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Biomedical subjects

A Thorne

Publications and source records attributed to A Thorne.

27 records · Page 2Linked to original sources
PubMed1996

Impact of missing data due to dropouts on estimates of the treatment effect in a randomized trial of antiretroviral therapy for HIV-infected individuals. Canadian HIV Trials Network A002 Study Group.

PURPOSE: To evaluate the impact of missing data due to nonrandom dropout on estimates of the effect of treatment on the CD4 count in a clinical trial of antiretroviral therapy for HIV infected individuals. METHODS: The effect of treatment on CD4 counts in a recent study of continued ZDV versus ddI in HIV-infected individuals was estimated from the observed data and after imputing missing CD4 counts for patients who dropped out of the study. Imputation methods studied were (a) carrying forward the last observed CD4 count, (b) predicting missing CD4 counts from regression models, and (c) assuming that CD4 counts of patients who dropped out declined at a rate of 100 cells per year. RESULTS: Of the 245 patients enrolled in the study, 52% completed the planned 48 weeks of follow-up. Patients with lower CD4 counts were more likely to drop out of the study (RR = 1.77; p = 0.0001). Patients receiving ZDV had a greater tendency to drop out than patients receiving ddI (p = 0.07). Mean CD4 counts calculated after imputing missing data were lower than those obtained from the observed data at all follow-up times for both treatment groups. Imputing CD4 counts with regression models yielded higher estimates of the effect of treatment than were obtained using the observed data. CONCLUSION: Missing outcome data due to dropouts can result in an underestimation of the treatment effect and overly optimistic statements about the outcome of participants on both treatment arms due to the selective dropout of participants with lower or decreasing CD4 counts. When there are significant dropout rates in randomized trials, imputation is a useful technique to assess the range of plausible values of the treatment effect.

Antiviral Agents↗
PubMed1996

Situating adolescent gender and self-esteem with personal memories.

To identify social schemas that are associated with self-esteem in adolescence, the contents of approximately 1,400 memories from a longitudinal sample of 41 males and 43 females were correlated with a Q-sort measure of self-esteem. Each memory concerned an important or problematic encounter, and was coded for social motive, affect, and identity of significant other. For young women, memories about wanting to help female friends were associated with chronically high and increasingly high levels of self-esteem from ages 14 to 23. For young men, memories about successfully asserting oneself with male friends were associated with chronically high and increasingly high levels of self-esteem. Low self-esteem in women, both chronic as well as decreasing, was associated with memories about failing to get approval from friends. Decreasing self-esteem for males was associated with memories about wanting love from female friends. The results confirm and refine prior findings that adolescent self-esteem is localized in relationships with peers rather than parents, and is based on different relational schemas for females than for males. The findings may help to identify contexts for preventative interventions to enhance adolescent self-esteem.

Adolescent↗
PubMed1995

Juxtaposed scripts, traits, and the dynamics of personality.

Although personality is theoretically composed of multiple facets that function in lively interrelatedness, the interplay among these multiplicities has mostly been missed by research that focuses on traits as the primary unit of personality. The juxtaposition of contrary interpersonal scripts is a promising way to capture dynamic processes of personality. A case study is used to illustrate the dynamic interplay between sociotropic (extraverted) and avoidant scripts. Whereas standard trait measures do not reveal how extraversion and avoidance co-relate in everyday experience, the dynamics are revealed by study of interpersonal scripts in narratives of memorable encounters. Similarities between the present approach and recent dialectical approaches to the self-concept are discussed (Hermans & Kempen, 1993). Such approaches, particularly when articulated so as to interface with more generalized units of personality, can be highly useful for advancing understanding of personality dynamics.

Adult↗
PubMed1995

Developmental truths in memories of childhood and adolescence.

This study of age-related changes in memories of personally important encounters showed "developmental truths," that is, patterns that converged with prior developmental theories and research. Participants were 47 males and 48 females in their early 20s. An average of 16 memories were collected from each person during an intensive personal interview. Memories were coded for age at the time of the episode, the identity of the other person with whom the study participant was interacting, what the participant wanted from the other person, and the outcome. As expected, memories of encounters with parents and about wanting help prevailed for childhood, whereas memories of encounters with close friends and about wanting intimacy prevailed by mid-adolescence. Memories about wanting to help others were sparse for this young-adult sample, but, like needs for intimacy, increased with age. Although patterns for males tended to be more dramatic than patterns for females, this trend appeared more attributable to actual developmental differences in social dynamics than to differences in the degree to which current concerns intruded into the memory process. The advantages of personally salient, event-specific retrospective reports for understanding personality development and change are discussed.

Adult↗
PubMed1995

Microclimatic effect on vertical migration of Haemonchus contortus and Haemonchus placei third-stage larvae on irrigated Kikuyu pasture.

The influence of microclimate on numbers of third-state larvae of haemonchus contortus and Haemonchus placei in four strata of irrigated Kikuyu pasture was assessed. On 36 different, interspersed days three replicates of pasture samples were collected on three occasions per day from 1990-1992 for larval recovery and the log10 mean counts of the larvae recovered were analysed by use of ANOVA models. Because the ground-surface area from which herbage was collected was standardized, estimated larval counts for the different strata could be compared; this was not possible in our previous studies. For H. contortus, the estimated larval counts in the four strata were predicted by microclimatic air temperature, relative humidity and soil moisture, with the coefficient-of-determination (R2) values ranging from 0.15-0.35. Of these, air temperature had the greatest effect. The same three predictors, together with illumination and wind speed, featured for H. placei, with R2 values of 0.19-0.52. With the exception of wind speed and illumination, which (for H. placei) had the opposite effect, all the microclimatic parameters listed, predicted an increase in numbers of larvae from a lower to an upper strata.

Africa↗
PubMed1992

Esmolol infusion during nitroprusside-induced hypotension: impact on hemodynamics, ventricular performance, and venous admixture.

The impact of esmolol infusion on hemodynamics, ventricular performance, venous admixture, sympathoadrenal, and renin-angiotensin system responses during sodium nitroprusside (SNP)-induced hypotension was studied in 11 patients undergoing lymph node dissection during general anesthesia with 60% nitrous oxide and fentanyl. Radial arterial and thermistor-tipped pulmonary catheters were employed for hemodynamic monitoring. Arterial and mixed venous blood gas tensions, arterial plasma renin activity (PRA), and plasma catecholamine levels were measured. Derived hemodynamic parameters and venous admixture (Qs/Qt) data were obtained from standard equations. Transesophageal echocardiography (6 patients) was used to assess left ventricular performance using the relationship between end-systolic wall stress (ESWS) and velocity of circumferential shortening (VCFC). After surgical incision, arterial hypotension was induced with SNP alone. Esmolol was infused at each of the following rates in sequence: 200, 300, and 400 micrograms/kg/min. Each esmolol infusion lasted 20 minutes and the SNP dose was adjusted to maintain MAP at 55 to 60 mm Hg. The mean dose of SNP required to induce hypotension was 5.5 micrograms/kg/min +/- 0.5 SE. Compared to prehypotension values, SNP induced significant increases in Qs/Qt and reductions in PaO2, systemic vascular resistance (SVR), and stroke volume index (SVI). Esmolol infusion caused dose-dependent (highest with 400 micrograms/kg/min) reductions in the SNP requirement, heart rate (HR), SVI, Qs/Qt, and PRA, and also led to significant increases in SVR and left ventricular (LV) internal diameter in diastole as well as systole. Furthermore, esmolol infusion was associated with a dose-dependent downward and leftward shift of the ESWS versus VCFC relationship, implying diminished contractility.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1990

Pharmacologic treatment of noncognitive behavioral disturbances in elderly demented patients.

Fifty-nine elderly residents of long-term care facilities who had DSM-III diagnoses of dementia were studied in an 8-week randomized, double-blind comparison trial of haloperidol, oxazepam, and diphenhydramine to test the efficacy of these agents in the treatment of clinically significant behavioral disturbances in patients with dementia. All three agents demonstrated modest but significant efficacy as measured by clinician ratings of agitated behavior and activities of daily living. The absolute magnitude of improvement was greater for haloperidol and diphenhydramine than for oxazepam, but differences among groups did not approach statistical significance. Frequencies of acute adverse events during the trial were similar across the drug treatment groups. Although these drugs may differ in terms of long-term safety and efficacy, they appear to be equivalent for short-term management of agitated behavior in severely demented patients.

Activities of Daily Living↗
PubMed1989

Esmolol for potentiation of nitroprusside-induced hypotension: impact on the cardiovascular, adrenergic, and renin-angiotensin systems in man.

Esmolol infusion at rates of 200, 300, and 400 micrograms.kg-1.min-1 was used to potentiate hypotension (mean arterial pressure = 60 mm Hg) induced with sodium nitroprusside (SNP) in 10 male patients undergoing radical cancer surgery during nitrous oxide-oxygen and fentanyl anesthesia. Heart rate (HR), blood pressure (radial arterial catheter), and plasma levels of renin activity (PRA), norepinephrine (N), epinephrine (E), and dopamine (D) were measured: 1) while patients were awake; 2) after induction of anesthesia (nitrous oxide, 60% in oxygen, fentanyl = 5 micrograms/kg followed by an infusion at 10 micrograms.kg-1.hr-1); 3) after surgery had begun; 4) after 20 minutes of SNP-induced hypotension; 5) after 20 minutes of esmolol at each of the above infusion rates; and 6) after the completion of surgery. Compared to awake values, SNP-induced hypotension (mean infusion rate = 3.1 micrograms.kg-1.min-1 +/- 0.6 SE) during surgery resulted in significant (P less than 0.05) increases in heart rate, PRA, N, and D. Infusion of esmolol resulted in significant (P less than 0.05) dose-dependent reductions in SNP requirement to maintain MAP = 60 mm Hg. At 200 micrograms.kg-1.min-1, SNP requirement was 2.1 micrograms.kg-1.min-1 +/- 0.4, at 300 micrograms.kg-1.min-1, it was 1.0 micrograms.kg-1.min-1 +/- 0.2, and at 400 micrograms.kg-1.min-1, was 0.5 micrograms.kg-1.min-1 +/- 0.3. Concomitant with the decrease in SNP requirement, there were significant reductions in HR and PRA at all infusion rates of esmolol.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗