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Biomedical subjects

G Simpson

Publications and source records attributed to G Simpson.

At least 73 records · Page 4Linked to original sources
PubMed1987

Accuracy and precision of breath-alcohol measurements for a random subject in the postabsorptive state.

The accuracy of estimates of blood-alcohol concentration based on measurements of breath-alcohol concentration in a randomly selected subject by a random quantitative evidential breath-alcohol analyzer is evaluated with respect to the breath analyzer itself, its calibration, and the biological variables of the subject being tested. There are no suitable experimental data for rigorous determination of the overall accuracy, so I estimate it from the CV of the available data. I find that the uncertainty in these breath-analyzer readings for a random subject in the postabsorptive state is at least +/- 15%, +/- 19%, or +/- 27%, depending on whether +/- 2 CV, the experimental range, or +/- 3 CV, respectively, is used to express the overall uncertainty. Over 90% of this uncertainty is due to biological variables of the subject, and at least 23% of subjects will have their actual blood-alcohol concentration overestimated. Manufacturers' specifications for the accuracy and precision of these instruments are inconsistent with the experimental values reported in the literature and I recommend that an appropriate amount of uncertainty be reflected in the results from these breath analyzers, especially when they are used for law-enforcement purposes.

Absorption↗
PubMed1986

Reduction by enprostil of aspirin-induced blood loss from human gastric mucosa.

Enprostil's ability to protect human gastric mucosa against aspirin-induced damage was investigated in a controlled study. Damage was assessed as blood loss into gastric washings measured spectrophotometrically using orthotolidine in the presence of hydrogen peroxide. Phenol red was used to correct for recovery rates. Five doses of aspirin, 600 mg, given over 48 hours increased blood loss ninefold compared with placebo. Administration of enprostil 35 micrograms twenty minutes before each dose of aspirin halved this blood loss. After enprostil administration, the pH of both aspirated gastric juice and washings was significantly elevated, suggesting that an antisecretory dose had been used. Increased losses of phenol red occurred following both aspirin and enprostil administration, suggesting enhanced gastric emptying or possible absorption of phenol red as a result of aspirin damage. Side effects related mainly to the alimentary system were associated with enprostil treatment. Enprostil reduced aspirin-induced mucosal blood loss but the mechanism is unclear.

Adult↗
PubMed1986

A comparison of the pharmacokinetics of propranolol in obese and normal volunteers.

The pharmacokinetics of intravenous and oral propranolol have been compared in six obese and six normal subjects matched for age and sex. After intravenous administration there was no difference in plasma clearance but the volume of distribution was greater (V = 339 l vs 198 l) and the half-life was longer (t1/2 = 5.0 h vs 3.0 h) in the obese group. No important difference in the rate of oral absorption was observed. A trend towards higher systemic availability in the obese group (35% vs 27%) was not statistically significant.

Administration, Oral↗
PubMed1984

Tranylcypromine vs nortriptyline vs placebo in depressed outpatients: a controlled trial.

This study was designed to compare the therapeutic and adverse effects of tranylcypromine (a monoamine oxidase inhibitor), nortriptyline (a tricyclic antidepressant), and placebo. A total of 122 depressed outpatients randomly assigned to double-blind treatment with one of these agents completed the 4-week protocol. Treatment groups were balanced for proportions of endogenous versus nonendogenous depressions, defined according to the Research Diagnostic Criteria; however, nonendogenous depressions outnumbered endogenous depressions by such a large proportion (4:1) that meaningful statistical comparisons were limited to the nonendogenous group. In this group, both active drugs proved more effective than placebo, with little differences between the two active drugs except in the areas of side effects and of differential sensitivity of the outcome scales to a given drug. It was concluded that tranylcypromine, a drug which has received relatively little use and study in recent years, represents an effective and reasonably safe treatment for nonendogenous depression, although significant advantages over tricyclics with this disorder remain to be demonstrated.

Adolescent↗
PubMed1984

Argon laser and soft tissue interaction.

The interaction of the argon laser with the mucous membrane of the upper aerodigestive tract was studied. The advantages of the argon laser are a small spot that can be varied in size and intensity, selective vascular absorption, the capability of being incorporated into a flexible delivery system, and a coincident aiming beam. The acute soft tissue effects are characterized by subepithelial extension, with a variable delayed reaction between the application of the laser and a detectable break in the epithelium. Postoperative edema persisted, with an increase in the lateral spread of the lesion over 3 days and an acute inflammatory reaction extending over 7 days. By 21 days the lesions were reepithelialized and healed, but their width was 30% greater than the original defect. The unpredictable interaction with soft tissue, the postoperative edema, and the quality of wound healing are disadvantages. The argon laser appears to have limited clinical potential as a surgical tool for the air and food passages.

Animals↗
PubMed1984

The combined use of MAOIs and tricyclics.

Combined MAOI-tricyclic treatment remains a plausible approach to depressions refractory to single drugs. Adherence to published guidelines should minimize special risks of the combined treatment. However, such risks do exist, and should be borne in mind. Most severe reactions - characterized by hyperthermia, delirium, convulsions, and sometimes fatal outcome - have occurred after a tricyclic was added to established MAOI treatment. Combined treatment may be associated with a lower risk of hypertensive crisis than treatment with MAOI alone. There are no data from double-blind, control-group studies to demonstrate an advantage for the MAOI-tricyclic combination in refractory depression. However, almost no such data exist to establish the advantage of any other treatment in this clinical situation. Clinical experience provides the primary basis for continued consideration of this approach when usual treatments have failed.

Aged↗
PubMed1983

The safety and efficacy of combined amitriptyline and tranylcypromine antidepressant treatment. A controlled trial.

Sixty patients meeting DSM-III criteria for major depression were assigned randomly to double-blind treatment for four weeks according to fixed-dosage steps with (1) amitriptyline hydrochloride alone, up to a maximum dosage of 300 mg/day; (2) tranylcypromine alone, up to 40 mg/day; or (3) the combination of amitriptyline hydrochloride, up to 150 mg/day, and tranylcypromine, up to 20 mg/day. The conditions of patients in all three treatment groups improved equally. The combined treatment did not produce a higher frequency of side effects, and no side effects, such as hypertensive or hyperthermic crises, occurred in any patient. Both amitriptyline alone and combined treatment produced substantially more anticholinergic side effects than did tranylcypromine. These results support the safety and efficacy of the combined treatment, although claims for superior efficacy over single-antidepressant treatments in this heterogenous population were not supported.

Adult↗
PubMed1983

Reversed hemispheric organization in a lefthander.

For left-handers, cognitive functions are organized in the brain similarly to right-handers or they are more diffusely represented. In this study, we report a left-handed patient with a focal right temporal-parietal lesion who evidenced a lasting Wernicke's aphasia and visual-spatial functioning typical of a right-hander with left-hemisphere in involvement. The patient's performance on other tasks (e.g. praxis, singing) as well as observed behavioral changes also resembled those of a right-hander with left-hemisphere compromise. This case suggests that it is possible for cognitive functions to be inversely represented in the two hemispheres.

Aged↗
PubMed1983

Laser bronchoscopic surgery.

Endoscopic laser bronchoscopy can be used to effectively palliate patients with compromised airways. The CO2 laser was utilized with a ventilating bronchoscope. This form of endoscopic surgery has the advantage of less postoperative edema, better hemostasis, more accurate tumor vaporization, and shortened operating time. Between 1975-79 33 laser bronchoscopies were carried out for airway obstruction. Palliation was achieved in most cases. Complications included intra-operative bleeding, tissue fragment occlusion of the airway, and an endotracheal fire. Laser bronchoscopy should be avoided in the presence of widespread metastatic disease, poorly differentiated or rapidly growing tumors, extrinsic tumor compression, or highly vascular tumors. A preliminary report is presented on the soft tissue effects of the argon laser, passed through a flexible coaxial cable in the canine trachea. Multiple transmural lesions were created. The use of the argon laser in the field of bronchoscopy remains controversial.

Adult↗
PubMed1981

Combined MAOI-tricyclic antidepressant treatment: a reevaluation.

Recent studies have shown that monoamine oxidase inhibitors (MAOIs), in appropriate patients and with proper precautions, are not as dangerous as once thought, especially in comparison to alternative antidepressants. We review the literature regarding the combined use of MAOIs and tricyclic antidepressants, which has been reported to be both highly toxic and highly effective. A large number of reports of adverse effects and their management, uncontrolled clinical trials, and animal studies are summarized. We also discuss the three controlled studies of combined MAOI-tricyclic therapy that have been undertaken. We conclude that the hazards of combination therapy have been exaggerated and that MAOI-tricyclic therapy is a reasonable approach in patients found resistant to standard antidepressant treatment if certain precautions are observed.

Animals↗