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Biomedical subjects

J H Evans

Publications and source records attributed to J H Evans.

At least 19 recordsLinked to original sources

Physicians' response to length-of-stay profiling.

One of the techniques adopted recently by certain hospitals to meet the competitive pressure for reducing costs is physician profiling. Profiling produces periodic reports that compare a physician's resource consumption to a benchmark figure. This study analyzes the effectiveness and implications of one hospital's introduction of physician patient length-of-stay profiling. Data for 24,000 patients treated by 400 physicians in 450 diagnosis-related groups over 42 months were analyzed, including both preprofiling and postprofiling periods. Statistical tests examined whether more physicians achieved the length-of-stay benchmark after profiling was introduced, controlling for physician, disease category (diagnosis-related group), and patient severity level. First, the results establish a significant increase in the percentage of physicians who achieve the length-of-stay benchmark after the introduction of profiling. Second, it was found that physicians who had initially failed to meet the benchmark reduced their patients' average length of stay much more than those physicians who initially achieved the benchmark. Further, reductions occurred primarily at intermediate severity levels, and in diagnosis-related groups with a large economic impact for the hospital. Although the profiling program did achieve the objective of reducing patient length of stay, further improvement may be possible. First, providing different benchmarks or targets for different physicians may extend the improvement to a greater percentage of all physicians involved. Second, an analysis of monthly data on total weighted procedures reveals that the reduction in length of stay resulted in an increase in the number of procedures performed per patient day. This finding suggests that to achieve a reduction in hospital costs and charges, profiling programs should be combined with process improvement initiatives.

Diagnosis-Related Groups

Mathematical modelling of haemodialysis in children.

The single-pool urea kinetic model (UKM), utilising "Kt/V" (the normalised whole body urea clearance), is widely used to help assess the adequacy of haemodialysis in adults. In the presence of an adequate dietary protein intake, a value of unity is acceptable for thrice weekly dialysis. Children could benefit from this approach but, with their relatively higher protein intakes and dialysis needs, this model may not be applicable. Urea kinetics, studies in six children with chronic renal failure by serial timed blood urea measurements during and after haemodialysis, were compared with the kinetics of a one-pool and a two-pool UKM. The two-pool UKM with intra- and extracellular pools best fitted the observed data, re-equilibration between pools accounting for the marked rebound increase in blood urea seen in the 1st h after dialysis (mu 17%, SD 5). Kt/V calculated using the end-dialysis blood urea was higher (mu 21%, SD 5) than when the more correct equilibrated value was used. The post-dialysis rebound indicates significant disequilibrium between the two pools at the end of dialysis. Dialysis efficiency may be substantially overestimated unless this is allowed for by using the rebounded post-dialysis blood urea when calculating Kt/V.

Adolescent

Paediatric haemodialysis: estimation of treatment efficiency in the presence of urea rebound.

The 2-pool urea kinetic model has been developed analytically and applied to the description of the observed increase in blood levels of urea following dialysis (urea rebound), assuming that the dialyser urea clearance K less than 0.4X where X is the urea mass transfer coefficient between the intracellular and extracellular pools (volumes V1, V2 respectively). Urea generation was also neglected. Measurements were made in a group of six children suffering from chronic renal failure. From the model X, the efficiency of dialysis, and the equilibrium urea concentration C infinity were estimated in the presence of urea rebound using a blood urea measurement taken 90 min following start of dialysis, in addition to the conventional samples taken immediately pre- and post-dialysis. In three of the patients agreement between the experimental value of X derived from a multi-blood-sample technique post-dialysis, and the model value, was within 10%, for the range V1 = 0.4 W - 0.38 W, V2 = 0.2 W - 0.238 W, (W = patient's weight). Experimental values of X were in the range 93 - 300 ml min-1. Model estimates of C infinity were accurate to within 10%. An approximate technique was also developed which permitted an estimate of C infinity which was independent of V1, V2, K. The results indicated that C infinity was estimated to within 10% of the true equilibrium urea concentration. The error in the estimate of dialysis efficiency based on a single pool model was reduced by at least 50% using the model. The model may be applied clinically to the estimation of dialysis efficiency in the presence of significant urea rebound.

Child

Desmopressin for bed wetting: length of treatment, vasopressin secretion, and response.

Fifty five children with nocturnal enuresis referred to a hospital enuresis clinic entered a controlled trial to compare the efficacy of one month and three month courses of intranasal desmopressin (Desmospray). There was no significant difference in outcome between the two groups. Overall 36% improved by at least two dry nights/week during treatment, but only five children (18%) in the one month group and three (11%) in the three month group became completely dry and only one in each group remained dry after treatment. To determine whether nocturnal polyuria was associated with a therapeutic response to desmopressin, the nocturnal urine volume, osmolality, and vasopressin concentration were measured in desmopressin responsive enuretics, desmopressin non-responders, and non-enuretic control children. There were no significant differences between the three groups. A three month course of desmopressin is no more effective than a one month course. Although many children will improve during treatment, only a small number become dry and most will relapse when treatment is stopped.

Adolescent

Biocompatibility assessment: application of fluorescent probe response (FPR) technique.

An in vitro test procedure capable of discriminating effectively between intact and membrane-damaged cells has been developed. This procedure utilizes fluorescein diacetate and ethidium bromide as fluorescent probes. The properties of the probes and the collapse in the selective cytoplasmic membrane permeability barrier of the damaged cells ensure the principal feature of the test procedure, that functional cells fluoresce bright green, but membrane-damaged cells fluoresce bright red. Investigations with natural rubber, silicone and acrylic polymers confirmed the suitability of the procedure to distinguish between materials on the basis of cytotoxicity.

Acrylic Resins

Pharmacokinetics of recombinant human erythropoietin in children with renal failure.

The single-dose pharmacokinetics of recombinant human erythropoietin (rHuEpo; 40 units/kg1) were investigated in children (9-16 years) with end-stage renal failure. After an intravenous (i.v.) dose, serum rHuEpo concentrations declined in a monoexponential manner with a mean half-life (t1/2) of 5.6 +/- 3 h (+/- SEM; n = 9). Serum clearance and the apparent volume of distribution were estimated to be 10.1 +/- 0.9 ml h-1 kg-1 and 79.5 +/- 5.0 ml kg-1 (n = 9) respectively. Subcutaneous (s.c.) delivery resulted in serum values that peaked at 10 h, and thereafter concentrations declined slowly with a t1/2 of 21.1 +/- 4.5 h (n = 9). Serum rHuEpo concentrations were maximal at 14 h after i.p. administration and the t1/2 was 9.5 +/- 1.0 h (n = 3). The mean fraction absorbed of SC rHuEpo was 0.40 whereas after i.p. administration this fraction was only 0.17. These results show that after both s.c. and i.p. delivery, disposition of the hormone is rate-limited by absorption, and bioavailability for these extravascular routes is poor. In addition, comparison of the results with those available for adults indicates that rHuEpo is better absorbed but more rapidly cleared in children.

Adolescent

Can ultrasonography reliably predict the occurrence of multiple pregnancies in gonadotrophin ovulation induction?

A retrospective study of 78 patients with 106 stimulated conception cycles after successful gonadotrophin ovulation induction was made to analyze the relationship between the sizes and numbers of ovarian follicles seen on ultrasound and the eventual number of conceptions that resulted in each cycle. Fifteen cycles (14.2%) resulted in spontaneous abortions. There were 58 singleton pregnancies (54.8%), 26 sets of twins (24.5%), 6 sets of triplets (5.6%) and 1 set of quadruplets (0.9%). In 86 cycles with the last scans performed shortly before the ovulating dose of HCG, 3 or more mature follicles were found in 50 (58%). These cycles resulted in 31 (62%) singletons, 16 (32%) twin pregnancies and 3 (6%) triplet pregnancies. Pregnancies resulted even when there were no 'mature' follicles seen on scan. No statistical correlation was found between plurality of pregnancy and size or number of follicles, or oestradiol excretion on the day the ovulating dose of HCG was given, although high-order multiple pregnancies were more likely if the oestrogen excretion was more than 200 ug/24 hours (p = 0.001). The dosage of HCG correlated inversely with the occurrence of multiple pregnancies (p = 0.02). In conclusion, neither oestrogens nor ultrasonography could accurately predict multiple conceptions in gonadotrophin stimulated cycles.

Estrogens

Home-based immunoglobulin infusion therapy: quality of life and patient health perceptions.

Thirty-seven antibody-deficient patients who were participating in a multicenter trial evaluating home-based, self-administered IVIG therapy anonymously completed questionnaires regarding beliefs concerning health control, quality of life, and attitudes toward active participation in medical care. Their responses were compared with a group of 29 patients undergoing traditional IVIG therapy in a medical clinic setting. A subsample of the home-based group who later returned to clinic-based IVIG therapy allowed comparison of responses given by the same patients in both settings. Home-based therapy was preferred to clinic-based therapy. Independence, convenience, comfort, decreased disruption of activities, travel time, and costs were specific factors rated most favorably. On the Health Belief Questionnaires, patients preferred informed, self-involved medical care regardless of the setting for their IVIG treatments.

Adult

Lumbar intervertebral foramens. An in vitro study of their shape in relation to intervertebral disc pathology.

The lumbar intervertebral foramens of 20 isolated cadaveric spines were investigated by the use of a molding technique to assess their dimensions accurately and how intervertebral disc pathology altered their configuration. Oval foramens predominated over auricularly shaped foramens when the disc was normal, but when the disc was abnormal, the converse was true. Foraminal size varied from 40 to 160 mm2 but showed great variation even at individual levels; these were not accurately reflected by simple radiologic measurements.

Adolescent

Effects of birth weight and sociodemographic variables on mental development of neonatal intensive care unit survivors.

Neonatal intensive care unit survivors (N = 494) from 10 tertiary care centers were evaluated over the first 4 to 5 years of life to determine the relative contributions of birth weight and sociodemographic factors to mental development. Six sociodemographic factors were studied: sex, race, family income, and mother's marital status, age, and educational level; the last five factors also are known to be associated with premature birth. Mental development was measured with the Bayley Scales of Infant Development (12 to 24 months) and the Stanford Binet Intelligence Test (4 to 5 years). Each factor's influence was assessed by multivariate analysis. Birth weight had limited long-term implications; at 4 to 5 years, only infants with birth weights less than 1000 gm had significantly lower scores than those in other birth weight categories. Sociodemographic variables had a greater impact on mental development, with age-dependent differences found between nonwhite and white children and between children with mothers of low, medium, and high educational levels.

Adult

Q-switched ruby laser treatment of tattoos; a 9-year experience.

Nine years of clinical experience of the application of the Q-switched ruby laser to the removal of tattoos is presented. This laser achieves optimal removal of blue/black amateur tattoos by its selective interaction with the dermal suspensions of pigment which constitute the tattoos. The scar free cosmesis thus achieved is a considerable improvement on non-specific laser techniques whereby the laser is absorbed to a comparable degree in both pigmented and non-pigmented tissue. Long-term results are analysed and it is noted that a variety of professional tattoos may also respond to treatment. The mechanisms and appearance are discussed and correlated with short-term healing processes. It is found that power densities in the range 1200-2800 GW/m2 are most suitable. Appropriate dosimetry can be witnessed by the appearance of opaque intradermal vacuoles corresponding to the vaporization of the tissue water surrounding the pigment suspensions. Treatment by Q-switched ruby laser offers a viable scar-free option for a wide range of dark tattoos, leading to a more acceptable clinical outcome in most cases than other current therapies.

Dermatologic Surgical Procedures

Effect of birth weight, race, and sex on survival of low-birth-weight infants in neonatal intensive care.

Survival for low-birth-weight infants has traditionally been analyzed by birth weight categories spanning considerable ranges of weight. We developed a finer description of survival rates to allow estimation of survival percentages for infants of any specific birth weight between 500 and 2500 gm. Our sample consisted of 16,183 infants treated in tertiary neonatal intensive care between 1980 and 1987. Their survival data were analyzed by 50 gm increments between 500 and 2500 gm, and a continuous survival curve was constructed by log linear regression methods. Mortality differences between males and females and blacks and whites were analyzed. Survival for females was higher than males between 500 and 1500 gm and higher for blacks than whites between 650 and 1500 gm. Between 1500 and 2500 gm, no significant effects of birth weight, race, or sex were observed, with survival remaining stable at approximately 95% across all combinations of variables.

Birth Weight

Factors affecting fetal loss in induction of ovulation with gonadotropins: increased abortion rates related to hormonal profiles in conceptual cycles.

Thirty-six first-trimester abortions (9.7%), 16 second-trimester abortions (4.3%), 11 ectopic pregnancies (2.9%), and 10 stillbirths (2.7%) occurred in 373 conceptual cycles after gonadotropin induction of ovulation. Fetal wastage was higher in spontaneous pregnancies that occurred before therapy (54.3%, p less than 0.0001) and lower with subsequent spontaneous pregnancies (10.1%, p less than 0.05). Significant risk factors for overall fetal loss during induced ovulation were a continuous rise of estrogen excretion until ovulation (p less than 0.01) and previous abortion (p less than 0.05). For first-trimester abortion, the risk factor was continuous estrogen rise (p less than 0.01); for second-trimester abortion, the risk factors were a low luteal pregnanediol-to-estrogen excretion ratio (p less than 0.002), increased age at conception (p less than 0.02), and high baseline estrogen excretion (p less than 0.05). Multiple pregnancy was not significant. The continuous rising estrogen pattern may serve as a marker of abnormal oocyte maturation. We propose that future studies on infertility treatment should report on pregnancy outcome.

Abortion, Spontaneous

Clomiphene citrate and ovarian resistance.

An uncommon association between clomiphene citrate and the development of ovarian resistance to gonadotrophins is described. We advise against the use of clomiphene in the rare patient with the resistant ovary syndrome, and advise caution in any patient who exhibits a decreasing oestrogen response to clomiphene ovulation induction.

Adult

Treatment-independent pregnancies after cessation of gonadotropin ovulation induction in women with oligomenorrhea and anovulatory menses.

Life-table analysis was performed for the cumulative spontaneous pregnancy rate (CSPR) of 56 patients with oligomenorrhea and anovulatory cycles who had been treated with gonadotropin for ovulation induction between 1963 and 1985. Twenty-seven had at least one spontaneous pregnancy, giving rise to a CSPR of 66.4% (95% confidence limit [CL] 42.4% to 90.4%) at 115 months for the first spontaneous pregnancy, which is significantly lower than the cumulative induced pregnancy rate (CIPR) of 88.6% at 23 months for the first course of gonadotropin therapy (P less than 0.0001). This fertility potential was not affected by the baseline estrogen and follicle-stimulating hormone levels, diagnosis, result of gonadotropin therapy, and age and menstrual pattern during exposure to spontaneous pregnancy by Cox regression analysis. More multiple births occurred in the induced pregnancies than in the spontaneous pregnancies (P = 0.005).

Anovulation