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Biomedical subjects

R Lewis

Publications and source records attributed to R Lewis.

At least 199 records · Page 11Linked to original sources
PubMed1990

The Ohmeda 9000 syringe pump. The first of a new generation of syringe drivers.

The Ohmeda 9000 syringe pump was developed in response to the need for an infusion apparatus to administer intravenous anaesthetic agents. It incorporates a bolus facility for the rapid, controlled delivery of loading infusions, or incremental dosing over a background maintenance infusion, and may be interfaced with a controller for computer-driven infusions. The Ohmeda 9000 pump has undergone bench testing and detailed evaluation in clinical practice using a variety of syringe sizes and makes. It is capable of accurate delivery over a range of infusion rates provided the recommended manufacturers' syringes are used with the appropriate pump setting. The pump was easy to use and reliable in clinical research and routine clinical practice. It should find its niche as the first genuinely 'anaesthetist-friendly' infusion pump.

Anesthesia, Intravenous↗
PubMed1990

Comparison of once daily atenolol, nitrendipine and their combination in mild to moderate essential hypertension.

1. The aim of the study was to compare the efficacy and the tolerability of treatment with atenolol (50-100 mg once daily), nitrendipine (20-40 mg once daily) and their combination (atenolol 50 mg + nitrendipine 20 mg) once daily in patients with mild to moderate essential hypertension. 2. The study was a randomised, double-blind, placebo controlled parallel groups design: blood pressures were measured at 'trough' effect (i.e. 24 h after dosing) to assess the adequacy of once-daily treatment. 3. Mean blood pressures (mm Hg) recorded on four occasions over 12 weeks of treatment were significantly lower both with atenolol (155/97 sitting: 155/104 standing) and with the combination of atenolol plus nitrendipine (153/96 sitting: 152/104 standing) than with placebo (169/108 sitting: 169/114 standing). Nitrendipine alone had no significant effect on blood pressure 24 h after dosing (165/104 sitting: 165/110 standing). 4. Withdrawals due to adverse effects were more common during treatment with nitrendipine: 7/32 of the patients experienced adverse effects attributable to intense systemic vasodilatation (e.g., flushing, erythema, headache). 2/37 patients taking atenolol were withdrawn: one because he developed a psoriatic rash and the other because of impaired peripheral circulation. Of the 35 patients taking combination treatment, two were withdrawn: one developed headaches and dyspnoea, and the other asthma. 5. The results suggest that once daily dosing with nitrendipine does not control blood pressure throughout the 24 h period in the majority of patients, and is associated with a considerable burden of adverse effects. Combination treatment was better tolerated but appeared to offer no advantages over atenolol alone in terms either of blood pressure control or adverse effects.

Adolescent↗
PubMed1990

Tracheal stenosis.

A case report of tracheal stenosis is used to review the pathophysiology and surgical management of symptomatic tracheal stenosis following intubation and/or tracheostomy. The authors discuss tracheal resection and reconstruction, the preferred permanent method of managing benign tracheal stenosis.

Humans↗
PubMed1989

Induction of metachromasia in experimentally induced hyperplastic/hypertrophic changes in the prostate of the cynomolgus monkey (Macaca fascicularis).

Metachromasia has been shown to be a stromal marker for human benign prostatic hyperplasia (BPH). So far, it is not known whether comparable changes can be demonstrated in experimentally induced BPH in the dog or in a subhuman primate species. In the present study, the phenomenon of metachromasia could be demonstrated in the prostate of cynomolgus monkeys, too. The reaction was quantitatively intensified by the treatment with androstenedione--an aromatizable androgen which caused hyperplastic and hypertrophic changes--especially a stimulation of the smooth muscle--in the stroma of the prostate. Simultaneous treatment with the aromatase inhibitor 1-methyl-ADD prevented both the phenomenon of metachromasia and the stimulation of the stroma. In conclusion, it is not only possible to induce hyperplastic/hypertrophic changes in the prostate of a subhuman species by means of an aromatizable androgen but, in addition, this effect is accompanied by a phenomenon which is thought to be typical for human BPH suggesting the suitability of this type of experiment for the study of the factors involved in the pathogenesis of BPH.

Androstenedione↗
PubMed1989

Effect of exogenous ANP on initial renal function following 24-hour cold preservation.

The impact of synthetic atrial natriuretic peptide (sANP) on renal function following cold ischemic injury was studied in a canine autotransplant model. Following a prenephrectomy inulin clearance determination (CIn), the left kidney was excised, flushed with Eurocollins solution, and cold-stored for 24 hours. Immediately following reperfusion and a 10 minute equilibration period, baseline CIn was measured over a 20-minute time interval (Collection Period I). Experimental animals (N = 11) then received 1 mcg/kg sANP by intravenous bolus followed by a continuous infusion at 0.3 mcg/kg/min for 30 minutes. CIn was measured throughout the infusion (Collection Period II). Normal saline was substituted for sANP in control animals (N = 11). CIn was also measured 24 hours following reimplantation in seven control and seven sANP-treated animals. Autograft inulin clearance increased from 0.32 +/- 0.11 ml/min during Period I to 2.5 +/- 0.6 ml/min during sANP infusion (P less than 0.01). This increase in CIn associated with ANP infusion was accompanied by increases in urine flow rate (V) (0.15 +/- 0.05 ml/min to 0.98 +/- 0.21 ml/min, P less than 0.01) and renal blood flow (RBF) measured by electromagnetic flow probe (85 +/- 17 ml/min to 171 +/- 13 ml/min, P less than 0.05). No significant changes in CIn, V, or RBF occurred in control animals between periods I and II. Although systemic blood pressure declined during sANP infusion, it did not decrease to an extent that compromised peripheral perfusion. CIn determined 24 hours after autograft reimplantation in the ANP-treated animals approximated or exceeded values determined during ANP infusion (Period II).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Comparative evaluation of urographic contrast media, inulin, and 99mTc-DTPA clearance methods for determination of glomerular filtration rate in clinical transplantation.

Plasma clearance of inulin (Cin), 99mTc-DTPA (CDTPA), and urographic contrast media (CCM) were determined simultaneously in 31 patients with varying levels of renal function evaluated in the setting of affiliated cardiac and renal transplantation programs. Cin and CDTPA were calculated from the ratio of simultaneously measured plasma concentration and urine excretion rate of these test agents (UxV/P). CCM was derived from x-ray fluorescence measurement of plasma iodine (PI) content following intravenous injection of 50 ml of nonionic, low-osmolar contrast media (180 mg I/ml). Urine collections were not required for CCM determinations. No adverse reactions attributable to CM occurred in any patient, and follow-up serum-creatinine values did not differ significantly from prestudy levels. CCM determined from the rate of decline in PI between 3 hr and 4 hr following administration of contrast media ("slope-intercept" technique) [Ccm-SI] correlated closely with corresponding levels of Cin (r = .86, P less than 0.0001). and CDTPA (r = 0.89, P less than 0.0001). Mean CCM-SI/Cin and CCM-SI/CDTPA ratios for the entire study cohort were 1.09 +/- 0.06 and 1.08 +/- 0.06, respectively. CCM-SI determinations also correlated well with CCM levels derived from a single measurement of PI ("single sample" technique) made at 3 hr following injection of contrast media (r = 0.94, P less than 0.0001). Both CCM-SI and CCM determined by the "single sample" method (CCM-3 degrees SS) tended to overestimate Cin and CDTPA, however, when the latter were less than 20 ml/min/1.73 m2 (mean CCM-SI/Cin and Ccm-3 degrees SS/Cin ratios 1.36 +/- 0.14 and 1.95 +/- 1.0, respectively. Reproducibility was evaluated by paired comparison of 3-hr vs. 4-hr "single sample" CCM determinations (r = 0.99, P less than 0.0001). In addition, analysis of the variation in iodine content between duplicate specimens obtained at each of these time intervals revealed a mean ratio of 1.0 +/- 0.01 (P = NS vs. identity). Contrast clearance determination utilizing the slope-intercept method is accurate, safe, pragmatic, and more precise than serum-creatinine and endogenous-creatinine clearance for measurement of renal function in clinical transplantation.

Contrast Media↗
PubMed1989

Subendocardial infarction produces epicardial parasympathetic denervation in canine left ventricle.

Forty dogs underwent anterior descending coronary artery dissection with most having occlusion that was either maintained or reperfused. Study was performed 1-4 days later. Multiple electrodes placed in normal and ischemic zones were used to determine the depth of the epicardial rim overlying a subendocardial infarction. This was done by comparing voltage differential with respect to time (dV/dt) measurements of sequential bipolar electrograms along each needle. By this means, test sites with a rim were documented, and depths of epicardial biopsies for choline acetyltransferase were chosen. Epicardial effective refractory period (ERP) responses to vagal nerve stimulation were measured. In sham-operated controls, vagal stimulation prolonged ERP, and choline acetyltransferase activity was equivalent in all sites. In contrast, dogs with all durations of coronary occlusion and various thicknesses of subendocardial infarction had no significant prolongation of ERP limited to rim sites overlying the infarct during vagal nerve stimulation. Corresponding choline acetyltransferase activity was decreased in rim sites compared with remote areas. In addition, dogs given norepinephrine or physostigmine (to potentiate parasympathetic responses) did not demonstrate significant ERP prolongation with vagal stimulation. Infusion of acetylcholine into the distal ligated coronary artery produced dose-dependent prolongation of ERP in sites overlying the infarct. These data taken together support the hypothesis that subendocardial infarction, regardless of its homogeneity or thickness, produces parasympathetic denervation of the overlying epicardial rim.

Animals↗
PubMed1989

Relative influence of subject variables and neurological parameters on neuropsychological performance of adult seizure patients.

We present the results of a study examining relationships between subject characteristics (age, education, sex, race) and neurological factors on neuropsychological test performance of adult seizure patients. Test scores from a modified and expanded Halstead-Reitan test battery for 250 epileptics served as criterion variables for sets of multiple regression analyses using subject characteristics and neurological parameters as predictors. Initially, subjects were divided into two subsamples and separate analyses for subject and neurological variables were pursued. Double cross-validated results indicated that test performance was significantly related to both sets of predictor variables, yet the magnitudes of relationship were rather consistently highest for demographic attributes. The relative contribution of individual predictor variables subsequently was explored in a second set of multiple regression analyses examining both subject and neurological variables within the combined patient sample. Results indicated that one or more subject characteristic plus one or more neurological variable accounted for a significant amount of test variance for almost all of the measures under consideration. A subject variable was entered first in step-wise regression analyses for 78 % of the measures, with education proving to be the most potent predictor of test status. In general, these data support the need for test norms which make adjustments for nonneurological subject attributes.

Journal Article↗
PubMed1988

Antiseptic resistance in JK and other coryneforms.

Resistance to five antiseptics was compared in a group of JK coryneform isolates containing plasmids with resistance in cured derivatives of these isolates and in non-JK coryneforms. No evidence of plasmid-mediated resistance was found, but JK coryneforms were more resistant to some antiseptics, particularly DNA-binding compounds, than non-JK coryneforms.

Actinomycetales↗
PubMed1988

A comparison of bisoprolol and atenolol in the treatment of mild to moderate hypertension.

1. Fourteen patients (mean age 56.0, range 37-61 years; eight females) with mild essential hypertension (DBP greater than 90 mm Hg on placebo) completed a randomised, double-blind placebo controlled crossover study comparing the hypotensive effects of bisoprolol (10-20 mg) and atenolol (50-100 mg) each taken once daily. 2. Bisoprolol had a significantly greater antihypertensive effect than atenolol, reducing sitting blood pressures by 15.9 mm Hg (diastolic) and 21.9 mm Hg (systolic) compared with placebo. Corresponding figures for atenolol were 10.7 and 5.7 mm Hg respectively. Bisoprolol reduced standing blood pressures by 15.9 mm Hg (diastolic) and 22.8 mm Hg (systolic) compared with 7.3 and 8.6 mm Hg respectively for atenolol. 3. Examination of the pharmacokinetic data showed that bisoprolol had a median elimination half-life of 11.2 h during chronic dosing, compared with 6.4 h for atenolol. For bisoprolol, the median clearance fell from 264 ml min-1 after a single dose to 212 ml min-1 during chronic dosing, although clinically significant accumulation would not be expected during chronic administration. 4. Overall, the results suggest that bisoprolol may be a more effective antihypertensive agent than atenolol but larger studies are necessary to confirm these findings.

Adrenergic beta-Antagonists↗