The elderly patient. A special case for diuretic therapy.

Diuretics are among the most widely prescribed drugs, especially for the elderly with cardiac failure or hypertension. Progressive structural and functional changes occur in the kidneys after the fourth decade, leading to impairment of the ability of the kidneys to handle sodium, water and solutes. The renal reserves of the elderly are about half those of the young. In addition, the renin-aldosterone system shows reduced activity in old age. The pharmacokinetics and pharmacodynamics of diuretics in the elderly are reviewed, and the influence of congestive cardiac failure is emphasised with regard to the kinetics of diuretics and the deleterious effect of diuretic-induced hypokalaemia and hypomagnesaemia on the pharmacology of digoxin. Guidelines are suggested for the use of diuretics in the elderly, including the avoidance of unnecessary use, the careful choice of diuretic used, the need for small initial doses, and the prevention of hypokalaemia. The place of potassium-sparing agents for the elderly and adverse effects of diuretics, either mechanical, metabolic or toxic are discussed. Mechanical problems are related to the rate and volume of urine produced, and the resulting effects on bladder function and on blood volume. Although toxic effects are relatively rare, metabolic effects include electrolyte changes, impairment of glucose tolerance, and increased serum uric acid and lipids. Most of these adverse effects are preventable by careful management; the consensus is that they are not of sufficient clinical significance to outweigh the long record of efficacy and safety of diuretic therapy in the elderly. Diuretics will, and should, continue to be used extensively in elderly patients with hypertension and/or cardiac failure.

Imaging the carotid bifurcation using continuous-wave Doppler-shift ultrasound and spectral analysis.

A non-invasive method is described for visualizing the carotid bifurcation using a continuous-wave Doppler-shift technique simultaneously with spectral analysis of the blood velocities from all parts of the vessel lumen. The system is directional so that arteries can be visualized in the presence of signals from adjacent veins. The technique uses a transducer which is attached to a position-sensing arm so that the position of the ultrasound beam on the neck, when sensing arterial blood flow-velocities, can be translated onto a storage oscilloscope. By repeated passes of the transducer across the vessel lumen a 2 dimensional image of the carotid bifurcation is formed. As each image point is marked, the full spectrum of blood-velocities corresponding to that position is continuously displayed on a second oscilloscope beside the image scope. Ultrasound images are compared with arteriograms and both continuous-wave and pulsed Doppler ultrasound imaging systems are discussed.

Screening for carotid junction disease by spectral analysis of Doppler signals.

The established test for disease in the internal carotid artery using continuous wave Doppler is to listen for flow velocity changes over the supraorbital artery with ipsilateral temporal (or facial) artery compression. This is only reliable when there is a reduction in mean pressure (and flow) distal to disease in the internal carotid artery, ie reduction of lumen diameter by more than 85%. In this study, 101 vessel segments (48 with disease at the carotid junction, 53 normal) were compared with the results of angiography. Seven gave a positive temporal artery occlusion test, all of which showed severe disease. However, spectral analysis of the Doppler signals from supraorbital and common carotid arteries showed sonagram changes both with ageing and with disease. In particular, the ratio of primary peak (A) to secondary peak (B) in systole falls, the A/B ratio being lower in disease than in health. At A/B ratios less than 1.05 there was an 88% probability of disease at the carotid junction. 36/48 (75%) diseased junctions were detected, including almost all major lesions. The method did not so reliably detect small lesions (less than 2 mm plaques, less than 60% lumen diameter stenosis, and 'minimal atheroma'). In 5/53 normal junctions the A/B ratio was in the disease range. Scanning the carotid junction for turbulence yielded additional information in some cases.

Combined use of clofibrate and cholestyramine or DEAE sephadex in hypercholesterolaemia.

A comparison was made of the effect of DEAE (diethylaminoethyl) Sephadex (an anion exchange resin) and cholestyramine (Questran) with and without the addition of clofibrate in normal and hypercholesterolaemic patients. DEAE Sephadex (12-15 g/day) alone appeared to be as effective as cholestyramine in lowering the plasma cholesterol by 12-15%. Clofibrate acted synergistically with DEAE Sephadex and increased the activity of the latter by over twofold. This combination proved superior to that of clofibrate and cholestyramine and has the greatest potential use in the treatment of type II pattern hyperlipoproteinaemia.