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Biomedical subjects

Y K Chan

Publications and source records attributed to Y K Chan.

At least 37 records · Page 2Linked to original sources
PubMed2000

Which and what headache were we treating? Epidural blood patch for atypical headache following obstetric epidural anaesthesia.

We present a case of headache following epidural anaesthesia for caesarean section. The patient did not exhibit the classical features of post dural puncture headache and the cause was uncertain. The headache was complicated by post partum seizure and a history of pregnancy-induced hypertension. A diagnostic lumbar puncture had to be done to exclude meningitis as she had a raised white blood count. An epidural blood patch performed 12 days post partum resolved the headache immediately.

Journal Article↗
PubMed2000

A survey of the current practice of obstetric anaesthesia and analgesia in Malaysia [correction of Malaysis].

OBJECTIVE: A survey covering 30% of the deliveries in Malaysia was done to determine the practice of obstetric anaesthesia and analgesia for 1996. RESULTS: From the survey, it was found that the regional anaesthesia rate for caesarean section was 46% in the government hospitals compared to 29.2% in the private hospitals, with spinal anaesthesia being the most common regional anaesthetic technique used in both types of hospitals. The epidural rate for labour analgesia was only 1.5% overall for the country. Epidural analgesia services were available in all private hospitals whereas 17.6% of government hospitals surveyed did not offer this service at all. CONCLUSIONS: Although the use of epidural analgesia for labour was low in Malaysia, the overall rate of regional anaesthesia for caesarean section (41.9%) is very much in keeping with the standards of safe practice recommended by the United Kingdom.

Analgesia, Obstetrical↗
PubMed2000

Epidural analgesia in primigravidae in spontaneous labour at term: a prospective study.

OBJECTIVES: To prospectively study the intervention rate, duration of labour, malpositions, fetal outcome, maternal satisfaction, voiding complications and adverse events in healthy primigravidae in spontaneous labour at term following epidural analgesia. METHODS: A prospective randomized study involving 55 patients in the epidural group and 68 in the control pethidine--inhalational entonox group. RESULTS: There were significantly more obstetric interventions (instrumental deliveries) in the epidural group (p < 0.01). The total duration of labour and the duration of the second stage was prolonged in the epidural group (p < 0.01). There were more malpositions at the second stage of labour in the epidural group (p < 0.02). There were no differences in fetal outcome (Apgar scores and Special Care Nursery admissions). Patients in the epidural group were consistently happier with their method of pain relief (p < 0.01). Two patients required blood patches while another 2 patients had persistent backache post epidural analgesia. CONCLUSION: Epidural analgesia in primigravidae in spontaneous labour at term led to an increased instrumental delivery rate, prolonged duration of labour, greater rate of malpositions in the second stage, increased oxytocin requirements but with no difference in fetal outcomes but with happier mothers as compared to the control group.

Adult↗
PubMed2000

Comparison of four methods of assessing root surface debridement.

BACKGROUND: While there is great interest in measuring the efficacy of root surface debridement, there is little consensus on how this might be best achieved. The aim of this study was therefore to compare four different methods of assessing root surface debridement in their ability to discriminate between ultrasonically instrumented root surfaces and non-instrumented control surfaces. METHODS: Single-session subgingival root debridement was performed by an experienced operator on 30 teeth prior to their extraction. Following extraction, efficacy of root surface debridement was measured by percentage of remaining calculus, instrument efficiency, modified instrument efficiency, and percentage apical plaque border. In addition, the effect of probing depth landmark (apical plaque border versus connective tissue attachment) on outcomes was assessed. RESULTS: The results indicated that percentage apical plaque border demonstrated highly statistically significant differences between instrumented and control surfaces (P= 0.02). No other assessment method was able to discriminate between instrumented and non-instrumented surfaces, and this may be a function of the low amount of root surface calculus in the experimental sample. In addition, choice of probing depth landmark had a notable effect on the outcomes for instrument efficiency and modified instrument efficiency. Ninety-five percent limits of agreement of interexaminer reproducibility were found to be much higher than intra-examiner measurement for all four methods of assessment. CONCLUSIONS: Percentage apical plaque border appeared to be potentially more useful than other methods for assessing the efficacy of debridement of periodontally involved root surfaces, particularly for measuring instrument penetrability.

Coloring Agents↗
PubMed2000

The C282Y mutation of the HFE gene is not found in Chinese haemochromatotic patients: multicentre retrospective study.

OBJECTIVE: To detect two novel mutations (C282Y and H63D) of the HFE gene in Chinese patients with hepatic iron overload. DESIGN: Multicentre retrospective study. SETTING: Four public hospitals, Hong Kong. PARTICIPANTS: Fifty Chinese patients who presented from January 1987 through December 1999 with hepatic iron overload from various causes. MAIN OUTCOME MEASURES: The DNA from liver biopsy samples was tested for HFE mutations by restriction fragment length polymorphism analysis. RESULTS: The sample DNA quality was unsatisfactory for analysis of the C282Y mutation in one case and the H63D mutation in nine cases. The C282Y mutation was not detected in any of the 49 satisfactory samples. Three of the 41 samples were heterozygous for the H63D mutation and only one was homozygous, giving an allele frequency of 6.1%. Of the three H63D-heterozygotes, one had beta-thalassaemia major, one had beta-thalassaemia minor, and one had hereditary spherocytosis. None of the 12 patients who were presumed to have primary haemochromatosis were positive for either mutation. CONCLUSIONS: The classical form of human leukocyte antigen-linked hereditary haemochromatosis appears to be absent form this locality. The H63D mutation is found in a minority (9.8%) of the patients, in whom it may act synergistically with an erythropoietic factor.

Adolescent↗
PubMed2000

A comparison of the maintenance and recovery charcateristic of sevoflurane-nitrous oxide against isoflurane-nitrous oxide anaesthesia.

BACKGROUND: To compare the maintenance and recovery characteristics of sevoflurane and isoflurane anaesthesia in Malaysian patients. METHOD: This is a prospective, open labelled, randomized, controlled study. Sixty unpremedicated ASA I or II patients (aged 18-50 years), scheduled for elective breast lump excision were randomly allocated to receive either isoflurane or sevoflurane for the maintenance of anaesthesia following fentanyl and propofol intravenous induction. The systolic, diastolic, mean arterial blood pressure and heart rate were measured. The speed of recovery was measured by time to eye opening, time to following simple command, and time to correctly giving own names and address. The incidence of postoperative complication was also recorded. RESULTS: The trend of systolic blood pressure was significantly higher in the isoflurane group as compared to the sevoflurane group for the duration of anaesthesia (p < 0.001, by ANOVA for repeated measurement) but the trend of heart rate was similar for both groups. The recovery time was faster in the isoflurane group. [mean time of eye opening (SD) = 6.8 (2.2) vs 10.7 (4.4) min, p < 0.001; mean time of sticking tongue out (SD) = 7.9 (2.9) vs 11.5 (4.7) min, p < 0.01; mean time of giving own name (SD) = 7.8 (2.7) vs 11.8 (4.8) min, p < 0.001, mean time of giving own address (SD) = 8.4 (2.9) vs 12.0 (4.7) min, p < 0.01]. No major adverse effects were encountered postoperatively and the incidences of minor adverse effects were low in both groups. CONCLUSION: We concluded that sevoflurane is a safe alternative to isoflurane but in these short procedures, awakening time was surprisingly slower than after isoflurane.

Adolescent↗
PubMed1999

Pain during elective caesarean section under epidural anaesthesia: the effect of a 10 degrees head-up tilt position.

One hundred patients scheduled for elective caesarean section under epidural anaesthesia were randomized to have epidural loading doses in either the horizontal or a 10 degrees head-up position. They were assigned to their position only after an initial dose of 4 ml of 0.5% bupivacaine had been given. Ten minutes after this dose they were given 10 ml of 0.5% bupivacaine and 50 microg of fentanyl in their allocated position. Pain during surgery was assessed by the patients using a visual analogue scale and by a blinded anaesthetist. Giving the main dose in the head-up tilt position reduced the incidence of intea-operative pain significantly. The median pain score for the head-up position was zero while the score was two for the horizontal position. The inter-quartile range was 0 to 2 for the head-up tilt position and 0 to 4 for the horizontal position (P<0.05). Position had no significant effect on the blood pressure or Bromage score. A 10 degrees head-up tilt position is useful during the establishment of epidural anaesthesia to reduce the pain experienced by the patient during caesarean section.

Clinical Trial↗
PubMed1999

Comparison of periodontal pocket penetration by conventional and microultrasonic inserts.

Recently, 'microultrasonic' instruments have been developed with the aim of improving root-surface debridement. Whilst their reduced tip diameter and modified shape suggests that they may penetrate the periodontal pocket more easily than conventional inserts, there have been few studies investigating their efficacy. The aim of this investigation was therefore to compare the periodontal pocket penetration of a conventional ultrasonic insert (P10 insert--Dentsply) with microultrasonic inserts (Slimline FSI left and right--Dentsply). Efficacy of penetration was assessed by a modification of instrument limit. This modification permitted measurement of the linear % removal of the apical plaque border by image analysis. Debridement was carried out on randomly allocated surfaces of 30 teeth which had been treatment planned for extraction due to periodontitis. One surface on each tooth acted as an untreated control. The results of this study showed that both types of insert were able to reach and debride the apical plaque border, and at all pocket depths assessed. However no significant differences were found between the Slimline insert and the P10 tip. Trends between instruments were observed which suggest that the Slimline insert might more easily penetrate to and debride the apical plaque border in deep pockets, whereas the P10 insert might be more effective in disrupting the apical plaque border in shallow pockets. Future investigations using a larger sample size will be needed to confirm these observations.

Analysis of Variance↗
PubMed1999

Acute bereavement care in the emergency department: does the professional-supported volunteers model work?

The aims of our study were to study the early impact of bereavement and to evaluate the effectiveness of the bereavement care given by our multidisciplinary team to close relatives of a sudden death, measured by the intensity of grief reaction (Texas Revised Inventory of Grief). The study sample consisted of close relatives of patients certified dead at the accident and emergency department (AED) between March 1996 and February 1997. The relatives received immediate care at the AED and were supported continually by the members of the bereavement care team. The control sample (without acute bereavement care) consisted of close relatives contacted by the liaison nursing officer in the previous year. The intensity of grief reactions were assessed by the volunteer grief counsellors at 6 months. The mean score of the intensity of grief reactions were 41.8 and 34.6 in the control (n = 11) and study (n = 18) groups respectively among high risk sample (p = 0.04). However, in the low risk sample, the mean scores were 35.3 and 30.2 in the control (n = 18) and study (n = 25) groups respectively (p = 0.11). Our study suggests that the bereavement care was especially effective in reducing the intensity of the grief at 6 months in the high risk group.

Adolescent↗
PubMed1999

A comparison of the induction and emergence characteristics of sevoflurane and halothane in children.

This open labelled, randomised, controlled study was designed to compare the induction and recovery characteristics of sevoflurane and halothane anaesthesia in children. Forty American Society of Anaesthesiologist (ASA) physical status class 1 or 2 children (aged 1-10 year, weighed less than 25 kg) scheduled for elective urological procedure lasting less than one hour were allocated randomly to receive either sevoflurane (group S, n = 20) or halothane (group H, n = 20). The induction time in children receiving sevoflurane was significantly shorter than in those receiving halothane (mean (SD) 46 (13.6) second vs 69 (19.4) seconds, p < 0.005). The emergence from anaesthesia was also faster in children receiving sevoflurane than in those receiving halothane (mean (SD) 9 min (4.3 min) vs 21 min (8.9 min), p < 0.001). No major adverse effects were encountered in each group. We concluded that sevoflurane is comparable to halothane in Malaysian children.

Anesthesia, General↗
PubMed1998

The nos (nitrous oxide reductase) gene cluster from the soil bacterium Achromobacter cycloclastes: cloning, sequence analysis, and expression.

The nitrous oxide (N2O) reductase (nos) gene cluster from Achromobacter cycloclastes has been cloned and sequenced. Seven protein coding regions corresponding to nosR, nosZ (structural N2O reductase gene), nosD, nosF, nosY, nosL, and nosX are detected, indicating a genetic organization similar to that of Rhizobium meliloti. To aid homology studies, nosR from R. meliloti has also been sequenced. Comparison of the deduced amino acid sequences with corresponding sequences from other organisms has also allowed structural and functional inferences to be made. The heterologous expression of NosD, NosZ (N2O reductase), and NosL is also reported. A model of the CuA site in N2O reductase, based on the crystal structure of this site in bovine heart cytochrome c oxidase, is presented. The model suggests that a His residue of the CuA domain may be a ligand to the catalytic CuZ site. In addition, the origin of the spectroscopically-observed Cys coordination to CuZ is discussed in terms of the sequence alignment of seven N2O reductases.

Alcaligenes↗
PubMed1998

The combination of omeprazole, amoxycillin, and clarithromycin eradicates Helicobacter pylori in 95% of patients---7 days of therapy is as good as 10 days.

More than half of the known Helicobacter pylori strains are resistant to metronidazole, according to previous Hong Kong studies. The response rates to treatment regimens that comprise metronidazole as one of the antimicrobial agents have usually been disappointing in cases involving metronidazole-resistant strains. The objective of this open cohort evaluation was to assess the efficacy of an alternative regimen that combines omeprazole with amoxycillin and clarithromycin in Helicobacter pylor-positive ulcer and non-ulcer patients in Hong Kong. Furthermore, we aimed to investigate if 7 days were as good as 10 days of therapy. We studied 186 Helicobacter pylor-positive subjects; 149 subjects received 7 days of combination therapy and 37 subjects received 10 days. Our results showed that the overall Helicobacter pylori eradication efficiency was identical (94.6%) for both treatments. The incidences of adverse effects were also very similar (16.8% versus 16.2%) and both treatments were well tolerated. Thus, we propose that omeprazole in combination with amoxycillin and clarithromycin should be considered as one of the first-line therapies for patients with Helicobacter pylor infection in Hong Kong.

Journal Article↗
PubMed1997

Discordance of pressure recordings from biliary and pancreatic duct segments in patients with suspected sphincter of Oddi dysfunction.

It remains controversial whether manometric parameters recorded from the pancreatic and biliary segment of the sphincter of Oddi (SO) differ. We therefore studied 48 consecutive patients (40 women, 43 +/- 11 years) with suspected SO dysfunction, in 33 of whom successful dual-duct SO manometry was obtained. Measures of concordance between the two duct segments were moderate for basal sphincter pressure (K = 0.31) and for contractile frequency (0.35), and were low for peak pressure (0.15) and for proportion of retrograde propagation (-0.19). There was also low concordance (-0.13) for the overall manometric diagnosis, and in 48% (CI 31-66%) of patients a conflicting diagnosis (normal/abnormal) was obtained from the two ducts. There was no evidence of a differential motor effect of CCK on either duct, nor were there significant differences in the rate of manometric abnormality according to the order of initial duct cannulation. These results indicate that, if technically feasible, dual-duct manometry of the sphincter of Oddi is required for diagnostic precision.

Adult↗
PubMed1996

Extraperitoneal laparoscopy: anatomical dissections with experimental balloon dilators.

OBJECTIVES: To develop balloon dilators in vitro and in cadavers and to evaluate the anatomy of the extraperitoneal spaces and their surroundings created by such balloons. MATERIALS AND METHODS: Balloons of three different materials (condoms, fingers of surgical gloves, whole surgical gloves and 'party' balloons) were tested in an in vitro study and compared with a prototype balloon dilator used in cadavers. The balloon dilators were used to create extraperitoneal spaces in the pelvic, the loin and the iliac regions through stab incisions. The incisions were extended after dilatation to examine the spaces created and the consequent anatomical changes. RESULTS: In vitro, all balloons were found to have capacities of more than 10 L, except that made from the finger of a surgical glove. Early rupture after insertion and during dilatation was a problem in condom and party balloons. In cadavers, there was good exposure of anatomical structures within the extraperitoneal spaces created. Reflections of peritoneum in the loin and the iliac regions were unmoved by balloon dilatation. CONCLUSIONS: The prototype balloon dilator possessed all the characteristics desired of an ideal instrument for creating extraperitoneal spaces. Good exposure of anatomical structures by the balloon dilators allows a minimal dissection in extraperitoneal laparoscopic procedures in the aforementioned regions. That the peritoneal reflection was unmoved despite adequate expansion of the balloons also means that the exact placement of secondary laparoscopic ports is crucial in preventing peritoneal and colonic trauma.

Catheterization↗
PubMed1996

Identification and analysis of the dissimilatory nitrous oxide reduction genes, nosRZDFY, of Rhizobium meliloti.

The complete nos region essential for dissimilatory nitrous oxide reduction by the endosymbiotic diazotroph Rhizobium meliloti was identified in a cosmid (pYC7) carrying a 10.1-kb EcoRI fragment of the nod megaplasmid. This gene region was localized by Southern hybridization and Tn5 mutagenesis to within 8 kb downstream from the fixGHIS cluster. Nucleotide sequence determination of a 4.6-kb DNA segment including the structural gene nosZ and its flanking regions showed sequence homology and similarity in genetic organization with the nosRZDFY genes of Pseudomonas stutzeri Zobell. The genes were arranged in three complementation groups, comprising the nosZ structural gene, the nosR regulatory gene, and the nosDFY copper-processing genes. The derived amino acid sequence of the R. meliloti nosZ product (a multi-copper nitrous oxide reductase) was more similar to those of the analogous gene products of Paracoccus and Pseudomonas species than to that of Alcaligenes eutrophus. The nosZ gene was preceded by nosR, which encodes a regulatory protein containing C-terminal cysteine clusters similar to those present in the 4Fe-4S binding region of bacterial ferredoxins, The nosDFY genes, located downstream from nosZ, were identified as copper-processing genes encoding a periplasmic protein, an ATP/GTP-binding protein, and a membrane protein presumably forming a copper-processing system. A consensus sequence for an Anr- or Fnr-binding site similar to that in the upstream sequence of nosZ in Paracoccus denitrificans or P. stutzeri was absent in R. meliloti. No rpoN-binding site preceding the nos genes was detected, and none of the Tn5 insertions in the nos gene region affected symbiotic N2-fixing ability.

Amino Acid Sequence↗