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Biomedical subjects

R R Lewis

Publications and source records attributed to R R Lewis.

69 records · Page 4Linked to original sources
PubMed1980

Effects of a postexercise sauna bath on ECG pattern and other physiologic variables.

In an attempt to determine the risk of sauna bathing after heavy exercise, the responses of 10 clinically normal adult males (mean age 44 years) were observed and recorded for 26 min. during recovery from a standard, heavy exercise task on two separate days. On one of the 2d, recovery was interrupted by a 10-min (min 6-16) exposure to intense, dry heat (70-74 degrees C, 3-6% R.H.). The higher heart rate and rectal temperature during the treatment (min 6-16) and post treatment (min 16-26) phases on the experimental day were indicative of the expected response to the heat stress. Systolic blood pressure did not differ on experimental and control days during either phase of recovery, while diastolic blood pressure decreased during the heat exposure. Double product was higher during treatment and post-treatment phases on the experimental day indicating an increased myocardial O2 need in response to the heat. ECG (CM5) changes were limited to increased J-point displacement during the treatment phase on the experimental day, with S-T segment flattening (0.08 s) in one case, and prolongation of the Q-T interval (corrected for rate) with reduction in T-wave amplitude. The prolongation of electrical systole and T-wave flattening were not observed during exercise at comparable and higher heart rates and may be associated with reduced subendocardial perfusion. We concluded that sauna bathing of short duration after exercise represents a tenable risk for clinically normal males.

Adult↗
PubMed1979

Disease at the carotid bifurcation: diagnosis by Doppler ultrasound imaging.

A non-invasive method for visualising the carotid bifurcation using continuous-wave Doppler-shift ultrasound and spectral analysis is described. The system is directional so that arteries can be visualised without interference by signals from adjacent veins. The technique uses a transducer attached to a position-sensing arm so that the position of arterial flow-velocities can be translated onto a storage oscilloscope. A two dimensional image of the carotid bifurcation is formed by moving the transducer along the length of each vessel while repeatedly scanning across the vessel lumen. The clinical application of this technique is illustrated by some specific cases.

Adult↗
PubMedDate not supplied

Ultrasound screening for internal carotid disease-I. The temporal artery occlusion test--which periorbital artery?

Using continuous wave Doppler-shifted ultrasound and spectral analysis the response to the temporal artery occlusion test was compared when insonating the supraorbital and supratrochlear arteries of 203 internal carotid pathways. The test involved monitoring the periorbital artery whilst simultaneously compressing a single branch of the external carotid artery, the ipsilateral superficial temporal artery. In 41 instances carotid angiography demonstrated severe disease of the internal carotid artery, that is lesions of 75% or more reduction in lumen diameter. A positive response to the temporal artery occlusion test, when performed on the supraorbital artery, indicated severe disease with a sensitivity of 90% and a specificity of 89%. When this test was performed on the supratrochlear artery a low sensitivity of 36% was obtained, although specificity was high at 96%.

Angiography↗
PubMedDate not supplied

Ultrasound screening for internal carotid disease-II. Sensitivity and specificity of a single site periorbital artery test.

Supraorbital artery blood flow was examined non-invasively with continuous wave Doppler-shifted ultrasound and spectral analysis. The results were used to assess the ipsilateral internal carotid artery in 155 patients undergoing carotid angiography. The ultrasound parameters used were the temporal artery occlusion test and A/B ratios of both resting and augmented supraorbital sonagrams. A retrospective study showed this combination to have a sensitivity of 65% for internal carotid disease which did not encroach on the lumen and for all other angiographically demonstrated lesions an average sensitivity of 94% and specificity of 92%. Augmented supraorbital pulses were more sensitive for detection of carotid artery disease than resting supraorbital pulses. Of the 61 lesions in which both resting and augmented supraorbital A/B ratios were obtained, the augmented supraorbital pulse detected 48 (79%) whilst the resting supraorbital pulse detected 29 (48%). Localised carotid bruits were poor indicators of carotid artery disease, having a sensitivity of only 27%.

Angiography↗
PubMedDate not supplied

Doppler ultrasound assessment of the internal carotid artery following carotid endarterectomy.

Doppler-shifted ultrasound with spectral analysis was used to assess the internal carotid arteries of 48 patients who had undergone carotid endarterectomy (58 carotid endarterectomies). Three patients died in the immediate post-operative period, therefore 45 patients, who represented 54 endarterectomies, were assessed for up to six years following surgery (mean--thirty-four months). Ultrasound tests demonstrated total occlusion of the internal carotid artery in 7 patients within the first post-operative week. Sonograms from the supraorbital and common carotid arteries exhibit two peaks during cardiac systole (A and B). The post-operative A/B ratios were abnormal in 24 instances and these were associated with symptoms in seven. Of these 24, 7 developed severe disease in the internal carotid artery during the six year follow-up period; five were associated with symptoms. Post-operative A/B ratios were normal in 23 instances, 19 of which remained normal at follow-up. None of these nineteen developed symptoms. Only patients with abnormal post-operative A/B ratios subsequently developed severe occlusive disease in the internal carotid artery during the follow-up assessment. Thirty-eight patients underwent unilateral carotid endarterectomy, eight of whom had severe internal carotid artery disease at the contralateral bifurcation at the time of carotid endarterectomy. A further four patients developed severe occlusive disease in the contralateral internal carotid artery during the follow-up period, one of whom was symptomatic.

Adult↗
PubMedDate not supplied

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.

Adult↗
PubMedDate not supplied

Amitriptyline dosage prediction in elderly patients from plasma concentration at 24 hours after a single 100mg dose.

Fifteen depressed elderly patients (14 female, 1 male; mean age 85 years) received a single oral dose of amitriptyline. The concentration of amitriptyline plus nortriptyline in a blood sample taken 24 hours later was used to predict by means of a nomogram the amitriptyline dosage required for each patient. Each dose was selected to produce steady-state amitriptyline plus nortriptyline concentrations close to 140 micrograms/L. The daily dosage ranged from 20 to 100mg (mean 62mg). Patients received the individually calculated dose each night, and weekly blood samples were obtained for drug analysis. At 2 weeks, mean amitriptyline plus nortriptyline concentrations were 118 +/- 21 micrograms/L. Eight of the patients were studied for a further 2 weeks and the mean amitriptyline plus nortriptyline concentration was then 111 +/- 19 micrograms/L. The dose prediction test is easy to use and ensures each patient receives an adequate but safer dose of amitriptyline than might otherwise be prescribed routinely.

Aged↗
PubMedDate not supplied

An unusual cause of falls in an elderly patient.

Falls are common in the elderly, often causing considerable morbidity and mortality. Prevention is therefore important and is based on determining the cause. We present an elderly patient who had multiple falls during the day due to recurrent daytime sleep episodes, an entity we believe has not previously been reported.

Accidental Falls↗