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Biomedical subjects

R N Ross

Publications and source records attributed to R N Ross.

At least 19 recordsLinked to original sources
PubMed1995

Evaluation of the complication rate as a measure of quality of care in coronary artery bypass graft surgery.

OBJECTIVE: To determine whether hospital rankings based on complication rates provide the same information as hospital rankings based on mortality rates. DESIGN: A retrospective study of in-hospital death, complication, and death following complication (failure to rescue). Hospitals were ranked using residuals based on the difference between the observed and the expected number of events (from logistic regression models); rankings were compared using Spearman rank correlations. SETTING: Hospitals performing coronary artery bypass graft (CABG) surgery in the 1991 and 1992 MedisGroups National Comparative Data Bases. PATIENTS AND DATA SETS: Record abstraction data for 16,673 patients who underwent CABG procedures at 57 hospitals, linked with data from the 1991 American Hospital Association Annual Survey. RESULTS: After adjusting for patient admission severity of illness, there were low correlations between hospital rankings based on death or failure to rescue and those rankings based on complication (death vs complication, r = 0.07, P = .58; failure to rescue vs complication, r = -0.22, P = .11). In addition, many hospital characteristics that are generally associated with a higher quality of care were associated with higher complication rates but with expected or lower-than-expected mortality rates. CONCLUSIONS: Hospital rankings based on complication rates provide different information than those based on mortality rates. Until more is known about these differences, complication rates should not be used to judge hospital quality of care in CABG surgery.

Coronary Artery Bypass↗
PubMed1990

Determination of the interval during which one application of compound 48/80 to the rat conjunctiva influences the response to a second application.

We studied the effect of one application of compound 48/80 to the conjunctiva of the rat on the response to a subsequent challenge. Rats treated once showed conjunctival edema and marked degranulation of conjunctival mast cells. A second exposure to compound 48/80, applied after an interval of 24 h, produced slight clinical effects but had marked effects on conjunctival mast cells. Approximately 90% of the mast cells could no longer be observed by light microscopy. As the interval between initial challenge and rechallenge was increased, the clinical response returned, mast cells were again observable in normal numbers, and the extent of degranulation returned to approximately 50%. After an interval of 7 days, rats responded clinically as they had to the first application of compound 48/80. Although the number of mast cells in the conjunctiva was normal and extensive degranulation occurred, exocytosis was not observed. Thus some effects of the first application of compound 48/80 persisted for at least 1 week. Whether the effects observed depend upon the continued presence of compound 48/80 in the mast cell or granule membrane remains to be determined.

Analysis of Variance↗
PubMed1989

Asthma costs.

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Asthma↗
PubMed1989

Ocular anaphylaxis induced in the rat by topical application of compound 48/80. Dose response and time course study.

In the present study we sought to develop a model of ocular anaphylaxis based on the topical application of compound 48/80 to the surface of the rat eye. Doses ranging from 50 to 1000 micrograms were found to produce graded edema of the conjunctiva and swelling of the lid. On histologic examination, 50 microns compound 48/80 produced no changes distinguishable from those in PBS-treated controls, 150 microns produced mild alterations, and 250, 500, and 1000 micrograms compound 48/80 produced a marked increase in degranulated mast cells and a mild influx of neutrophils. The time course of the response to 250 micrograms and 1000 micrograms of compound 48/80 was evaluated over a 72-h period. Both doses elicited epithelial damage. A mild reduction in the number of mast cell was seen at 6 h in rats receiving 250 or 1000 micrograms. The reduction persisted to 72 h in rats receiving 1000 micrograms. The number of neutrophils was increased at 1 and 6 h in eyes treated with 250 micrograms and at 1, 6, and 24 h in eyes treated with 1000 micrograms compound 48/80. The clinical and histologic changes induced by application of 250 micrograms compound 48/80 resemble those seen in patients with allergic conjunctivitis suggesting that a model of ocular anaphylaxis based on the topical application compound 48/80 will be clinically relevant and experimentally practical.

Administration, Topical↗
PubMed1989

Morphologic evidence that compound 48/80-challenged rat eyelid mast cells differ in their states of maximal degranulation.

To determine the uniformity of response by mast cells in the rat eyelid, doses of compound 48/80 ranging from 50 to 1,000 micrograms in a 10-microliters drop were applied to one eye of 30 male Sprague-Dawley rats. Phosphate-buffered saline (PBS) was applied to the other eye. Every mast cell was counted throughout microscopic slides of the tissue of the lower eyelids. Both the position and degree of degranulation of every mast cell in each slide were recorded on schematic representations of the lower eyelid. Before histologic examination, animals were observed for clinical signs of ocular anaphylaxis. Doses of 50 and 150 micrograms had no observable clinical effect. At greater doses, edema of the lids and conjunctiva increased with dose. Doses less than 250 micrograms had no significant effect on the number of mast cells or degree of degranulation. Doses of more than 250 micrograms induced degranulation in approximately 50% of the eyelid mast cells. The degree and pattern of degranulation did not change with doses greater than 250 micrograms. The morphology of degranulated mast cells treated with 1,000 or 250 micrograms of compound 48/80 was indistinguishable. We conclude that once maximal stimulation for degranulation is achieved, higher levels of compound 48/80 will not increase the level or change the type of degranulation. In addition, the maximal level of degranulation varies from one mast cell to the next. Mast cells in close proximity may differ markedly in their level of maximal degranulation, with responses ranging from no degranulation to severe degranulation with exocytosis.

Administration, Topical↗
PubMed1989

Response of rat conjunctival mast cells to multiple versus single applications of compound 48/80.

A single application of the mast cell secretagogue compound 48/80 to the surface of the rat eye induces significant histologic changes. Ocular anaphylaxis is usually the result of repeated, not single, exposures to allergenic substances. The response of conjunctival mast cells to repeated daily applications of compound 48/80 was, therefore, evaluated. Ninety rats received one dose of compound 48/80 or phosphate-buffered saline almost daily for 17 days. The frequency and degree of mast cell degranulation and the number of mast cells and other inflammatory cells in the subepithelial conjunctiva were determined histologically. The clinical response was most marked after one application of compound 48/80; repeated daily applications markedly reduced the clinical response. In eyes treated with multiple applications, 75% fewer mast cells were observable in the conjunctiva by light microscopy compared with phosphate-buffered saline treated eyes. Most mast cells were granulated; a few showed mild to moderate degranulation. Except for epithelial damage, no tissue injury was associated with multiple applications of compound 48/80. In contrast to conjunctivae subjected to a single application of compound 48/80, conjunctivae receiving multiple applications resembled that of phosphate-buffered saline controls.

Administration, Topical↗
PubMed1988

Ocular allergy.

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Conjunctivitis, Allergic↗
PubMed1988

Retinal illuminance using a wide-angle model of the eye.

A computer model of relative retinal illuminance, based on our optical wide-angle model of the eye, is proposed for the cases of Ganzfeld illumination and the Maxwellian view through a range of visual field angles from 0 degrees to 80 degrees. The proposed model is designed to be functionally correct and to represent closely the anatomical parameters of the eye. Unlike earlier proposed models, this model is based on our previously reported measurements of spherical aberration in 100 eyes in vivo and is designed to be correct in the peripheral field and with large pupils. Data are reported for pupil diameters of 2, 4, and 8 mm. The effect of crystalline lens extinction on retinal illumination is also estimated for average eyes of young (age 19 years) and old (age 63 years) individuals at two wavelengths (410 and 532 nm). In the Ganzfeld case, illumination of the retina decreases with increasing visual angle. In the Maxwellian view, retinal illuminance increases with increasing visual angle.

Adult↗
PubMed1988

Dark-staining bodies in the conjunctival epithelium of rats after multiple topical challenges with compound 48/80.

Over a 17-day period, 96 Sprague-Dawley rats received approximately daily topical applications of compound 48/80 to the ocular surface of one eye and phosphate-buffered saline (PBS) to the other eye. On histologic examination, dark-staining bodies appeared in the conjunctival epithelium in all 48/80-challenged eyes after day 3. These epithelial dark bodies (EDBs) rarely appeared in PBS-challenged or in single-dose 48/80-challenged tissues. The EDBs, between two and 15 per 30 fields at x 1000 under light microscopy, were limited to the conjunctiva near the fornix rather than near or over the tarsal plate. We hypothesize that these EDBs are associated with repeated application of secretagogue to the conjunctiva.

Administration, Topical↗
PubMed1988

Cost-effectiveness of including cromolyn sodium in the treatment program for asthma: a retrospective, record-based study.

The treatment of chronic mild to moderately severe asthma is expensive for families and for society. Controlling the costs of asthma-related medications, physician visits, emergency room visits, and hospital admissions is therefore an important consideration. A retrospective, record-based study was undertaken to determine the costs of treating asthma in patients for whom cromolyn sodium was included in the routine treatment plan (n = 27) and those for whom treatment did not include cromolyn sodium (n = 26). Significant reductions in the number of emergency room visits and hospital admissions were obtained in patients who were treated with cromolyn sodium. The estimated average cost of emergency room visits was $33 a year for the patients given cromolyn sodium compared with $624 a year for patients in the comparison group. The estimated average cost of hospital admissions was reduced by $1,298 for the cromolyn sodium group compared with a $357 reduction for the comparison group. Computed for the entire course of treatment, the average (+/- SD) daily cost of medications for the comparison group was $0.84 +/- $0.37 versus $0.93 +/- $0.25 for the cromolyn sodium treatment group. Thus dramatic savings in costs of emergency room visits and hospitalizations when cromolyn sodium was included in therapy were effected at a small increase in the overall cost of medications. Analyzed visit by visit, the average daily cost of treatment that included cromolyn sodium decreased while that of the comparison group increased. We conclude that including cromolyn sodium in a regular anti-asthma regimen is a cost-effective and therapeutically effective treatment strategy.

Adrenal Cortex Hormones↗
PubMed1987

Effect of multiple applications of compound 48/80 on mast cells of rat conjunctiva.

We sought to determine the effect on rat conjunctival mast cells of chronic exposure to a degranulating agent. Compound 48/80 (250 micrograms in 10 microliter) was applied daily to the ocular surface of rats for a total of 13 treatments administered in 17 days. A single application of compound 48/80 was given to rats for comparison. Four groups of animals (6 in each group) were evaluated 1 or 48 h after the last application of compound 48/80 in both chronic exposure and single exposure studies. Although a single exposure to compound 48/80 induced significant degranulation of mast cells in animals observed 1 h after treatment, no significant degranulation of mast cells was observed 1 h after the last dose of compound 48/80 was given to rats whose conjunctiva had been chronically exposed to this degranulating agent. Thus, multiple applications of compound 48/80 attenuated the mast cell response to compound 48/80. This acquired tolerance to compound 48/80 was reflected in the lessened clinical signs in rats receiving repeated applications compared with those given a single application.

Animals↗
PubMed1984

Survey of ultrasound therapy devices in Manitoba.

In 1982 a survey was performed of 89 ultrasound therapy devices in use in medical and paramedical organizations in Manitoba. Field measurements of ultrasonic output power, intensity, and timer accuracy in the clinical operating range were made together with maximum output power and transducer operating frequency. Results of the measurements are presented and the performance characteristics of the units compared with manufacturers' performance criteria for ultrasound therapy devices as given in the Canadian Radiation Emitting Devices (RED) Act.

Equipment Safety↗
PubMed1984

Mast cells.

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Antigen-Antibody Reactions↗