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Biomedical subjects

B J Allen

Publications and source records attributed to B J Allen.

At least 109 records · Page 6Linked to original sources
PubMed1990

Total-body nitrogen by neutron activation in maintenance dialysis.

The nutritional status of 35 patients on continuous ambulatory peritoneal dialysis (CAPD) was assessed by the traditional methods of dietary history and anthropometric measurements, and was compared with simultaneous measurements of dietary protein intake (DPI) calculated from urea generation rate and total-body nitrogen (TBN) assessment by prompt neutron activation analysis (PNAA). DPI as determined by dietary recall was significantly higher than calculated DPI (1.04 +/- 0.42 v 0.84 +/- 0.28 g/kg/d; P less than 0.001). Anthropometric measurements did not differ significantly from the predicted normal values for sex, height, and age. However, PNAA measurements of TBN demonstrated significant nitrogen depletion, being 88.2% of normal for males (P less than 0.001) and 87.5% of normal for females (P less than 0.002); TBN correlated significantly with DPI calculated from urea generation rate (P less than 0.05). Assessment of these 35 patients 17.5 +/- 4.4 months later, demonstrated that patients who died or suffered serious morbidity requiring transfer from CAPD (n = 10) had significantly lower TBN than those who remained on CAPD or underwent successful renal transplantation (n = 25): 80.0% v 93.2% of normal (P less than 0.01). No difference in anthropometric measurements was observed between the two groups of patients. Eleven patients on maintenance home or satellite hemodialysis underwent identical dietary, anthropometric, and TBN assessments and results were similar to those obtained in the CAPD population, although no correlation with calculated DPI and TBN was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1990

The potential of neutron capture therapy in the management of uncontrollable localised tumours.

The role of Neutron Capture Therapy for the treatment of uncontrollable, localised tumours is examined. Several boron carrier biochemicals are already in use for the selective accumulation of boron in cancer cells, and therapeutic boron concentrations have been achieved in glioblastoma and melanoma in animal models and in patients. Local control of glioblastoma and subcutaneous melanoma has been reported after thermal neutron irradiation. Different neutron beam requirements apply for the treatment of these cancers, in the former case a thermal beam is adequate but a more penetrating epithermal beam is needed for the treatment of deep-seated tumours. A thermal facility for small animal irradiations is available in Australia, and the development of a patient thermal/epithermal facility is under active consideration.

Boron↗
PubMed1990

Body protein of patients undergoing haemodialysis.

The total body protein status of 18 patients undergoing regular haemodialysis was assessed by measuring total body nitrogen (TBN) using in vivo neutron activation analysis (NAA). Eighteen healthy controls, who were selected according to their height, age and sex match with the patients were also measured. The male and female patients were both found to have lower mean values for total body protein (P less than 0.01, P less than 0.025 respectively) although they had similar weights compared with their matched controls. Seven patients were measured on further occasions and only two patients showed a change in their body protein. One female showed an increase of 11 per cent in body protein (with an increase of 25 per cent in body weight) after intensive nutritional repletion therapy. In vivo NAA provides a direct means of measuring body protein and is a reliable method to monitor changes with treatment regimes.

Adult↗
PubMed1990

Determination of total body water by Fourier transform infrared analysis.

A new technique for determining body water using deuterium isotope dilution and Fourier transform infrared (FTIR) analysis is described. The advantages of the FTIR over conventional dispersion and filter infrared instruments include greater flexibility through computer controlled operations and availability of 'on-line' analytical software. The technique was further improved by the development of a simple procedure for determining D2O concentration in untreated serum samples. A validation study of six normal adults showed that the fat-free-mass determined from the deuterium-space (total body water) correlated well with the results obtained by total body nitrogen (r = 0.997), total body potassium (r = 0.996) and anthropometric (r = 0.995) measurements.

Adult↗
PubMed1990

Changes in body protein composition following aortic reconstruction.

Major surgery initiates a stress response due to the body's neuroendocrine reaction which leads to a breakdown of muscle protein with an increased urinary nitrogen excretion and a negative nitrogen balance. In vivo neutron activation analysis (IVNAA) is a technique which measures total body nitrogen. A total of 23 IVNAA studies were performed in six patients having aortic reconstruction to assess the effect of this major operation on body nitrogen and to determine the time required for a return to the pre-operative state. Aortic surgery caused a mean decrease of 2.9% in bodyweight (from a mean of 65.4 kg to 63.5 kg) but a much greater decrease of 9.9% in total body nitrogen (from a mean of 1778 g to 1602 g). Only two of six patients had recovered to pre-operative values by the end of the study period which extended for a mean of 92 days.

Aged↗
PubMed1989

Factors determining maintenance of sinus rhythm after chronic atrial fibrillation with left atrial dilatation.

Successful therapy of atrial fibrillation (AF) has been reportedly influenced by a variety of factors including patient age, type of underlying heart disease, duration of arrhythmia, left ventricular function and left atrial (LA) size. To determine which of these factors are associated with maintenance of sinus rhythm after conversion, 43 patients with symptomatic chronic AF in the setting of a dilated left atrium (greater than or equal to 45 mm, range 45 to 78) were followed for at least 6 months after the return of sinus rhythm. Class IA drugs, IC drugs or amiodarone were used for therapy. Life table analysis showed sinus rhythm to be maintained in 81% for 6 months, 79% for 12 months and 60% for 24 months. Factors positively associated with success were conversion with drug therapy alone, duration of chronic AF less than or equal to 1 year, absence of mitral valve disease and LA dimension less than or equal to 60 mm (all p less than 0.05). Patient age, left ventricular function and presence of coronary disease were not associated with outcome. Thus, patients with moderate LA dilatation (45 to 60 mm) and a short duration of chronic AF can often be maintained in sinus rhythm, especially if they convert with pharmacologic intervention alone.

Aged↗
PubMed1989

Antiarrhythmic efficacy of solitary beta-adrenergic blockade for patients with sustained ventricular tachyarrhythmias.

To assess the efficacy and predictability of solitary beta-adrenergic blocker (BB) therapy for ventricular tachyarrhythmia (VT), 30 patients (16 men and 14 women) with a mean age of 55 years, who initially had sustained ventricular tachycardia (70%) or ventricular fibrillation (30%), were studied. Results of baseline arrhythmia tests showed VT on ECG monitoring in 57% of the patients, during exercise in 50%, induced by programmed stimulation in 69%, increasing to 86% during isoproterenol. BB therapy prevented inducible VT during programmed stimulation in 37% of the patients, prevented VT on ECG monitoring in 54%, and prevented VT during exercise in 83%. Long-term BB therapy was given to 24 of 30 patients, whereas six other patients with hemodynamically unstable VT during BB therapy received other long-term treatment. During a mean follow-up of 824 days, 6 of 24 patients had recurrent VT. BB therapy was discontinued in two patients because of side effects. Long-term success was predicted by left ventricular ejection fraction greater than 45%, absence of coronary disease, and age less than 60 years (all p less than 0.02). Neither suppression of arrhythmia during exercise testing, nor results of programmed stimulation or ECG monitoring were predictive of outcome. Thus beta-adrenergic blockers can be effective as solitary antiarrhythmic therapy in selected patients with VT.

Adrenergic beta-Antagonists↗
PubMed1989

Magnesium therapy of cardiac arrhythmias in critical-care medicine.

A common complication of critically ill patients is cardiac tachyarrhythmia. The role played by magnesium is not well appreciated. Well-documented cases indicated that magnesium may be effective in controlling the rhythm when conventional methods fail. The following tachyarrhythmias respond favorably to magnesium: (1) intractable ventricular tachycardia and fibrillation, whether hypo- or normomagnesemic, (2) torsades de pointes, (3) digitalis-toxic ventricular tachyarrhythmia, (4) multifocal atrial tachycardia and (5) hypomagnesemic atrial tachyarrhythmia. It is recommended that 10-15 ml of 20% MgSO4 be infused over 1 min, followed by 500 ml of 2% MgSO4 over 5 h. A second 500 ml over 10 h may be necessary. Renal failure, disappearance of deep tendon reflex, rise in serum Mg above 5 mEq/l, drop in systolic blood pressure below 80 or drop in pulse below 60 contraindicate the continued use of magnesium. If serum potassium is at or falls below 4.0 mEq/l, 20-40 mEq/l KCl should be added. Magnesium deficiency can be confirmed by a low serum level or by a greater than 50% retention of administered magnesium. The causes of magnesium deficiency can be remembered under 10 DS: (1) Diarrhea and gastrointestinal losses, (2) Diuretics and renal losses, (3) Diabetes and endocrine causes, (4) Dietary lack, (5) Diverted to free fatty acids, (6) Drugs such as cisplatin, (7) Drinking alcohol to excess, (8) Delivery with toxemia, (9) Decompensated heart, lungs or liver and (10) Denuded skin, such as burns.

Arrhythmias, Cardiac↗
PubMed1988

Exercise testing in patients with life-threatening ventricular tachyarrhythmias: results and correlation with clinical and arrhythmia factors.

The results of exercise treadmill stress testing were analyzed in 64 consecutive patients presenting with either ventricular fibrillation (42%) or hemodynamically significant ventricular tachycardia (58%). Underlying diseases included coronary artery disease (55%), dilated cardiomyopathy (16%), and miscellaneous disorders (29%). Patients were additionally studied with ambulatory electrocardiographic monitoring and programmed stimulation. During exercise testing, 22 patients (34%) had nonsustained and five (8%) had sustained ventricular tachycardia. No patient experienced ventricular fibrillation or a major complication during exercise testing. Patients with a history of ventricular fibrillation were significantly less likely to have exercise-induced ventricular tachycardia than those with a history of ventricular tachycardia. Other clinical factors were not associated with the results of exercise testing. The results of programmed stimulation did not correlate with the results of exercise testing. Ventricular tachycardia was commonly documented during ambulatory monitoring (72%), but this was not predictive of ventricular tachycardia during exercise. However, patients who did not have ventricular tachycardia during ambulatory monitoring were predictably unlikely to have it during exercise testing (p less than 0.002). Thus exercise testing is safe and can provoke ventricular tachycardia in a significant proportion of patients with life-threatening arrhythmias.

Cardiac Pacing, Artificial↗
PubMed1988

Beta-blocker therapy in patients with ventricular tachyarrhythmias in the setting of left ventricular dysfunction.

Although several studies suggest beta blockers (BB) are effective in suppressing ventricular arrhythmias, less is known about their role in the treatment of patients with ventricular tachyarrhythmias associated with impaired left ventricular function. To assess the tolerance and efficacy of these agents, 32 patients presenting with either ventricular fibrillation (18) or sustained ventricular tachycardia (14) were studied during BB therapy. Left ventricular dysfunction (mean ejection fraction 29%) was present as a consequence of coronary artery disease (26) or cardiomyopathy (6). Baseline arrhythmia assessment revealed recurrent ventricular tachycardia in all patients. Antiarrhythmic drug therapy including BB was guided by programmed stimulation (10), exercise testing (8), ambulatory monitoring (12), or was given empirically (2). Beta blockers were well tolerated, as measured by exercise duration, which improved significantly, and by long-term maintenance, which continued in 23 of 32 (72%) patients. Over a mean follow-up of 668 days, patients treated with BB had a relatively low incidence of both sudden (3%) and nonsudden (9%) death. Thus, BB can be effective and well tolerated adjunct therapy in patients with a history of ventricular tachyarrhythmias in the setting of impaired left ventricular function.

Adrenergic beta-Antagonists↗
PubMed1988

Induction of double-strand breaks following neutron capture by DNA-bound 157Gd.

Irradiation of plasmid DNA/Gd3+ mixtures with thermal neutrons induces DNA double-strand breaks (dsb). However, the extent of breakage is markedly reduced by sequestering the Gd3+ from DNA by addition of EDTA. Since the 157Gd neutron capture event involves some internal conversion, we suggest that the DNA dsb induction results from Auger electron emission.

DNA↗