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Biomedical subjects

D Ashby

Publications and source records attributed to D Ashby.

At least 19 recordsLinked to original sources
PubMed1992

Power calculation for cohort studies with improved estimation of expected numbers of deaths.

This paper focuses on improving the accuracy of sample size calculations for cohort studies by careful calculation of the expected number of deaths in the population, taking into account either prior information or realistic assumptions about variables which may affect the mortality or incidence. Sometimes small changes in the assumptions can dramatically alter the expected numbers and may necessitate modifications in the design of the study. Possible modification include extension of the follow-up time, and recognition that the real strength of the study may lie in the potential for pooling several similar studies. The problem will be discussed with reference to two examples of occupational cohort studies where differing prior information was available.

Adult↗
PubMed1992

A prospective randomised controlled trial comparing the efficacy of somatostatin with injection sclerotherapy in the control of bleeding oesophageal varices.

Since previous reports have suggested that somatostatin may be of value in the control of acute variceal haemorrhage, we compared its efficacy with that of injection sclerotherapy in a randomised controlled clinical trial. Eighty consecutive patients with endoscopically-proven severe variceal bleeding were randomised to injection sclerotherapy (n = 41) or somatostatin (n = 39) given as a continuous infusion of 250 micrograms/h for 5 days plus daily bolus administration of 250 micrograms. The efficacy of injection sclerotherapy and somatostatin infusion in controlling haemorrhage and preventing rebleeding (censored at 5 days), mortality (censored at 28 days) and complications was compared. The aetiology of the portal hypertension and transfusion requirements was similar between the two groups, but there were more patients with severe liver disease (Child's C) in the somatostatin group. There was no significant difference between the two treatments in the initial (p = 1.0) or overall control of bleeding (p = 0.58). Furthermore, somatostatin was as effective as injection sclerotherapy in controlling bleeding in patients with severe liver disease or in those actively bleeding at the time of their endoscopy. The relative risk of rebleeding whilst receiving somatostatin compared to injection sclerotherapy was 1.39 [95% Confidence Interval (CI) 3.73; 0.52], but this was reduced to 0.98 (95% CI 0.37; 2.67) when readjusted for Child's grading, the only prognostic factor shown to be of significance. Mortality was not significantly different between the two groups of patients (p = 0.31). The relative risk of dying whilst receiving somatostatin compared to injection sclerotherapy was 1.6 (95% CI 3.93; 0.66) but was reduced to 1.03 (95% CI 0.47; 2.47) when adjusted for Child's grading, the only significant prognostic factor. Complications in the somatostatin group were minor and less frequent than after injection sclerotherapy. The results of this study indicate that somatostatin is a safe treatment, which is as effective an endoscopic injection sclerotherapy for acute variceal bleeding.

Adult↗
PubMed1991

High energy neutron treatment for pelvic cancers: study stopped because of increased mortality.

OBJECTIVE: To compare high energy fast neutron treatment with conventional megavoltage x ray treatment in the management of locally advanced pelvic carcinomas (of the cervix, bladder, prostate, and rectum). DESIGN: Randomised study from February 1986; randomisation to neutron treatment or photon treatment was unstratified and in the ratio of 3 to 1 until January 1988, when randomisation was in the ratio 1 to 1 and stratified by site of tumour. SETTING: Mersey regional radiotherapy centre at Clatterbridge Hospital, Wirral. PATIENTS: 151 patients with locally advanced, non-metastatic pelvic cancer (27 cervical, 69 of the bladder, seven prostatic, and 48 of the rectum). INTERVENTION: Randomisation to neutron treatment was stopped in February 1990. MAIN OUTCOME MEASURES: Patient survival and causes of death in relation to the development of metastatic disease and treatment related morbidity. RESULTS: In the first phase of the trial 42 patients were randomised to neutron treatment and 14 to photon treatment, and in the second phase 48 to neutron treatment and 47 to photon treatment. The relative risk of mortality for photons compared with neutrons was 0.66 (95% confidence interval 0.40 to 1.10) after adjustment for site of tumour and other important prognostic factors. Short term and long term complications were similar in both groups. CONCLUSIONS: The trial was stopped because of the increased mortality in patients with cancer of the cervix, bladder, or rectum treated with neutrons.

Fast Neutrons↗
PubMed1990

Urine flow rates in male and female urodynamic patients compared with the Liverpool nomograms.

The Liverpool male and female nomograms provide normal reference ranges for the maximum and average urine flow rates over a wide range of voided volumes. A known urine flow rate, in combination with the respective voided volume (and in men the age), can be converted into an equivalent centile ranking, using the equation for the relevant nomogram. Centile rankings allow the urine flow rates of specific male and female populations to be compared. The maximum and average urine flow rates of urodynamic patients (504 consecutive male and 168 consecutive female) were converted into centile rankings. These centile rankings were then compared with the respective urodynamic diagnoses. The median centile rankings for their maximum and average urine flow rates were 21 and 11 (male) respectively and 31 and 18 (female) (vs 50 for the normal populations). The low urine flow rates applied to all diagnostic groups, including those symptomatic men and women who were found to be urodynamically normal. Low urine flow rates may be one of a number of subtle manifestations of urological disease in these patients. Men with obstruction and women with voiding difficulties had the lowest urine flow rates. The 25th centile (men) and the 10th centile (women) appeared to be most appropriate lower limits of normality for both urine flow rates to identify those men more likely to be obstructed and those women at higher risk of voiding difficulties. Men and women with detrusor instability had the highest urine flow rates. Detrusor instability was present in 71% of men with centile rankings for the maximum urine flow rate over 50; 50% of women whose maximum urine flow rate centiles were over 90 had detrusor instability.

Adolescent↗
PubMed1990

Malignant hyperthermia: a potential crisis in the postanesthesia care unit.

This article pertains to malignant hyperthermia (MH). The disease and its physiologic aspects are described, and a general overall view of what takes place at the cellular level during an MH crisis is presented. Also described is the drug of choice, dantrolene sodium, and its functioning during an MH crisis. The care of an MH patient in the PACU is presented, correlating all the above mentioned aspects of MH.

Dantrolene↗
PubMed1989

The ordered logistic regression model in psychiatry: rising prevalence of dementia in old people's homes.

Ordered logistic regression is an extension of binary logistic regression, and is particularly well suited to the analysis of many psychiatric scores. Its use is demonstrated in a pair of linked cross-sectional surveys of dementia in residents of old people's homes, first to model the association of dementia with demographic characteristics, and then to explore possible reasons for a rise in the prevalence of dementia in the homes over a four-year period.

Age Factors↗
PubMed1989

The accuracy of measurement of residual urine in women by urethral catheterisation.

Two potential sources of error in the measurement of residual urine volumes in women were quantified. These were (i) whether a diuresis is operating at the time of measurement, and (ii) the time between voiding and residual urine volume collection. A regime is suggested for the accurate measurement of residual urine in women by urethral catheterisation.

Diuresis↗
PubMed1989

Maximum and average urine flow rates in normal male and female populations--the Liverpool nomograms.

The study of voiding in men and women has been handicapped by the lack of a normal reference range covering urinary flow rates over a wide range of voided volumes. Normal volunteers (331 males and 249 females) were studied. Each voided once into a calibrated Dantec Urodyn 1000 mictiograph. On a second occasion 282 men and 46 women voided. The maximum and average urine flow rates of the first voids in both sexes were compared with the respective voided volumes. Nomogram charts, in centile form, for both the maximum and average urine flow rates were constructed using statistical transformations of the data. Males showed a significant decline in both urinary flow rates with age, although there was no statistically significant variation in either urine flow rate with respect to first versus repeated voiding. Females showed no statistically significant variation in either urine flow rate with respect to age, parity or first versus repeated voiding. The maximum and average urine flow rates in both sexes showed an equally strong relationship to voided volume. No artificial restriction of voided volume, e.g. minimum 200 ml, appeared appropriate. These nomograms offer reference ranges for both maximum and average urinary flow rates in both sexes covering a wide range of voided volumes (15-600 ml).

Adolescent↗
PubMed1989

Diurnal variations in serum biochemical and haematological measurements.

Twenty five biochemical and haematological measurements were determined on nonfasting blood and serum samples collected between 9 am and 7 pm from a representative group of 7685 British middle-aged men. Most measurements showed significant diurnal variations, but only for bilirubin, phosphate, and triglyceride did time of day account for more than 5% of the between subject variance. Serum bilirubin concentrations showed a pronounced downward trend in the afternoon, the mean value after 6 pm being 30% lower than the mean value in the morning. Mean serum triglyceride and phosphate concentrations increased steadily through the day. Mean concentrations of potassium, haemoglobin, and haematocrit and red cell count were higher in the morning, while urea and creatinine concentrations and white cell count had higher means in the afternoon. Glucose showed a pattern consistent with short term response to meals. The effects of these diurnal trends on routine use of biochemical tests needs careful consideration, and a greater understanding of their biological mechanisms is required.

Adult↗