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Biomedical subjects

John Stevens

Publications and source records attributed to John Stevens.

At least 19 recordsLinked to original sources

Bayesian decision procedures for dose-escalation based on evidence of undesirable events and therapeutic benefit.

In this paper, Bayesian decision procedures are developed for dose-escalation studies based on bivariate observations of undesirable events and signs of therapeutic benefit. The methods generalize earlier approaches taking into account only the undesirable outcomes. Logistic regression models are used to model the two responses, which are both assumed to take a binary form. A prior distribution for the unknown model parameters is suggested and an optional safety constraint can be included. Gain functions to be maximized are formulated in terms of accurate estimation of the limits of a 'therapeutic window' or optimal treatment of the next cohort of subjects, although the approach could be applied to achieve any of a wide variety of objectives. The designs introduced are illustrated through simulation and retrospective implementation to a completed dose-escalation study.

Anticoagulants↗

Standards for humidification and filtration devices.

This synopsis of the background to the standardization of medical devices allows a comparison of the functional operation of two regulatory authorities, the FDA and the European Commission. It can be seen that with time they have developed many common features. However, there remains a significant difference with the older style of regulation imposed by the FDA, in particular the obligation to comply with USA Federal Law and Federal Codes of Regulation. Further, the FDA expects manufacturers, when submitting medical devices for approval, to provide their own supportive evidence by showing compliance with ISO and IEC good manufacturing practice and safety standards. Finally, it is only pragmatic to accept that marketing permission for all devices is ultimately overseen, inspected and enforced solely by the FDA. By comparison, within Europe it is the more modern Medical Device Directives of the European Commission that are the statutory legislation. In order to market a medical device, the only fundamental responsibility of the manufacturer is that it must have a CE marking, which is achieved by showing compliance with the Essential Requirements. One means of accomplishing this is to conform with the provisions of relevant harmonized standards. Such concurrence may be verified if needed, by one of the international pool of independent Notified Bodies, who are ultimately overseen by the Competent Authorities of the individual States of the Community. The preparation of standards for medical devices is a slow process, involving the cooperation of the multiple stakeholders with an interest in the device. They are expected to produce a final document that is fair, consistent and practical for all the parties involved, from the initial designer to the final patient to whom the device is attached. Analysis of the three standards applicable to humidifiers, HME and BSF demonstrates some of the difficulties encountered in meeting these obligations. It is to be hoped that the solutions which were found achieve the ultimate goal of all medical device standards-specifically that the equipment should not cause a hazard to either the patient or user. But it is interesting to wonder whether it can be shown that any BSF meets one of the prime requirements of the FDA, to wit that all medical devices must be able to demonstrate efficacy. There is a dearth of clinical trials supporting the allegation of BSF manufacturers that the routine use of these devices improves patient care, which can only be taken to mean that to date such claims are difficult to vindicate. This paralogism must be countered by the indisputable fact that BSF can significantly increase the work of breath-ing, enlarge the deadspace and even, as has been shown recently, result ina complete blockage of the breathing system. Whatever standards are in place with reference to any particular medical device, it must never be forgotten that it is only the clinician who will finally be accountable for the safe and effective operation of the equipment. While caveat emptor must always be the shibboleth of the purchaser, statutory or advisory regulations are no defense for an incompetent user.

Canada↗

Preimplantation genetic diagnosis reduces pregnancy loss in women aged 35 years and older with a history of recurrent miscarriages.

OBJECTIVE: To determine whether preimplantation genetic diagnosis (PGD) and transfer of euploid embryos would decrease spontaneous abortion rates in recurrent miscarriage (RM) patients. DESIGN: Controlled clinical study. SETTING: In vitro fertilization centers and PGD reference laboratory. PATIENT(S): Recurrent-miscarriage patients with three or more prior lost pregnancies with no known etiology. INTERVENTION(S): Biopsy of a single blastomere from each day 3 embryo, followed by fluorescence in situ hybridization analysis. MAIN OUTCOME MEASURE(S): The rate of spontaneous abortions in RM subjects undergoing PGD were compared with [1] their own a priori expectations and [2] a comparison group of women undergoing PGD for advanced maternal age (> or =35 years). RESULT(S): Before PGD, RM patients had lost 87% (262/301) of their pregnancies, with an expected loss rate of 36.5%. After, they only lost 16.7% pregnancies. This difference was mostly due to reduction in pregnancy loss in the > or =35-years age subgroup, to 12% from an expected 44.5%. CONCLUSION(S): Preimplantation genetic diagnosis aneuploidy screening has a beneficial effect on pregnancy outcome in RM couples, especially those in which the woman is aged > or =35 years. Our data indicate that PGD reduces the risk of miscarriage in RM patients to baseline levels.

Abortion, Habitual↗

Pseudo-Meigs syndrome secondary to ovarian germ cell tumor.

An 11-year-old white girl presenting with fever, dyspnea, and cough demonstrated a left pleural effusion, ascites, and a suprapubic mass on physical and radiologic examinations. Surgical resection of the mass found a stage Ic malignant mixed germ cell tumor of the ovary. The pleural effusion and ascites were benign and resolved spontaneously after complete resection of the tumor, which is characteristic of a pseudo-Meigs syndrome.

Ascites↗

Single blastocyst transfer: a prospective randomized trial.

OBJECTIVE: To determine the efficacy of single blastocyst transfer. DESIGN: Prospective randomized trial. SETTING: Private assisted reproductive technology unit. PATIENT(S): Forty-eight women undergoing IVF-embryo transfer with day 3 FSH 12 mm in diameter on day of hCG administration. INTERVENTION(S): Embryo culture to the blastocyst stage in sequential media G1/G2 followed by transfer of either one or two blastocysts. MAIN OUTCOME MEASURE(S): Implantation rate, ongoing pregnancy rate, and twinning. RESULT(S): The transfer of a single blastocyst resulted in an implantation and ongoing pregnancy rate of 60.9% with no twins. The transfer of two blastocysts resulted in an implantation rate of 56%, an ongoing pregnancy rate of 76% with a 47.4% incidence of twins. CONCLUSION(S): Single blastocyst transfer is an effective method of eliminating multiple births while maintaining high pregnancy rates in this selected group of patients.

Adult↗

Voxel-based morphometry detects patterns of atrophy that help differentiate progressive supranuclear palsy and Parkinson's disease.

Progressive supranuclear palsy (PSP) and Parkinson's disease (PD) are neurodegenerative diseases with distinctive pathological appearances. Early clinical diagnosis can be difficult. MRI may help differentiate PSP from PD, but the differences are often only obvious with advanced disease. It would be useful to have an unbiased assessment of difference to guide visual assessment of MRI as an aid to clinical diagnosis. Voxel-based morphometry (VBM) offers nonbiased, observer-independent morphometric MRI analysis. Our objectives were to assess structural differences between PSP, PD, and normal controls and test the clinical utility of the results. T1-weighted MR images in 12 patients with clinically diagnosed PSP, 12 with PD, and 12 age- and sex-matched controls were normalized to a common stereotaxic space and segmented into gray matter (GM) and white matter (WM) then analyzed using VBM. MRI scans were reviewed by a neuroradiologist blinded to the clinical diagnosis and assigned to the "non-PSP" or "PSP" group based on regional differences highlighted using VBM. VBM revealed significant group differences between PSP and PD as well as PSP and controls, with tissue reduction demonstrated in the region of the cerebral peduncles and midbrain. With these regional differences as a guide, neuroradiological diagnosis achieved a sensitivity of 83% and a specificity of 79%. VBM did not detect dramatic changes in frontal regions despite significant frontal cognitive decline in the PSP group. Pathology in the basal ganglia rather than tissue loss in the frontal lobes could be responsible for this. This information may help in the differentiation of PSP in clinical practice.

Aged↗

An evaluation of a bayesian method of dose escalation based on bivariate binary responses.

Recently, various approaches have been suggested for dose escalation studies based on observations of both undesirable events and evidence of therapeutic benefit. This article concerns a Bayesian approach to dose escalation that requires the user to make numerous design decisions relating to the number of doses to make available, the choice of the prior distribution, the imposition of safety constraints and stopping rules, and the criteria by which the design is to be optimized. Results are presented of a substantial simulation study conducted to investigate the influence of some of these factors on the safety and the accuracy of the procedure with a view toward providing general guidance for investigators conducting such studies. The Bayesian procedures evaluated use logistic regression to model the two responses, which are both assumed to be binary. The simulation study is based on features of a recently completed study of a compound with potential benefit to patients suffering from inflammatory diseases of the lung.

Algorithms↗

Post operative pain experiences of central Australian aboriginal women. What do we understand?

OBJECTIVE: The aim of this study was to explore the postoperative pain experiences of Central Australian Aboriginal women and the subsequent interpretation of that pain experience by non-Aboriginal female nurses. DESIGN: Qualitative study using grounded theory methodology. SETTING: Postoperative surgical setting of a Central Australian regional hospital. SUBJECTS: Five Aboriginal female clients who had undergone a surgical procedure, eight non-Aboriginal female nurses and four Aboriginal female health workers employed by a Central Australian regional hospital. RESULTS: Aboriginal women have culturally appropriate ways of expressing and managing pain that are not well understood by non-Aboriginal female nurses. In addition, the Aboriginal women inappropriately endow non-Aboriginal nurses with the same powers and skills expected of healers from their culture. This phenomenon resulted in the non-Aboriginal nurses lacking the cultural insight and the appropriate knowledge and tools required to assess and manage the postoperative pain of Central Australian Aboriginal women effectively or efficiently. CONCLUSIONS: Non-Aboriginal nurses have a profound knowledge deficit about the postoperative pain experiences of Central Australian Aboriginal women. This deficit is evident through the use of culturally inappropriate and unreliable pain assessment strategies and tools and the misinterpretation of traditional pain relief strategies, such as the use of pituri, rubbing and centreing. The findings of this study suggested that nurse/client interactions related to language and role interpretation were in cultural conflict. The nurses expected the Aboriginal women to adopt pain behaviours as understood from the nurses' culture. The nurses anticipated that the client would contribute to their own care by communicating pain experiences in ways that are familiar and are believed to be universal. The Aboriginal women expected the nurses to conduct business similar to that of their own traditional tribal healers, 'to see within' and to 'just know'.

Anecdotes as Topic↗

An unusual case of X-linked adrenoleukodystrophy with auditory processing difficulties as the first and sole clinical manifestation.

X-linked adrenoleukodystrophy (X-ALD) is characterized by demyelination that is associated with a deficient beta-oxidation of very long chain fatty acids. We report the unusual case of a male adult with X-ALD who was diagnosed at the age of 26 by a brain MRI performed because his brother had been diagnosed with a rapidly deteriorating form of X-ALD. His sole symptom was hearing difficulties in the presence of a normal audiogram since childhood. He has remained stable for seven years. Central auditory testing in our patient revealed severe deficits in several auditory processes. These findings correlated with involvement of the auditory pathway at the level of the trapezoid body, and posterior corpus callosum in particular, on his brain MRI. This case highlights not only the need for thorough audiological investigation of the patient who complains of hearing difficulties in the presence of a normal audiogram, but also that audiological investigations could be of value in the phenotypic evaluation of cases with adrenoleukodystrophy.

Acoustic Impedance Tests↗

Changing the start temperature and cooling rate in a slow-freezing protocol increases human blastocyst viability.

OBJECTIVE: To determine the effect of start temperature and cooling rate of a slow freezing protocol on human blastocyst viability. DESIGN: Controlled-rate freezing of human blastocysts using different start temperatures and cooling rates. SETTING: Private assisted reproductive technology unit. PATIENT(S): Patients donated with consent cryopreserved pronucleate embryos. INTERVENTION(S): Culture of thawed pronucleate embryos in G III series media, containing hyaluronan, followed by cryopreservation of 36 blastocysts with subsequent noninvasive analysis of embryo metabolism. MAIN OUTCOME MEASURE(S): Pyruvate and glucose consumption and blastocyst reexpansion and quality. RESULT(S): Glucose consumption and blastocyst reexpansion after thaw were significantly higher when a start temperature of -6 degrees C and a cooling rate of 0.5 degrees C/min to -32 degrees C were used compared with a start temperature of 20 degrees C and a cooling rate of 2 degrees C to -6 degrees C, followed by cooling at 0.3 degrees C to -35 degrees C. Pyruvate uptake after thaw was not affected by the freezing procedure. Clinical use of the lower start temperature and quicker cooling rate, combined with culture in hyaluronan-based media, has led to the establishment of a 30% implantation rate. CONCLUSION(S): Human embryos cultured to the blastocyst stage in hyaluronan-based sequential media are readily cryopreserved and maintain their viability after thaw.

Blastocyst↗

Comparing the effects of femoral nerve block versus femoral and sciatic nerve block on pain and opiate consumption after total knee arthroplasty.

The goal of this study was to compare femoral and femoral plus sciatic nerve blocks in the postoperative pain management of patients undergoing total knee arthroplasty (TKA). A total of 97 patients participated in a convenience sample, comparative study. Patients who received femoral nerve block only (n = 30) reported statistically higher pain scores (P <.05) and showed 61% higher opiate consumption than those who received femoral and sciatic nerve blocks (n = 67) in the first 24 hours after surgery. The results suggest that the combined femoral and sciatic nerve block provides superior pain management in the early postoperative period after TKA.

Aged↗

The ennursement of old age in NSW: a history of nursing and the care of older people between white settlement and Federation.

The public perception of old age has come to be strongly associated with the nursing profession. This perception persists in Australian culture despite recent attempts by government and some sectors of industry to remove or dilute nursing from nursing homes as well as a trend by nurses themselves to not highly regard caring for older people. The history and heritage of the relationship between older people and nursing is not well known or appreciated in Australia. How and when did: 1) older people emerge as a social group identifiable not only by chronological age but also by their specific needs; and 2) nurses come to care for older people in Australia? The following is a brief history examining this unique phenomenon.

Aged↗

Partial epilepsy with pericentral spikes: a new familial epilepsy syndrome with evidence for linkage to chromosome 4p15.

The genetic analysis of simple Mendelian epilepsies remains a key strategy in advancing our understanding of epilepsy. In this article, we describe a new family epilepsy syndrome, partial epilepsy with pericentral spikes, which we map to chromosome 4p15. We distinguish it clinically, electrophysiologically, and genetically from previously described Mendelian epilepsies. The family described is a large Brazilian kindred of Portuguese extraction in which affected family members manifest a variety of seizure types, including hemiclonic, hemitonic, generalized tonic-clonic, simple partial (stereotyped episodes of epigastric pain), and complex partial seizures consistent with temporal lobe epilepsy. The syndrome is benign, either requiring no treatment or responding to a single antiepileptic medication. Seizure onset is in the first or second decades of life, with seizures in individuals up to the age of 71 years and documented encephalogram changes up to the age of 30 years. A key feature of partial epilepsy with pericentral spikes is a characteristic encephalogram abnormality of spikes or sharp waves in the pericentral region (centroparietal, centrofrontal, or centrotemporal). This distinctive encephalogram abnormality of pericentral spikes unites these several seizure types into a discrete family epilepsy syndrome. As with other familial epilepsies, the inherited nature of this new syndrome may be overlooked because of the variability in penetrance and seizure types among affected family members.

Adolescent↗

A randomized, controlled trial comparing compression bandaging and cold therapy in postoperative total knee replacement surgery.

PURPOSE: To examine the difference between compression bandaging and cold therapy after total knee arthroplasty. SAMPLE: Eighty-four postoperative, unilateral, total knee replacement, surgical clients. PROCEDURE: Clients were randomized into two groups: those receiving compression bandaging, and those receiving cryo-pad technology. Subjects were assessed for total length of stay, blood loss, blood transfusion, swelling, flexion, pain, and opiate use. FINDINGS: Unlike other studies, the results of these data showed no significant differences between groups on the measured outcomes. A simple cost benefit analysis shows that the compression bandage is cheaper and more labor efficient than the cold therapy as delivered by cryo-pad technology.

Arthroplasty, Replacement, Knee↗