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Biomedical subjects

R C Evans

Publications and source records attributed to R C Evans.

At least 19 recordsLinked to original sources
PubMed1992

The normal range and a simple diagram for recording whole gut transit time.

The time taken for radio-opaque markers to pass through the intestine has been measured in 25 healthy men, and 18 healthy women in both the follicular and luteal phases of the menstrual cycle. The subjects collected all stools after ingestion of the markers, the number of markers present in each stool was counted on a radiograph, and the number of markers retained in the body was thus determined for 12 hourly intervals after ingestion. The mean values (2 standard deviations) for men and women in both phases of the menstrual cycle proved to be so similar that the results have been combined to provide a single normal range. These data for the normal range for retained markers (as assessed by plain radiograph) are presented in diagrammatic form for clinical use. To assess whether a patient's whole gut transit time lies within the normal range a single type of marker can be used and an abdominal radiograph performed at 12 or 120 hours, the limits of the normal range. Normal subjects retain more than 20% of markers within 12 hours and less than 80% after 120 hours. If desired more information can be gained by giving different types of marker on successive days, so that several transit studies providing intermediate values can be obtained from a single abdominal radiograph at 120 hours.

Adolescent↗
PubMed1991

In vitro study of the transfer of cytokine-inducing substances across selected high-flux hemodialysis membranes.

The in vitro transfer of cytokine-inducing substances (CIS) across cellulose triacetate and polyacrylonitrile hollow-fiber high-flux hemodialyzers was studied using culture filtrates of gram-negative bacteria isolated from hemodialysis center environments. With Enterobacter cloacae, no transfer of CIS was seen despite the potent cytokine inducibility and endotoxin content of the challenge solution. In contrast, interleukins 1 and 6 and tumor necrosis factor inducing substances did penetrate both dialyzer types challenged with Pseudomonas aeruginosa culture filtrates containing a high endotoxin content. Transfer was not seen, however, upon dilution of the challenge solution to lower, yet clinically very high levels of endotoxin. These results show that, in vitro, the transfer of CIS across high-flux membranes is critically dependent upon the quality and the quantity of the challenge material employed.

Cytokines↗
PubMed1989

Application of an empirically derived growth curve model to characterize Staphylococcus epidermidis biofilm development on silicone elastomer.

An in vitro model permitting the development of a staphylococcal biofilm on silicone elastomer is described. Biofilm was determined over time by viable cell quantitation for S. epidermidis strains 8-14B, RP62 and SP2. The log10 viable count data were analysed empirically as a function of time using a negative exponential growth curve model. Although initial colonization and biofilm 72 h cell density of silicone was significantly higher for strain RP62 than SP2, biofilm growth rates did not differ. Strain 8-14B demonstrated a faster biofilm growth rate for the initial 24 h than did RP62 or SP2. The statistical model described was sensitive enough to detect strain differences in biofilm development on silicone elastomer and can be further employed to evaluate the ability of selected biomaterials to retard biofilm development, and the ability of various antimicrobial agents to influence biofilm microbe development.

Biocompatible Materials↗
PubMed1987

Effect of vancomycin hydrochloride on Staphylococcus epidermidis biofilm associated with silicone elastomer.

Peritonitis is a major complication of continuous ambulatory peritoneal dialysis. Relapsing peritonitis after the cessation of antimicrobial therapy is frequently reported and often involves Staphylococcus epidermidis. To investigate the potential role of catheter-associated biofilm in the pathogenesis of relapsing peritonitis, we describe an in vitro model permitting the development of an S. epidermidis biofilm on silicone elastomer biomaterial. This model has been used to investigate the ability of vancomycin hydrochloride to kill biofilm-encased organisms by using an antibiotic regimen typical of peritonitis therapy. No significant differences were seen between vancomycin-exposed and control groups in biofilm viable and total cell counts after 10 days. Vancomycin-exposed silicone-associated biofilm populations decreased by only 0.5 log10 CFU/cm2 over the study period. MICs and MBCs for the original S. epidermidis suspension were 3.125 and 6.25 micrograms/ml, respectively. For biofilm homogenate suspensions, MICs were 3.125 micrograms/ml, but MBCs were greater than 400 micrograms/ml. These data indicate that the biofilm organisms associated with an indwelling peritoneal catheter may display a form of tolerance, thereby suggesting one possible mechanism behind relapsing peritonitis.

Humans↗
PubMed1987

Improving facilities for children in an accident department.

A separate waiting and treatment area for children was established within an existing general accident and emergency department at relatively little cost. We describe how this was achieved and how it has benefited the children attending the department.

Child↗
PubMed1986

Admission guidelines for head injuries: variance with clinical practice in accident and emergency units in the UK.

Guidelines for the initial management of head injuries were formulated by neurosurgeons and a multidisciplinary group of clinicians and administrators attending a seminar convened by the UK Department of Health and Social Security (DHSS). Analysis of data collected previously by the Royal College of Radiologists in nine accident and emergency units in the UK shows that admitting practice varied between centres and was very different from that recommended subsequently in the guidelines. Only 49 per cent (range 22 to 71 per cent) of patients who had skull X-rays and possessed symptoms and signs warranting admission were admitted to hospital and 14 per cent (range 1 to 20 per cent) of those without appropriate symptoms and signs were admitted. Rates of admission for patients with a history of unconsciousness, which according to the guidelines is not a criterion for admission, were up to ten-fold higher than for comparable patients with no such history. Implementation of the guidelines could have a substantial effect on clinical practice and could reduce admissions of patients who had skull X-rays by up to 46 per cent.

Adult↗
PubMed1985

Selective surgical management of neural tube malformations.

The physical characteristics of 49 children with spina bifida cystica, survivors of a group subjected to selection for early surgery are compared with 39 children alive from an earlier unselected series, born in the 1960s, and reviewed retrospectively. Sixteen children were also studied in whom the initial decision not to operate had been followed by survival and subsequent treatment. Children selected for initial surgery have a significantly lower mortality than those not selected and their mobility at 5 to 7 years of age is better, although only marginally so compared with the unselected group. Selection does not decrease the need for shunt treatment of the associated hydrocephalus. None of those not initially selected for surgery have normal faecal or urinary continence, whereas 35% of the selected in group have normal continence and urinary tracts. Children treated immediately have significantly higher degrees of intelligence than both the unselectively treated and those whose treatment was delayed but a fifth of the latter group were intellectually normal. There were only small differences in intelligence between children given delayed treatment and those unselectively treated, suggesting that postponing surgery does not necessarily have a deleterious effect on ability.

Cerebrospinal Fluid Shunts↗
PubMed1984

Implementation of guidelines for the use of skull radiographs in patients with head injuries.

Guidelines formulated by the Royal College of Radiologists' Working Party on the Effective Use of Diagnostic Radiology were introduced into an accident-and-emergency department to determine their effect on the use of skull radiographs in patients with head injuries and on the number of admissions for observation. After approval by senior staff and substitution of the routine casualty record with a head-injury casualty card, the guidelines were distributed throughout the department, and seminars on the suggested use of skull radiographs were held for junior medical staff. The proportion of new accident-and-emergency attenders having skull radiographs fell by 51%. The average number of skull examinations carried out in the department decreased from 373 to 189 per month, but there was no increase in the number of patients with head injuries admitted for observation.

Adolescent↗
PubMed1976

Shunt blockage in hydrocephalic children: the use of the valvogram.

Shunt blockage in valve-dependent hydrocephalic children is not always recognised, as symptoms may be non-specific and signs inconclusive. Valvography is a simple, easily interpreted technique for the investigation of shunt patency in children with Spitz Holter values in the shunt system. The technique affords a simple, rapid method of demonstrating patency at the cardiac end of the shunt. Fifty-one valvograms have been performed in 36 children. In 25 obstruction of the lower end was demonstrated. The unreliability of some associated signs is demonstrated. No serious complications have been observed and the technique has proved an invaluable addition to the practical management of these children.

Catheterization↗
PubMed1976

The reliability of prediction of outcome in spina bifida.

The clinical findings in 85 neonates with spina bifida were given to two neurosurgeons and two paediatricians, who were asked to predict from them the length of survival and quality of survival with regard to intellect, locomotion and continence, without their knowing the actual outcome. All four clinicians correctly predicted the survival of infants with meningocele, closed myelocele and encephalocele. The paediatricians correctly predicted the survival of all infants with open myelocele who actually survived, but also included some who had died. The surgeons correctly predicted the deaths of all those with open myelocele who actually died, but expected a considerable number to die who in fact survived. All four clinicians were similar in their predictions of intellect: they underestimated the outcome in patients with successfully shunted hydrocephalus, they overestimated the intellect in patients who had developed intracranial infection and shunt blockage, and they largely underestimated the outcome in the patients who did not require shunts. They made correct predictions for limb and sphincter function in nearly all the survivors. This investigation underlines the problem of selection for treatment caused by the inability to predict the complications of hydrocephalus and infection. Reasons for the differences between the expectations of the paediatricians and surgeons, and the implications of the results of this study for selection for surgery are discussed. It is suggested that limb paralysis and incontinence ought not to be considered as factors excluding infants from treatment.

Child↗
PubMed1975

The use of the valvogram for the detection of shunt blockage in hydrocephalic children.

Valvography is a simple, safe, rapid, easily interpreted technique for the investigation of possible blockage of the distal end of the shunt system containing a Spitz-Holter valve. Details are presented of 64 investigations in 46 children, 30 of which demonstrated distal obstruction of the shunt system. The unreliability of some physical signs is discussed. No serious complications were encountered and the procedure has proved to be a valuable addition to the practical management of shunt-dependent children.

Cerebrospinal Fluid Shunts↗