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Biomedical subjects

K L Chan

Publications and source records attributed to K L Chan.

At least 19 recordsLinked to original sources
PubMed2006

Laparoscopic repair of recurrent childhood inguinal hernias after open herniotomy.

BACKGROUND: Open repair of recurrent paediatric inguinal hernias (IH) is difficult and there is definite risk of damaging the vas deferens and testicular vessels during dissection of the previous open herniotomy field. Laparoscopic repair (LR) has the benefit of avoiding the previous operative site. METHOD: Records of patients with recurrent IH that had LR after open repair were reviewed and evaluated retrospectively. The results were compared with data from cases in which the LR method was used in the initial IH repair. RESULTS: From September 2002 to October 2005, four boys and one girl (mean age 58.8 months) were treated in our institution for recurrent IH after open repair. Operative time, success rate and complications did not show any statistically significant difference when compared with our previous prospectively collected data for primary repairs. CONCLUSION: Laparoscopic repair is the preferred operation for recurrent childhood IH after open repair.

Child↗
PubMed2006

Convergent validity of six methods to assess physical activity in daily life.

The purpose was to examine the agreement (convergent validity) between six common measures of habitual physical activity to estimate durations of light, moderate, vigorous, and total activity in a range of free-living individuals. Over 7 consecutive days, 49 ethnic Chinese (30 men, 19 women), aged 15-55 yr, wore a Polar heart rate monitor, a uniaxial MTI, and triaxial Tritrac accelerometer, plus a Yamax pedometer for > or = 600 min/day. They also completed a daily physical activity log and on day 8 a Chinese version of the 7-day International Physical Activity Questionnaire. At each level of activity, there was good agreement between the two questionnaire-derived instruments and the two accelerometry-derived instruments, but wide variation across different instruments, with two- to fourfold differences in mean durations often seen. The heart rate monitor overestimated light activity and underestimated moderate activity compared with all other measures. Spearman correlation coefficients were low to moderate (0.2-0.5) across most measures of activity, with the pedometer showing correlations with total activity that were often superior to the other movement sensors. We conclude that, with the use of commonly accepted cut points for defining light, moderate, vigorous, and total activity, little convergent validity across the instruments was evident, suggesting these measures are sampling different levels of habitual physical activity and care is needed when comparing their results. To provide a more stable comparison of activity among different people, across studies, or against accepted physical activity promotion guidelines, further work is needed to fine tune the different cut points across a range of common activity monitors to provide more consistent results during free-living conditions.

Activities of Daily Living↗
PubMed2006

Reliability and validity of the Chinese version of IPAQ (short, last 7 days).

The aim of this study was to examine the reliability and validity of the Chinese version of the International Physical Activity Questionnaire (IPAQ-C). The IPAQ-C was administered three times to each participant to examine the stability and reliability of the self-reported physical activity, whilst data to examine concurrent validity were acquired over 7 consecutive days using a physical activity log (PA-log), and an MTI accelerometer. A complete set of data was obtained from 49 Chinese residents (range 15-55 years; 30 males). The total physical activity recorded by IPAQ-C was acceptably reliable (ICC of 0.79 and %CV of 26%). There was weak agreement between IPAQ-C and the total MTI-derived activity and any of its constituent sub-components. Better agreement was seen between IPAQ-C and the PA-log data, with no significant difference between average total activity (3931 and 4047 MET min week(-1), respectively, p=0.51), and a bias and LOA of 3% and 94% of the mean score, respectively. Although these statistics are not dissimilar to those reported on other self-report physical activity questionnaires, suggesting the IPAQ-C is adequately reliable and valid for the measurement of total physical activity in a Chinese population, care needs to be taken, especially as the sub-components of total activity were markedly less valid and reliable.

Adolescent↗
PubMed2006

Evaluation of the sensitivity of a rapid polymerase chain reaction for detection of group B streptococcus.

The objective of this study was to compare detection of group B streptococcal (GBS) carriage using 'real-time' polymerase chain reaction (PCR) and microbiological standard culture. The study design was a test accuracy study comparing a novel molecular technique against the standard microbiological cultural technique in normal pregnant women. The setting and population consisted of 143 pregnant women with pre-labour rupture of the membranes, recruited from two large teaching hospitals in the UK. The study examined the efficacy of a polymerase chain reaction (PCR) assay for screening pregnant women who presented with term rupture of the membranes. Low vaginal specimens were obtained from the women. The specimens were tested for GBS by conventional culture and with a GBS-specific real-time PCR assay. The main outcome measure was the sensitivity and specificity of the PCR assay with 95% confidence intervals (CI) compared with the standard culture. The length of time to obtain a result was also reported for both methods. Among the 143 women, the results of the culture were positive (at least one colony) for GBS in 20 women (14%). The PCR assay detected GBS carriage in 10 women (7%). As compared with the culture method, the sensitivity and specificity of the PCR assay were 45% and 99%, respectively. The positive and negative predictive values of the PCR assay were 90% and 92%, respectively. The length of time required to obtain results for the majority of women (94%) was <2.5 h for the PCR assay and at least 24 h for culture. While a rapid result (within 3 h) of carriage of GBS can be obtained by the PCR assay, at present, it cannot replace conventional culture without further optimisation of the DNA extraction method. The sensitivity may further be improved by testing both low vaginal and rectal specimens.

Carrier State↗
PubMed2006

Targeting antioxidative signal transduction and stress response system: control of pathogenic Aspergillus with phenolics that inhibit mitochondrial function.

AIMS: The aim of this study was to show whether antioxidative response systems are potentially useful molecular targets for control of Aspergillus fumigatus and Aspergillus flavus. Selected phenolic agents are used in target-gene-based bioassays to determine their impact on mitochondrial respiration. METHODS AND RESULTS: Vanillyl acetone, vanillic acid, vanillin, cinnamic acid, veratraldehyde, m-coumaric acid (phenolic agents to which Saccharomyces cerevisiae sod2delta mutant showed sensitivity), carboxin (inhibits complex II of the mitochondrial respiratory chain), strobilurins/antimycin A (inhibits complex III of the mitochondrial respiratory chain) and fludioxonil/fenpiclonil [antifungals potentiated by mitogen-activated protein kinase (MAPK)] were examined in A. fumigatus, A. flavus and S. cerevisiae. Individual or combined application of phenolics with inhibitors of mitochondrial respiration showed some of the phenolics effectively inhibited fungal growth. Target-gene bioassays were performed using a sakAdelta (MAPK deletion) strain of A. fumigatus and a complementation analysis using the mitochondrial superoxide dismutase (Mn-SOD) gene (sodA) of A. flavus in the ortholog mutant, sod2delta, of S. cerevisiae. The results demonstrated that mitochondrial antioxidative stress system plays important roles in fungal response to antifungal agents tested. CONCLUSIONS: Antioxidative response systems of fungi can be an efficient molecular target of phenolics for pathogen control. Combined application of phenolics with inhibitors of mitochondrial respiration can effectively suppress the growth of fungi. SIGNIFICANCE AND IMPACT OF THE STUDY: Natural compounds that do not pose any significant medical or environmental risks could serve as useful alternatives or additives to conventional antifungals. Identifying the antioxidative response systems in other pathogens could improve methods for fungal control.

Antifungal Agents↗
PubMed2006

Splenic rupture in a premature neonate.

Splenic injuries are very rare in neonates. We report a case of splenic injury in a premature neonate, highlighting the importance of a high-index suspicion in early recognition of this rare but potentially fatal intra-abdominal injury. We also review the literature on possible aetiologies and mechanism of splenic injury, as well as its management. This is the first reported case of a very low-birth-weight neonate with splenic rupture who survived with intact neurology.

Cesarean Section↗
PubMed2005

Prospective randomized single-center, single-blind comparison of laparoscopic vs open repair of pediatric inguinal hernia.

BACKGROUND: The repair of indirect inguinal hernia (IH) is one of the most common pediatric surgical procedures, and open surgery (OS) is the standard treatment. The aim of this study was to determine whether the recently developed laparoscopic repair (LR) of IH is superior to OS. METHODS: Between February 2003 and February 2004, we randomly assigned 97 consecutive IH patients at our institution into OS and LR groups. Fourteen patients were excluded from the study for various reasons, leaving study population of 83 patients. After operation, multiple dressings were placed to blind observers to the operation type. Two pain scales, the children and Infants Postoperative Pain were used to assess postoperative pain. Acetaminophen (15 mg/kg/dose every 6 h) was given at a fixed pain score. Analgesic doses were compared. Parents also provided assessments of their children's recovery and wound appearance. RESULTS: The amount of acetaminophen taken by the OS group (n = 42) was 1.05 +/- 1.248 doses per patient, whereas the amount taken by the LR group (n = 41) was 0.54 +/- 0.84 dose per patient (p = 0.032; 95% confidence interval 0.45-0.976). Laparoscopy detected 11 more bilateral hernias (p = 0.006). Although the operative times did not differ significantly for bilateral hernias (39.08 +/- 13.37 min vs 34.0 +/- 11.31 min, p = 0.623), it did differ for unilateral hernias (18.38 +/- 5.71 vs 23.25 +/- 6.26 min, p = 0.001). Five contralateral hernias were detected in the OS group on follow-up, but none were found in the LR group (p = 0.026). The scores given by parents for recovery and wound appearance were higher in the LR group (p = 0.05). CONCLUSIONS: As compared with IH patients who undergo open surgery, those who have a laparoscopic repair suffer less pain, and their recovery and wound cosmesis are more satisfactory. With LR, contralateral hernias can be detected and repaired in a single operative procedure. This procedure takes slightly longer for unilateral than for bilateral hernias.

Child, Preschool↗
PubMed2005

Meconium peritonitis: prenatal diagnosis, postnatal management and outcome.

OBJECTIVES: Prenatal ultrasonography (USS) is a routine screening test for fetal abnormalities. Its accuracy for detecting meconium peritonitis (MP), which may carry high mortality, is important for prenatal counseling. The aim of this study was to assess the accuracy of prenatal USS for diagnosing MP and predicting patient outcomes. METHODS: The prenatal and postnatal medical records of all patients referred to our institutions with confirmed MP were reviewed, with emphasis on prenatal USS findings, results of postnatal investigations, operative findings, outcomes, and possible causes of MP. RESULTS: From January 2000 to November 2004, seven fetuses were confirmed to have MP at birth. Three MP patients (3/7, 43%) were diagnosed prenatally because of USS showing ascites and calcification/dilated or hyperechoic bowel loops. One (1/7, 14.3%) suspected cystic MP was confirmed by prenatal MRI. In the other three cases, USS showed only ascites. All patients had postnatal contrast CT scans. Two patients' CT scans showed persistent intestinal perforation not visible with prenatal USS, and required emergency operations. All patients survived and prospered, and were sweat test negative. CONCLUSIONS: Prenatal USS allows suspected MP babies to be transferred to a tertiary centre for delivery and appropriate management. In this way, the chances of survival of these babies can be excellent if they are not associated with cystic fibrosis (CF). Prenatal MRI can improve the low diagnostic yield of prenatal USS for MP. Postnatal contrast CT scan is required to define persistent intestinal perforation invisible with prenatal USS.

Female↗
PubMed2005

Unexpected intrauterine death following resolution of hydrops fetalis after betamethasone treatment in a fetus with a large cystic adenomatoid malformation of the lung.

Without intervention, the development of hydrops fetalis secondary to cystic adenomatoid malformation of the lung (CAML) implies a 100% mortality rate. Conversely, four CAML cases with in-utero resolution of hydrops fetalis after prenatal betamethasone therapy with good clinical outcome have been reported in the literature. The mechanism is speculated to be the effect of corticosteroid in improving lung maturation. Here we present another CAML case with resolution of hydrops fetalis after prenatal betamethasone therapy but which was followed by later intrauterine death. We speculate that the resolution of the CAML lesion itself may be more important in determining the clinical outcome than the resolution of hydrops. The association between prenatal betamethasone therapy and resolution of hydrops may be related to a different mechanism other than improvement of lung maturation.

Adult↗
PubMed2005

Roles of the Bloom's syndrome helicase in the maintenance of genome stability.

The RecQ family of DNA helicases is highly conserved in evolution from bacteria to humans. Of the five known human RecQ family members, three (BLM, WRN and RECQ4, which cause Bloom's syndrome, Werner's syndrome and Rothmund-Thomson syndrome respectively) are mutated in distinct clinical disorders associated with cancer predisposition and/or premature aging. BLM forms part of a multienzyme complex including topoisomerase IIIalpha, replication protein A and a newly identified factor called BLAP75. Together, these proteins play a role in the resolution of DNA structures that arise during the process of homologous recombination repair. In the absence of BLM, cells show genomic instability and a high incidence of sister-chromatid exchanges. In addition to a DNA structure-specific helicase activity, BLM also catalyses Holliday-junction branch migration and the annealing of complementary single-stranded DNA molecules.

Adenosine Triphosphatases↗
PubMed2005

Guidelines for the provision of echocardiography in Canada: recommendations of a joint Canadian Cardiovascular Society/Canadian Society of Echocardiography Consensus Panel.

Recognizing the central role of echocardiographic examinations in the assessment of most cardiac disorders and the need to ensure the provision of these services in a highly reliable, timely, economical and safe manner, the Canadian Cardiovascular Society and Canadian Society of Echocardiography undertook a comprehensive review of all aspects influencing the provision of echocardiographic services in Canada. Five regional panels were established to develop preliminary recommendations in the five component areas, which included the echocardiographic examination, the echocardiographic laboratory and report, the physician, the sonographer and indications for examinations. Membership in the panels was structured to recognize the regional professional diversity of individuals involved in the provision of echocardiography. In addition, a focus group of cardiac sonograhers was recruited to review aspects of the document impacting on sonographer responsibilities and qualification. The document is intended to be used as a comprehensive and practical reference for all of those involved in the provision of echocardiography in Canada.

Canada↗
PubMed2005

Device closure of a patent foramen ovale in a patient with lipomatous hypertrophy of the atrial septum.

The presence of a patent foramen ovale has been recognized as a risk factor for embolic stroke, and transcatheter device closure of patent foramen ovales is increasingly performed to reduce future neurological events. The present report discusses a patient who continued to have residual shunting following percutanous closure because of improper seating of the device in the presence of a lipomatous atrial septum.

Cardiac Catheterization↗
PubMed2004

Technical refinements in laparoscopic repair of childhood inguinal hernias.

BACKGROUND: This study aimed to evaluate the laparoscopic repair of childhood hernias and to identify technical refinements for improvements. METHODS: The records of 49 boys and 13 girls who underwent laparoscopic hernia repair in the authors' institution between July 2002 and July 2003 were reviewed. Their mean age was 4.5 years (range, 3 months to 15 years). No hernia opening was found in two patients, whereas 17 bilateral hernias (28%, 17/60) were found laparoscopically. Two bilateral hernias were diagnosed preoperatively. Four patients had the operation for recurrent hernias after open procedures. RESULTS: Over a mean follow-up period of 7.5 months (range, 3-15 months), there was one recurrence (1%, 1/79), but no other complication. With saline injection administered extraperitoneally, laparoscopic hernia repair can be performed safely for boys. Use of the "needle" sign avoided damage to the testicular vessel and vas. Placement of the needle medial to a prominent inferior epigastric artery and the presence of a "complete ring" sign prevented recurrence. The use of reusable 3-mm ports and round polypropylene stitches lowered the cost of the operation and improved the cosmesis for the patients. For recurrent hernias after open repair, the laparoscopic method was as simple as fresh hernia repair. CONCLUSIONS: Laparoscopic hernia repair allows detection and repair of contralateral hernias during the same operation. With refinements in technique, the procedure can be safely performed for boys, with the added advantages of lower costs, fewer recurrences, and improved cosmesis.

Adolescent↗
PubMed2004

Magnetic resonance screening of iron status in transfusion-dependent beta-thalassaemia patients.

The clinical utility of dual sequence (T1- and T2-weighted) magnetic resonance (MR) imaging in estimating liver iron concentration (LIC) in 32 transfusion-dependent beta-thalassaemia major (24 females; age 18.5+/-5.9 years) patients on desferrioxamine was evaluated. Signal intensity ratios (SIR) between liver, spleen and pancreas to psoas muscle were determined on both sequences. Relationships between clinical and MR parameters, and accuracy of SIR thresholds in determining adequacy of chelation from LIC were analysed. Liver T1- and T2-SIR were related to LIC (P < 0.001). T1-SIR < 0.60 predicted severe iron overload (LIC > 15 mg/g) with sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 100%, 87%, 33% and 100% respectively. T2-SIR < 0.1 yielded 100% sensitivity, 93% specificity, 50% PPV and 100% NPV. T1-SIR > or = 1.1 predicted LIC < 7 mg/g with 69% sensitivity, 88% specificity, 85% PPV and 74% NPV. T2-SIR > or = 0.20 yielded 56.5% sensitivity, 94% specificity, 90% PPV and 71% NPV. LIC correlated with liver T1-SIR, liver T2-SIR and serum ferritin (r = -0.76, -0.65, 0.47, respectively; P < 0.01). Serum ferritin was inversely related to liver T1-SIR, liver T2-SIR and spleen T2-SIR (r = -0.35, -0.43, -0.40, respectively; P < 0.05). Mean total transfusion burden was not related to any MR parameter. Although neither MR sequence was a highly accurate predictor of LIC, SIR thresholds are useful to determine presence of iron overload and adequacy of chelation treatment.

Adolescent↗
PubMed2003

Pathogenesis of neonatal necrotizing enterocolitis: a study of the role of intraluminal pressure, age and bacterial concentration.

The pathogenesis of neonatal necrotizing enterocolitis (NEC) is unknown. Intestinal dilatation and preferred occurrence of NEC at sites of bacterial overgrowth (colon and ileum) are common findings. The study attempted to produce NEC with increasing intraluminal pressures and bacterial concentrations in two different aged groups of rats. First, 10-cm terminal ileum segments were isolated with intact vascular pedicles in 1-and 3-month-old rats, and a dose of 10(11) E. coli in 1 ml was injected into each segment. Intraluminal pressure was sustained for 1 h at 150, 100, 50 and 0 cmH(2)0, respectively, in four experimental groups ( n=6). The isolated loop was then returned to the abdominal cavity and assessed grossly for NEC after 24 h. Histological examination was performed by a pathologist (KWC) who was blinded to the procedures. Second, the procedure was repeated with doses of 10(8), 10(5) and 0 bacteria/ml ( n=6) at intraluminal pressure of 100 cmH(2)0 in 1-month-old rats. Third, in another experimental group, oxygenation of the pedicled loop was assessed by oximetry as the intraluminal pressure increased and the findings were correlated with aortic blood pressure. The blood pressures (mean+/-SD) for 3- and 1-month-old rats were 110+/-6 and 72+/-4 mmHg, respectively. Hypoxia (<50% oxygen saturation) of the bowel was detected when the intraluminal pressure exceeded the mean blood pressure. The relative incidences of NEC in the bowel with intraluminal pressure above and below mean blood pressure were 100% (6/6) vs. 4% (1/24; P<0.05) in 3-month-old rats, and 100% (12/12) vs. 11% (2/18; P<0.05) in 1-month-old rats. There was no occurrence of NEC in bowel injected with 10(5) E. coli/ml and less at 100 cm intraluminal pressure. Increased intraluminal pressure results in bowel hypoxia and in the presence of adequate bacterial concentration predisposes to the development of NEC. Young age is associated with a lower threshold for increased intraluminal pressure leading to NEC.

Age Factors↗
PubMed2003

Mainstream vs. sidestream capnometry for prediction of arterial carbon dioxide tension during supine craniotomy.

We compared the performance of mainstream capnometry as a measure of arterial carbon dioxide tension (Paco2) with sidestream recordings in adult neurosurgical patients undergoing supine craniotomy. Two hundred and forty patients were randomly assigned so that the end-tidal carbon dioxide tension (PEco2) was measured using either a mainstream or sidestream infrared capnometer. All patients received propofol anaesthesia and ventilation was adjusted according to clinical requirement. Arterial blood gas analyses were performed after induction, prior to dural incision, during surgery and before wound closure. Simultaneous haemodynamic and ventilatory parameters were also recorded. For 1007 paired measurements of PEco2 and Paco2 (mainstream, n = 503; sidestream, n = 504), the mean (SD) mainstream arterial to end-tidal carbon dioxide tension difference, 0.64 (0.16) kPa, was smaller than the corresponding sidestream values, 0.99 (0.40) kPa (p < 0.001). The limits of agreement for the mainstream analyser, 0.32-0.96 kPa, were also narrower than the sidestream recordings, 0.19-1.79 kPa (p < 0.001). In both capnometers, the arterial to end-tidal difference in carbon dioxide tension did not change with time. However, there was greater within-patient variation in the sidestream group. Our study showed that mainstream PEco2 provided a more accurate estimation of Paco2 than sidestream measurement.

Adolescent↗