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Biomedical subjects

J A Williamson

Publications and source records attributed to J A Williamson.

At least 19 recordsLinked to original sources
PubMed1997

A Queensland family with ciguatera after eating coral trout.

Ciguatera (poisoning caused by eating fish contaminated with algal toxins) is usually diagnosed clinically. We describe a Queensland family of four (including a pregnant woman) with ciguatera, confirmed by bioassay of the implicated fish for ciguatoxin. All four recovered, illustrating the effectiveness of treatment with intravenous mannitol. At birth, the infant appeared to suffer no adverse effects attributable to ciguatera; to our knowledge, this is the first report of the effect of severe ciguatera in the first trimester of pregnancy.

Adult↗
PubMed1996

Chromosomal localisation of the human envoplakin gene (EVPL) to the region of the tylosis oesophageal cancer gene (TOCG) on 17q25.

Envoplakin is a membrane-associated precursor of the epidermal cornified envelope. Envoplakin is homologous to desmoplakin I and desmoplakin II (DPI/II), bullous pemphigoid antigen 1 (BPAG1), and plectin and is proposed to link desmosomes and keratin filaments to the cornified envelope. We describe the isolation of cosmids and yeast artificial chromosomes containing the complete human envoplakin gene (EVPL) and show, by analysis of somatic cell hybrids and chromosomal in situ hybridisation, that the envoplakin gene, unlike the genes encoding BPAG1 and DPI/II, maps to 17q25 and is physically linked to D17S1603. This sequence-tagged site segregates with the autosomal dominant human disease focal nonepidermolytic palmoplantar keratosis (NEPKK; "tylosis"), which is associated with an increased risk of oesophageal cancer. The chromosomal localisation of the envoplakin gene, the homology of the encoded protein to keratin-binding proteins, and its expression in epidermal and oesophageal keratinocytes all raise the possibility that loss of envoplakin function could be responsible for this form of palmoplantar keratoderma.

Chromosome Mapping↗
PubMed1996

Chromosomal mapping of the human and mouse homologues of two new members of the AP-2 family of transcription factors.

The AP-2 transcription factor has been shown to play an important role in the development of tissues of ectodermal origin and has also been implicated in mammary oncogenesis. It has recently been found that AP-2 is encoded by a family of related genes, AP-2alpha, AP-2beta, and AP-2gamma. As a further step in understanding the role each of these genes has in development, we have used fluorescence in situ hybridization to map the chromosomal locations of the mouse and human homologues of the newly isolated AP-2beta and AP-2gamma genes. Tcfap2b and Tcfap2c map to mouse chromosomes 1A2-4 and 2H3-4, respectively, while TFAP2B and TFAP2C map to human chromosomes 6p12 and 20q13.2, the latter being a region that is frequently amplified in breast carcinoma.

Animals↗
PubMed1996

Polyclonal origin of colonic adenomas in an XO/XY patient with FAP.

It is widely accepted that tumors are monoclonal in origin, arising from a mutation or series of mutations in a single cell and its descendants. The clonal origin of colonic adenomas and uninvolved intestinal mucosa from an XO/XY mosaic individual with familial adenomatous polyposis (FAP) was examined directly by in situ hybridization with Y chromosome probes. In this patient, the crypts of the small and large intestine were clonal, but at least 76 percent of the microadenomas were polyclonal in origin.

Adenomatous Polyposis Coli↗
PubMed1995

Guess LOD approach: sufficient conditions for robustness.

Analysis of genetic linkage between a disease and a marker locus requires specifying a genetic model describing both the inheritance pattern and the gene frequencies of the marker and trait loci. Misspecification of the genetic model is likely for etiologically complex diseases. In previous work we have shown through analytic studies that misspecifying the genetic model for disease inheritance does not lead to excess false-positive evidence for genetic linkage provided the genetic marker alleles of all pedigree members are known, or can be inferred without bias from the data. Here, under various selection or ascertainment schemes we extend these previous results to situations in which the genetic model for the marker locus may be incorrect. We provide sufficient conditions for the asymptotic unbiased estimation of the recombination fraction under the null hypothesis of no linkage, and also conditions for the limiting distribution of the likelihood ratio test for no linkage to be chi-squared. Through simulation studies we document some situations under which asymptotic bias can result when the genetic model is misspecified. Among those situations under which an excess of false-positive evidence for genetic linkage can be generated, the most common is failure to provide accurate estimates of the marker allele frequencies. We show that in most cases false-positive evidence for genetic linkage is unlikely to result solely from the misspecification of the genetic model for disease or trait inheritance.

Genetic Linkage↗
PubMed1993

First aid treatment of jellyfish stings in Australia. Response to a newly differentiated species.

Vinegar has been shown to inhibit neomatocyst discharge in Chironex fleckeri, the deadly north Australian box-jellyfish, and application of vinegar has become accepted first aid, not only for box-jellyfish stings, but also for stings by other Australian jellyfish. However, in a newly differentiated species of Physalia in Australian waters, which causes severe envenomation, vinegar was found to cause discharge in up to 30% of neomatocysts. In treating these stings, the use of vinegar is not recommended as it may increase envenomation. Stings from the single-tentacled Physalia utriculus (the "bluebottle") are not severe, tentacles with unfired nematocysts rarely adhere to the victim's skin and vinegar dousing is not required. Vinegar treatment is therefore an unnecessary step in the first aid management of any Physalia sting but remains an essential first aid treatment for all cubozoan (box) jellyfish tested to date.

Acetates↗
PubMed1993

Path analysis and sib-pair linkage.

When the distance between linked loci is expressed in terms of the correlation between the identity-by-descent (idb) values of the loci, then a path model may be used to order loci with data on sib-pairs and their parents. The relationship between the recombination fraction and the correlation coefficient is developed and a method for fitting a covariance matrix predicted by a specific ordering of loci to an observed covariance matrix is proposed.

Epidemiologic Methods↗
PubMed1993

Plasma catecholamine levels during exposure to an environment of hyperbaric oxygen.

Plasma catecholamine levels were measured before, during and after hyperbaric oxygen therapy in nine subjects. Adrenaline levels were elevated immediately prior to hyperbaric oxygen therapy, but then fell and stabilized once treatment commenced. No significant fluctuations in plasma dopamine or noradrenaline levels were noted during the treatment period. This study does not support the premise that there is a suppression of endogenous plasma catecholamine levels during hyperbaric oxygen as has been previously reported. The observed initial increase in adrenaline can be attributed to stress/anxiety and the subsequent decline in this stress, rather than the result of the hyperbaric oxygen treatment itself.

Adult↗
PubMed1993

The Australian Incident Monitoring Study. Errors, incidents and accidents in anaesthetic practice.

Human error is a pervasive and normal part of everyday life and is of interest to the anaesthetist because errors may lead to accidents. Definitions of, and the relationships between, errors, incidents and accidents are provided as the basis to this introduction to the psychology of human error in the context of the work of the anaesthetist. Examples are drawn from the Australian Incident Monitoring Study (AIMS). An argument is put forward for the use of contemporaneous incident reporting (eliciting relevant contextual information as well as details of use to cognitive psychologists), rather than the use of accident investigation after the event (with the inherent problems of scant information, altered perception and outcome bias). A classification of errors is provided. "Active" errors may be classified into knowledge-based, rule-based, skill-based and technical errors. Different strategies are required for the prevention of each type and it may now be useful to place more emphasis in anaesthetic practice on categories to which little attention has been directed in the past. "Latent" errors make an enormous contribution to problems in anaesthesia and several categories are discussed (e.g. environment, physiological state, equipment, work practices, personnel training, social and cultural factors). An approach is provided for the prevention and management of errors, incidents and accidents which allows clinical problems to be categorized, the relative importance of various contributing factors to be established, and appropriate preventative strategies to be devised and implemented on the basis of priorities determined from the AIMS data. Accidents cannot be abolished; however, an understanding of the factors underlying them can lead to the rational direction of resources and effort to prevent them and minimise their effects.

Accident Prevention↗
PubMed1993

The Australian Incident Monitoring Study: an analysis of 2000 incident reports.

The Australian Patient Safety Foundation was formed in 1987; it was decided to set up and co-ordinate the Australian Incident Monitoring Study as a function of this Foundation; 90 hospitals and practices joined the study. Participating anaesthetists were invited to report, on an anonymous and voluntary basis, any unintended incident which reduced, or could have reduced, the safety margin for a patient. Any incident could be reported, not only those which were deemed "preventable" or were thought to involve human error. The Mark I AIMS form was developed which incorporated features and concepts from several other studies. All the incidents in this symposium were reported using this form, which contains general instructions to the reporter, key words and space for a narrative of the incident, structured sections for what happened (with subsections for circuitry incidents, circuitry involved, equipment involved, pharmacological incidents and airway incidents), why it happened (with subsections for factors contributing to the incident, factors minimising the incident and suggested corrective strategies), the type of anaesthesia and procedure, monitors in use, when and where the incident happened, the experience of the personnel involved, patient age and a classification of patient outcome. Enrollment, reporting and data-handling procedures are described. Data on patient outcome are presented; this is correlated with the stages at which the incident occurred and with the ASA status of the patients. The locations at which the incidents occurred and the types of procedures, the sets of incidents analysed in detail and a breakdown of the incidents due to drugs are also presented.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. Which monitor? An analysis of 2000 incident reports.

The role of monitors in patients undergoing general anaesthesia was studied by analysing the first 2000 incidents reported to the Australian Incident Monitoring Study; 1256 (63%) were considered applicable to this study. In 52% of these a monitor detected the incident first; oximetry (27%) and capnography (24%) detected over half of the monitor detected incidents, the electrocardiograph 19%, blood pressure monitors 12%, a low pressure (circuit) alarm 8%, and the oxygen analyser 4%. Of the other monitors used, 5 first detected 1-2% of incidents, and the remaining 8 less than 0.5% each. The oximeter would have detected over 40% of the monitor detected incidents had its more informative modulated pulse tone always been relied upon instead of the "bleep" of the ECG. A theoretical analysis was then carried out to determine which of an array of 17 monitors would reliably have detected each incident had each monitor been used on its own and had the incident been allowed to evolve. To facilitate "scoring" of monitors, the incidents were categorized empirically into 60 clinical situations; 40% of applicable incidents were accounted for by only 5 clinical situations, 60% by 10 and nearly 80% by 20. 98% were accounted for by the 60 situations. A pulse oximeter, used on its own, would theoretically have detected 82% of applicable incidents (nearly 60% before any potential for organ damage). These figures for capnography are 55% and 43% and for oximetry and capnography combined are 88% and 65%, respectively. With the addition of blood pressure monitoring these become 93% and 65%, and of an oxygen analyser, 95 and 67%. Other monitors, including the ECG, each increase the yield by by less than 0.5%. The international monitoring recommendations and those of the Australian and New Zealand College of Anaesthetists are thoroughly vindicated by the patterns revealed in this study. The priority sequence of monitor acquisition for those with limited resources should be stethoscope, sphygmomanometer, oxygen analyser if nitrous oxide is to be used, pulse oximeter, capnograph, high pressure alarm, and, if patients are to be mechanically ventilated, a low pressure alarm (or spirometer with alarm); an ECG, a defibrillator, a spirometer and a thermometer should be available.

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. The capnograph: applications and limitations--an analysis of 2000 incident reports.

The first 2000 incidents reported to the Australian Incident Monitoring Study were analysed with respect to the role of the capnograph. One hundred and fifty-seven (8%) were first detected by a capnograph and there were a further 18 (1%) in which capnography was contributory. Of the 1256 incidents which occurred in association with general anaesthesia 48% were "human detected" and 52% "monitor detected". The capnograph was ranked second and detected 24% of these monitor detected incidents; this figure would have been nearly 30% if a correctly checked, calibrated capnograph had always been used. The capnograph is a "front-line" monitor for oesophageal intubation, failure of ventilation, anaesthetic circuit faults, gas embolism, sudden circulatory collapse and malignant hyperthermia. It is a valuable "back-up" monitor when other monitors (e.g. low pressure alarm, pulse oximeter) are not in use, are being used incorrectly or fail. Such situations, in order of frequency of detection were: circuit-leak, overpressure of the breathing circuit, bronchospasm, leak of ventilator-driving-gas into the patient circuit, aspiration and/or regurgitation and hypoventilation. There were 20 reports of "failure", over two-thirds of which would not have occurred with appropriate checking and calibration. Seven were due to gas sampling problems and 6 to apnoea alarm failure. Two circuit leaks and 2 faulty unidirectional valves were not detected; on 3 occasions problems occurred due to power failure, calibration problems, or misinterpretation of an alarm.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. Crisis management--validation of an algorithm by analysis of 2000 incident reports.

Anaesthetists are called upon to manage complex life-threatening crises at a moment's notice. As there is evidence that this may require cognitive tasking beyond the information-processing capacity of the human brain, it was decided to try and develop a generic crisis management algorithm analogous to the "Phase I" immediate response routine used by airline pilots. Such an algorithm, based on the mnemonic "COVER ABCD, A SWIFT CHECK", was developed and refined over 3 meetings, each attended by 60-100 anaesthetists and aviation psychologists. It was validated against 1301 relevant incidents among the first 2000 incidents reported to the Australian Incident Monitoring Study. It proved sufficiently robust and safe to recommend its general use as an initial response to any incident or crisis which occurs when a patient is breathing gas from an anesthetic machine. It requires a limited knowledge base and is easily learnt and rehearsed during the anaesthetist's working day. It will provide a functional diagnosis in over 99% of cases and will correct 62% of the problems in 40-60 seconds. In the remaining 37% it will allow the anaesthetist to proceed with a "sub-algorithm", confident in the knowledge that some important step has not been missed. In just over 30% of incidents this will be for a problem familiar to all anaesthetists (e.g. laryngospasm, bradycardia); in just over 6% it will be for a less common, more complex, but finite, set of problems (3% cardiac arrest, 1% air embolism, 1% anaphylaxis, 1% for the remaining desaturations); in less than 1% diagnosis and correction will require a more complex checklist (e.g. for malignant hyperthermia, pneumothorax). The next stage, the development of specific sub-algorithms and a structured team approach for ongoing problems, is in progress.

Algorithms↗
PubMed1993

The Australian Incident Monitoring Study. The "wrong drug" problem in anaesthesia: an analysis of 2000 incident reports.

Amongst the first 2000 incidents reported to the Australian Incident Monitoring Study, there were 144 incidents in which the "wrong drug" was nearly or actually administered to a patient. Thirty-three percent of the incidents involved ampoules and just over 40% syringes; in over half of the latter the syringes were of the same size, and also, in over half, they were correctly labelled. In 81% of the 144 incidents the "wrong drug" was actually given. This was more common with syringes (93%) than ampoules (58%). Thus the most common error was actually giving the wrong drug from a correctly labelled syringe. The most common drug involved was a muscle relaxant in both ampoule and syringe incidents. In 74% of all reports, there was the potential for serious harm to the patient; however no deaths were reported. Factors which contributed significantly to the incidents were similar appearance, inattention and haste. "Failure of communication" was a significant factor in syringe incidents when two or more staff were involved. The only significant factor which minimised the outcome was rechecking of the syringe or drug ampoule before giving the drug. Strategies suggested to address the "wrong drug" problem include education of staff about the nature of the problem and the mechanisms involved; colour coding of selected drug classes for both ampoules and syringes; the use of standardised drug storage, layout and selection protocols; having a drawing up and labelling convention; and the use of checking protocols.

Anesthesia↗
PubMed1993

The Australian Incident Monitoring Study. Difficult intubation: an analysis of 2000 incident reports.

The first 2000 incidents reported to the Australian Incident Monitoring Study were analysed with respect to the incidence and circumstances of problems with endotracheal intubation; 85 (4%) indicated difficulties with intubation. One third of these were emergency cases, one third involved an initially unassisted trainee and one fifth were outside normal working hours. Failure to predict a difficult intubation was reported in one third of the cases, with another quarter presenting serious difficulty despite preoperative prediction. Difficulties with ventilation were experienced in 1 in 7 of the 85 reports; there was one cardiac arrest, but no death. Endotracheal intubation was not achieved in one fifth of the cases. The commonest complications reported amongst the 85 incidents were oesophageal intubation (18 cases), arterial desaturation (15 cases), and reflux of gastric contents (7 cases). Emergency trans-tracheal airways were required in 5 cases. Obesity, limited neck mobility and mouth opening, and inadequate assistance together accounted for two thirds of all the contributing factors. The most successful intubation aid in this series was a gum elastic bougie. A capnograph contributed to management in 28% and a pulse oximeter in 12% of the cases in which they were used. The most serious desaturations were associated with accidental oesophageal intubation. These data suggest a lack of reliable preoperative assessment techniques and skills for the prediction of difficult intubations. They also suggest the need for a greater emphasis on ensuring that the necessary equipment is available, and on teaching and learning drills for difficult intubation and any associated difficulty with ventilation.

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. Problems related to the endotracheal tube: an analysis of 2000 incident reports.

The first 2000 incidents reported to the Australian Incident Monitoring Study were analysed with respect to problems with the endotracheal tube; 189 (9%) were reported. The most common problem was endobronchial intubation which accounted for 42% of these 189 reports; endobronchial intubation was the most common cause of arterial desaturation in the 2000 incidents. Obstructions and oesophageal intubation each accounted for 18% of the 189 problems with tubes. The remainder was made up of disconnections and leaks (7% each), misplacements other than endobronchial or oesophageal (4%), inappropriate choice of tube (3%), cuff herniation (1%), failure to deflate the cuff and foreign body in the tube (0.5% each). The pulse oximeter and capnograph first detected 58% of these incidents; a further 25% were detected clinically. The pulse oximeter is the "front-line" monitor for endobronchial intubation, and the capnograph the "front-line" monitor for oesophageal intubation, disconnection and obstruction. Recommendations are made for how to prevent problems and how to determine the nature of those that do occur.

Accidents↗