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Biomedical subjects

N Buchanan

Publications and source records attributed to N Buchanan.

At least 55 records · Page 3Linked to original sources
PubMed1993

Postpartum bilateral renal vein thrombosis in the primary antiphospholipid syndrome.

A young Caucasian woman developed bilateral deep vein thromboses (DVT) while taking the oral contraceptive (OC) in 1984. After a 9-month period of longterm anticoagulation therapy with warfarin, she experienced recurrent DVT 2 weeks following discontinuation of anticoagulation. She was then maintained with warfarin for the following 6 years. Elevated antibodies to cardiolipin (IgG aCL) were first detected in 1988. In 1990, warfarin was switched to aspirin and low molecular weight heparin as she wished to become pregnant. At 24 weeks she developed eclampsia and labor was induced. During the first postpartum week she experienced loin pain, associated with rapidly rising creatinine levels and features of a nephrotic syndrome. An abdominal ultrasound showed bilateral renal vein thrombosis with enlarged kidneys. She was treated with continuous ambulatory peritoneal dialysis (CAPD) for 4 months and her renal function is now recovering. Our patient is another example of the primary antiphospholipid syndrome.

Adult↗
PubMed1993

Avascular necrosis of bone and antiphospholipid antibodies in systemic lupus erythematosus.

Of a total of 800 patients with systemic lupus erythematosus, 37 were found to have developed avascular necrosis of bone (4.6%). Routine radiological screening of all joints was not performed and these 37 represented symptomatic patients only. Twenty-seven of these were positive for antiphospholipid antibodies (aPL) (73%). Both aPL positive and aPL negative patients had received large doses of oral steroids. The frequency of vasculitis and livedo reticularis, as well as arterial thrombosis was higher in the aPL positive group, but this did not reach statistical significance, perhaps because of the small numbers of patients involved. Although the difference in the frequency of thrombocytopenia was more marked in the aPL positive group (p < 0.08), once again, this was not statistically significant at the 5% level. Since the prevalence of aPL positivity in the general lupus population is about 30-40%, the presence of the aPL may be associated with an increased tendency to develop avascular necrosis. This is supported by recent reports of avascular necrosis occurring in patients with primary antiphospholipid syndrome in the absence of previous steroid administration.

Adolescent↗
PubMed1992

Gadolinium-enhanced magnetic resonance imaging of the central nervous system in systemic lupus erythematosus.

Gadolinium (Gd)-DTPA enhanced magnetic resonance imaging (MRI) was performed in 15 systemic lupus erythematosus patients with past (12) or present (3) features suggesting central nervous system (CNS) involvement. Symptomatic Gd-DTPA enhancing lesions were seen in 2 patients, and immunosuppressive treatment was associated with a rapid reversal of enhancement. The pattern of enhancement was different from that usually seen in multiple sclerosis. Gd-DTPA enhanced MRI may sometimes be useful in demonstrating the activity of CNS lupus.

Adolescent↗
PubMed1992

Ventilatory mechanisms of exercise intolerance in chronic heart failure.

Mechanisms that have been suggested to underlie the abnormal ventilatory response to exercise in patients with chronic congestive heart failure (CHF) include high pulmonary pressures, ventilation-perfusion mismatching, early metabolic acidosis, and abnormal respiratory control. To evaluate the role that ventilation and gas exchange play in limiting exercise capacity in patients with CHF, data from 33 patients with CHF and 34 normal subjects of similar age who underwent maximal exercise testing were analyzed. Maximal oxygen uptake was higher among normal subjects (31.7 +/- 6 ml/kg/min) than among patients with CHF (17.7 +/- 4 ml/kg/min; p less than 0.001). The ventilatory equivalent for oxygen, expressed as a percentage of maximal oxygen uptake, was 25% to 35% higher among patients with CHF compared with normal subjects throughout exercise (p less than 0.01). A steeper component effect of ventilation on maximal oxygen uptake was observed among normal subjects compared with patients with CHF, which suggests that a significant portion of ventilation in CHF is wasted. Maximal oxygen uptake was inversely related to the ratio of maximal estimated ventilatory dead space to maximal tidal volume (VD/VT) in both groups (r = -0.73, p less than 0.001). Any given oxygen uptake at high levels of exercise among patients with CHF was accompanied by a higher VD/VT, lower tidal volume, and higher respiratory rate compared with normal subjects (p less than 0.01). Relative hyperventilation in patients with CHF started at the beginning of exercise and was observed both below and above the ventilatory threshold, which suggests that the excess ventilation was not directly related to earlier than normal metabolic acidosis. Thus abnormal ventilatory mechanisms contribute to exercise intolerance in CHF, and excess ventilation is associated with both a higher physiologic dead space and an abnormal breathing pattern. The high dead space is most likely due to ventilation-perfusion mismatching in the lungs, which is related to poor cardiac output, and the abnormal breathing pattern appears to be an effort to reduce the elevated work of breathing that is caused by high pulmonary pressures and poor lung compliance.

Adult↗
PubMed1992

The occurrence, management and outcome of antiepileptic drug side effects in 767 patients.

This study reports the nature of adverse drug reactions (ADR) occurring in 767 epilepsy clinic patients (adults and children), the drugs most commonly involved, how they were managed and the outcome of such management. One hundred and thirty four patients were found to have 155 separate ADRs. The majority appeared to be pharmacodynamic in nature, although 21 were clearly pharmacokinetic in origin and four due to drug interactions. The antiepileptic drugs (AED) perceived to be causative, in order of frequency were phenytoin, sodium valproate, carbamazepine, clonazepam, barbiturates, vigabatrin and clobazam. Management most often involved withdrawing the offending drug(s), usually replacing them with another AED. Of the 155 ADRs, 40.6% resolved totally, 27.7% showed a marked improvement, 16.1% improved, 14.8% did not change and one patient deteriorated. This study emphasizes the need to be vigilant for ADRs and demonstrates that their management is essentially clinical with some 85% of patients experiencing benefit.

Adolescent↗
PubMed1992

Liver function tests in persons receiving anticonvulsant medications.

Liver function tests were carried out in 206 adults and children taking anticonvulsants to ascertain the prevalence of biochemical abnormalities in asymptomatic patients. It was observed that serum gamma-glutamyl transpeptidase was elevated in 74.6% of patients, alkaline phosphatase in 29.7% and alanine aminotransferase in 25.2% of cases. These figures are similar to those previously reported in the literature and probably reflect hepatic enzyme induction by the anticonvulsants. It is suggested that there is no value in the routine performance of liver function tests in patients with epilepsy. However, such patients should be informed of the symptoms of hepatic dysfunction and asked to report for liver function tests should they have such symptoms.

Adolescent↗
PubMed1992

Epilepsy: patient perceptions of their condition.

The objective of this study was to ascertain the perceptions of people with epilepsy about their condition. Nine hundred and eight questionnaires were sent to members of epilepsy associations, with a 45% response rate, and 625 questionnaires were sent to neurologists for their patients to complete, with a response rate of 16.5%. The results reinforce and extend previous observations that there is an ongoing need for educating health care professionals and persons with epilepsy about the condition. Matters pertaining to driving, the unpredictability of seizures, lack of employment and cognitive difficulties were of major concern to the respondents. The present data also highlighted the vexed relationship between stress and seizure control, which needs to be further investigated. These data should be of value to doctors and other health care professionals in their dealings with people with epilepsy. It should also provide epilepsy associations with data upon which they might be able to plan education services.

Activities of Daily Living↗
PubMed1992

Individualized ramp treadmill. Observations on a new protocol.

The many different approaches to exercise testing have hindered the consistent interpretation of hemodynamic, electrocardiographic, and ventilatory gas exchange responses. One of the most influential approaches is the choice of the exercise protocol. Recent data suggest that the protocol can have an important impact on test sensitivity, the reason for test termination, the ST/HR slope calculation, the interpretation of gas exchange responses, and the accuracy with which oxygen uptake is predicted from work rate. Recent recommendations for optimizing the test have focused on the test duration, reducing the increments in work rate, and individualizing the test relative to the purpose of the test and the subject tested. We describe a treadmill test which considers these recommendations for optimizing exercise testing.

Adult↗
PubMed1991

The ventilatory threshold: method, protocol, and evaluator agreement.

To evaluate the effects of different methods of detection, exercise modes, protocols, and reviewers on oxygen uptake (VO2) at the ventilatory threshold (ATge), 17 men with heart disease (mean age 59 +/- 6 years) and six healthy men (mean age 60 +/- 11 years) underwent six exercise tests on different days. Each subject performed three treadmill tests (Bruce, Balke, and ramp) and three bicycle ergometer tests (50 W/stage, 25 W/stage, and ramp) in random order. The ventilatory threshold was determined for each of the six exercise tests by three independent, blinded reviewers by means of graphic plots of three commonly used methods of determination: (1) changes in the ventilatory equivalents for VO2 and VCO2, (2) changes in end-tidal oxygen and carbon dioxide pressures, and (3) the intersection of the slope of VCO2 and VO2 (V slope). The largest variability in the ATge was observed with changes in the exercise protocol. The greatest absolute (ml/min) and percentage differences in oxygen uptake at the ATge as a result of changes in protocol, method of determination, and observers were 336 (36%), 125 (12%), and 70 (7%), respectively. The overall intraclass correlation coefficient for VO2 at the ATge among the three reviewers was 0.60 and among the three protocols was 0.85 (p less than 0.01). The V slope method of detection had consistently good agreement among reviewers and was least affected by the protocol. The variance in the ATge (excluding intersubject and error variance) accounted for by differences in protocol, method, and reviewer was 82%, 14%, and 4%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaerobic Threshold↗
PubMed1991

Trypanosoma brucei rhodesiense: characterisation of stocks from Zambia, Kenya, and Uganda using repetitive DNA probes.

We have previously described a system for characterising the relationships between trypanosome stocks of the T.brucei group based on Southern blotting with repetitive DNA probes followed by cluster analysis of resultant banding patterns (G. Hide et al. Molec. Bioch. Parasitol. 39, 213-226, 1990). In this study, we extend this analysis to examine the relationships between trypanosome stocks isolated from major sleeping sickness foci in Zambia, Kenya, and Uganda. We show that the trypanosome strains responsible for disease in Zambia are quite distinct from those sampled from the Kenya/Uganda foci. Furthermore, the human serum resistant stocks isolated from the Kenya/Uganda foci which were isolated from man (or from animals) were found to form a tight group in the cluster analysis, while stocks isolated from nonhuman sources in the same area or stocks from elsewhere were found in separate groups. Thus, the human infective trypanosome strains found in these foci may have common origins and have, perhaps, arisen by clonal selection from a common source.

Animals↗
PubMed1991

Comparison of the ramp versus standard exercise protocols.

To compare the hemodynamic and gas exchange responses of ramp treadmill and cycle ergometer tests with standard exercise protocols used clinically, 10 patients with chronic heart failure, 10 with coronary artery disease who were asymptomatic during exercise, 11 with coronary artery disease who were limited by angina during exercise and 10 age-matched normal subjects performed maximal exercise using six different exercise protocols. Gas exchange data were collected continuously during each of the following protocols, performed on separate days in randomized order: Bruce, Balke and an individualized ramp treadmill; 25 W/stage, 50 W/stage and an individualized ramp cycle ergometer test. Maximal oxygen uptake was 16% greater on the treadmill protocols combined (21.4 +/- 8 ml/kg per min) versus the cycle ergometer protocols combined (18.1 +/- 7 ml/kg per min) (p less than 0.01), although no differences were observed in maximal heart rate (131 +/- 24 versus 126 +/- 24 beats/min for the treadmill and cycle ergometer protocols, respectively). No major differences were observed in maximal heart rate or maximal oxygen uptake among the various treadmill protocols or among the various cycle ergometer protocols. The ratio of oxygen uptake to work rate, expressed as a slope, was highest for the ramp tests (slope +/- SEE ml/kg per min = 0.80 +/- 2.5 and 0.78 +/- 1.7 for ramp treadmill and ramp cycle ergometer, respectively). The slopes were poorest for the tests with the largest increments in work (0.62 +/- 4.0 and 0.59 +/- 2.8 for the Bruce treadmill and 50 W/stage cycle ergometer, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗