Biomedical subjects
N W White
Publications and source records attributed to N W White.
Workmens' compensation and byssinosis in South Africa: a review of 32 cases.
Byssinosis has been compensable in the Republic of South Africa (RSA) since 1973. The legal and administrative provisions for byssinosis compensation are reviewed. A series of 32 cases of presumed byssinosis was submitted to the compensation authorities by the authors. Identical reports were submitted to an independent medical panel. The findings and outcomes in these cases are presented and compared. Seventeen of the 32 claims initially received compensation and four were subsequently accepted following appeals. Analysis of the medical basis of decision making indicated that seven claims were refused and at least four had their awards reduced as a consequence of inconsistent decisions. Arguable decisions resulted in five claims being refused and one award being reduced. Our experience illustrates problems inherent in the compensation system in South Africa. Initiation of a claim is expensive relative to wages in the industry, and awards are low since they are linked to wages (mean $60.47 per week). Processing of a claim took a mean of 13.8 months, while appeals for refusal to compensate took a further 29.8 months. It is argued that consensus medical definitions of compensable occupational disease should be used routinely and that provision must be made to facilitate entry of claimants into the compensation system.
Silicosis among gemstone workers in South Africa: tiger's-eye pneumoconiosis.
Six cases of silicosis in workers involved in the processing of semiprecious gem stones have been seen in our clinic since 1976. They had been employed as stone sculptors in lapidaries where they processed tiger's-eye, rose quartz, amethyst, quartz crystal, and a variety of other locally occurring semiprecious stones. In five of the cases, exposure was in small and poorly regulated lapidaries without specific dust control measures. The sixth was detected during the course of a health and hygiene survey (including dust sampling) that was conducted in one of two lapidaries still operating in our area. Progressive massive fibrosis (PMF) or accelerated silicosis was noted in four of the six cases, three of whom had progression of their disease after cessation of exposure. With the development of PMF, the initial restrictive pulmonary function abnormalities were followed by steadily worsening airflow obstruction. Lung biopsies confirmed silicosis in three cases. Tuberculosis was confirmed in two cases and suspected and treated in a third. Workmen's Compensation was awarded in five cases. The survey confirmed that in semiprecious gem stone processing, the risk of silicosis appears to be confined to stone sculptors. Tried and proven techniques of general and local exhaust ventilation combined with water or oil to control dust at source were capable of effectively reducing dust emission to acceptable levels.
Asthma and hyperthyroidism. A report of 4 cases.
For many years it has been known that thyrotoxicosis can worsen asthma, increasing both the frequency and severity of asthma attacks and increasing requirements for medication. Clinical recognition of this association may be difficult. Thyrotoxic asthmatics frequently experience side-effects from medications, particularly beta-receptor agonists and theophyllines. Four case reports of asthmatics in whom thyrotoxicosis was diagnosed are presented. All 4 patients improved on returning to euthyroid status. The mechanism responsible for the harmful interaction is not known.
Comparison of dissection rates and angiographic results following directional coronary atherectomy and coronary angioplasty.
Directional coronary atherectomy is a new percutaneous transluminal technique for treating occlusive coronary artery disease. In this study, angiographic results (i.e., residual stenosis and angiographic evidence of postprocedure dissection) after directional coronary atherectomy and balloon angioplasty were compared. The atherectomy group consisted of 91 lesions in 83 consecutive patients who underwent either left anterior descending artery or right coronary artery atherectomy. The angioplasty group consisted of 91 lesions in 84 patients that were matched with the atherectomy lesions with respect to vessel and whether the lesion was a restenosis lesion. The mean preprocedure diameter stenosis was 76% in both groups as measured quantitatively with electronic calipers. After the procedure, the mean residual diameter stenosis of the atherectomy lesions was 13 +/- 17%, whereas for the angioplasty lesions it was 31 +/- 18% (p less than 0.001). Success rates in both groups were similar (94.5 and 93.4%, respectively). The incidence of postprocedure dissection was 11% in the atherectomy group and 37% in the angioplasty group (p less than 0.0001). Directional coronary atherectomy results in significantly improved postprocedure angiographic appearances due to significantly less severe residual stenosis and lower incidence of dissection.
Venous thrombosis and rifampicin.
In a retrospective analysis of clinically diagnosed and lower limb deep vein thrombosis (DVT) proven by contrast venography, DVT complicated admissions in 46 (3.4%) of 1366 adult patients treated in a tuberculosis hospital during 1986. Analysis of 7542 admissions during 1978-86 showed a relative risk of 4.74 in patients treated with regimens including rifampicin compared with other regimens. DVT was significantly more common in winter months and usually occurred within 2 weeks of treatment being started. This probable association between rifampicin and DVT does not contraindicate use of this drug, but measures to prevent DVT should be taken in inpatients receiving rifampicin.
Byssinosis in South Africa. A survey of 2411 textile workers.
The first study of the prevalence of byssinosis in the South African cotton textile industry is described. Questionnaires were administered to 2411 subjects from six textile mills. Height and weight were measured and pulmonary function was tested before and after the first shift of a working week. Dust concentrations were measured using a Lumsden-Lynch vertical elutriator sampler. The prevalence of byssinosis (all grades) according to work departments was as follows: spinning 11.2%, winding 6.1%, and weaving 6.4%. Subjects with symptoms of byssinosis had a significantly reduced forced expiratory volume in 1 second (FEV1) and FEV1/forced vital capacity ratio when compared with controls matched for age, height and weight. Dust concentrations in many areas of the preparation and spinning processes exceeded the World Health Organisation's recommended permissible exposure limit for cotton dust in spinning operations. The prevalence of byssinosis in this study appears to be lower than that documented elsewhere. The mill design, machinery in use and environmental conditions in the South African cotton textile industry appear to be similar to those in Egypt and the USA before 1978. South Africa differs from these and other countries, including the UK, in having an exceptionally high labour turnover rate, which has reduced exposure periods. The subjects were found to have a high prevalence of previously treated pulmonary tuberculosis (3.4% for males and 2.2% for females), and in this population this disease appeared to cause more respiratory impairment than byssinosis.(ABSTRACT TRUNCATED AT 250 WORDS)
Bilateral chorea associated with caudate nuclei lacunar infarcts. A case report.
A woman with ischaemic heart disease, hypertension and diabetes, who presented with bilateral chorea associated with lacunar infarcts in the caudate nuclei, is described.
Clinical applications of intravascular ultrasound imaging in atherectomy.
This paper discusses the potential application of intravascular ultrasound imaging in the context of catheter-based atherectomy. The advantages and limitations of ultrasound in this application are discussed, and representative cases are presented.
Intravascular ultrasound: catheter-based Doppler and two-dimensional imaging.
Intracoronary Doppler and two-dimensional imaging devices have been developed to aid in the search for more precise information about vessel pathology and local vessel hemodynamics. Measurement of coronary flow reserve using Doppler catheters has been well-validated experimentally and is being used clinically in certain groups of patients. Current designs using Fast-Fourier Transform of the signal and real-time video spectral display allows for instantaneous modification in positioning of the catheter within the artery to minimize artifacts. Studies are underway to assess whether measurement of coronary flow reserve and estimations of absolute flow add practical information to the quantitative assessment of vascular disease. Contrast angiography has been the "gold standard" for in vivo study of vascular disease. The recent development of two-dimensional imaging catheters has potentially opened up a new frontier of clinical assessment of vessel pathology. Imaging catheters can be used in a diagnostic role as a means of guiding therapeutic interventions. Direct analysis of the radiofrequency output of the catheter may allow for more precise characterization of plaque composition.
Pharmacokinetic evaluation of the digoxin-amiodarone interaction.
Amiodarone is known to raise serum digoxin levels. This study was designed to evaluate the pharmacokinetic basis of this interaction in 10 normal subjects. The pharmacokinetic variables for digoxin were determined after a 1.0 mg intravenous dose of digoxin in each subject, before and after oral amiodarone, 400 mg daily for 3 weeks. During amiodarone administration, systemic clearance of digoxin was reduced from 234 +/- 72 ml/min (mean +/- standard deviation) to 172 +/- 33 ml/min (p less than 0.01). This was due to reductions in both renal clearance (from 105 +/- 39 to 84 +/- 15 ml/min) (p less than 0.05) and nonrenal clearance (from 130 +/- 38 to 88 +/- 20 ml/min) (p less than 0.01). Digoxin half-life of elimination was prolonged from 34 +/- 13 to 40 +/- 16 hours (p less than 0.05). Digoxin volume of distribution was not significantly changed. Amiodarone caused a three- to fivefold increase in serum reverse triiodothyronine levels, but changes in thyroid function were not quantitatively related to the changes in digoxin pharmacokinetics. These alterations in digoxin pharmacokinetics produced by amiodarone explain the increase in serum digoxin level that has been observed when this drug combination has been used clinically.