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Y S Tan

Publications and source records attributed to Y S Tan.

At least 19 recordsLinked to original sources
PubMed2006

Schwannoma of the gastrointestinal tract: a clinicopathological, immunohistochemical and ultrastructural study of 33 cases.

AIMS: Thirty-three cases of gastrointestinal schwannomas were analysed to elucidate their peculiar clinicopathological, immunohistochemical and ultrastructural features. METHODS AND RESULTS: The patients were 16 men and 17 women, whose ages ranged from 27 to 81 years (median 52.6 years). Tumour size ranged from 10 to 120 mm in diameter. Follow-up in 23 cases from 6 months to 13 years showed no recurrences or metastases. Microscopically, all tumours were composed of spindle cells with focal epithelioid cells in four cases. In all cases except one, there were peripheral cuff-like lymphoid aggregates. Immunohistochemically, tumours were strongly positive for S100 protein and vimentin, the tumours were variably positive for nestin (78.8%, 26/33) and glial fibrillary acidic protein (63.6%, 21/33), three tumours had CD34+ cells, but all were negative for CD117, alpha-smooth muscle actin and desmin. Ultrastructurally, the tumours were composed of elongated spindle shaped cells with prominent parallel membranous structures. CONCLUSIONS: Gastrointestinal schwannomas have characteristic histological features, especially the presence of a lymphoid cuff, that are different from their soft tissue and central nervous system counterparts. Gastrointestinal tract schwannomas behave in a benign fashion.

Adult↗
PubMed2005

Numerical study on the pulsatile flow characteristics of proximal anastomotic models.

Haemodynamics was widely believed to correlate with anastomosis restenosis. Utilizing the haemodynamic parameters as indicator functions, distal anastomosis was redesigned by some researchers so as to improve the long-term graft patency rate. However, there were few studies upon the proximal anastomosis. Therefore, in this study, flow characteristics and distributions of the haemodynamic parameters in proximal anastomosis under physiological flow condition have been investigated numerically for three different grafting angles: namely, 45 degrees forward facing, 45 degrees backward facing, and 90 degrees anastomotic joints. The simulation results showed a flow separation region along the graft inner wall immediately after the heel at peak flow phase and it decreased in size with the grafting angle shifting from 45 degrees forward facing to 45 degrees backward facing. At the same time, a pair of vortex was found in the cross-sectional planes of the 45 degrees backward facing and 90 degrees grafts. In addition, stagnation point was found along the graft outer wall with small shifting during the physiological cycle. High spatial and temporal wall shear stresses gradients (WSSG) were observed around the anastomotic joint. Low time-averaged wall shear stress (WSS) with elevated oscillation shear index (OSI) was found near the middle of anastomosis at the aorta wall and along the graft inner wall respectively, while high time-averaged WSS with low OSI was found at the heel, the toe, and the region downstream of the toe. These regions correlated to early lesion growth. Elevated time-averaged WSSG was found at the same region, where the elevated low-density lipoprotein (LDL) permeability was observed as reported in the literature. The existence of nearly fixed stagnating location, flow separation, vortex, high time-averaged WSS with low OSI, low time-averaged WSS with elevated OSI, and high time-averaged WSSG may lead to graft stenosis. Moreover, the simulation results obtained were consistent with those of experimental measurements. Based on the validated simulation results, the 45 degrees backward-facing graft was found to have the lowest variation range of time-averaged WSS and the lowest segmental average of WSSG among the three models investigated. The 45 degrees backward-facing graft is thus recommended for the bypass operation with expected higher patency rate.

Anastomosis, Surgical↗
PubMed2003

Fever attribution in the SARS outbreak.

Fever as a somatised symptom is not commonly described. We report a patient who complained of recurrent unexplained "fevers" during the severe acute respiratory syndrome (SARS) outbreak in Singapore. The presentation, while likely to be peculiar to the outbreak, posed challenges and difficulties to the primary care doctors. Investigations did little to allay her anxiety. Instead, appreciating the psychosocial backdrop and how the SARS outbreak affects patient and doctor may be useful.

Depression↗
PubMed2000

Cardiopulmonary exercise testing in heart transplant candidates.

INTRODUCTION: We evaluated the results of patients with congestive heart failure (CHF) who underwent cardiopulmonary exercise testing (CPET) as part of their assessment for heart transplantation in order to examine the relationship between exercise capacity and resting indices of left ventricular function in these patients. MATERIALS AND METHODS: Twenty-seven ambulatory heart transplant candidates underwent CPET using a cycle ergometer and an incremental work-rate protocol till symptom-limitation. These patients included 24 men and 3 women with a mean age of 42.3 years. The aetiology of CHF was coronary artery disease in 14 patients, dilated cardiomyopathy in 11 patients, and congenital heart disease in 2 patients. Mean resting left ventricular ejection fraction (LVEF) was 19% (range 7% to 36%). RESULTS: Thirteen of the 27 tests performed were maximal studies and all except 2 subjects attained a measurable anaerobic threshold during CPET. Of the 13 maximal tests, the causes of exercise limitation were cardiomyopathy in 3 patients, ischaemic heart disease in 2 patients, significant oxygen desaturation in 2 patients, ventilatory limitation due to obstructive lung disease in 1 patient, ventilatory limitation secondary to a restrictive lung disease in 3 patients, and combined obstructive ventilatory and cardiovascular limitation in 2 patients. There was no significant correlation between resting LVEF and peak VO2 percent predicted (r = 0.14, P = 0.49). CONCLUSIONS: Exercise intolerance in patients with CHF may not be related to limited cardiac reserve and non-cardiac causes of exertional symptoms should also be considered. CPET is useful for the evaluation of functional capacity and mechanisms of exercise intolerance in patients with CHF.

Adult↗
PubMed1999

Changing the institutional practice of prolonged mechanical ventilation after coronary artery bypass graft surgery to early extubation.

Since 1997 some of our cardiac anaesthetists have, whenever possible, extubated the patients early after cardiac surgery to improve their level of comfort, to allow an early return of the cardiopulmonary physiological function, and to help reduce health care costs. After a few months of implementing this practice, an audit was carried out to evaluate the success of early extubation after coronary artery bypass graft (CABG) surgery. Over a 6-month period starting from May 1997, the perioperative data of 110 consecutive patients with good or moderate left ventricular function scheduled for elective CABG were prospectively collected and analysed. The anaesthetic regime was according to the preference of the anaesthetists. Initially consent was obtained from the surgeons when the extubation criteria were fulfilled, but subsequently as the practice became more accepted by the surgeons, extubation was initiated by the anaesthetists. Within 4 hours of admission into the intensive care unit (ICU), 50 (45.5%) of the 110 patients satisfied the early extubation criteria and were extubated. The extubation criteria are described in the article. For the remaining patients, the median duration of mechanical ventilation was 14.3 hours. The profiles of the two groups of patients and the possible reasons for not extubating early are discussed. Forty-five per cent of the patients with moderate to good ventricular function were extubated safely within 4 hours of admission into the ICU after CABG surgery. With gradual acceptance of the practice and a change in mindset amongst all the care givers, more patients can benefit from this practice. This article highlights the challenges associated with changing institutional practices with respect to the postoperative care of cardiac patients.

Analysis of Variance↗
PubMed1999

Control of hypertension in postoperative patients.

In this paper, adaptive control systems have been developed for the closed-loop control of mean arterial pressure using vasoactive drugs. An adaptive algorithm based on generalized predictive control law has been presented. A adaptive PI controller has been designed. The recursive least-square identification algorithm is used for on-line parameter estimation. The supervisor is added to provide safety and efficacy of control under the consideration of the physical and physiological constraints. Extensive computer simulation in the presence of unpredictable disturbances shows the system is capable of inducing hypertension.

Algorithms↗
PubMed1997

Smoking in the Singapore Armed Forces.

The Singapore Armed Forces has, since 1986, established a comprehensive smoking control programme which combines health education, counselling and administrative measures aimed at discouraging non-smokers from smoking, and encouraging smokers to quit the habit. The prevalence of regular smoking decreased from 28.6% in 1987 to 20.7% in 1993. The latest, 1993 survey as in past surveys covered 3,545 respondents, made up of regulars (32.0%), NSF (62.2%) and NUSAF (5.6%). The 1993 survey revealed that the majority of smokers (88.9%) in the SAF who consist primarily of 18 to 20-year-olds, had started smoking before enlistment. Most acquired the habit on their own (49.8%) or through influences outside the SAF (40.3%). Very few smokers became smokers through the influence of fellow soldiers (4.9%). The majority (87.7%) of smokers readily agreed that smoking is harmful, but this is not translated into practice. Health education efforts need to focus more on bringing about positive attitudinal and behavioural changes, rather than merely give information and advice. The young age of smoking onset (mean age of 14.3 years) In the SAF population surveyed points to the need to focus preventive efforts further upstream than hitherto emphasised.

Humans↗
PubMed1995

The effect of recombinant growth hormone on nitrogen balance in malnourished patients after major abdominal surgery.

The effect of recombinant growth hormone (rGH) on nitrogen balance was studied in malnourished patients receiving total parenteral nutrition after major abdominal surgery. Fifteen patients were randomized to receive either subcutaneous rGH (0.2 iu/kg) or placebo (saline) injection daily for seven days after surgery. Positive nitrogen balance was achieved throughout the treatment period with rGH administration and was significant on days 3 and 6. This was associated with increase in mid-arm muscle circumference and significant weight gain. Plasma insulin-like growth factor-1 (IGF-1) concentration was significantly raised in the rGH group at day 7, suggesting its role in the anabolic effect of growth hormone. Plasma pre-albumin and retinol-binding protein concentrations were raised in both the rGH and control groups, indicating improvement in the nutritional status. We conclude that the postoperative catabolic response can be attenuated using recombinant growth hormone.

Abdomen↗
PubMed1994

Autotransfusion: is there a benefit in a current practice of aggressive blood conservation?

Findings from early studies suggested that the autotransfusion of shed mediastinal blood (ATS) after cardiac surgical procedures led to a reduction in the postoperative banked blood requirements. However, changes in baseline patient characteristics and other blood conservation methods may now negate the benefits of ATS. To determine whether the routine use of ATS is effective in the context of current surgical practice, risk factors related to postoperative banked blood requirements were analyzed in a prospective series of 155 consecutive patients undergoing cardiac operations: 71 patients before and 84 patients after the addition of ATS to an already aggressive standardized blood conservation protocol. The overall mean patient age was 66 +/- 11 years; the mean preoperative patient hemoglobin level was 11.8 +/- 1.8 g/dL; 48% of the procedures were elective and 12% were reoperations; coronary artery bypass grafting was performed in 73% of the patients and valve repair or replacement in 34%, with no differences between the non-ATS and ATS groups (all, p = not significant). The mean 24-hour postoperative blood loss was 1,278 +/- 814 mL in the non-ATS group and 1,721 +/- 1,510 mL in the ATS group (p < 0.03). The mean volume autotransfused in the ATS group was 1,122 +/- 97 mL. The overall reoperation rate for bleeding was 0.6% (70% confidence interval, 0 to 1.3%) and the hospital mortality was 1.9% (70% confidence interval, 0.8% to 3.1%), which did not differ between the non-ATS and ATS groups (both, p = not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

[Nuclear morphometric analysis of colorectal adenocarcinoma and its clinicopathologic significance].

A nuclear morphometric analysis was performed on the histologic sections of 64 colorectal adenocarcinomas with a 5-year follow-up. The parameters selected in this study were nuclear area (NA), nuclear perimeter (NP), standard deviation of nuclear area (SDNA), nuclear volume (NV), nuclear diameter of an equivalent circle (ND). No clear correlation was found between the five parameters and the clinicopathologic data of colorectal adenocarcinomas. The five parameters were important prognostic factors in colorectal adenocarcinomas. It was found that the grade II colorectal adenocarcinomas were a heterogenous group and could be divided prognostically into various subgroups by nuclear morphometry.

Adenocarcinoma↗
PubMed1994

[Torticollis and C1-C2 rotation subluxation. Apropos of a case. The value of a dynamic scanner and of a 3-dimensional scanner].

The authors report the rare and complex case of a girl who had been followed since the age of 3 years for hydrocephalus the cause of which was found only when she was 6-year old. The causative agent was a pilocytic astrocytoma of the cerebellum. On April 10, 1990, she underwent subtotal excision of the tumour, associated with radiotherapy. Four months later she developed an increasingly painful and irreducible torticollis which did not respond to tractions. Dynamic CT scans and 3-dimensional CT scans were performed in the fourth month and provided a diagnosis of right C1-C2 rotatory subluxation. There was no history of injury and no sign of inflammatory process. Rotatory subluxation is a very rare lesion difficult to diagnose, and few cases have been published, although the signs are those of classical torticollis in children. When medical treatment fails, often due to belated diagnosis, the only surgical treatment is uni- or bilateral C1-C2 arthrodesis. If the diagnosis can be made at an early stage, reduction of the rotatory luxation is usually easy and without consequences to the child. It is therefore recommended to perform a dynamic CT scan and a 3D CT scan as soon as possible in all children with lasting painful torticollis.

Astrocytoma↗
PubMed1992

[Residual liver cancer after transcatheter hepatic arterial chemoembolization in patients with large primary hepatic carcinoma].

15 cancer specimens resected after hepatic arterial chemoembolization (TCE) were studied pathologically. It was found that residual tumor tissue was present in three forms: failure of complete tumor necrosis; tumor emboli in small portal veins; and multiple cancer foci in adjacent liver parenchyma. It is believed that presenting residual tumor tissue after TCE may be attributed to one of the following conditions: low drug concentration in residual tumor tissue; the larger tumor size after TCE; more residual cancer tissue in ASCCL than in HCC, collaterals formed soon after hepatic arterial occlusion.

Carcinoma, Hepatocellular↗
PubMed1992

Prevalence of protein calorie malnutrition in general surgical patients.

The prevalence of protein calorie malnutrition (PCM) based on ten nutritional parameters was studied in 307 patients undergoing major elective surgical operations. These parameters included anthropometric measurements (weight/height, triceps skin fold thickness, arm muscle circumference) and biochemical (serum total proteins, albumin, transferrin, prealbumin, retinol binding protein) and immunological tests (total lymphocyte count and delayed hypersensitivity test). Using these criteria, the prevalence of PCM was high. Eighty-six percent of patients had at least one abnormal parameter. The prevalence of PCM as judged by weight/height and arm muscle circumference was 49% and 62% respectively. The incidence was higher in cancer than non cancer patients (63% vs 43%). Although serum albumin and total protein levels were normal in 93.5% of patients, acute serum protein markers such as transferrin, prealbumin and retinol binding protein were low in 20-30%. Lymphopenia of 1500 cells/cu mm or less was found in 18% and abnormal delayed hypersensitivity test in 60%. We found that only weight/height, serum protein, transferrin and lymphopenia had predictive values in postoperative morbidity and mortality. By identifying PCM patients early, adequate nutritional support can be given in order to reduce the risk of major surgical complications.

Adolescent↗
PubMed1992

Surgical management of intrathoracic aortic aneurysm.

The pathology, clinical features, indications for surgery and the results of intrathoracic aneurysm are analysed in thirty-nine consecutive patients who underwent surgery at Singapore General Hospital from January 1986 through December 1990. There were twenty cases of non-dissecting aneurysm and nineteen cases of dissecting aneurysm or aortic dissection. The 30 day survival for the twenty patients with non-dissecting aneurysm was sixteen patients (80%). The best results were obtained in patients with aortic root aneurysms. The overall 30-day survival for the nineteen patients with aortic dissection was twelve patients (64%). The mortality was especially high in patients with acute aortic dissection (46%). Recent advances in the management of these aneurysms make early recognition and diagnosis mandatory to achieve the best results.

Adult↗
PubMed1989

[Thymus pathological changes in perinatal babies and children].

The most outstanding pathological changes of perinatal babies and children, based on the review of the autopsy files in the 1st Affiliated Hospital of West China University of Medical Sciences, are lymphocytic depletion, and reticuloepithelial cell swelling and/or fusiform malformation in the cortex, while in the medulla apoptosis is more prominent. We suppose that these alterations are due to immaturity of cortical thymocytes, and in the diseased condition, they are easily affected by extraordinary factors, especially the influence of corticosterone inducing acute severe necrosis, so the number of lymphocytes are obviously diminished. But, in the medulla, as intact mature lymphocytes exist, physiological phenomenon such as apoptosis is rather prominent in it. While in the medulla, Hassall's corpuscles have various characteristic changes, such as cornification, calcification, fusion, cystic change and disintegration. Besides, we observed a new alteration in the thymus defined as vacuolization. All the above pathological changes reached the peak in the 28- day group; there after, they might become either worse or better according to the condition of the disease and growth of the body. However, these are still problems to be further studied separately.

Adolescent↗