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Biomedical subjects

M MacMahon

Publications and source records attributed to M MacMahon.

15 recordsLinked to original sources
PubMed1996

Syncope: driving advice is frequently overlooked.

Consecutive referrals to a syncope clinic were asked about the frequency of enquiries about driving status by referring general practitioners and/or hospital specialists. Although 40% were drivers, only 13% of patients had been previously asked about driving, and 12% of drivers had experienced symptoms whilst driving. This represents an important oversight on the part of referring doctors.

Adult↗
PubMed1996

[Evaluation of trough/peak ratio of indapamide 1.5 mg sustained-release form assessed by ambulatory blood pressure monitoring].

Because of the high variability of casual blood pressure measurements. ABPM has become a complementary clinical tool for evaluating antihypertensive treatment. Nevertheless, there is still a lack of practical guidelines to interpret the data. A review of the literature shows that ABPM efficacy data are analyzed differently, especially the trough-to-peak ratio proposed by the Food and Drug Administration. Published trough-to-peak ratios are widely disparate due to the diversity of the calculation methods which are most often not justified. Thus inappropriate comparisons of these results can easily produce incorrect conclusions. The aim of this review is to select, through the literature, basic methodological requirements commonly agreed on for accurate assessment of trough-to-peak ratio, and to apply them to the ABPM data on indapamide, a diuretic related to the thiazides. Six methodological requirements commonly agreed on at this time are the following: 1. study design: placebo-controlled study with a placebo run-in period; 2. patients selection: compliance with the study protocol, record obtained before and after treatment for each patient; 3. population analysis: whole and responder population: 4. quality control of the records: 5. placebo effect subtraction; 6. global and individual calculation with the indication of median values. Given that, no T/P ratio, especially for a diuretic, has yet been calculated according to these requirements, the above methodological points were taken into account for the T/P calculation of indapamide, from a placebo-controlled dose-finding study involving 285 patients.

Adult↗
PubMed1995

Combined bezafibrate and simvastatin treatment for mixed hyperlipidaemia.

The safety and efficacy of combined bezafibrate-simvastatin therapy was evaluated in 49 patients with diet-resistant mixed hyperlipidaemia (type IIb). After a two-month placebo phase, patients were randomized to receive either Bezafibrate Slow Release (SR) 400 mg mane or simvastatin 20 mg nocte followed by three months combination therapy. Total cholesterol, triglycerides and high-density lipoprotein (HDL) cholesterol were measured at monthly intervals. Apolipoproteins (apo) A1 and B, lipoprotein (a) [Lp(a)] and fibrinogen were measured before and after each treatment. Simvastatin was more effective than Bezafibrate SR in reducing total cholesterol (2.0 vs. 1.1 mmol/l, p = 0.003) and lowering LDL cholesterol (1.7 vs. 0.4 mmol/l, p = 0.0001) whereas Bezafibrate SR was more effective in reducing triglycerides (by 41% vs. 17%, p = 0.001) and fibrinogen (by 23% vs. 3%, p = 0.004). Compared with simvastatin monotherapy, combined drug therapy induced further reductions in triglycerides (by 26%, p = 0.0003) and apoB (by 11 mg/dl, p = 0.03) and an increase in apoA1 (by 21 mg/dl, p = 0.0008). Symptomatic and biochemical adverse events did not occur more frequently on combined drug therapy than on monotherapy. The combination of bezafibrate and simvastatin was more effective in controlling mixed hyperlipidaemia than either drug alone and did not provoke more adverse events.

Adolescent↗
PubMed1995

Haemodynamics, cardiac conduction and pharmacokinetics of mibefradil (Ro 40-5967), a novel calcium antagonist.

OBJECTIVES: Mibefradil (Ro40-5967) is a chemically novel non-dihydropyridine calcium antagonist. In this phase II study we compared its acute and chronic effects on blood pressure, heart rate and atrioventricular conduction (electrocardiographic PQ interval) with those of verapamil and diltiazem. PATIENTS AND METHODS: After a 4-week placebo run-in, 18 patients with mild to moderate essential hypertension were given single doses of mibefradil (150 mg), slow-release (SR) verapamil (240 mg), diltiazem (240 mg) and placebo at weekly intervals; pharmacokinetics and the effects on blood pressure, heart rate and PQ interval were studied on four 10-h study days. Seventeen of the same patients subsequently underwent 4 weeks of treatment with either mibefradil (100 mg daily; n = 10) or verapamil SR (240 mg daily; n = 7), and on the last day, they attended a further 10-h study day. Two studies were conducted: an acute, single-dose, double-blind, randomly allocated, placebo-controlled, crossover study and a chronic, open-label, randomly allocated, parallel-group study. RESULTS: Mibefradil was well tolerated. In the acute study, the antihypertensive effect (difference from placebo) of mibefradil 150 mg was of slower onset than that of verapamil or diltiazem, but comparable blood pressure reductions had been achieved by 6 h. The mean +/- SD maximal PQ prolongation (difference from placebo) was 15.6 +/- 16.1 ms, compared with 44.0 +/- 22.6 ms for verapamil and 56.0 +/- 48.9 ms for diltiazem (P<0.05 mibefradil versus verapamil; P<0.01 mibefradil versus diltiazem). In the chronic study there were no significant differences during steady-state conditions between mibefradil at 100 mg and verapamil SR at 240 mg in their effects on blood pressure, PQ and heart rate. The mean +/- SD elimination half-life (t1/2) of mibefradil under steady-state conditions was 26.8 +/- 5.5 h (versus an apparent t1/2 of 16.9 +/- 11.1 h for verapamil SR, P<0.05). CONCLUSIONS: Mibefradil is a well-tolerated and efficacious antihypertensive agent well suited to single daily dosing because of its intrinsic long plasma half-life. The effects on both blood pressure and PQ interval are of more gradual onset than those of unmodified verapamil and diltiazem after single doses.

Adolescent↗
PubMed1994

Small intestinal bacterial overgrowth--an incidental finding?

OBJECTIVES: To assess the prevalence of typical clinical features and need for treatment of small intestinal bacterial overgrowth (SIBO) in the elderly. DESIGN: Random selection of patients, regardless of their nutritional status. SETTING: Acute admissions ward in the Dept. of Medicine for the Elderly. PATIENTS: Thirty elderly patients between 68 and 90 years of age. MEASUREMENTS: Active clinical problems, including the presence of recent weight loss and diarrhea, were recorded. Routine blood tests, including serum vitamin B12, red cell folate, albumin and calcium, and qualitative small bowel bacteriology results, were analyzed. The effect of age on all variables was studied. RESULTS: Twenty of the 30 small bowel aspirates had proven SIBO, and strict anaerobes were isolated in 15. The mean blood test values did not differ significantly between culture-positive and culture-negative patients. There was no significant correlation between those variables and the total bacterial counts. Of the 20 proven SIBO cases, eight had anemia, five had hypoalbuminemia, five had diarrhea, four complained of recent weight loss, and none had B12 deficiency. Alternative causes other than SIBO were identified for many of these abnormalities. Advancing age correlated significantly with rising counts of small bowel strict anaerobes. CONCLUSIONS: These data suggest that age may be a predisposing factor in the development of anaerobic overgrowth but that SIBO is a benign entity in the elderly. Contrary to previous recommendations, treatment of this condition is not routinely indicated.

Age Factors↗
PubMed1993

Observing the brachial artery through a pressure cuff.

A technique is described which enables ultrasonic imaging of the brachial artery whilst pressure is applied via a pressure cuff. This involves a new instrument--a sphygmomanometer, which uses water as opposed to air as the pressure medium, in order to permit ultrasonic imaging through the cuff. The technique was found to be acceptable in the clinical setting, and gave a measurement of the systolic blood pressure which correlated with the conventional cuff measurement in eleven elderly subjects (r = 0.89, p < 0.001). The technique should have an important role to play in studying the origin of differences which occur between direct and indirect blood pressure measurements.

Blood Pressure Determination↗
PubMed1993

Measurement of arterial closing pressure.

It has been suggested that certain artifacts in blood pressure measurement by auscultation stem from stiffness of the tissues underneath the pressure cuff, resulting in a component of cuff pressure being required to overcome resistance to brachial artery collapse. This paper describes a technique for measuring the pressure required to collapse a segment of the brachial artery which has been isolated from central arterial pressure. This measurement is termed the arterial closing pressure. In a study of eleven elderly subjects, the artery collapsed spontaneously (zero closing pressure) after being isolated from central pressure in seven subjects. The remaining four required external pressures ranging from 4.6 to 10.7 kPa (35 to 81 mmHg) in order to collapse the artery. Thus arterial closing pressure may frequently be a significant fraction of arterial blood pressure in the elderly population, and may contribute to error in the measurement of blood pressure by auscultation. Arterial closing pressure may be a useful tool for investigating the origin of differences between indirect and direct blood pressure measurements, and also in the investigation of spontaneous arterial closure.

Aged↗
PubMed1993

Endoscopic retrograde cholangiopancreatography in the elderly: a single unit audit.

Endoscopic retrograde cholangiopancreatography (ERCP) has an established role in the management of pancreato-biliary disease, but its role in elderly patients has not been evaluated. A prospective study was carried out in 50 elderly patients, aged between 65 and 94 years, to compare the sensitivity and specificity of ERCP in this age group with ultrasound and liver blood tests, and to examine its safety and therapeutic effectiveness. ERCP was successful in 46 of 50 (92%) procedures. Thirty-four patients had abnormal findings, and 18 sphincterotomies were performed. No complications were recorded. There was a poor correlation between ultrasound and ERCP with agreement in only 45% of cases; sensitivity 35% and specificity 75%. Liver blood tests, alkaline phosphatase and gamma-glutamyl transferase were elevated in all 30 cases with obstructed ducts on ERCP. Ultrasound revealed obstruction in only 10 (33%) of these. Thus, liver biochemistry proved a more reliable indicator of biliary obstruction than ultrasound. In 22 cases endoscopic stone clearance or demonstration of inoperable lesions obviated surgery while in 9 cases surgery was indicated, because of multiple large stones not cleared at ERCP, or for bypass of a malignant stricture. ERCP is therefore safe and effective with a high diagnostic and therapeutic yield even in the poor risk elderly.

Aged↗
PubMed1981

Rectal mercury.

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Child, Preschool↗