poor, medically ill, and functionally disabled older adults.

Academic Medical Centers↗

PubMed2004

Joint modeling of longitudinal and survival data via a common frailty.

We develop a joint model for the analysis of longitudinal and survival data in the presence of data clustering. We use a mixed effects model for the repeated measures that incorporates both subject- and cluster-level random effects, with subjects nested within clusters. A Cox frailty model is used for the survival model in order to accommodate the clustering. We then link the two responses via the common cluster-level random effects, or frailties. This model allows us to simultaneously evaluate the effect of covariates on the two types of responses, while accounting for both the relationship between the responses and data clustering. The model was motivated by a study of end-stage renal disease patients undergoing hemodialysis, where we wished to evaluate the effect of iron treatment on both the patients' hemoglobin levels and survival times, with the patients clustered by enrollment site.

Algorithms↗

PubMed2004

Deviations from the population-averaged versus cluster-specific relationship for clustered binary data.

There has been much debate about the relative merits of mixed effects and population-averaged logistic models. We present a different perspective on this issue by noting that the investigation of the relationship between these models for a given dataset offers a type of sensitivity analysis that may reveal problems with assumptions of the mixed effects and/or population-averaged models for clustered binary response data in general and longitudinal binary outcomes in particular. We present several datasets in which the following violations of assumptions are associated with departures from the expected theoretical relationship between these two models: 1) negative intra-cluster correlations; 2) confounding of the response-covariate relationship by cluster effects; and 3) confounding of autoregressive relationships by the link between baseline outcomes and subject effects. Under each of these conditions, the expected theoretical attenuation of the population-averaged odds ratio relative to the cluster-specific odds ratio does not necessarily occur. In all cases, the naive fitting of a random intercept logistic model appears to lead to bias. In response, the random intercept model is modified to accommodate negative intra-cluster correlations, confounding due to clusters, or baseline correlations with random effects. Comparisons are made with GEE estimation of population-averaged models and conditional likelihood estimation of cluster-specific models. Several examples, including a cross-over trial, a multicentre nonrandomized treatment study, and a longitudinal observational study are used to illustrate these modifications.

Animals↗

PubMed2003

Precision of the CASL-perfusion MRI technique for the measurement of cerebral blood flow in whole brain and vascular territories.

PURPOSE: To analyze the precision of cerebral blood flow (CBF) measurements made with continuous arterial spin labeling(CASL) perfusion magnetic resonance imaging (MRI) over experimentally relevant intervals. MATERIALS AND METHODS: CASL perfusion MRI measurements of CBF on a 1.5-T GE Signa magnet were repeated in young healthy male and female subjects at one hour and one week. Precision of the measurement was evaluated at both time intervals. RESULTS: CASL perfusion MRI measurements of CBF yielded within-subject coefficients of variation (wsCV) of 5.8% for global and 13% for individual vascular regions when measurements were repeated within one hour. Differences in these values represent the error in post-processing. Global and regional CBF measurements over one week yielded wsCVs of 13% and 14%, respectively. At one week, error secondary to physiologic variability affected global and regional measurements to the same degree and masked the software post-processing error seen at one hour. The magnitude of the difference in repeated measures correlated with the magnitude of the measurement. CONCLUSION: CASL perfusion MRI CBF measurements are accurate and precise. Variability over longer periods of time appears attributable to physiologic factors. Repeatability of the CASL measurement is sensitive to the magnitude of the measurement. This should be taken into account when studies requiring repeated measures involve subjects with significant variability in CBF.

Adult↗

PubMed2002

Functional data analysis with application to periodically stimulated foetal heart rate data. I: functional regression.

Functional regression is used to model longitudinal data where the number of measurements on the functional covariate is much greater than the number of subjects in the study. Thus, functional regression can be thought of as singular longitudinal analysis. We have modified existing functional regression techniques to the case of a functional covariate with a repeated stimulus. We applied this modified functional regression to periodically stimulated foetal heart rates. The heart rate tracings were used as a predictor of the child's psychomotor development at approximately 18 months of age. In the past, this type of data has been analysed using the partially subjective concept of habituation. By using the entire heart rate tracings through functional regression, we have the advantage that habituation does not need to be defined and all available information is used to predict later child development.

Adult↗

PubMed2002

Functional data analysis with application to periodically stimulated foetal heart rate data. II: functional logistic regression.

We present a basis solution for the modelling of a binary response with a functional covariate plus any number of scalar covariates. This can be thought of as singular longitudinal data analysis as there are more measurements on the functional covariate than subjects in the study. The maximum likelihood parameter estimates are found using a basis expansion and a modified Fisher scoring algorithm. This technique has been extended to model a functional covariate with a repeated stimulus. We used periodically stimulated foetal heart rate tracings to predict the probability of a high risk birth outcome. It was found that these tracings could predict 94.1 per cent of the high risk pregnancies and without the stimulus, the heart rates were no more predictive than chance.

Adult↗

PubMedDate not supplied

Acceptance of hepatitis B vaccination by pregnant adolescents.

PURPOSE: To determine (1) the rate of prenatal hepatitis B virus (HBV) vaccine acceptance in HBV nonimmune pregnant adolescents, (2) if postulated behavioral and attitudinal factors are associated with HBV vaccine, and (3) the rate of actual receipt of HBV vaccine postpartum in eligible subjects. DESIGN AND METHODS: During 1999-2000, at an inner-city tertiary-care center prenatal clinic, 160 HBV nonimmune adolescents <18 years who were receiving prenatal and delivery care at the center were identified. The research nurse provided an HBV information pamphlet and offered immediate in-hospital postpartum HBV vaccination. Risk factors for nonacceptance of the vaccine were measured with structured questionnaires and medical record review documenting care attendance. Subsequently, all subjects, irrespective of prenatal acceptance of vaccine, were offered vaccine before postpartum discharge, and the rate of actual acceptance was determined. RESULTS: In these predominantly African American (95%) adolescents, the rate of vaccine acceptance was 91%. Actual vaccination rate was 86%, but it was not associated with prior acceptance of vaccination or behavioral or attitudinal factors. CLINICAL IMPLICATIONS: Acceptance of vaccination and actual vaccination were high in this population of high-risk adolescents. The authors found that reoffering vaccine was a successful intervention, even with adolescents who had less-than-optimal attendance at prenatal visits. Given the high rate of acceptance and vaccination in this setting, the authors would encourage public health programs to implement vaccination programs in adolescent prenatal clinics and to offer vaccination postpartum to those who do not receive it prenatally.

Adolescent↗

PubMedDate not supplied

Development of preterm infants: feeding behaviors and brazelton neonatal behavioral assessment scale at 40 and 44 weeks' postconceptional age.

The purpose of this study was twofold: (1) to explore potential changes in the Brazelton Neonatal Behavioral Assessment Scale (BNBAS) from 40 to 44 weeks postconceptional age (PCA) and (2) to determine the relationship between the BNBAS scores and feeding behaviors in preterm infants at 40 and 44 weeks PCA. The BNBAS and sucking behavior measurements were completed on 104 preterm infants at 40 and 44 weeks PCA. The Orientation (p = .001), Motor (p = .001), Range of State (p = .001), Autonomic Regulation (p = .01), and Reflexes (p = .00) clusters were significantly more mature at 44 weeks PCA than at 40 weeks. Infants that were extremely early born (n = 24) had a significantly larger change in BNBAS scores over time as compared to the more mature preterm infants (n = 77), largely catching up with their more mature preterm counterparts. At 40 and 44 weeks PCA, the BNBAS cluster scores for orientation (p = .02), motor (p = .048), range of state (p = .048), and regulation of state (p < .001) were significantly related to the average maximum pressure, adjusted for gestational age and weeks PCA. Significant neurobehavioral maturation takes place between 40 and 44 weeks PCA in preterm infants, with the greatest changes occurring in the most preterm infants. These findings highlight the relationship between neurobehavioral maturation and feeding behaviors.

Child Development↗

PubMedDate not supplied

The cost of prenatal care attendance and pregnancy outcomes in low-income working women.

OBJECTIVE: To examine personal costs (dollar costs and time spent) associated with prenatal care (PNC) attendance and outcomes (gestation length, PNC adequacy, and birth weight) for low-income, working women (N = 165). DESIGN: Prospective, descriptive study. SETTING: Participants were recruited from a pre-natal clinic located at an inner city tertiary care center. PARTICIPANTS: A convenience sample of 165 low-income, working women. MAIN OUTCOME MEASURES: Personal costs were measured as dollar costs and time spent associated with PNC attendance. Perinatal outcomes were measured as gestation length, PNC adequacy, and birth weight. RESULTS: Per visit, the mean cost associated with PNC was 33.31 dollars (range 1-125.60 dollars, SD = 32.33 dollars) and the time needed to attend care was 228 min (20-720, SD = 205). Women delivered at 37.8 (18-42) weeks; 17.6% of the women received inadequate PNC, and 17.0% of the women delivered low-birth-weight newborns. CONCLUSIONS: The findings indicated that personal costs associated with PNC attendance were not associated with inadequate care attendance.

Absenteeism↗