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Biomedical subjects

R R Lewis

Publications and source records attributed to R R Lewis.

At least 55 records · Page 3Linked to original sources
PubMed1987

Plasma concentrations of mianserin after single dose and at steady-state in depressed elderly patients.

Plasma mianserin and desmethylmianserin concentrations were measured in 17 clinically depressed elderly patients after a single 30 mg dose of mianserin. The patients then received mianserin 30 mg daily for up to 6 weeks and the plasma concentrations were measured at weekly intervals. The relationship between concentrations of mianserin and desmethylmianserin at steady-state and at 16 and 24 hours after the single test dose was not good enough to be used for prediction of dosage requirements. Reasons for this finding are discussed.

Aged↗
PubMed1986

Transcranial measurement of blood velocities in the basal cerebral arteries using pulsed Doppler ultrasound: a method of assessing the Circle of Willis.

Transcranial pulsed Doppler ultrasound and spectral analysis were used for detection of blood velocities in the basal cerebral arteries. The Doppler transducer was placed superior to the zygomatic arch and during insonation of the middle cerebral artery care was taken to obtain maximum Doppler-shift frequency signals since this allowed a small angle between the ultrasound beam and this artery. Doppler signals were obtained from the middle, anterior, and posterior cerebral arteries in 20 volunteers with the average depth of the Doppler gate at 4.9 (4.6-5.2 cm), 5.2 (4.9-5.4 cm), and 6.3 cm (6.0-6.9 cm), respectively. These measurements were in agreement with those obtained for 15 cadaver studies, in whom the distance from the proposed site of the Doppler transducer to each basal cerebral artery was measured as 4.7 +/- 0.6, 5.3 +/- 0.5, and 5.9 +/- 0.9 cm, respectively. The reproducibility of middle cerebral artery blood velocity values was tested in seven subjects and showed a variation of not more than 8% in any individual. The method was used in combination with common carotid compression to assess four patients who had occlusive extracranial carotid disease; in three the disease was more severe on one side and reversal of blood flow in the proximal ipsilateral anterior cerebral artery was demonstrated, consistent with cross flow from the contralateral side via the anterior communicating artery of the Circle of Willis. In the fourth patient augmentation of posterior cerebral artery blood velocities during common carotid compression indicated the major collateral source was from the vertebrobasilar system.

Adult↗
PubMed1985

Red blood cell velocity changes with age and sex in the common carotid and supra-orbital arteries.

Doppler-shifted ultrasound and spectral analysis were used to assess signals from the resting supra-orbital artery and the common carotid artery at the base of the neck of 658 (270 male, 388 female) asymptomatic subjects aged 5 to 90 years. The sonagrams obtained showed two peaks (A and B) during cardiac systole. The ratio of these peaks (A/B) decreased from 20 to 50 years and then levelled out. The male A/B ratios from both arteries were higher than those for the females between 20 and 50 years, and for the common carotid these differences were highly significant (P less than 0.001).

Adolescent↗
PubMed1985

Erythrocyte flow velocity changes with age and sex in augmented supraorbital, superficial temporal and common carotid pulses.

Doppler-shifted ultrasound and spectral analysis were used to assess signals from augmented supraorbital and superficial temporal pulses, and the common carotid pulse 4 cm above the base of the neck of 658 (270 male, 388 female) asymptomatic subjects aged 5-90 years. The sonagrams obtained showed two peaks (A and B) during cardiac systole and the ratio of these peaks (A/B) decreased between the ages of 20 and 50 years, and then levelled out. Mean male values of common carotid sonagrams were significantly higher than female values during this age range (p less than 0.001).

Adolescent↗
PubMed1984

Doppler ultrasound screening for arterial disease in elderly stroke patients.

Doppler-shifted ultrasound and spectral analysis were used to assess the carotid arteries of 77 elderly stroke patients, which represented 154 carotid bifurcations. Severe carotid disease was demonstrated at 19 of the 154 carotid bifurcations and in eight of these complete occlusion of the internal carotid artery was present. In 12 of the 19 instances the severe disease was in the internal carotid artery associated with the stroke. Localized carotid bruits were present in five patients and only three of these were associated with severe disease of the internal carotid artery. Minor disease was detected in 80 of the 154 carotid bifurcations and no disease was detected at the remaining 55 carotid bifurcations. An abnormally low ankle/arm systolic pressure ratio, which indicated occlusive arterial disease of the legs, was obtained in 19 of the 43 patients examined. No relationship was found between the severity of carotid artery disease and the presence of haemodynamically significant disease of the lower limbs. Ultrasound measurement of aortic compliance gave significantly lower values in elderly stroke patients compared to elderly asymptomatic volunteers. Comparison of flow-velocity transit times from the stroke-affected and non-affected limbs showed no consistent effect of the stroke on vascular tone in the patients assessed.

Aged↗
PubMed1984

Rapid diagnosis of urinary tract infection using a simple photometer.

A photometric method which detects bacterial multiplication in urine is described. The apparatus is both inexpensive and easy to use, and results are obtained within four hours. A total of 217 urine specimens from 181 patients were assessed and the results compared with the corresponding laboratory tests, which showed a significant growth in 102 specimens. The sensitivity and specificity of the photometric method was 77% and 99%, respectively, with a positive accuracy of 99%. The photometer detected 83% of significant enterobacterial infections and 76% of mixed infections. It is suggested the false negative results (23%) may have included high laboratory colony counts not associated with active urinary tract infection.

Adult↗
PubMed1983

Toxicological investigations in the detection of drug-induced disease in elderly patients.

1 During 1978--1980 general toxicological investigations were performed on specimens from 211 patients (62 male, 149 female) aged 65 years and over. 2 The investigations were an important factor in establishing the diagnosis in 32 of 91 (28 male, 63 female aged 65--92 years, median 73 years) poisoned patients, most (75) of whom had deliberately taken overdoses. 3 Seventy-one patients were severely poisoned (grade 3--4 coma) and 10 died. Benzodiazepines (49%) and barbiturates (43%) were the drugs encountered most frequently, although 54% had ingested more than one pharmaceutical preparation. 4 In the survivors the depth of coma was usually greatest in patients poisoned principally with barbiturates, whilst the duration of coma and the incidence of respiratory complications were greater in those poisoned with benzodiazepines. However, there was considerable variability in the depth and duration of coma associated with a given initial plasma concentration within both groups. 5 Although general toxicological investigations can provide useful diagnostic information when poisoning is suspected in elderly patients, unequivocal interpretation of the results obtained is not always possible.

Aged↗
PubMed1982

Detection of carotid bifurcation disease: comparison of ultrasound tests with angiography.

Doppler-shift ultrasound with spectral analysis permits the measurement of the relative heights of systolic peaks (the A/B ratio) in blood velocity sonograms from supra-orbital and common carotid arteries, the temporal artery occlusion test, the common carotid resistance index and transit times of flow-velocity waves in the internal carotid pathway. The results are compared with 201 carotid angiograms and expressed in terms of sensitivity (true positive) and specificity (true negative). Supra-orbital and common carotid A/B ratios, in combination with the temporal artery occlusion test, detected all grades of carotid artery disease with a sensitivity of 72 per cent and a specificity of 93 per cent. The corrected transit time gave a sensitivity of 57 per cent and a specificity of 89 per cent, whilst the Resistance Index gave a sensitivity of 60 per cent and a specificity of 80 per cent. The values of ultrasound parameters associated with severe disease, defined as reductions in lumen diameter of 75 per cent or more, of the internal carotid artery are examined. The temporal artery occlusion test gave a sensitivity of 91 per cent and a specificity of 94 per cent. These results were more accurate than those obtained for the corrected transit time (sensitivity 83 per cent, specificity 92 per cent) and for the Resistance Index (sensitivity 75 per cent and specificity 92 per cent). The results show that of the tests described the supra-orbital and common carotid artery A/B ratios, together with the temporal artery occlusion test, gave the best sensitivity and specificity for detection of both severe and minor carotid bifurcation disease.

Adolescent↗
PubMed1982

Assessment of a new calendar pack--the 'C-Pak'.

Seventy-eight elderly patients in hospital were studied for up to four weeks to assess drug compliance. Forty patients received medication from individualized calendar packs ('C-Pak') and 38 received medication from standard bottles. There was no difference in compliance between the two groups, the percentage error for each group being 26%. This result suggests that C-Pak is unlikely to improve drug compliance in unselected elderly patients.

Aged↗
PubMed1981

Nortriptyline therapy in elderly patients: dosage prediction from plasma concentration at 24 hours after a single 50 mg dose.

Ten depressed elderly female patients in hospital (mean age 82 years) received a single oral dose of 50 mg nortriptyline prior to commencing treatment with this drug. The nortriptyline concentration in a plasma sample obtained 24 hours afterwards was used to predict the daily dose required to achieve a steady-state concentration within the range of 50-150 micrograms. l-1. The mean daily dose prescribed was 50 mg (range 20-100 mg). These dosage regimes provided a mean observed steady-state nortriptyline concentration of 104 micrograms. l-1, with a range of 76-180 microgram. l-1 (S.D. 30 microgram. l-1). Use of this prediction test can prevent the development of toxic plasma concentrations and enhance the possibility of therapeutic success.

Aged↗
PubMed1980

Diagnosis by ultrasound of severe carotid artery disease in patients undergoing cardiopulmonary bypass operations.

A non-invasive method using continuous wave Doppler shift ultrasound and spectral analysis was used as a screening test for severe carotid artery disease in patients undergoing cardiopulmonary bypass operations. One hundred and eighty-eight patients were examined before cardiac surgery (91 for ischaemic heart disease, 17 for ischaemic heart disease and valve replacement, 66 for valve replacement alone, and 14 for congenital abnormalities). The mean age of the 108 patients suffering from ischaemic heart disease was 54 years (+/- 8) and that of the 80 patients admitted either for valve replacement alone or for congenital abnormalities was 52 years (+/- 12). Five of the 108 patients suffering from ischaemic heart disease were found to have severe occlusive disease of the internal carotid artery by the ultrasound test, while the test was normal in the other two groups. Patients with severe carotid artery disease proceeded to carotid arteriography and endarterectomy before the planned heart operation.

Cardiac Surgical Procedures↗
PubMed1980

Detection of disease at the carotid bifurcation using ultrasound--including an imaging system.

A two-stage approach is described for the detection of occlusive arterial disease at the carotid bifurcation using continuous wave Doppler-shift ultrasound with spectral analysis of backscattered signals from erythrocytes. The first stage involves analysis of Doppler-shift signals from the supraorbital and common carotid arteries. Abnormal signals from these arteries are frequently caused by the presence of atheroma at the carotid bifurcation and are used to indicate the necessity for imaging the bifurcation. This latter technique produces a physiological image of the arteries, as it depends on detecting erythrocyte velocities beneath a transducer which is guided over the surface of the neck. The investigation has advantages over arteriography in that it is noninvasive, has no attendant risk and may be repeated as often as required.In order to evaluate the accuracy of these methods the results have been compared with x-ray findings in patients undergoing carotid arteriography. In 20 comparisons there were no false positives and one false negative in which the arteriogram showed a small lesion. These results indicate that the two noninvasive methods may be used in sequence to demonstrate operable disease around the carotid junction.

Adult↗