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Biomedical subjects

J G Roberts

Publications and source records attributed to J G Roberts.

At least 37 records · Page 2Linked to original sources
PubMed1988

Infusion thrombophlebitis: a prospective comparison of 645 Vialon and Teflon cannulae in anaesthetic and postoperative use.

A prospective study of the incidence and severity of infusion thrombophlebitis in peripheral intravenous infusions used for anaesthetic and postoperative purposes in 645 patients was conducted over a four-month period. Conditions of insertion were carefully controlled while ward management was according to standard practice. A total of 330 polyurethane Vialon and 315 FEP-A Teflon cannulae were used. The results show that the nature of the cannula was the single most important factor in the incidence and severity of infusion thrombophlebitis, Vialon cannulae being associated with a 46% lower incidence than the Teflon type. Less important but significant factors included intravenous antibiotics, duration of infusion, cannula tip damage and caesarean section. Factors not associated with infusion thrombophlebitis included potassium therapy, blood transfusion or site of insertion in the upper limb. Heparinisation increased duration of infusion without affecting the incidence of infusion thrombophlebitis.

Adult↗
PubMed1987

Comparison of questionnaires determining patient satisfaction with medical care.

This study compares the results of previously developed patient satisfaction questionnaires which quantitatively assessed the personal attitudes of 59 patients toward their medical care. These patients, hospitalized for acute myocardial infarction, were admitted to the intensive care unit of a community hospital in southern Ontario, Canada. The questionnaires were completed by these patients at four and six months post-myocardial infarction. This quantitative assessment of patient satisfaction, as indicated by Hulka and Ware questionnaires, provided data to compare the relative effectiveness of these questionnaires in measuring satisfaction. Generally, these questionnaires were reliable (r = .64, r = .59) and evidence of criterion concurrent validity was noted (r = .75-.81). Both questionnaires have comparable results concerning the prevalence of dissatisfaction (0-7 percent).

Adult↗
PubMed1987

Calcaneal bone density reduction in patients with restricted mobility.

This cross-sectional study revealed a prevalence of reduced calcaneal bone density in a population of 49 chronic continuing care patients with restricted mobility. Calcaneal bone density was measured using the Compton gamma ray scattering technique, which permits examination of trabecular bone. Predicted densities were determined from the ages and weights of the subjects. Descriptive factors such as gender, diagnosis, duration of the condition, and muscle tone were correlated with bone density. Twenty-eight patients (57%) had indications of reduced calcaneal bone density. None of the descriptive factors was associated with the variability in bone density ratio (forward stepwise regression analysis, p = NS). The reduced calcaneal density found in these patients with restricted mobility is probably a result of their not bearing weight and the inevitable severe reduction in their physical activity.

Absorptiometry, Photon↗
PubMed1984

Photon scattering measurements of calcaneal bone density: results of in vivo longitudinal studies.

Sequential measurements of the density of calcaneal trabecular bone were made in normal postmenopausal women and in patients treated for osteoporosis. Cross-sectional measurements of density were made in previously normal patients who had been without ovarian function for a known length of time of at least one year. There was a significant reduction in calcaneal density associated with aging in normal postmenopausal women. Estrogen lack was also associated with density reductions and the reduction was related to the length of time of estrogen deprivation. When osteoporotic patients were treated with combination therapy, density rose in females while in males the expected age dependent reduction was prevented. It is concluded that photon scattering measurements of calcaneal density can be used to monitor changes in the mineral status of the skeleton.

Adolescent↗
PubMed1981

An integrated study of pharmacokinetics and pharmacodynamics of chlormethiazole in healthy young volunteers.

Chlormethiazole ethanedisulphonate (0.8%) (Hemineurin, Astra) was administered to 10 healthy unpremedicated volunteers at a constant-rate infusion of 2.5 ml/min for 60 min (Phase 1, n = 5) and 113 min (Phase 2, n = 5). With one exception, chlormethiazole blood concentration-time data were described by a two-compartment open model. Total body clearance was the same in both phases (1.151 . min-1, SD 0.49; and 1.051 . min-1, SD 0.49; and 1.051 . min-1, SD 0.36 respectively) and was similar to the clearance of indocyanine green. No correlation was found between clearance, initial dilution volume (1371, SD 62; and 1251, SD 33 in 1 and 2 phases respectively) or volume of distribution at steady-state equilibrium (3081, SD 91; and 2241, SD 59) with either body weight or estimated lean tissue mass. Slow half-life was 289 min (SD 169) in Phase 1 and 253 min (SD 172) in Phase 2. Moderately heavy sedation associated with amnesia while retaining the ability to readily obey verbal commands was achieved in one subject of Phase 1 and 4 subjects of Phase 2 and occurred at a mean chlormethiazole ethanedisulphonate blood concentration of 9.2 mg . 1(-1) (SD 2.9). Transient nasal irritation was experienced by all subjects during the initial stages of infusion. A rise in pulse rate (33%, SD 8) was a prominent feature but blood pressure and respiratory rates were very stable.

Adolescent↗
PubMed1981

Two-stage infusion of chlormethiazole for basal sedation.

The effectiveness of chlormethiazole in providing basal sedation was studied using a two-stage infusion regimen consisting of an initial loading dose of 60 mg min-1 for 25 min (in the lateral position) followed by a maintenance constant-rate infusion of 10 mg min-1 for 60 min (in the supine position). The regimen was evaluated in five healthy young volunteers who were all moderately sedated throughout most of the infusion, lapsing into sleep when left undisturbed, yet awakened easily to obey commands. Varying periods of amnesia, corresponding with a mean chlormethiazole ethanedisulphonate blood concentration of 10.3 mg litre-1 (SD 3.8) were obtained. Light sedation occurred during the first 10 min and the last 20 min of the total infusion period, corresponding to chlormethiazole blood concentrations of 7.9 mg litre-1 (SD 1.9) and 7.4 mg litre-1 (SD 2.3) respectively. Adverse side-effects were transient nasal irritation, flushing and a coryza-like syndrome. Other side-effects of tachycardia and hypertension may be beneficial in counteracting cardiovascular depression associated with central neural blockade. A high total body clearance of chlormethiazole (mean 1.39 litre min-1, SD 0.58) was found and would contribute to the brief duration of action after termination of the infusion.

Adolescent↗
PubMed1981

Oxprenolol and the circulation during anaesthesia in the dog: influence of intrinsic sympathomimetic activity.

Oxprenolol is a non-selective adrenergic beta-receptor antagonist displaying beta-mimetic activity. To test the hypothesis that beta-mimetic activity could minimize the response of the circulation to adrenergic beta-receptor blockade, cumulative dose-response curves to oxprenolol 0.1-1.6 mg kg-1 were obtained in seven anaesthetized dogs. Anaesthesia was maintained with 0.5% halothane supplementing nitrous oxide 66% in oxygen, under moderately hypocapnic IPPV. Oxprenolol, up to 0.4 mg kg-1 i.v., caused modest increases in heart rate, LV dP/dt max and cardiac output. With the largest dose (1.6 mg kg-1), significant increases in heart rate (+19%), LV dP/dt max (+13%) and cardiac output (+27%) were observed while arterial pressure remained unchanged and systemic vascular resistance decreased (-18%).

Anesthesia, Inhalation↗
PubMed1981

Minaxolone, clinical effects and pharmacokinetics. Subanaesthetic infusion regimen.

Minaxolone, infused at a constant rate of 0.01 mg/kg/min produced drowsiness followed by a sleep-like state from which subjects could be easily awakened. After the infusion was stopped, initial recovery was rapid, and completed within 45 minutes. The ability to produce this state rapidly and reversibly would have great value in outpatient surgery, short operative procedures and for basal sedation during procedures performed under regional anaesthesia. In common with many intravenous induction agents, involuntary skeletal muscle movement and twitching during the latter part of the infusion regimen was observed in some subjects. The rapid recovery was consistent with the pharmacokinetic characteristics of Minaxolone, i.e. high total body clearance (near or even exceeding that of indocyanine green) and rapid redistribution. However, renal clearance of unchanged Minaxolone was negligible.

Adult↗
PubMed1981

Thermodilution cardiac output--a systematic error.

The purpose of this study was to examine the mechanism and magnitude of a systematic error in thermodilution cardiac output measurement. One hundred and seventy-one thermodilution cardiac output measurements in dogs using a Swan-Ganz catheter were compared with simultaneously made dye dilution measurements under different conditions over a wide range of cardiac outputs. A systematic error with the thermodilution technique was confirmed and was almost identical to that observed in the literature. It is proposed that its mechanism is loss of thermal indicator between the injectate orifice and detection. Application of a further correction factor for thermal indicator loss is suggested.

Animals↗
PubMed1981

An evaluation of thermodilution cardiac output measurement using the Swan-Ganz catheter.

Errors in thermodilution cardiac output measurement were quantitated to determine the order of accuracy of routine measurements performed by unskilled personnel. In vitro and in vivo studies were undertaken to examine factors affecting the volume and temperature of the injectate, catheter thermistor and computer performance, effect of respiration, use of cold (0-4 degrees C) versus ambient temperature (20-25 degrees C) injectate, and the interpretation of measurements. Ambient temperature injectate incurred unacceptably large errors; cold injectate (injections were timed with respiration) produced variations in performance by equipment and personnel which accounted for only 2% of the variation between successive measurements. Real changes in cardiac output and inherent variability of the downslope of the thermal curve, necessitating an empirically based calculation, account for up to 10% variation between successive measurements. When cold injectate was used, and the average of three corrected measurements taken, thermodilution cardiac output measurements were within 10% of a simultaneous dye dilution measurement.

Animals↗
PubMed1981

Pharmacodynamics of minaxolone, a new steroidal anesthetic.

Studies were designed to examine blood concentration-response relationships for minaxolone administered to sheep by either i.v. infusion or bolus injection in both clinical doses and overdoses. Responses examined included effects on sensory nervous, cardiovascular and respiratory systems. The ratio of fatal blood concentrations to anesthetic blood concentrations (therapeutic ratio) was 3 to 4 without respiratory support other than endotracheal intubation to maintain a patent airway. Minaxolone consistently depressed respiration rate, raised PACO2 and depressed PAO2. Death resulted from respiratory failure. With intermittent positive pressure ventilation, the therapeutic ratio was raised to 30 to 40. Duration of anesthesia after bolus doses was directly related to the logarithm of the dose. Cardiovascular effects were minimal with clinical doses and mild overdoses and included slight tachycardia, slightly elevated blood pressure and increased total peripheral resistance with little or no change in cardiac output. With gross overdoses, stable hypotension and depressed cardiac output resulting from decreased stroke volume occurred. Its excellent anesthetic properties and lack of deleterious effects at normal doses on the cardiovascular system commend minaxolone for further evaluation.

Anesthetics↗
PubMed1980

An important factor in drug usage......and the adoption of a positive role.

How can drug use be controlled and what is the most effective way of organising pharmaceutical services? In these two articles P.I. Harrison, BSc, MPhil, MPS, APO, Ealing Hammersmith and Hounslow AHA and J.G. Roberts, FPS, OBE, RPO, Mersey RHA, discuss the answers to these questions.

Drug Information Services↗