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Biomedical subjects

T Y Chan

Publications and source records attributed to T Y Chan.

At least 55 records · Page 3Linked to original sources
PubMed1998

Anti-diabetic drugs as a cause of hypoglycaemia among acute medical admissions in Hong Kong and Singapore--relationship to the prescribing patterns in diabetic patients.

Severe hypoglycaemia due to anti-diabetic drugs is a more important cause of medical admissions in Hong Kong (1.5%) than in Singapore (0.4%-0.8%), although the prevalence and pattern of diabetes mellitus in the two Chinese populations are similar. Review of the available drug utilisation data indicated that glibenclamide and tolbutamide are the most frequently used sulphonylurea in Hong Kong and Singapore, respectively. These drugs also predominate among diabetic patients admitted with hypoglycaemia in the respective population. Since the risk of hypoglycaemia is greater for glibenclamide than other sulphonylureas, the increased incidence of anti-diabetic drug-induced hypoglycaemia in Hong Kong may, at least in part, be related to the frequent use of glibenclamide.

Acute Disease↗
PubMed1998

Drug interactions as a cause of overanticoagulation and bleedings in Chinese patients receiving warfarin.

Little is known about the incidence and consequences of drug interactions in patients receiving warfarin. Hence, drug interactions as a cause of overanticoagulation and bleedings were determined in Chinese patients admitted to our medical unit during a 9-month period in 1994/95. Only patients with an admission international normalized ratio (INR) of > 3.0 (target range 2.0-2.5) were included since the drug interactions, if present, were more likely to be of clinical significance. Of 35 patients reviewed, 7 had a predisposing condition such as peptic ulcer and 19 received drugs or folk medicines that can interact with warfarin. Based on the temporal relationship between the initiation of the interacting agent(s) and the rise in INR/onset of bleedings, drug-warfarin interactions were definitely (n = 6) or possibly (n = 1) responsible in 7 patients (drugs for common cold 2, piroxicam plus piroxicam gel 2, medicated oil (15% methyl salicylate) plus Salvia miltiorrhiza Bge 1, "analgesic balm" (50% methyl salicylate) 1, diclofenac gel 1). These agents were prescribed by their physicians (n = 1), family doctors (n = 1) and other specialists (n = 1) or bought over-the-counter (n = 2). One other patient used the drugs from previous consultations. Five of the 7 patients developed bleedings. Drug interactions accounted for 20% of all patients with an INR of > 3.0 and 5 (36%) of 14 patients with bleedings. Patients receiving warfarin should be warned about the danger of self-medication. When prescribing warfarin, physicians should be aware of other medications that their patients are taking.

Adult↗
PubMed1998

Childhood poisoning: the scope for prevention.

Many deaths and disabling sequelae in children following poisoning could be prevented if more attention were given to implementing preventive measures at home. Medications and chemicals should always be safely packed and stored. Education on which products are highly dangerous and the giving of precautionary advice to parents would also help to reduce the incidence of childhood poisoning. In Hong Kong, imported vegetables (contaminated by methamidophos) and coral reef fish (containing ciguatoxins) cause poisoning in both children and adults. Advice on preventive measures should be given to the public.

Adult↗
PubMed1997

Design of compounds that increase the absorption of polar molecules.

Hydrophilic drugs are often poorly absorbed when administered orally. There has been considerable interest in the possibility of using absorption enhancers to promote absorption of polar molecules across membrane surfaces. The bile acids are one of the most widely investigated classes of absorption enhancers, but there is disagreement about what features of bile acid enhancers are responsible for their efficacy. We have designed a class of glycosylated bile acid derivatives to evaluate how increasing the hydrophilicity of the steroid nucleus affects the ability to transport polar molecules across membranes. Some of the glycosylated molecules are significantly more effective than taurocholate in promoting the intestinal absorption of a range of drugs, showing that hydrophobicity is not a critical parameter in transport efficacy, as previously suggested. Furthermore, the most effective glycosylated compound is also far less damaging to membranes than the best bile acid absorption promoters, presumably because it is more hydrophilic. The results reported here show that it is possible to decouple absorption-promoting activity from membrane damage, a finding that should spark interest in the design of new compounds to facilitate the delivery of polar drugs.

Animals↗
PubMed1997

Co-trimoxazole-induced severe haemolysis: the experience of a large general hospital in Hong Kong.

The sulphamethoxazole component of co-trimoxazole can cause clinically significant haemolysis, particularly in subjects with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Erythrocyte G6PD deficiency is common amongst Southern Chinese in Hong Kong, affecting 4.4% of the males and 0.35% of the females. The incidence of this complication amongst the 0.9 million subjects aged > or =15 years residing in the New Territories East during a 12-month period in 1994-95 was determined. A search of the computerized medical record system in our medical unit at the Prince of Wales Hospital, the sole general hospital for the region, was used to identify such cases. Of a total of 46 patients having a diagnosis ICD code of 282 (hereditary haemolytic anaemias), 283 (acquired haemolytic anaemias) or 960 (poisoning by antibiotics), none had haemolysis due to co-trimoxazole. Based on the consumption of co-trimoxazole tablets in the Prince of Wales Hospital, it was estimated that 2163 subjects aged > or =15 years received this drug from the hospital alone. The number of subjects who were treated in the community was not known but experience in Sweden suggested that there could be 2-3 times more. Severe haemolysis due to co-trimoxazole appears to be exceedingly rare in Hong Kong as in the United States and Sweden.

Journal Article↗
PubMed1997

Differences in vitamin D status and calcium intake: possible explanations for the regional variations in the prevalence of hypercalcemia in tuberculosis.

The prevalence of hypercalcemia in patients with untreated tuberculosis (TB) varies widely between countries. Since the vitamin D status and calcium intake are important determinants of hypercalcemia in TB, these two factors were compared among four populations (U.K., Hong Kong, Malaysia, Thailand) with a low prevalence (<3%) and two populations (Sweden, Australia) with a high prevalence (>25%). In the three Asian countries, the circulating vitamin D levels are abundant, but the calcium intakes are low. Subjects from the U.K. have the lowest circulating vitamin D level of all, although their calcium intake is high. In Sweden and Australia, both the circulating vitamin D levels and calcium intakes are high. Since serum 1,25(OH)2D concentration will only be raised if its substance for extrarenal conversion, 25(OH)D, is plentiful and the effect of a given serum 1,25 (OH)2D concentration on serum calcium is determined by the calcium intake, it is postulated that the regional variation in the prevalence of hypercalcemia in TB may be due to differences in the circulating vitamin D levels and calcium intakes in these populations.

Calcium↗
PubMed1997

Improvements are needed in the existing packaging of medicated oils containing methyl salicylate.

In view of the toxic potential of medicated oils containing methyl salicylate, we have studied the existing packaging of 10 commonly used preparations from Hong Kong and Singapore and identified areas for improvement with respect to the prevention of poisonings. They were all packed in translucent bottles without child-resistant closures. The methyl salicylate content ranged from 15 to 67%. Many preparations also contained other potentially toxic ingredients in significant amounts, such as turpentine oil and camphor. The contents of the larger bottles could generally be emptied more easily because of the greater size of their openings. The product with the highest methyl salicylate content also had the biggest opening of all. The threat from ingestion of medicated oils containing methyl salicylate can probably be 'reduced' by: (i) using child-restraint closures; (ii) restricting the size of both the openings and the bottles; and (iii) reducing the methyl salicylate content.

Camphor↗
PubMed1997

Heparin therapy in the Chinese--lower doses are required.

Warfarin requirements are lower in the Chinese, but it is not known if this applies to heparin. We investigated the optimal dose for heparin therapy in Chinese patients, and to assess relationship between i.v. heparin dosage and anticoagulation efficacy. One hundred Chinese patients requiring intravenous heparin therapy were given an initial bolus followed by continuous intravenous infusion. The main outcome measures were: (i) Efficacy of anticoagulation assessed by blood coagulation studies (APTT) compared to heparin dosage, (ii) Determinants of dosage variation-age, gender, body weight, height, indication for heparin therapy and number of medications, other disease, and serum albumin level. It was found that the mean therapeutic infusion dose requirement of heparin was 848.7 +/- 274.7 units/h, 79% required a dose of 1000 units/h or less. Heparin dose correlated negatively with age (r = -0.40; p < 0.001) and positively with weight (r = 0.44 p < 0.001) and height (r = 0.49; p < 0.001). Chinese subjects require lower heparin doses (about 800 units/h) than usually recommended for Caucasians (usual dose 1000-1500 units/h). This can be partly explained by the lower body weight in Chinese patients.

Adult↗
PubMed1997

Alteration in leukocyte adhesion molecule expression following minor, moderate and major trauma.

An understanding of the mechanisms of post-injury leukocyte trafficking is essential to the development of future therapeutic interventions aimed at preventing infection and multiple organ failure in trauma patients, yet very little is known about the cellular and molecular events resulting in mobilization of members of the leukocyte family following trauma. We have studied the post-injury expression of the lymphocyte, monocyte and neutrophil adhesion molecules CD11a (LFA-1), CD11b, CD11c, CD29 (beta-1 integrin) and CD62L (L-selectin) in a group of 36 trauma patients, 13 of whom had suffered major trauma (ISS > or = 16), 15 moderate trauma (ISS = 9-15) and eight minor trauma (ISS < 9). Three ml blood samples were taken within 2.5 h of injury (mean sample time = 1.2 h, median = 1 h) into EDTA anticoagulant. Fifty-three normal control subjects were also studied for comparison. Leukocytes were stained using fluorescent-labelled monoclonal antibodies specific for each adhesion molecule, and the mean receptor density per cell measured using flow cytometry. Monocytes, neutrophils and lymphocytes in the trauma patients showed significantly increased mean-receptor density of L-selectin (p < 0.0001, 0.0001 and 0.004 respectively). Neutrophils and monocytes showed a significantly decreased level of expression of CD11a, and neutrophils showed a significant decrease in expression of CD11c. Our results indicate that there is a reduction in CD11a expression after trauma which may play an important role in the demargination of neutrophils and monocytes. The strong increase in L-selectin expression in all cell populations was unexpected, and is potentially important because this molecule supports rolling behaviour in all members of the leukocyte family, and would promote close contact between leukocytes and the endothelium at the site of injury without firm adhesion taking place. These events may be of significance in planning future strategies to combat post-trauma complications.

Cell Adhesion Molecules↗
PubMed1997

Cryptogenic fibrosing alveolitis and the fibrosing alveolitis of systemic sclerosis: morphological differences on computed tomographic scans.

BACKGROUND: The purpose of this study was to identify morphological differences on the computed tomographic (CT) scan between cryptogenic fibrosing alveolitis (CFA) and the fibrosing alveolitis associated with systemic sclerosis (FASSc), and to examine their biological relevance. METHODS: One hundred and seven patients with CFA (n = 55) or FASSc (n = 52) who had undergone thin section CT scanning were included. Multivariate analysis was used to identify morphological differences on the CT scans between lone CFA and FASSc, and to determine whether the pattern and distribution of disease on the CT scans were functionally significant (as judged by the lung transfer factor (TLCO), forced vital capacity (FVC), and arterial oxygen tension (PaO2)) or predictive of survival (independent of the type and extent of fibrosing alveolitis, age, sex, and smoking history). RESULTS: Increasingly extensive disease on CT scans was associated with a coarser reticular pattern (increase in reticular score per percentage increase in disease extent = 0.06, 95% confidence interval (CI) 0.03 to 0.09, p < 0.0005) and increasing upper zone involvement (increase in ratio of upper zone to total disease per percentage increase in disease extent = 0.002, 95% CI 0.000 to 0.003, p < 0.04). Patients with CFA were characterised by a higher upper zone ratio (difference = 0.08, 95% CI 0.02 to 0.13, p < 0.004) and a weak trend towards a coarser reticular pattern (p = 0.09), independent of disease extent. Smokers with CFA had more upper zone involvement (difference = 0.11, 95% CI 0.05 to 0.16, p < 0.0005) and a coarser reticular pattern (difference in reticular score = 1.92, 95% CI 0.27 to 3.55, p < 0.02) than smokers with FASSc. The extent of disease on the CT scan was predictive of lung function impairment and survival but the pattern and distribution of disease were not. CONCLUSIONS: Patients with CFA have relatively more upper zone involvement than those with FASSc independent of the extent of disease on the CT scan. This finding may result from smoking related damage but is not functionally significant.

Diagnosis, Differential↗
PubMed1997

Antihypertensive and anti-albuminuric effects of losartan potassium and felodipine in Chinese elderly hypertensive patients with or without non-insulin-dependent diabetes mellitus.

After a 4-week placebo baseline period, 29 Chinese elderly hypertensive patients were randomized, double-blind, to 12 weeks of treatment with either losartan potassium (n = 19), an angiotensin II antagonist at the AT1 receptor, or felodipine (n = 10), a calcium channel blocking agent. Of these 29 patients 12 had coexisting non-insulin-dependent diabetes mellitus. At week 12, the mean reductions (95% confidence intervals) in mean arterial pressure were similar in both groups: losartan -18 (range -22 to -14) mm Hg; felodipine -19 (range -25 to -11) mm Hg. In the whole group, the 24-hour urinary albumin excretion was reduced by 27% with losartan as compared with no change in the felodipine-treated group (p = 0.03; analysis of variance). In the diabetic group, losartan treatment reduced the urinary albumin excretion by 24% as compared with 11% in the felodipine-treated group. In the non-diabetic patients, the urinary albumin excretion fell by 29% in the losartan-treated group, but increased by 14% in the felodipine-treated group (p < 0.001; repeated-measures analysis of variance). Plasma sodium increased to a similar extent in both groups. The fasting plasma triglyceride level declined by 25% (p < 0.001 within group) with losartan, but was not significantly reduced in the felodipine-treated group. For comparable reductions in blood pressure, a greater reduction in albuminuria was seen with losartan than with felodipine treatment in Chinese hypertensive patients with or without non-insulin-dependent diabetes mellitus. Long-term studies are required to examine whether these antiproteinuric effects of losartan can be translated to renoprotection.

Aged↗
PubMed1997

Epidural infusion of bupivacaine 0.0625% plus fentanyl 3.3 micrograms/ml provides better postoperative analgesia than patient-controlled analgesia with intravenous morphine after gynaecological laparotomy.

One hundred and twenty women undergoing gynaecological abdominal operations were randomized to receive either epidural bupivacaine 0.0625% + fentanyl 3.3 micrograms/ml infusion (Group EPI, n = 57), or patient-controlled intravenous morphine analgesia (Group PCA, n = 54) for postoperative pain relief. The groups were comparable in demographic data, types and duration of operation. Group EPI achieved significantly lower verbal rating scale of pain (VRS) at rest at 0, 4, 12, 16, 20, 28 and 40th postoperative hours. The VRS during cough were also significantly lower in Group EPI at 0, 4, 8, 12, 28 and 36th postoperative hours. None of the patients had respiratory depression or hypotension. Nausea/vomiting occurred in 52.6%/33.3% of patients in Group EPI and 52.7%/37.0% in Group PCA. Most patients (84.2% in Group EPI and 72.2% in Group PCA) rated their pain management as "good". We conclude that epidural infusion of bupivacaine 0.0625% and fentanyl 3.3 micrograms/ml provide better analgesia than patient-controlled intravenous morphine after gynaecological laparotomy.

Analgesia, Epidural↗
PubMed1997

Epidemiology of poisoning in the New Territories south of Hong Kong.

Little is known about the incidence and pattern of poisonings in Hong Kong. Hence, adults (subjects aged > or = 15 years) and children (subjects aged < or = 14 years) hospitalized in the Princess Margaret Hospital in 1994 with ICD codes of 960-977 (medicinal poisonings) or 980-989 (non-medicinal poisonings) were studied. This is the main general hospital with a 24-hour emergency department for the 0.68 million people living in the New Territories South. Sex and age specific rates per 100,000 population were calculated. The incidence of poisoning in 1994 was 113.5/100,000. The incidence was higher in males than in females (130.0 vs 96.4/100,000). Poisoning was more common in adults than in children (128.8 vs 44.9/100,000). Subjects with medicinal poisonings were predominantly young females and hypnotics/sedatives were the main agents involved. In contrast, males aged 35-64 years predominated in non-medicinal poisonings, which were mostly related to alcohol. In children, medicinal poisonings were more common than non-medicinal poisonings (24.9 vs 20.2/100,000). All of the nine deaths were adults.

Adolescent↗
PubMed1997

Granulocyte-colony stimulating factor in the treatment of colchicine poisoning.

1. Colchicine is a highly active alkaloid used in the treatment of gouty arthritis and pseudogout. In overdose colchicine inhibits cell division effecting organs with a high rate of cell turn-over, such as the gastrointestinal tract and bone marrow. Early fatality results from cardiovascular collapse and respiratory failure, however pancytopenia and overwhelming septicaemia can occur later. 2. We describe a case of suicidal ingestion of 25-30 mg of colchicine in a previously healthy 43-year-old woman. Initial symptoms were mainly gastrointestinal. By day 5 she had developed severe pancytopenia and early sepsis, which were successfully treated using granulocyte colony stimulating factor (G-CSF) 600 micrograms s.c. 3. In vitro G-CSF is produced by the haematopoietic system. However, G-CSF can now be produced by recombinant DNA cloning technology and thus is available clinically. 4. There is no recognised antidote for colchicine poisoning and treatment is symptomatic. Fab fragments may have a promising future in eliminating colchicine from the body, but are currently not clinically available. In those patients that survive the initial phase of poisoning, G-CSF offers an effective method of treating the pancytopenia and preventing overwhelming septicaemia. Daily monitoring of the patient's haematological status is strongly recommended.

Adult↗
PubMed1997

Monitoring the safety of herbal medicines.

Extremely limited knowledge about the ingredients in herbal medicines and their effects in humans, the lack of stringent quality control and the heterogenous nature of herbal medicines all necessitate the continuous monitoring of the safety of these products. In Hong Kong, safety information on herbal medicines has come from the enquiries and reports received by our Drug and Poisons Information Service, on-going surveillance of patients treated in a large general teaching hospital and review of reports from the medical literature. Circumstances under which poisonings have occurred are also analysed in order to devise preventive measures. Once collected, this information is then distributed to health professionals in Hong Kong and abroad. WHO projects and pilot studies in Europe are also under way to promote and facilitate reporting of adverse reactions to herbal medicines.

Drug Monitoring↗