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Biomedical subjects

T Y Chan

Publications and source records attributed to T Y Chan.

At least 127 records · Page 7Linked to original sources
PubMed1995

Indapamide-induced severe hyponatremia and hypokalemia.

OBJECTIVE: To describe 2 patients with severe indapamide-induced hyponatremia and hypokalemia and to discuss the incidence and mechanisms of diuretic-induced hyponatremia and hypokalemia. CASE SUMMARY: Two women aged 60 and 62 years presented with severe hyponatremia (plasma sodium concentrations of 103-104 mmol/L) and hypokalemia (plasma potassium concentrations of 1.6-2.2 mmol/L) 5-6 weeks after they received indapamide 2.5 mg/d therapy for arterial hypertension. Central nervous system symptoms of hyponatremia were observed in both patients. One patient experienced severe postural hypotension, a plasma potassium concentration of 1.6 mmol/L, and electrocardiographic abnormalities consistent with hypokalemia. Hyponatremia was initially mistaken in this patient for the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Both patients recovered completely after withdrawal of indapamide therapy and correction of the hyponatremia and hypokalemia. DISCUSSION: Previous studies of administration of indapamide 2.5 mg/d for 10-24 months in hypertensive patients showed a low incidence (0.6-1.2%) of hypokalemia severe enough to require withdrawal of drug therapy. Serum sodium concentrations were unaltered in these studies. All case reports, except 1, of indapamide-induced electrolyte disturbances described only hypokalemia. CONCLUSIONS: Indapamide can cause both severe hypokalemia and hyponatremia. The predominant clinical features can be a result of severe hyponatremia. The latter can have diverse clinical presentations and may be mistaken for SIADH. As with other diuretics, plasma sodium and potassium concentrations must be monitored during indapamide therapy, especially in patients at risk for hyponatremia and hypokalemia.

Diabetes Mellitus, Type 2↗
PubMed1995

Adverse interactions between warfarin and nonsteroidal antiinflammatory drugs: mechanisms, clinical significance, and avoidance.

OBJECTIVE: To review the mechanisms and clinical significance of adverse interactions between warfarin and nonsteroidal anti-inflammatory drugs (NSAIDs) and discuss how these interactions can be avoided. DATA SOURCES: Previous studies of interactions between warfarin and NSAIDs or reports of adverse interactions were identified from a MEDLINE search (1976 to present) and from the reference lists of pertinent articles. STUDY SELECTION AND DATA EXTRACTION: All articles were considered for inclusion in the review. Pertinent information was selected for discussion. DATA SYNTHESIS: All NSAIDs can prolong bleeding time by inhibiting platelet function. High-dose aspirin has a direct hypoprothrombinemic effect. Phenylbutazone and its analogs enhance the hypoprothrombinemic effect of warfarin through a pharmacokinetic interaction by inhibiting the hepatic metabolism of warfarin. Mefenamic acid also enhances the anticoagulant effect of warfarin, but the mechanism is not known. The clinical relevance of protein binding displacement in the interaction between warfarin and NSAIDs has been overstated, although a significant one may be more likely in the presence of high concentrations of NSAIDs in patients with slow elimination of warfarin (e.g., those with severe heart failure or impaired liver function). NSAIDs can induce gastrointestinal bleeding, which is likely to be more severe if warfarin is also given. CONCLUSIONS: The combined use of warfarin and NSAIDs is generally discouraged because of the increased risk of bleeding in these patients. In patients receiving warfarin who also require NSAIDs, phenylbutazone and its analogs, high-dose aspirin, mefenamic acid, excessive use of topical methyl salicylate, and NSAIDs that are associated with a higher risk of bleeding peptic ulcers should be avoided. Patients should be closely monitored for anticoagulant control and bleeding complications during the combined use of warfarin and NSAIDs.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1995

Use and abuse of benzodiazepines in Hong Kong 1990-1993--the impact of regulatory changes.

To control benzodiazepine abuse in Hong Kong, the Government's Pharmacy and Poisons Board reclassified benzodiazepines as Dangerous Drugs in October 1990. Apart from formal prescriptions, detailed records were then required for the supply and dispensing of these drugs. These regulations were applied initially only to brotizolam, triazolam and flunitrazepam, and were extended in January 1992 to include all benzodiazepines. The impact of these regulatory changes on benzodiazepine use has been studied by analyzing the sales patterns of seven benzodiazepines between 1990-1993. In 1991, the sales of flunitrazepam and triazolam fell, but the sales of five unrestricted benzodiazepines increased. In 1992-1993, the sales of all but one of the benzodiazepines fell. Comparing 1993 to 1990, the fall in sales was particularly marked for triazolam, chlordiazepoxide and flunitrazepam. A regulation requiring the use of proper prescriptions and detailed records for the supply and dispensing of benzodiazepines, appears to have curbed, at least partially, their abuse in Hong Kong.

Benzodiazepines↗
PubMed1995

Renal failure is uncommon in Chinese patients with paracetamol (acetaminophen) poisoning.

The reported incidence of renal failure in unselected patients with paracetamol poisoning is about 1-2%. Since the introduction of antidotal therapy for paracetamol poisoning in 1973, renal failure is now mainly seen in those admitted too late for effective therapy and is usually associated with liver damage. To determine the incidence of renal failure in Chinese patients with paracetamol poisoning, a retrospective survey was conducted of 224 patients admitted to the Prince of Wales Hospital, Hong Kong, with paracetamol poisoning from January 1988 to January 1994. Of the 28 patients at risk (plasma paracetamol concentrations above the recommended treatment line), 13 developed liver damage which was severe in 5. One patient with severe liver damage developed a transient increase in plasma creatinine concentration from 90 to 116 umol/L. All 28 patients completely recovered. Renal failure was uncommon in Chinese subjects (0.4%), and this was probably related to a lower incidence of liver damage which may be due to less chronic alcoholism as well as ethnic differences in paracetamol metabolism resulting in an inherent reduced susceptibility to its liver and renal toxicity.

Acetaminophen↗
PubMed1995

Anticholinergic poisoning due to Chinese herbal medicines.

Serious poisoning may occur following the consumption of Chinese herbal medicines (CHM) containing anticholinergics. The great majority of cases are probably related to the use of yangjinhua, the dried flower of Datura metel L, for treating bronchial asthma, chronic bronchitis, pains and flu symptoms. In some cases the use of CHM contaminated by atropine-like substances or fake herbs were suspected. Some ginseng (Panax ginseng) preparations might have been adulterated with Mandragora officinarum (scopolamine) and other herbs.

Cholinergic Antagonists↗
PubMed1995

The clinical value of screening for salicylates in acute poisoning.

In this retrospective study, we evaluated the clinical value of screening for salicylates in 347 patients with acute poisoning presenting to the Prince of Wales Hospital, Hong Kong, between January 1992 and June 1993. In 83 patients (24%), ingestion of salicylates was suspected; the incidence of elevated plasma salicylate concentrations (> 0.1 mmol/L) in those who had taken identifiable drugs, unidentifiable drugs but known type, or topical medicaments was 71%, 16% and 61%, respectively. In 264 patients (76%), ingestion of salicylates was not suspected, and of these, 3 had elevated (0.2-0.4 mmol/L) plasma salicylate concentrations. Routine screening for salicylates in all patients with acute poisoning in Hong Kong appears unnecessary, especially as many authorities consider that 1 of the main indications for treating salicylate poisoning is clinical evidence of toxicity. Restricting plasma measurements to only those suspected of having ingested salicylates would have saved up to 76% of requests. All physicians should be aware of the high salicylate content of some Chinese proprietary topical medicaments.

Acute Disease↗
PubMed1995

Poisoning due to common household products.

From 1988 to 1992, 187 patients were admitted in four general medical wards at the Prince of Wales Hospital, Hong Kong with poisoning due to common household products. The main agents involved included "Dettol" liquid (46%), cleaning products (19%), pesticides (14%), and shampoos (10%). The majority of patients had only relatively mild symptoms. Ingestion of Dettol liquid and strong corrosives tended to be associated with serious complications and deaths. Two patients died after aspiration of Dettol liquid and detergent before and/or during gastric lavage. One other patient died after swallowing sulphuric acid. As with all poisoning, it is very important that the airway is adequately protected before gastric lavage is performed.

Adult↗
PubMed1995

Shellfish-borne illnesses. A Hong Kong perspective.

This article provides an overview of the spectrum of infectious and toxic illnesses that may occur following the consumption of contaminated shellfish in Hong Kong. These include hepatitis A, hepatitis E, infections due to vibrio species, paralytic shellfish poisoning, neurotoxic shellfish poisoning and heavy metal poisoning. Possible preventive measures are discussed.

Adolescent↗
PubMed1994

Response of cerebral endothelial cells to hypoxia: modification by fructose-1,6-bisphosphate but not glutamate receptor antagonists.

Damage to the cerebral endothelium from ischemia could exacerbate brain injury by altering vascular integrity, but little is known concerning the response of cerebral endothelial cells to hypoxia. To address this issue, cerebral capillary endothelial cells were isolated from 14-day-old rats, grown to confluence, and placed in hypoxic chambers for up to 62 h. Cells were undamaged by 24 hours of hypoxia as assessed by lactate dehydrogenase release and ethidium bromide staining, but 48 h resulted in marked damage. Hypoxia was probably exacerbated by hypoglycemia because glucose levels fell to < 1 mM by 24 h, at which point ATP levels began to fall in hypoxic cultures (3.25 +/- 1.48 nmol/mg protein; mean +/- S.D.) relative to normoxic cultures (9.52 +/- 1.41 nmol/mg protein). Cells treated with 4 mM fructose-1,6-bisphosphate (FBP) had significantly less damage at 48 h of hypoxia than controls. FBP had little effect on rate of glucose depletion from the media, but ATP depletion due to hypoxia was significantly less. Thus, the protective effect of FBP may be mediated by the ability of treated cells to maintain higher ATP levels. Unlike FBP, glutamate receptor antagonists including MK-801, NBQX, DNQX, and kynurenic acid were ineffective in ameliorating hypoxia-induced endothelial cell injury.

Adenosine Triphosphate↗
PubMed1994

Admittance models for open ended coaxial probes and their place in dielectric spectroscopy.

Starting from a rigorous formulation for the admittance of an open ended coaxial probe, this paper identifies the simplifying assumptions that are introduced to obtain more practical solutions. The predictions of the models are compared to each other and to experimental data obtained on an independently calibrated experimental set-up. The advantages and limitations of a model are determined by the theoretical derivation and the numerical solution. The model identified as most suitable for the measurement of the dielectric properties of biological materials is used to determine the relative permittivity and conductivity of muscle and skull bone in the frequency range 1 MHz to 20 GHz.

Animals↗
PubMed1994

Sustained-release isradipine compared with spirapril in the treatment of elderly patients with isolated systolic hypertension.

The benefits of treating isolated systolic hypertension (ISH) have been established, but the most appropriate choice of drug is still uncertain. For this reason, a sustained-release formulation of isradipine was compared with spirapril in a double-blind randomized study in elderly Chinese patients with ISH. The dosage was titrated if necessary after 4 weeks of treatment. The reduction in systolic/diastolic blood pressure after 8 weeks was similar for both treatments--20/10 mm Hg with isradipine versus 24/6 mm Hg with spirapril--measured in the supine position. There were no orthostatic symptoms and both treatments were well tolerated.

Aged↗
PubMed1994

Urinary dopamine and noradrenaline outputs during large acute changes in oral salt intake in healthy Chinese subjects.

1. In order to investigate the role of renal dopamine and sympathetic activity in the natriuretic response to oral sodium loading in Chinese subjects, we studied the effects of two different sodium intakes (20 followed by 220 mmol day-1 each given for 5 days) on mean arterial pressure (MAP) and the urinary excretion of sodium, dopamine (DA) and noradrenaline (NA) in eight healthy subjects. 2. MAP did not change. There was an eight- to ninefold increase in sodium excretion (P < 0.01). An 8-17% increase in urinary DA (P < 0.05) over the first 3 days, and a 22% decrease in urine NA (P < 0.05) on the last day of the high sodium intake were seen. 3. The relatively small increase in urinary DA, despite an eleven-fold increase in sodium intake from a state of marked sodium deprivation, may suggest that, in healthy Chinese subjects, the renal DA mechanism only contributes partly to the acute natriuretic response. Furthermore, the renal DA response appeared to be attenuated during the period of high sodium intake. 4. There is no evidence from the present study that a reduction in sympathetic activity plays an important role in the acute natriuretic response to sodium loading in this group of subjects.

Administration, Oral↗
PubMed1994

Drug overdosage and other poisoning in Hong Kong--the Prince of Wales Hospital (Shatin) experience.

From 1988 to 1991, 732 patients (91.1% Chinese) were admitted to four general medical wards at the Prince of Wales Hospital in Hong Kong with acute poisoning. The patients were predominantly female (68.9%) and relatively young (86.3% below the age of 40). Further analysis of 655 patients indicates that the vast majority of patients (96%) were admitted after self-poisoning with drugs or chemicals while 4% of cases were due to accidental poisoning. The main agents used by the former group included hypnotics/sedatives (33.1%), household products (15.7%), and analgesics (13.7%). There were nine deaths (1.4%). When compared to other Western countries, two important variations in the pattern of acute poisoning were seen. A substantial proportion of drugs ingested by our patients were not precisely identified. 'Dettol', a household product, was commonly used for self-poisoning in Hong Kong. Territory-wide studies of longer duration are needed to provide the physicians in Hong Kong with much needed information on the incidence and the pattern of acute poisoning.

Adolescent↗