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Biomedical subjects

G Whyte

Publications and source records attributed to G Whyte.

At least 19 recordsLinked to original sources
PubMed1999

Characteristics of hepatitis C-positive blood donors in Victoria, Australia.

Data from 3156 voluntary blood donors in Victoria, Australia, who were repeatedly reactive on anti-HCV screening test were analysed. It showed that between 1990 and 1997, 0.97% of routine blood donors were anti-HCV repeat reactive. Sixty-four (64) donors tested positive for HCV RNA. They were more likely to be male, had a mean age of 32.7 +/- 10.9 years and a mean serum ALT level of 70.9 +/- 46.5 i.u.L-1: the latter value being significantly different from donors with biological false reactivity (P < 0.0001). Among HCV antibody-positive donors there was a significantly increased rate of prior injecting drug use (34 vs. 1%), transfusion (25 vs. 10%) and tattooing (31 vs. 7%) than among donors with biological false reactivity (all P < 0.0001). The association of these risk factors is stronger with positivity for both immunoblot and HCV RNA than immunoblot alone. The data suggest that efforts should be made to increase the efficacy of donor questioning about prior drug use.

Adult↗
PubMed1999

Scaling cardiac structural data by body dimensions: a review of theory, practice, and problems.

Robust estimates of the "true" bivariate relationship between body size (X) and heart size (Y) have seldom been determined empirically. The removal of the covariate influence of body size from cardiac dimension variables facilitates both correct inter- or intra-group comparisons, and the construction of reference standards for normality. In the literature to date this "scaling" or normalisation of cardiac dimensions has been performed typically via a per-ratio standards method, (Y/X), with body surface area chosen as the size denominator. This review demonstrates that the per-ratio standards approach may be theoretically, mathematically, and empirically flawed. The most appropriate scaling procedure appears to be a curvilinear, allometric model of the general form Y = aXb. The cardiac dimension variable (Y) may be regressed upon the body size variable (X) to derive a power function ratio (Y/Xb) that is allegedly size-independent. The current consensus is that an estimate of fat-free mass (FFM) provides the most appropriate body size variable. In the scaling literature allometric modelling procedures have generally yielded FFM exponents (b) consistent with the theory of geometric similarity. We suggest that cardiac dimension data should be scaled by appropriate powers of FFM, derived from allometric modelling. However, despite the potential superiority of FFM as a scaling denominator, reference standards for normality based on FFM have not been developed or proposed. Future research should examine the robustness of the FFM-cardiac dimension relationship in large samples.

Body Constitution↗
PubMed1999

Alterations in cardiac morphology and function in elite multi-disciplinary athletes.

Early echocardiographic studies of left ventricular (LV) morphology and function focused on single discipline athletes, primarily endurance and strength trained. To date there are few studies examining multi-disciplinary trained athletes. The present echocardiographic study examined LV morphology and function in 18 elite triathletes (swimming, cycling, and running) and 11 elite modern pentathletes (running, swimming, shooting, fencing, and show-jumping) compared with age- and sex-matched controls. Elite triathletes demonstrated significantly (p < 0.05) increased LV wall thickness and cavity dimensions together with LV mass, both in absolute terms and scaled for body surface area, compared with controls. Elite modern pentathletes demonstrated significantly (p < 0.05) increased LV wall thickness with a non-significant increase in LV internal diameter. Despite significant LV enlargement, the distribution of hypertrophy and diastolic filling indices were normal in both triathletes and modern pentathletes and significantly increased in the triathletes. It is concluded that multi-disciplinary training results in variations in LV morphology. The inciting stimulus resulting in LV enlargement in triathletes is associated with prolonged endurance activity, together with an isometric component accompanying cycling. In contrast, elite modern pentathletes experience a reduced endurance component combined with a high isometric component associated with fencing.

Adult↗
PubMed1999

Echocardiographic examination of cardiac structure and function in elite cross trained male and female Alpine skiers.

OBJECTIVE: To assess cardiac structure and function in elite cross-trained male and female athletes (Alpine skiers). METHODS: Sixteen athletes (10 male, six female) and 19 healthy sedentary control subjects (12 male, seven female) volunteered to take part in the study. Basic anthropometry determined height, body mass, body surface area, and fat free mass. Cardiac dimensions and function were determined by two dimensional, M mode, and Doppler echocardiography. Absolute data and data corrected for body size (allometrically determined) were compared by two way analysis of variance and post hoc Scheffé tests. RESULTS: Absolute left ventricular internal dimension in diastole (LVIDd), septal and posterior wall thickness and left ventricular mass were larger in athletes than controls (p < 0.05) and also increased in the men (p < 0.05) compared with women (except for septal thickness in controls). An increased LVIDd, septal thickness, posterior wall thickness, and left ventricular mass in athletes persisted after correction for body size except when LVIDd was scaled by fat free mass. Cardiac dimensions did not differ between the sexes after correction for body size. All functional indices were similar between groups. CONCLUSION: There is evidence of both left ventricular chamber dilatation and wall enlargement in cross trained athletes compared with controls. Differences in absolute cardiac dimensions between the sexes were primarily due to greater body dimensions in the men.

Adult↗
PubMed1999

Electrocardiographic changes in 1000 highly trained junior elite athletes.

OBJECTIVES: To evaluate the spectrum of electrocardiographic (ECG) changes in 1000 junior (18 or under) elite athletes. METHODS: A total of 1000 (73% male) junior elite athletes (mean (SD) age 15.7 (1.4) years (range 14-18); mean (SD) body surface area 1.73 (0.17) m2 (range 1.09-2.25)) and 300 non-athletic controls matched for gender, age, and body surface area had a 12 lead ECG examination. RESULTS: Athletes had a significantly higher prevalence of sinus bradycardia (80% v 19%; p<0.0001) and sinus arrhythmia (52% v 9%; p<0.0001) than non-athletes. The PR interval, QRS, and QT duration were more prolonged in athletes than non-athletes (153 (20) v 140 (18) milliseconds (p<0.0001), 92 (12) v 89 (7) milliseconds (p<0.0001), and 391 (27) v 379 (29) milliseconds (p = 0.002) respectively). The Sokolow voltage criterion for left ventricular hypertrophy (LVH) and the Romhilt-Estes points score for LVH was more common in athletes (45% v 23% (p<0.0001) and 10% v 0% (p<0.0001) respectively), as were criteria for left and right atrial enlargement (14% v 1.2% and 16% v 2% respectively). None of the athletes with voltage criteria for LVH had left axis deviation, ST segment depression, deep T wave inversion, or pathological Q waves. ST segment elevation was more common in athletes than non-athletes (43% v 24%; p<0.0001). Minor T wave inversion (less than -0.2 mV) in V2 and V3 was present in 4% of athletes and non-athletes. Minor T wave inversion elsewhere was absent in non-athletes and present in 0.4% of athletes. CONCLUSIONS: ECG changes in junior elite athletes are not dissimilar to those in senior athletes. Isolated Sokolow voltage criterion for LVH is common; however, associated abnormalities that indicate pathological hypertrophy are absent. Minor T wave inversions in leads other than V2 and V3 may be present in athletes and non-athletes less than 16 but should be an indication for further investigation in older athletes.

Adolescent↗
PubMed1999

Quantitating donor behaviour to model the effect of changes in donor management on sufficiency in the blood service.

BACKGROUND AND OBJECTIVE: To describe donor behaviour quantitatively and apply the information on actual donations derived during observed changes in blood collection in Melbourne between July 1990 and June 1996 to construct a logical model to examine the effects of changes in donor management on the sufficiency of the blood supply. METHOD: Computerised donation data files were searched to determine time to next or previous donation for donors giving blood between 1990 and 1996 stratified by age, donation history and venue. Actual numbers of whole blood donation given by new and repeat donors, July 1990 to June 1996, and numbers of donors refused were used to construct and test a logical predictive model. RESULTS: 558,682 donation intervals were analysed. Donor return rates at 2 years were shown to increase with donor donation history and donor age. The prediction model showed that a 25% decline in whole blood collections over 2 years could be explained by the cumulative effect of a decrease in donor return rates of 2-4%. Between 1990 and 1996 many donors moved from static city collection sites to suburban mobiles. New donor attendance correlated with repeat donor attendance. Donor complaints correlated with donor deferral numbers. CONCLUSIONS: The model showed that large shifts in nett blood collections can be explained by relatively small shifts in donor return rates at 2 years.

Behavior↗
PubMed1998

Recasting Janis's Groupthink Model: The Key Role of Collective Efficacy in Decision Fiascoes.

This paper advances an explanation for decision fiascoes that reflects recent theoretical trends and was developed in response to a growing body of research that has failed to substantiate the groupthink model (Janis, 1982). In this new framework, the lack of vigilance and preference for risk that characterizes groups contaminated by groupthink are attributed in large part to perceptions of collective efficacy that unduly exceed capability. High collective efficacy may also contribute to the negative framing of decisions and to certain administrative and structural organizational faults. In the making of critical decisions, these factors induce a preference for risk and a powerful concurrence seeking tendency that, facilitated by group polarization, crystallize around a decision option that is likely to fail. Implications for research and some evidence in support of this approach to the groupthink phenomenon are also discussed. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Risk management in blood transfusion services.

Risk is usually simplistically defined as the probability of an adverse outcome, under-recognising the importance of perception. The intuitive centre of the risk structure is 1 in a million (10(-6)), the background risk of death in developed countries. In Australia, current risks of transmission of HIV and HCV by blood transfusion are about 10(-6), the risk is higher for HBV and lower for HTLV1, but the risk of death from the infections is much less, particularly for HTLV1. When blood service professionals take risk related actions, their judgement must be tempered by contemporary political and social realities and the public's real and disproportionate horror of catastrophe.

Australia↗
PubMed1993

Stabilization of von Willebrand factor in banked blood by leucocyte depletion.

The von Willebrand factor (vWf) activity, as measured by the ristocetin co-factor (vWf:RCo) and collagen binding (vWf:CBA) assays, declined progressively in standard blood units stored at 4 degrees C after a 2-day storage period. This loss of activity was accompanied by a loss and degradation of high molecular weight (HMW) vWf multimers. In studies using a paired design, filtration of blood with a high efficiency leucocyte-removal filter, prior to storage at 4 degrees C, led to significantly improved maintenance of vWf:RCo and vWf:CBA compared with unfiltered units (P < 0.01 after 8 days). Loss and degradation of HMW vWf decreased when blood was filtered prior to 4 degrees C storage. Filtration had no effect on vWf-associated activities when blood was stored at 22 degrees C for 10 days. These results indicate that part of the storage lesion of vWf in banked blood is due to leucocyte-mediated removal and degradation of HMW vWf. This has implications when specifying plasma for the production of vWF concentrates and may also play a role in the haemostatic lesion associated with massive transfusion of stored blood.

Blood Banks↗
PubMed1993

Red cell, plasma and albumin transfusion decision triggers.

Hypothetical clinical cases were used to investigate transfusion-related decision-making. Three red cell, three fresh frozen plasma (FFP) and three albumin transfusion decision cases were administered by questionnaire to 228 medical staff. The transfusion decision triggers were identified and comparisons made between resident and specialist groups and between Melbourne and Sydney participants. Factors important in red cell transfusion decisions included haemoglobin, symptoms of anaemia, presence of co-morbidities or surgery, gender, period of hospitalisation and the degree of documented blood loss. FFP administration was influenced by an abnormal coagulation test, the presence of co-morbidities and by the number of red cell units transfused. The administration of albumin, concentrated or 5% SPPS, was influenced by the period of hospitalisation and clinical circumstances such as a falling urine output postoperatively, and by the presence of hypotensive complications. Different transfusion responses were noted: resident staff transfused red cells and FFP earlier than specialists; Sydney specialists were more conservative of red cell transfusion; Melbourne specialists more conservative of FFP administration and surgeons were four times more likely to transfuse patients than physicians or anesthetists at certain haemoglobin values.

Abruptio Placentae↗
PubMed1992

Modulation of fibrinogen content in cryoprecipitate by temperature manipulation during plasma processing.

In routine blood bank production of single-donation cryoprecipitate, the introduction of a 16-hour hold at 4 degrees C, with the frozen plasma units packed into polystyrene containers, resulted in plasma prethaw temperatures of -4 degrees C to -8 degrees C. This in turn resulted in cryoprecipitate fibrinogen levels that were 214 percent of those obtained when units were thawed immediately after removal from -30 degrees C storage. In scale-model production of factor VIII concentrate, plasma warmed from -30 to -10 to -15 degrees C over 18 hours before pooling and thawing yielded cryoprecipitate fibrinogen levels that were 66 percent of those found in plasma warmed to -2 to -5 degrees C over the same period. Processing -30 degrees C plasma without a warming period led to cryoprecipitate fibrinogen levels that were 40 percent of those obtained from plasma warmed to -2 to -5 degrees C. These differences were accentuated after purification of the cryoprecipitates to an intermediate-purity factor VIII concentrate. These results suggest that simple modifications in production methods allow the fibrinogen content of cryoprecipitate to be tailored to specific uses.

Blood Banks↗
PubMed1992

Red cell and platelet concentrates from blood collected into half-strength citrate anticoagulant: improved maintenance of red cell 2,3-diphosphoglycerate in half-citrate red cells.

This study confirms previous work suggesting equivalent in vitro properties in blood components prepared from donations collected into half-citrate preservative (HCPD) compared to components derived from donations collected into standard citrate-phosphate-dextrose (CPD) preservatives. In addition, red cell products harvested from HCPD donations showed significantly improved maintenance of pH over storage, and this was reflected in improved maintenance of intracellular 2,3-diphosphoglycerate (2,3-DPG). This effect was observed in whole blood and in red cells suspended in a phosphate-containing additive solution (Tuta AAS). Collection into HCPD also improved 2,3-DPG maintenance in red cell concentrates processed following an 18-hour hold at 22 degrees C. These improvements were less pronounced in red cells suspended in a non-phosphate-containing medium (Fenwal Adsol) in which a higher pH was maintained even in units collected in CPD. Platelets harvested from HCPD blood and suspended in plasma showed equivalent quality to platelets from standard donations. Some deterioration of platelet properties was observed when HCPD platelets were stored in a non-citrate synthetic medium. Together with data indicating improved coagulation factor stability, these results suggest that collection into HCPD improves stored blood quality and may also allow logistical benefits in blood component preparation.

2,3-Diphosphoglycerate↗
PubMed1991

Human immunodeficiency virus antibodies in sera of Australian blood donors: 1985-1990.

OBJECTIVE: To describe the results of human immunodeficiency virus type 1 (HIV-1) antibody testing of blood donations in Australia. DESIGN: Blood transfusion services tabulated the number of HIV-1 antibody tests carried out on blood donations and the number of donations found to be positive, from 1985 to 1990. SETTING: All blood transfusion services in Australia. PARTICIPANTS: All donors of blood in Australia from 1 May 1985 to 31 December 1990. OUTCOME MEASURES: The proportion of blood donations found to have HIV-1 antibody, according to State or Territory, year of donation and, when available, age, sex and donation status (repeat or first-time) of the donor. RESULTS: To the end of December 1990, 5,367,970 donations had been tested for HIV-1 antibody, and 46 were found to have the antibody, giving an overall prevalence rate of 0.86 per 100,000 donations. The highest rate was recorded in New South Wales, followed by Western Australia, and four of eight Australian States and Territories reported no donors with HIV-1 antibody. There has been no clear trend with time, but the rate is about 20% higher for 1989-1990 than for 1985-1986. Of donors found to have HIV-1 antibody, 67% were male and 33% female, and 41% reported no known or potential exposure to HIV-1 other than heterosexual contact. Among blood donors in two major Australian cities, the overall prevalence of HIV antibody was higher in those who were male, younger, and first-time donors. There has been a recent increase in the number of blood donors with HIV-1 antibody who were women reporting heterosexual contact as their only potential exposure. CONCLUSION: The rate of HIV-1 antibody in Australian blood donations remains very low and shows no clear temporal trend, but specific donor characteristics define higher rates of antibody prevalence.

Adult↗