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Biomedical subjects

Kenneth Wong

Publications and source records attributed to Kenneth Wong.

At least 19 recordsLinked to original sources
PubMed2005

Oil coating of hydrophobic surfaces from aqueous media: formation and kinetic study.

We perform oil coating of hydrophobic solid surfaces via aqueous media, from emulsions, and under the presence of a shear flow. The principle of such coating is based on the use of a system at the limit of aggregation to give rise to adhesion, with asymmetrical interfaces (oil droplet/water and solid surface/water) in order to favor the oil/surface adhesion in comparison to the oil/oil adhesion. This way, droplets stick to the solid substrate, whereas they are stable and homogeneously dispersed in the bulk. We have realized coatings from two systems of emulsions made of a mixture of hydroxy-terminated silicone oil and classical silicone oil and a mixture of sunflower oil and mineral oil. The kinetics of the coating is described by a Langmuir model where the adhesion between the oil particle and the surface is modeled as a first-order reaction. The resulting coatings are formed of oil droplets uniformly covering the solid surface. The coating density can vary with the nature of the experimental systems.

Journal Article↗
PubMed2005

Paraformaldehyde induces elevation of intracellular calcium and phosphatidylserine externalization in platelets.

Paraformaldehyde fixation of platelets stabilizes surface antigens while altering some that are associated with cellular activation. Present experiments show that the asymmetric distribution of phosphatidylserine in platelets was especially sensitive to paraformaldehyde treatment. It was found that this reagent induced a dose- and time-dependent translocation of phosphatidylserine to the membrane surface as measured by annexin V binding and flow cytometry. The percent phosphatidylserine-positive cells increased from about 5% to >90%. Chelation of extracellular Ca(2+) with EGTA partially blocked this translocation. Spectrofluorimetric analysis of fluo-3 loaded platelets indicates that paraformaldehyde caused a concomitant elevation of intracellular Ca(2+) concentrations, [Ca(2+)](i). ATP levels also declined in paraformaldehyde-treated cells, suggesting that the rise in [Ca(2+)](i) ensued in part from decreased activity of calcium pumps. Previous studies indicate that phosphatidylserine externalization arises from Ca(2+)-activated randomization of membrane phospholipids and decreased transport of phosphatidylserine from the outer to the inner leaflet of the plasma membrane. In light of present results, paraformaldehyde fixation is best avoided particularly in studies involving platelet apoptosis or activation.

Adenosine Triphosphate↗
PubMed2005

Interhospital transfers of patients with surgical emergencies: areas for improvement.

OBJECTIVE: To review mortality associated with interhospital transfers of patients with surgical emergencies from rural and peripheral metropolitan areas. DESIGN: A retrospective case note review. SETTING: All hospitals within an area health service including metropolitan and rural hospitals. SUBJECTS: All patients with a surgical emergency who died in hospital after interhospital transfer within an area health service. MAIN OUTCOME MEASURES: Factors associated with death and interhospital transfer. RESULTS: In total, 22 patients were identified. The mean age was 77 years. Thirty-six per cent of patients were assessed by a surgeon prior to transfer. The mean time taken for transfer was five hours. Ten patients were physiologically unstable prior to transfer. No medical escort accompanied these patients. Four patients deteriorated during the transport process. Seventy-three per cent of patients arrived out of normal working hours. Fifty per cent of patients required an operation within 24 hours of arrival. All of these patients had significant medical co-morbidities. Seventy-two per cent of these operations were performed out of hours as an emergency case. Twenty-three per cent did not receive any operative intervention or intensive care admission at the tertiary referral centre. Forty-one per cent of deaths were related to peritonitis and intra-abdominal soiling. CONCLUSIONS: Hospital systemic issues associated with mortality included extensive time delays in transfers, an inadequate transport process and frequent out-of-hours emergency operations. Patient features related to mortality included advanced age, significant medical co-morbidity and surgical pathology with a poor prognosis. Improvements concerning interhospital transfers of patients should address both systemic and patient issues.

Aged↗
PubMed2005

Severe trauma caused by stabbing and firearms in metropolitan Sydney, New South Wales, Australia.

BACKGROUND: Stabbing and firearm trauma causing severe injuries (injury severity score (ISS) >15) and death is uncommon in Australia. The present study describes the experience with stabbings and firearm trauma causing severe injuries at a major Australian urban trauma centre. METHODS: Data from a prospectively generated trauma registry regarding all patients presenting to Royal Prince Alfred Hospital (RPAH), Sydney, Australia with penetrating trauma causing severe injuries from July 1991 to June 2001 was retrospectively analysed. RESULTS: Of all patients presenting to RPAH with stabbing and firearms wounds over the 11 year study period, 28% received an ISS >15. One hundred and forty patients were identified. 94% were male. The mean age was 34 years (15-82 years). The number of cases/year has not shown an increasing trend. Thirty per cent of patients sustained firearm related injuries, with the remainder mainly caused by knives or machetes. Fifteen per cent of injuries were self inflicted. The most common location of injury was on a public street. Fifty-two per cent of patients were injured in more than one anatomical region, with the abdomen being the most common site of injury (53%). On hundred and seventy-four operations were performed - laparotomies (43%), thoracotomies (26%), craniotomies (5%) and orthopaedic, vascular, wound explorations and other procedures (26%). Twenty-eight per cent of patients suffered at least one complication during their admission, with coagulopathy being the most common complication (20%). Mean length of stay was 10.4 days (1-107 days). The total mortality rate for the severely injured patients was 21%, with gun-related injuries having a higher mortality rate than stabbing injury (36%vs 15%). Sixty per cent of deaths were related to exsanguination. CONCLUSIONS: Stabbings and firearm trauma are associated with significant morbidity, mortality and utilization of hospital resources in metropolitan Sydney. Overall mortality rates are similar to institutions with higher volumes of penetrating trauma.

Adolescent↗
PubMed2005

Do surgeons need to look after unwell patients? The role of medical emergency teams.

BACKGROUND: Medical emergency teams (MET) have been shown to reduce in-hospital morbidity and mortality of surgical patients. The present study reviews the experience with the use of MET in the care of critically unwell surgical patients. METHODS: Data were prospectively collected on all patients in a general surgical unit of a tertiary referral centre meeting the criteria for activating a MET over a 6 month period. These data were retrospectively analysed with respect to surgical team and MET involvement in the care of these patients. RESULTS: Over the 6 month study period, 22 patients qualified for a MET response based on criteria of physiological instability. A MET was activated for 13 of these patients (59%), with the remainder being managed by direct consultation with intensive care and medical staff. Forty-six per cent of MET activations were outside of normal working hours. Respiratory distress including tachypnoea and desaturation was the most commonly identified physiological abnormality (13 patients), accounting for 62% of MET activations. A MET was activated by a surgical registrar in 46% of cases. Seventy-seven per cent of MET activations were preceded by at least one registrar level assessment without resolution of the patient's clinical deterioration. The most common MET interventions were supplementation of oxygen therapy and initiation of pharmacotherapy (11 patients). The surgical team complemented the MET response by providing detailed information regarding the patient's surgical condition, premorbid status (13 patients), organized transfer to the operating theatre (three patients), initiated blood transfusions (two patients) and deciding to order abdominal computed tomography (two patients). Urgent surgical decision making was required in 23% of MET activations. CONCLUSIONS: Medical emergency team activations for critically unwell surgical patients are complemented by surgical team involvement in the decision making and management process. The MET may be underutilized in the management of unwell surgical patients.

Aged↗
PubMed2004

Heterogeneity in styrene-butadiene latex films.

Low-Tg styrene-butadiene (SB) latex films were investigated by noncontact atomic force microscopy and scanning electric potential microscopy, revealing a number of different morphologies and electric potential patterns across films cast from the same SB latex dispersions under the same conditions. Surface leveling and charge dispersion throughout the films are, thus, restrained even at temperatures above Tg and the minimum film-formation temperature. An unprecedented electric pattern is observed, in which the particle cores are more positive than the contacting particle outer layers. Different packing patterns, including cubic and hexagonal arrays, coexist in neighboring areas. Zonal centrifugation of the SB latex in sucrose density gradient shows that particles cover a broad range of densities. Thus, film surface heterogeneity is at least partly due to particle heterogeneity. Fractal dimensions of topographic profiles are lower than those of the electric potential profiles, showing that charge mobility is much more restrained than polymer chain motion at the film surface and that it imposes a limit to the charged chain-ends motion.

Butadienes↗
PubMed2004

Nitric oxide infusion alleviates cellular activation during preparation, leukofiltration and storage of platelets.

Nitric oxide (NO) is a reversible inhibitor of platelet activation that generates S-nitrosylated compounds in plasma. Since platelets are activated during processing to platelet concentrates and storage, NO is anticipated to dampen the rate of lesion development. Platelet-rich plasma (PRP) was separated into aliquots that were unfiltered, filtered to remove leukocytes, or treated with NO or nitrite before filtration. Platelets were resuspended and stored up to four days at 22 degrees C. Samples removed were measured for S-nitrosylation of plasma, P-Selectin release, complement activation, and cGMP levels. Direct infusion of a NO solution (authentic NO) to PRP before filtration decreased adherence of platelets and improved yields. An infusion rate resulting in 1/1000 dilution of a saturated NO solution was optimal. C3a formation and soluble P-Selectin released from NO-treated-filtered platelets were about half that in unfiltered and filtered controls after four days (p<0.05 by Student-Newman-Keuls method after ANOVA for repeated measures). Plasma isolated from NO-treated PRP combined with untreated platelets protected the latter to a similar extent. Increases in S-nitrosylated compounds in PRPs were correlated with NO effects on platelet recovery and storage. Sodium nitrite failed to inhibit platelet activation and cyclic GMP levels were significantly increased in NO-treated cells. Results indicate that NO inhibited platelet activation associated with processing and storage and suggest that slow release of NO from S-nitrosylated plasma components afforded long-term protection. The infusion of authentic NO into PRPs is potentially an efficacious method for generating anti-platelet compounds to inhibit storage lesions.

Blood Platelets↗
PubMed2004

Early in-hospital management of burn injuries in Australia.

BACKGROUND: The accurate initial assessment and management of burn injuries influences subsequent clinical outcome. The purpose of the present study was to evaluate, over a 12-year period (1989-2001), changes in the practices of referring hospitals in terms of early management of patients with burn injuries prior to transfer to a burns unit. METHODS: The details of all consecutive patients over two separate 12-month periods between June 1989 to May 1990 and between April 2000 and March 2001 who were transferred to the Burns Unit, Concord Repatriation General Hospital, Sydney, were prospectively recorded and retrospectively reviewed. In particular, the referral procedure, the accuracy of the referring hospital's assessment of burn size and initial fluid resuscitation were compared between the two time frames. RESULTS: There were 51 patients in the initial 12-month period and 57 patients in the latter 12-month period. Regarding the transfer of the latter group of patients, the referring hospital liaised directly by telephone with the Burns Unit registrar or consultant significantly more often (77%vs 45%, respectively, P < 0.05). Similar proportions of patients in the two time periods received correct initial assessment of burn size (39% in the 1989-1990 group vs 42% in the 2000-2001 group, P = 0.76). The latter group of patients was significantly more likely to receive the correct choice of fluid for initial resuscitation at the referring hospital (98%vs 61%, respectively, P < 0.05). CONCLUSIONS: Over this 12-year period, there has been marked improvement in referral practices and appropriate initial fluid resuscitation for patients with burn injuries. Referring hospitals' assessment of burn size has not improved. Possible reasons for the observed changes include: increased postgraduate education programmes by the Royal Australasian College of Surgeons and the Australian and New Zealand Burns association; the formalization of emergency medicine training programmes by the Australasian College of Emergency Medicine and increasing awareness within the medical community of the presence of dedicated burns units.

Adolescent↗
PubMed2004

Competency-based training of basic trainees using human cadavers.

BACKGROUND: Increasing constraints on operative training in the clinical setting provide impetus for the development of alternative training models. Anatomy dissection courses utilizing human cadavers have been useful in imparting knowledge of human anatomy for surgical trainees. The present study evaluates the impact of competency-based technical skills instruction as an adjunct to cadaveric dissection courses on the procedural skills of basic surgical trainees (BST). METHODS: A single cohort of BST was prospectively evaluated regarding their self-reported confidence and competency in performing saphenous vein cutdowns immediately before and after an anatomy dissection course. RESULTS: Nine BST were evaluated (66% were male). One subject withdrew from the study, leaving eight BST for final analysis. Mean number of years since graduation from medical school was 2.5 years (range: 2-4 years). Seven BST were in their first year of training. All subjects had completed an early management of severe trauma (EMST) course. Total prior experience of saphenous vein cutdowns for all subjects was a single attempt on a sheep cadaver at the EMST course. The percentage of BST expressing little or no confidence in performing cutdowns decreased after the dissection course (50% vs 0, P < 0.05). Mean time taken for completion of cutdown decreased after the dissection course. (5 min 52 s vs 3 min 52 s, P < 0.05). Mean size of incision used to perform cutdown decreased after the course. (4.5 cm vs 3.4 cm, P < 0.05). The percentage of subjects experiencing complications during cutdown decreased after the course (38% vs 0, P < 0.05). CONCLUSIONS: Anatomy dissection courses using human cadavers may contribute to improving the confidence and competency of BST in performing saphenous vein cutdowns. Technical training components should be considered as an adjunct to future anatomy dissection courses involving surgical trainees.

Anatomy↗
PubMed2004

Resources for managing trauma in rural New South Wales, Australia.

BACKGROUND: Trauma bypass is not always appropriate in the management of rural trauma because of the large distances and travel times. Rural hospitals in New South Wales, Australia are an essential component of the statewide integrated trauma system. The present study profiles the trauma resources of base hospitals in rural New South Wales. METHODS: A structured questionnaire, addressed to the 'Director, Emergency Department' was distributed to all rural base hospitals in New South Wales. Follow-up telephone interviews were administered to complete data collection. RESULTS: Fourteen hospitals were identified. General and orthopaedic surgeons provided trauma care in all hospitals. Forty-three per cent of hospitals had resident subspecialty surgeons. Fifty per cent of hospitals had a formal hospital trauma team. In the remaining hospitals, the most common reason (86%) stated for the absence of a formal trauma team was a lack of personnel to provide 24 h immediate response to all trauma presentations. Seventy-one per cent of hospitals are staffed by a single doctor after hours. All hospitals had 24 h access to plain radiography and blood products. 86% had 24 h access to ultrasound and computed tomography, although always on an 'on-call' basis after hours. All hospitals had the capability to maintain ventilated patients, averaging two ventilated beds per hospital. An average of two trauma patients per hospital per month is transferred to a larger institution. Sixty-four per cent of hospitals participated in a trauma retrievals for their surrounding areas. Seventy-one per cent of hospitals engaged in quality assurance activities regarding trauma outcomes. CONCLUSIONS: Formal responses to major trauma in rural base hospitals in New South Wales are often restricted by a lack of specialist medical personnel. Nevertheless, the majority of hospitals have the resources to manage major trauma.

Australia↗
PubMed2004

Paediatric trauma teams in Australia.

BACKGROUND: Trauma teams have been associated with improved survival probability of paediatric trauma patients. The present study seeks to estimate the use of trauma teams in Australian paediatric tertiary referral centres and describe their medical composition, leadership and criteria for activation. METHODS: Australian paediatric tertiary referral centres were identified. A structured questionnaire assessing the presence, composition and means of activation of a trauma team was mailed to the 'Director, Emergency Department' of all identified hospitals. Three months later, all hospitals were contacted by telephone to complete and verify data collection. RESULTS: Questionnaires were distributed to eight hospitals. Seventy-five per cent had an established trauma team. Hospitals without a trauma team claimed to have insufficient doctors to form a team and insufficient trauma caseload to justify a team. All trauma teams were potentially activated by prehospital paramedic data (field triage) and required a combination of anatomical, physiological and mechanistic criteria for activation. The two methods of mobilizing a trauma team were by dispatching a common call onto individual pagers (66%) or a specific trauma pager (33%) carried by trauma team members. Fifty per cent of hospitals had a two-tier, stratified trauma team response. All teams consisted of emergency, surgical and intensive care unit registrars. Trauma team leaders were emergency medicine specialists/registrars (33%), surgical registrars (33%) and non-defined (33%). Consultant surgeons were not members of any trauma team. Eighty-three per cent of trauma teams consisted of more junior members after hours. Fifty per cent of hospitals did not have a surgical registrar on site outside of business hours. Eighty-eight per cent of hospitals engaged in some form of trauma audit. CONCLUSIONS: Trauma teams are utilized by most Australian paediatric tertiary referral centres, with fairly uniform medical composition and criteria for activation. Paediatric surgeons presently have limited leadership roles and membership of Australian paediatric trauma teams.

Australia↗
PubMed2004

Surgical risk management: the value of a weekly surgical radio-pathological meeting.

BACKGROUND: Clinical risk management in surgery involves organizational practices focused on the prevention of adverse outcomes. The present study evaluates the value of a weekly clinical meeting involving surgeons, radiologists and pathologists as a model of clinical risk management within a general surgical department. METHODS: Data for all meetings conducted over a 6-month period were prospectively collected. Changes to previously reported pathology and radiology results, revisions to patient diagnosis, management and recommendations for subsequent patient care arising from the meetings were recorded. RESULTS: Data were collected for 18 meetings. One hundred and eleven patients were reviewed. Seventy-six patients had previously reported radiological investigations. Sixty-five patients had previously reported pathology specimens. Four per cent of radiology reports and 8% of pathology reports were amended at the meeting. Seven per cent of patients received a revised diagnosis. Twenty-seven per cent of patients had suggestions for changes in management. Changes to patient care arose from pathologist input in seven patients, from radiologist input in nine patients and from clinician input in 14 patients. Four patients were recommended for an alternative surgical procedure. Five patients were recommended for cancellation of a planned procedure. Adjuvant chemo/radiotherapy was considered for four patients. Referral to specialist surgeons was suggested for two patients. CONCLUSIONS: Weekly multidisciplinary clinical meetings allow early revision and refinement of patient diagnosis and management. As such, they are an effective pre-emptive incident monitoring system, facilitating regular audit and quality control as part of an overall strategy for surgical clinical risk management.

Disease Management↗