PubMed Health⌕ Search

Biomedical subjects

M T Chan

Publications and source records attributed to M T Chan.

At least 19 recordsLinked to original sources
PubMed2001

Structured preoperative patient education for patient-controlled analgesia.

STUDY OBJECTIVE: To investigate the effectiveness of a structured preoperative education program in patients receiving patient-controlled analgesia (PCA). DESIGN: Randomized controlled trial. SETTING: University-affiliated hospital. PATIENTS: 60 ASA physical status I and II women undergoing major gynecologic surgery. INTERVENTIONS: Patients were randomly allocated to receive either standard information given during routine preanesthetic assessment (n = 30) or additional structured preoperative education on the use of PCA (n = 30). MEASUREMENTS: All patients received standard anesthesia and PCA was provided for postoperative analgesia. Patients were reviewed bid by an independent team of pain specialists and nurses. Patient satisfaction, severity of postoperative pain, nausea, dizziness, and morphine consumption were measured at discharge from recovery room, 24, and 48 hours after operation. Recovery characteristics of patients were also measured. MAIN RESULTS: Pain scores and morphine consumption decreased over time (p < 0.01), but there was no significant difference between groups. The overall analgesic efficacy, side effects, and recovery times was not affected by the education program. Patient satisfaction in the education group was better than control during early recovery (p= 0.03), but there was no additional benefit in the remaining postoperative period. CONCLUSIONS: Structured preoperative PCA education did not affect patient outcome. The early improvement in patient satisfaction was minimized by continued education and pain team supervision during the rest of the postoperative period.

Adult↗
PubMed2001

Risk factors for citation errors in peer-reviewed nursing journals.

BACKGROUND: Citation errors are common among nursing journals. But, there are no data regarding the factors that predispose to these errors. OBJECTIVE: To determine the risk factors that predispose to citation error in peer-reviewed nursing journals. METHODS: Five hundred and fifty references were selected randomly from articles published in eleven nursing journals for the year 1998. The incidences of major and minor citation errors were determined by comparing with the original articles. The relative odds of citation errors for the number of authors, collaborating institutions and the length of the reference list were calculated. The correlation between the scientific quality of the journal (by means of journal impact factor and immediacy index) and the incidence of citation error were also determined. RESULTS: The incidence of citation errors is comparable to those reported previously. Long reference lists in articles written by a single author predicted strongly the occurrence of minor citation errors. Journals with a high impact factor and immediacy index tend to contain fewer minor mistakes. None of these factors affect the incidence of major errors. CONCLUSION: Contributors to journals should be aware of the various risk factors for citation errors. Citation accuracy may be improved by modifying these factors.

Authorship↗
PubMed2000

Transcranial Doppler ultrasonography (TCD) in ventilated head injured patients: correlation with stable xenon-enhanced CT.

Disturbance of cerebral vasomotor regulation has been shown to be associated with the severity of traumatic brain injury (TBI). The transient hyperaemic response (THR) test is a test of the pressure autoregulatory response in terms of cerebral blood flow velocity after a brief carotid artery compression. Correlating with the test of cerebral vascular reactivity (CVR) to carbon dioxide by means of passive hyperventilation suggested that the THR test is a simple clinical test for the assessment of cerebral haemodynamic status in head-injured patients.

Adolescent↗
PubMed2000

Diagnostic strategies in young patients with ischemic stroke in Canada.

BACKGROUND: A preliminary national survey of ischemic stroke in the young (15-45 years) undertaken by the Canadian Stroke Consortium indicated that in 44% of 356 patients, no cause was found. OBJECTIVE: To determine the reason for this high incidence of diagnostic uncertainty in young patients with ischemic stroke. METHODS: Neurologists in the ten Canadian stroke centers completed a detailed questionnaire for patients aged 15-45 years admitted to hospital between January 1993 and December 1997. Using a stepwise diagnostic algorithm incorporating clinical, neuroimaging, neurovascular and laboratory data, we divided patients into three groups: (1) those with established cause for the ischemic stroke, (2) those who remained unexplained despite adequate investigation, (3) those who remained unexplained but were, in our opinion, under-investigated. RESULTS: In 197 patients (56%), an identified cause was established including cardioembolic sources (14%), extracranial arterial dissection (13%), lacunar infarcts (8%) atherosclerosis (6%). A miscellaneous group of 15%, included cerebral venous thrombosis, coagulopathies, vasculitis and others. In 159 patients (44%) with no apparent cause for their stroke, we considered only 81 (23%) adequately investigated, and 78 (21%) inadequately investigated. CONCLUSION: About one in five young patients was inadequately investigated by a stroke-oriented group of neurologists. The major problem appears to be restriction of investigations to neuroimaging alone (usually computerized cerebral tomography), without further tests such as cerebral angiography and cardiac imaging.

Adolescent↗
PubMed1999

Mechanisms of glucocorticoid reduction in asthmatic subjects treated with intravenous immunoglobulin.

BACKGROUND: Intravenous immunoglobulin (IVIG) has been used as an oral glucocorticoid (GC)-sparing agent in patients with steroid-dependent asthma. Despite its use, little is known regarding its mechanism of action. OBJECTIVE: We sought to determine whether the GC-sparing effects of IVIG in severe asthma are related to improved GC receptor (GCR)-binding affinity and subsequent enhanced GC sensitivity. METHODS: In an open-label study, 11 steroid-dependent asthmatic subjects (6 GC-insensitive, 5 GC-sensitive) received monthly infusions of IVIG (2 g/kg) for 6 months. Peak expiratory flow rates and oral GC dose were recorded daily, and spirometry was performed monthly. Blood was drawn for lymphocyte stimulation assays and GCR assays at baseline and after 3 and 6 months of therapy. Lymphocytes were stimulated ex vivo with PHA in the presence and absence of IVIG and increasing concentrations of dexamethasone (DEX). RESULTS: IVIG resulted in significant reductions in oral GC dose (P <.02), number of GC bursts (P =.033), and hospitalizations (P =.001) after 6 months of IVIG. Those with GC-insensitive asthma responded equally well to IVIG as those with GC-sensitive asthma. Associated with the improved clinical efficacy, IVIG acted synergistically with DEX in suppressing lymphocyte activation as measured by a shift in the DEX dose-response curve by 1 log-fold (P =.03). IVIG therapy was also associated with significantly improved GCR-binding affinity (P =.01). CONCLUSIONS: IVIG resulted in significant reductions in oral GC requirements and hospitalizations in a group of patients with severe asthma, with IVIG being as effective in patients with GC-insensitive asthma as in patients with GC-sensitive asthma. IVIG therapy acted synergistically with DEX in suppressing lymphocyte activation and significantly improved GCR-binding affinity after 3 and 6 months of therapy.

Administration, Oral↗
PubMed1999

Propofol requirement is decreased in patients with large supratentorial brain tumor.

BACKGROUND: The anesthetic requirement is decreased in animals with head injury, but there are no data regarding the effect of intracranial tumor on the potency for intravenous anesthetics. The authors compared the quantal dose-response curves for propofol in patients having large (> or = 30 mm, mass effect) brain tumor with those having smaller (< 30 mm) lesions and with control patients undergoing noncranial surgery. METHODS: Sixty patients in each group were randomly assigned to receive one of the six doses of propofol (0.5, 0.7, 1.0, 1.3, 1.8, or 2.5 mg/kg) over 10 s. Two minutes after drug administration, patients were asked to open their eyes as a test for response to verbal command. Patients who failed to respond were given a 10-s, 50-Hz, 80-mA transcutaneous tetanic electrical current to the ulnar nerve as a test for response to painful stimulus. Purposeful movement indicated positive response. Log dose-response curves for loss of response to verbal command and tetanic stimulus were calculated after logit transformation. RESULTS: The median effective doses (ED50s; 95% confidence interval) for suppressing response to verbal command and tetanic stimulus were 0.75 (0.65-0.86) mg/kg and 1.28 (1.11-1.49) mg/kg, respectively, in patients with large brain tumor. These values were significantly less than the corresponding ED50s in patients with small tumor, 1.01 (0.88-1.15) mg/kg and 1.76 (1.51-2.07) mg/kg, or healthy control subjects, 0.98 (0.86-1.12) mg/kg and 1.89 (1.62-2.23) mg/kg. CONCLUSIONS: The doses of propofol required to suppress response to verbal command and tetanic stimulus were 23% less and 32% less in patients with large brain tumor compared with control subjects. Small tumor did not affect potency of propofol.

Adolescent↗
PubMed1998

The 3' untranslated region of a rice alpha-amylase gene functions as a sugar-dependent mRNA stability determinant.

In plants, sugar feedback regulation provides a mechanism for control of carbohydrate allocation and utilization among tissues and organs. The sugar repression of alpha-amylase gene expression in rice provides an ideal model for studying the mechanism of sugar feedback regulation. We have shown previously that sugar repression of alpha-amylase gene expression in rice suspension cells involves control of both transcription rate and mRNA stability. The alpha-amylase mRNA is significantly more stable in sucrose-starved cells than in sucrose-provided cells. To elucidate the mechanism of sugar-dependent mRNA turnover, we have examined the effect of alphaAmy3 3' untranslated region (UTR) on mRNA stability by functional analyses in transformed rice suspension cells. We found that the entire alphaAmy3 3' UTR and two of its subdomains can independently mediate sugar-dependent repression of reporter mRNA accumulation. Analysis of reporter mRNA half-lives demonstrated that the entire alphaAmy3 3' UTR and the two subdomains each functioned as a sugar-dependent destabilizing determinant in the turnover of mRNA. Nuclear run-on transcription analysis further confirmed that the alphaAmy3 3' UTR and the two subdomains did not affect the transcription rate of promoter. The identification of sequence elements in the alpha-amylase mRNA that dictate the differential stability has very important implications for the study of sugar-dependent mRNA decay mechanisms.

Base Sequence↗
PubMed1998

Difficult-to-control asthma: clinical characteristics of steroid-insensitive asthma.

BACKGROUND: Although widely used, little is known regarding the patterns of response that subjects with severe asthma exhibit to oral glucocorticoid (GC) therapy. METHODS: We retrospectively reviewed the charts of 164 consecutive adolescents admitted to the National Jewish Medical and Research Center for difficult-to-control asthma. Data collected included medical history, pulmonary function measures by plethysmography, methacholine challenge results, AM cortisol levels, serum IgE, total eosinophil counts (TEC), serum eosinophil cationic protein (ECP), soluble IL-2 receptor (sIL-2R), and spirometry. RESULTS: Eighty-seven patients (53%) required a GC burst during the hospitalization secondary to poor asthma control. Those requiring a GC burst had a significantly longer history of asthma, a greater degree of bronchial hyperresponsiveness, and lower pulmonary function. Twenty-one patients (24%) failed to respond with a greater than 15% improvement in their AM prebronchodilator FEV1 after the GC burst and were termed steroid insensitive (SI). Although those with SI asthma had a similar duration of asthma, they required oral GC therapy at a younger age, required a larger maintenance oral GC dose on admission, and were more likely to be African-American, compared with those with steroid-sensitive asthma. Furthermore, two distinct spirometry patterns were noted among the SI asthmatic subjects: "chaotic" and "nonchaotic." Patients with the chaotic pattern were characterized by a significant degree of variability (greater than 30%) in daily pulmonary function, whereas those with nonchaotic, SI asthma were characterized by less than 15% variability in daily lung function. Those with nonchaotic SI were diagnosed with asthma and treated with oral GCs at a later age. CONCLUSIONS: This retrospective study suggests that SI asthma is quite common (25%) among adolescents with severe asthma evaluated at a national referral center. In addition, two distinct patterns of SI asthma have been identified that may constitute different pathophysiologic processes. Finally, the overrepresentation of African-Americans in the SI group supports the need for further epidemiologic studies investigating the prevalence of SI asthma and the impact early asthma intervention may have on this severe form of asthma.

Adolescent↗
PubMed1998

The 3' untranslated region of a rice alpha-amylase gene mediates sugar-dependent abundance of mRNA.

A decrease in transcript stability is one of the important mechanisms that control the sugar repression of alpha-amylase gene expression in rice suspension cells. In this study, we investigated the function of the 3' untranslated region (3'UTR) of a rice alpha-amylase gene, alpha Amy3, in relation to sugar-dependent accumulation of mRNA. By examining the transient expression of chimeric genes in rice protoplasts, we were able to demonstrate that the alpha Amy3 3'UTR mediated the sugar-dependent repression of fused heterologous gene expression. The same kinetics of accumulation of alpha Amy3 mRNA and reporter mRNA carrying the alpha Amy3 3'UTR in response to glucose deprivation were observed, suggesting that the alpha Amy3 3'UTR is sufficient, and probably the major determinant for controlling the abundance of these transcripts. Functional analysis of two subdomains of alpha Amy3 3'UTR by insertion into a sugar-inducible chimeric gene confirmed their roles in sugar repressibility. The regulatory sequences in the alpha Amy3 3'UTR may act as potent determinants of mRNA stability in response to sugar availability. This finding has important implications for studying the regulatory mechanism of sugar repression in eukaryotes.

3' Untranslated Regions↗
PubMed1998

Postpartum patients have slightly prolonged neuromuscular block after mivacurium.

UNLABELLED: Postpartum patients have decreased plasma cholinesterase activity, which may slow the metabolism of mivacurium. We compared the duration of a mivacurium neuromuscular block in 11 women undergoing postpartum tubal ligation 36-99 h after delivery with that in 11 control women undergoing gynecological surgery. Anesthesia was induced with propofol and fentanyl and maintained with propofol and nitrous oxide. Neuromuscular block was monitored by electromyography, and the ulnar nerve was stimulated transcutaneously using a train-of-four pattern. Patients received a bolus dose of mivacurium 0.15 mg/kg. The median (range) duration of neuromuscular block until 25% recovery of the first twitch response was longer in the postpartum group, 19.4 (15.6-25.2) min, compared with the control group, 16.3 (11.0-23.4) min (P = 0.04). The median (range) plasma cholinesterase activity was decreased in the postpartum group, 4.0 (0.1-5.5) kU/L, compared with the control group, 7.1 (6.2-10.0) kU/L (P < 0.001). The duration of neuromuscular block was inversely correlated with cholinesterase activity (Kendall rank correlation tau = -0.43, P = 0.005). The slight prolongation of neuromuscular block should not be significant clinically. IMPLICATIONS: Postpartum patients have decreased amounts of the plasma cholinesterase enzyme. This would slow the metabolism of the muscle relaxant mivacurium. However, the duration of muscle paralysis is only prolonged by approximately 3 min, which would not normally cause any significant problems.

Adult↗
PubMed1998

Single-dose tropisetron for preventing postoperative nausea and vomiting after breast surgery.

UNLABELLED: In this randomized, double-blind, placebo-controlled study, we compared the efficacy of tropisetron 5 mg with tropisetron 2 mg for the prevention of postoperative nausea and vomiting (PONV) after breast surgery. One hundred forty-eight female patients were randomized to receive either tropisetron 5 mg (n = 49), tropisetron 2 mg (n = 49), or saline (n = 50) before the induction of anesthesia with thiopental and morphine. Anesthesia was maintained with nitrous oxide and isoflurane. Postoperative analgesia was provided by patient-controlled analgesia with i.v. morphine. The incidence of PONV, the pain score, and the analgesic requirement were recorded for 48 h. There was no difference among groups in patient characteristics, risk factors for PONV, morphine consumption, or side effects. During the first 6 h postoperatively, the incidence of PONV after tropisetron 2 mg and 5 mg were similar and were superior to placebo (P < 0.001). After 6 h, the incidence of PONV increased significantly in patients who had received tropisetron 2 mg (P = 0.01) and was greater than that in patients who had received tropisetron 5 mg (P = 0.001). We conclude that single-dose tropisetron 5 mg is more effective than tropisetron 2 mg in the prevention of PONV after breast surgery. IMPLICATIONS: Breast surgery is associated with a high incidence of postoperative nausea and vomiting. A single dose of i.v. tropisetron 5 mg is well tolerated and decreases the number of vomiting and nausea episodes after surgery.

Adolescent↗
PubMed1998

Occupational chromate allergy in Singapore: a study of 87 patients and a review from 1983 to 1995.

BACKGROUND: The prevalence of chromate allergy among all patients tested at the Contact and Occupational Dermatoses Clinic at the National Skin Centre in Singapore had fallen progressively from 1983 to 1989. Chromate has also become a less common occupational allergen because of the decline in the number of cases of allergic contact dermatitis from cement. OBJECTIVE: The aim of this report was to study and update the epidemiology of occupational chromate allergy among workers seen in a tertiary dermatology referral centre in Singapore from 1990 to 1995 and to review the changing trends of occupational chromate allergy in our local setting since 1983. The occurrence of concomitant contact allergens among was also studied. METHODS: All patients diagnosed to have occupational allergic contact dermatitis together with positive reactions to chromate, at the Joint Occupational Dermatosis Clinic at the National Skin Centre in Singapore, between January 1990 to December 1995, were included. Causes of chromate allergy and frequency of occurrence of concomitant contact allergens among construction and nonconstruction workers were compared. RESULTS: Eight hundred and fifty workers were seen during the 6-year-study period. Six hundred and thirty three (74.5%) were diagnosed to have occupational contact dermatitis, of which 257 (40.6%) had allergic contact dermatitis. Eighty-seven (33.8%) of these workers had positive reaction to chromate on patch testing. Ninety-five percent of these workers were men with a mean age of 33.4 years. The construction industry contributed 59% of the workers with chromate allergy. Cement (61%) remained the most common source of chromate allergy in our workers, and chromate from sources other than cement (39%) accounted for the rest. Of workers allergic to chromate from cement, 96% (51 of 53) came from the construction industry. Sixty percent of the workers with chromate allergy had concomitant contact allergens and the coexistence of two or more allergens was significantly more common among nonconstruction workers (53%) than construction workers (22%). The three most common concomitant contact allergens were cobalt (28%), rubber chemicals (21%) and nickel (18%). Nonconstruction workers had significantly higher rates of nickel allergy (36% v 6%) than construction workers (P < .03). Simultaneous reactivity to cobalt and nickel was also significantly more common among nonconstruction workers (22%) than construction workers (6%) (P < .03). CONCLUSION: Chromate has progressively become a less common occupational allergen at the National Skin Centre in Singapore from 1983 to 1989, because of a progressive fall in the number of cases of allergic contact dermatitis from cement. However, our study showed that occupational chromate allergy had now increased from 1990 to 1995, because of an increase in chromate allergy from sources other than cement. Chromate allergy from cement is declining, although still frequent, and sources other than cement are increasing in recent years. Concomitant nickel allergy, as well as simultaneous nickel and cobalt allergies, were more common among nonconstruction workers than construction workers.

Adult↗
PubMed1997

Single-dose pharmacokinetics of paracetamol and its conjugates in Chinese non-insulin-dependent diabetic patients with renal impairment.

OBJECTIVE: A single oral dose of paracetamol (20 mg.kg-1) was given to 38 Chinese patients with non-insulin-dependent diabetes mellitus (NIDDM) who had either normal renal function or varying degrees of renal impairment, with creatinine clearances ranging from 4 to 123 ml.min-1.1.73 m-2. The plasma and urinary concentrations of paracetamol and its major metabolites were measured by high-performance liquid chromatography (HPLC). RESULTS: The absorption and elimination of paracetamol were unaffected by renal impairment. However, the area under the plasma concentration time curve and the elimination half-life of paracetamol metabolites increased significantly with worsening renal insufficiency. Mean renal clearances of paracetamol and its conjugates were significantly reduced in these subjects. There was no evidence of altered metabolic activation with renal impairment. CONCLUSION: The results demonstrate that paracetamol disposition is minimally affected by diabetic nephropathy; however, extensive accumulation of conjugates may occur.

Acetaminophen↗
PubMed1997

Decreased thiopental requirements in early pregnancy.

BACKGROUND: Anesthetic requirements for inhalational agents are decreased during pregnancy, but there are no data regarding requirements for intravenous agents. The quantal dose-response curves for thiopental were calculated for 70 nonpregnant women having gynecologic surgery and for 70 pregnant women of 7-13 weeks' gestation having elective abortions. METHODS: Groups of 10 patients were given 2, 2.4, 2.8, 3.3, 3.8, 4.5, or 5.3 mg/kg thiopental as a bolus dose during a period of 10 s. Two minutes later, patients were asked to open their eyes as a test for hypnosis. Patients who did not open their eyes were given a 10-s, 50-Hz, 80-mA transcutaneous tetanic electrical stimulus to the ulnar nerve as a test for anesthesia. Purposeful movement indicated that there was no anesthesia. Log dose-response curves for hypnosis and anesthesia were calculated after logit transformation. RESULTS: In the nonpregnant women, the median effective doses (ED50s) (95% confidence interval) for hypnosis and anesthesia were 3.1 (2.8-3.4) mg/kg and 4.9 (4.5-5.4) mg/kg, whereas in the pregnant women the corresponding ED50s were 2.6 (2.3-2.8) mg/kg and 4 (3.7-4.4) mg/kg. In the non-pregnant women, the ED95s (95% CI) for hypnosis and anesthesia were 4.4 (3.9-5.4) mg/kg and 6.4 (5.7-7.9) mg/kg, whereas in the pregnant women the corresponding ED95s were 3.7 (3.3-4.5) mg/kg and 5.2 (4.7-6.3) mg/kg. The pregnant to nonpregnant relative median potency (95% CI) ratio for hypnosis was 0.83 (0.67-0.96) and for anesthesia it was 0.82 (0.62-0.94). CONCLUSIONS: The dose of thiopental for hypnosis was 17% less and that for anesthesia was 18% less in pregnant women of 7-13 weeks' gestation compared with that in nonpregnant women.

Adult↗
PubMed1996

Sugars act as signal molecules and osmotica to regulate the expression of alpha-amylase genes and metabolic activities in germinating cereal grains.

The molecular mechanisms that initiate and control the metabolic activities of seed germination are largely unknown. Sugars may play important roles in regulating such metabolic activities in addition to providing an essential carbon source for the growth of young seedlings and maintaining turgor pressure for the expansion of tissues during germination. To test this hypothesis, we investigated the physiological role of sugars in the regulation of alpha-amylase gene expression and carbohydrate metabolism in embryo and endosperm of germinating rice seeds. RNA gel blot analysis revealed that in the embryo and aleurone cells, expression of four alpha-amylase genes was differentially regulated by sugars via mechanisms beyond the well-known hormonal control mechanism. In the aleurone cells, expression of these alpha-amylase genes was regulated by gibberellins produced in the embryo and by osmotically active sugars. In the embryo, expression of two alpha-amylase genes and production of gibberellins were transient, and were probably induced by depletion of sugars in the embryo upon imbibition, and suppressed by sugars influx from the endosperm as germination proceeded. The deferential expression of the four alpha-amylase genes in the embryo and aleurone cells was probably due to their markedly different sensitivities to changes in tissue sugar levels. Our study supports a model in which sugars regulate the expression of alpha-amylase genes in a tissue-specific manner: via a feedback control mechanism in the embryo and via an osmotic control mechanism in the aleurone cells. An interactive loop among sugars, gibberellins, and alpha-amylase genes in the germinating cereal grain is proposed.

Carbohydrates↗