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K W Lam

Publications and source records attributed to K W Lam.

At least 19 recordsLinked to original sources
PubMed2006

Continued reduction in the incidence of birth trauma and birth asphyxia related to instrumental deliveries after the study period: was this the Hawthorne effect?

BACKGROUND: The incidence of birth trauma and birth asphyxia related to instrumental deliveries in our obstetric unit was high (2.8%) in 1998-1999. A study was performed in 2000 to identify the risk factors. Unexpectedly, the incidence (0.6%) was reduced significantly during the study period. We attributed this phenomenon to the famous Hawthorne effect (tendency to improve performance because of awareness of being studied). OBJECTIVES: The objectives were to study whether there is a continued reduction in the incidence of birth trauma and birth asphyxia related to instrumental deliveries in the post-study period (2001-2003) and to investigate the presence of underlying confounding factors apart from the Hawthorne effect. METHOD: To compare the hospital obstetric statistics among the pre-study period (1998-1999), the study period (2000) and the post-study period (2001-2003), in particular the incidence of birth trauma and birth asphyxia related to instrumental deliveries, the instrumental delivery rate, the overall Caesarean section rate, the Caesarean section rate for no progress of labour, the incidence of failed instrumental delivery, the incidence of attempted instrumental delivery in the operating theatre, and incidence of direct second-stage Caesarean sections. RESULTS: The incidence of birth trauma and birth asphyxia related to instrumental deliveries (0.6%) during the study period (2000) was significantly lower than that (2.8%) during the pre-study period (1998-1999; RR 0.27, 95% CI 0.11-0.70). This phenomenon continued into the post-study period (2001-2003) when the incidence of 1.0% was similarly lower than that in the pre-study period (RR 0.35, 95% CI 0.20-0.64). The instrumental delivery rate decreased further in the post-study period (13.5%) compared with those in the study (16.6%) and pre-study (19.5%) periods (RR 0.81, 95% CI 0.75-0.89 and RR 0.69, 95% CI 0.65-0.74, respectively). There was a marked increase in the direct second-stage Caesarean section rate in the post-study period (7.1%) compared to those in the study (0.4%) and pre-study (0.7%) periods (RR 15.9, 95% CI 5.05-49.73 and RR 9.77, 95% CI 5.28-18.08, respectively). CONCLUSION: A change in obstetric practice was identified that may explain the continued reduction in the incidence of birth trauma and birth asphyxia related to instrumental deliveries in the post-study period.

Asphyxia Neonatorum↗
PubMed2006

The practice of episiotomy in public hospitals in Hong Kong.

OBJECTIVE: To review the use of episiotomy during vaginal delivery in Hong Kong public hospitals. DESIGN: Prospective observational survey. SETTING: Public hospitals, Hong Kong. PARTICIPANTS: Women who underwent normal vaginal delivery of a singleton foetus with cephalic presentation. MAIN OUTCOME MEASURES: Number of women having an episiotomy, severe-degree (third- or fourth-degree) tear, other types of tear, blood loss at delivery, postpartum haemorrhage, need for blood transfusion, puerperal pyrexia, wound infection, gaping wound that required suture removal, and drainage or resuturing of a perineal wound. RESULTS: Between 1 January and 31 March 2003, there were 6222 singleton spontaneous normal vaginal deliveries in the public hospitals of Hong Kong. Of the 6167 women in whom the status of the perineum was known, episiotomy was performed in 5274 (85.5%). Primiparous women were more likely to undergo episiotomy at delivery than multiparous women (97.9% vs 71.4%). Women with episiotomy had significantly less perineal tearing of any kind than those without. The occurrence of any type of perineal tear and severe-degree (third- or fourth-degree) tear was significantly lower in primiparous women who had an episiotomy than those without (P<0.05). Women with episiotomy had increased mean blood loss at delivery but other complications were not significantly increased. CONCLUSIONS: In Hong Kong, episiotomy is routinely performed during normal vaginal delivery. It is associated with a significantly lower overall rate of perineal tearing. This study was observational, nonetheless the occurrence of other complications was likely to increase when episiotomy was performed. Firm evidence from several randomised controlled studies shows that routine episiotomy is unjustified and possibly harmful. Routine episiotomy should not be promoted in Hong Kong without further randomised controlled study.

Adolescent↗
PubMed2005

Biofilm formation and sloughing in Serratia marcescens are controlled by quorum sensing and nutrient cues.

We describe here a role for quorum sensing in the detachment, or sloughing, of Serratia marcescens filamentous biofilms, and we show that nutrient conditions affect the biofilm morphotype. Under reduced carbon or nitrogen conditions, S. marcescens formed a classical biofilm consisting of microcolonies. The filamentous biofilm could be converted to a microcolony-type biofilm by switching the medium after establishment of the biofilm. Similarly, when initially grown as a microcolony biofilm, S. marcescens could be converted back to a filamentous biofilm by increasing the nutrient composition. Under high-nutrient conditions, an N-acyl homoserine lactone quorum-sensing mutant formed biofilms that were indistinguishable from the wild-type biofilms. Similarly, other quorum-sensing-dependent behaviors, such as swarming motility, could be rendered quorum sensing independent by manipulating the growth medium. Quorum sensing was also found to be involved in the sloughing of the filamentous biofilm. The biofilm formed by the bacterium consistently sloughed from the substratum after approximately 75 to 80 h of development. The quorum-sensing mutant, when supplemented with exogenous signal, formed a wild-type filamentous biofilm and sloughed at the same time as the wild type, and this was independent of surfactant production. When we removed the signal from the quorum-sensing mutant prior to the time of sloughing, the biofilm did not undergo significant detachment. Together, the data suggest that biofilm formation by S. marcescens is a dynamic process that is controlled by both nutrient cues and the quorum-sensing system.

Biofilms↗
PubMed2005

A novel artificial prosthetic replacement for the proximal interphalangeal joint of the hand--from concept to prototype.

This article describes the development of a proximal interphalangeal (PIP) joint prosthesis based on the principles of replicating anatomical surface components, the use of macrolocking intramedullary stem and the use of a cobalt-chrome alloy material. The design features are intended to obtain an optimal range of motion while retaining stability and longevity. The final prototype, for which a patent has been filed, is described.

Chromium Alloys↗
PubMed2004

Efficacy of preemptive analgesia for wound pain after laparoscopic operations in infertile women: a randomised, double-blind and placebo control study.

OBJECTIVE: To compare preemptive analgesia and preclosure analgesia in reducing wound pain after laparoscopic operation. DESIGN: Randomised, double-blind and placebo control. SETTING: University referral centre. POPULATION: Infertile women undergoing diagnostic laparoscopy with or without additional procedures. METHODS: One hundred and forty-four women were randomised to receive 10 mL of 1% lignocaine at the surgical sites before incision and 10 mL of normal saline before closure of incision (the preemptive group), saline before incision and lignocaine before closure of incision (the preclosure group) and saline at the surgical sites both before incision and closure of incision (the placebo group). MAIN OUTCOME MEASURES: Post-operative wound pain measured by linear visual analogue scale and amount of analgesic use. RESULTS: The women in the preclosure group had significantly lower pain scores at 2, 4 and 24 hours than those in the placebo group, whereas the women in the preemptive group only showed significantly lower pain scores at 2 hours than the placebo group. The pain score at 24 hours in the preclosure group was significantly lower than that in the preemptive group. There was no significant difference in the post-operative analgesic requirement among the three groups. CONCLUSION: The preclosure analgesia is better than preemptive analgesia and no analgesia in reducing post-operative wound pain.

Adult↗
PubMed2003

Unexpected reduction in the incidence of birth trauma and birth asphyxia related to instrumental deliveries during the study period: was this the Hawthorne effect?

OBJECTIVE: The study was originally designed to identify the risk factors that could predict those difficult instrumental deliveries resulting in birth trauma and birth asphyxia. DESIGN: A prospective study on all singleton deliveries in cephalic presentation with an attempt of instrumental delivery over a 12-month period (13 March 2000 to 12 March 2001). SETTING: A local teaching hospital. SAMPLE: Six hundred and seventy deliveries. METHODS: A codesheet was designed to record the demographic data, characteristics of first and second stages of labour and neonatal outcome. In particular, the doctor had to enter the pelvic examination findings before the attempt of instrumental delivery. MAIN OUTCOME MEASURES: Birth trauma and birth asphyxia. RESULTS: There was a significant reduction in the incidence of birth trauma and birth asphyxia related to instrumental deliveries during the study period (0.6%) when compared with that (2.8%) in the pre-study period (1998 and 1999) (RR 0.27, 95% CI 0.11-0.70). There was more trial of instrumental deliveries in the operating theatre although this was not statistically significant (RR 1.19, 95% CI 0.88-1.60). The instrumental delivery rate decreased during the study period (RR 0.88, 95% CI 0.82-0.94). The caesarean section rate for no progress of labour, the incidence of direct second stage caesarean section and the incidence of failed instrumental delivery did not increase during the study period. CONCLUSIONS: Apart from the merits of regular audit exercise and increasing experience of the staff, the Hawthorne effect might be the major contributing factor in the reduction of birth trauma and birth asphyxia related to instrumental deliveries during the study period.

Asphyxia Neonatorum↗
PubMed2002

Left upper quadrant approach in gynecologic laparoscopic surgery using reusable instruments.

STUDY OBJECTIVE: To determine the usefulness of the left upper quadrant approach in gynecologic laparoscopic surgery. DESIGN: Retrospective study (Canadian Task Force classification II-2). SETTING: University referral center. PATIENTS: Twenty-four women with longitudinal scars from previous laparotomy through or close to the umbilicus. INTERVENTION: Left upper quadrant was chosen as the site of primary entry of the reusable Veress needle (ninth or tenth left intercostal space) and reusable primary cannula (left upper quadrant just below the left subcostal margin). MEASUREMENTS AND MAIN RESULTS: Intraabdominal adhesions between old longitudinal scars and underlying bowel or omentum were present in 14 patients. Adhesions involving omentum only were present in 10 patients, bowel only in 2, and both omentum and bowel in 2. The only intraoperative complication was emphysema in one woman. All operative procedures were completed laparoscopically. CONCLUSION: The left upper quadrant approach is a safe entry point for reusable instruments at laparoscopic surgery in patients with midline incisions close to the umbilicus.

Emphysema↗
PubMed2001

Optimized analytical method for cyclosporin A by high-performance liquid chromatography-electrospray ionization mass spectrometry.

The Micromass Platform LCZ mass detector parameters were optimized for simultaneous recording of the protonated (CsA-H+), sodium adduct (CsA-Na+) and potassium adduct (CsA-K+) of cyclosporin A eluted from a Symmetry Shield RP8 column. The optimized procedure allows a precise analysis of CsA in whole blood or serum without removal of salts prior to analysis. The ratio of the three forms of CsA varied depending on the assay condition and the types of specimens being analyzed. The summation of three ionic forms of CsA detected by LC-ESI-MS is a reliable and simple method to assess CsA concentration in the blood.

Cations, Monovalent↗
PubMed2001

Chromatographic identification of a biochemical alteration in the aqueous humour of megalophthalmic Black Moor goldfish.

PURPOSE: To observe if any biochemical abnormalities exist between the eye of megalophthalmic and non-megalophthalmic goldfish by high-performance liquid chromatography (HPLC). METHOD: Aqueous humour and sera from megalophthalmic and non-megalophthalmic goldfish were subjected to HPLC and monitored by photodiode array detection (Waters, MA, USA). RESULTS: An unusual accumulation of a compound with a UV absorption maximum at 290 nm was observed in the aqueous humour of megalophthalmic eye. This compound was also present in the sera of both normal goldfish and one of its megalophthalmic mutant. However, it was significantly elevated in the aqueous humour of the megalophthalmic eye only. This compound concentration was very high in the eye of small fish and its concentration increased only slightly with the expansion of the eye in larger fish. CONCLUSIONS: The presence of this compound in the serum and aqueous humour indicates a specific systemic metabolic variation in Black Moor goldfish not seen other animal species we had studied (humans, bovine, chick, rabbits and rats). The marked elevation of this compound in the megalophthalmic eye indicates a possible association of this compound with the metabolic variation accounting for the expansion of the eye in megalophthalmic goldfish.

Animals↗
PubMed1999

Periocular accumulation of timolol and betaxolol in glaucoma patients under long-term therapy.

PURPOSE: To determine if betaxolol or timolol is present in measurable concentration in the Tenon capsule in patients under long-term topical therapy. METHODS: Small (1-cc) specimens of Tenon capsule were removed at the time of filtering surgery from 15 glaucoma patients under long-term preoperative topical therapy, nine of whom had been treated with timolol and six of whom had been receiving betaxolol. Methanol extracts of these tissue samples were analyzed quantitatively for the presence of either beta-adrenergic antagonist by high-performance liquid chromatography. RESULTS: Drug was detected in every specimen. A mean total of 2.6 (range, 0.1-30.0) microg of betaxolol was detected per 1-cc specimen. CONCLUSION: Timolol and betaxolol penetrate the conjunctiva and accumulate in the Tenon capsule. In patients under long-term therapy, the periocular tissue can accumulate a greater quantity of beta-antagonist than is present in a daily dosage of applied eyedrops, manyfold higher than the maximal intraocular concentration.

Adrenergic beta-Antagonists↗
PubMed1999

Noninvasive cerebrospinal fluid shunt flow measurement by Doppler ultrasound using ultrasonically excited bubbles: a feasibility study.

Because normal cerebrospinal fluid (CSF) has almost no natural Doppler scatterers, patency testing of ventriculoperitoneal cerebrospinal fluid shunts (small silastic tubing with lumen diameter of approximately 1 mm draining excessive CSF from the brain) cannot be performed by Doppler ultrasound. We have developed a low-frequency bubble excitation system that generates microbubble scatterers in both distilled water and CSF. Doppler ultrasound can then be used for flow measurement in a ventriculoperitoneal shunt. By using low duty-cycle (approximately 10%), low-frequency (approximately 30 kHz), and low-amplitude (approximately 30 kPa) ultrasound, a population of microbubbles can be maintained for sufficiently long times (>10 min) for Doppler ultrasound measurement, although bubble initiation is inconsistent. The minimum pressure needed for bubble maintenance was found to decrease with increasing burst length and duty cycle. It has been possible to detect the presence of CSF shunt flow down to a mean flow rate of 3 mL/h (mean velocity approximately 0.6 mm/s). The bubble maintenance scheme developed satisfies the safety parameters specified by the American Institute of Ultrasound in Medicine (AIUM) and the US Food and Drug Administration (FDA). Results from both in vitro and in vivo (externalized shunts) experiments indicate the feasibility of this scheme for determining realistic CSF shunt flows, though some practical problems remain before the technique will be ready for clinical use.

Child↗
PubMed1999

The identification of dipalmityl zeaxanthin as the major carotenoid in Gou Qi Zi by high pressure liquid chromatography and mass spectrometry.

The carotenoid in Gou Qi Zi was extracted by hexane, followed by repeated chromatography on a silica column. The major carotenoid recovered from the chromatographic step was subjected to hydrolysis in potassium hydroxide (KOH). The hydrolytic products were separated on a silica column followed by analysis for their molecular sizes by a Micromass Platform LCZ. The retention time of the carotenoid in Gou Qi Zi is 2.3 min. Upon hydrolysis, new carotenoid peaks appeared. The molecular ions detected by APCI- of the carotenoid at 2.3, 6.8 and 28 min are 1044, 806 and 568, respectively. The molecular sizes matched to that of dipalmityl zeaxanthin, monopalmityl zeaxanthin and zeaxanthin, respectively. The monopalmityl zeaxanthin peak appeared first and faded away as the free zeaxanthin peak reached the maximal size.

Carotenoids↗
PubMed1998

Aqueous humor uric acid and ascorbic acid concentrations and outcome of trabeculectomy.

OBJECTIVE: To determine if there is an association between the surgical outcome of trabeculectomy and uric acid and ascorbic acid concentrations in the aqueous humor at the time of the procedure. PATIENTS, MATERIALS, AND METHODS: Aqueous humor samples were collected from the eyes of 169 of 249 adult patients who underwent trabeculectomy alone for any type of glaucoma between April 1989 and July 1995. Postoperatively, all medical records were reviewed and outcomes were classified as successful, unsuccessful, or indeterminate. The ascorbic acid and uric acid concentrations were determined in masked fashion by high-pressure liquid chromatography. Factors associated with surgical outcome were determined. RESULTS: Uric acid concentration was higher in unsuccessful eyes (mean+/-SD, 0.21+/-0.08 mmol/L, n=26) than in successful eyes (0.15+/-0.09 mmol/L, n=91, 95% confidence interval for difference, 0.02-0.10 mmol/L). Ascorbic acid levels were not significantly different in the eyes with unsuccessful (1129.9+/-601.9 micromol/L) and successful (1334.3+/-511.0 micromol/L) surgery (95% confidence interval for difference, -475.2 to 66.4 micromol/L, P=.13) surgery. Other factors associated with failure were previous surgery and surgery performed at the inferior limbus. A multiple polytomous logistic regression analysis was performed, after excluding the small number of operations performed at the inferior limbus. The odds ratio for failure increased by a factor of 1.68 for every 1-mmol/L increase in uric acid (95% confidence interval, 1.16-2.43, P=.006). CONCLUSIONS: Uric acid levels were higher at the time of surgery in eyes that had unsuccessful outcomes than in those with successful outcomes. No significant difference in ascorbic acid levels was detectable. A higher uric acid level in the aqueous humor is a risk factor for trabeculectomy failure and might be tested as a prognostic indicator [corrected].

Aged↗
PubMed1998

The occurrence of retinol and carotenoids in human subretinal fluid.

PURPOSE: To investigate if retinol and carotenoids are present in the subretinal space following rhegmatogenous retinal detachment. METHODS: Blood and subretinal fluid were collected from patients at the time of surgical repair of retinal detachment. After removal of cellular contents in a specimen by centrifugation, the supernatant fraction was analyzed by liquid chromatography using a silica column eluted by 16% dioxane in hexane. Retinol and carotenoids were identified in the chromatograms based on their retention time and absorption spectrum. RESULTS: The retinol concentrations (mean+/-SD) in the serum and subretinal fluid were 305+/-144 and 166+/-96 ng/ml respectively. The 450 nm chromatogram had 7 peaks with the characteristic absorption spectrum of carotenoids. Peak 1 and 7 coincided with the retention time of beta-carotene (1.8 min) and lutein (10.8 min) respectively. The concentrations of beta-carotene and lutein in serum were 161+/-63 and 142+/-98 ng/ml respectively. There was very little beta-carotene in subretinal fluid (4.7+/-2.4 ng/ml). Lutein was the major carotenoid peak in subretinal fluid (41.4+/-14.1 ng/ml). The minor carotenoid peaks of serum were not observed in subretinal fluid. CONCLUSION: There is a substantial amount of retinol and lutein in subretinal fluid. The high proportion of lutein and very low amount of beta-carotene in the subretinal fluid support the occurrence of a highly selection transport mechanism of lutein from the blood to the retina.

Adult↗
PubMed1998

Iron-induced apoptosis in the photoreceptor cells of rats.

PURPOSE: To determine whether apoptosis is involved in retinal degeneration induced by intravitreal implantation of 5 iron particles in rat eyes. METHODS: Autoclaved iron particles were implanted in the vitreous cavities of the experimental eyes. Glass chips were implanted in the control eyes. The experimental eyes were enucleated at various time intervals from days 1 to 15. Retinal degeneration was examined using the TdT-mediated, dUTP-biotin nick-end labeling (TUNEL) method. Electrophoresis on agarose gel was used to detect internucleosomal DNA fragmentation. RESULTS: TUNEL-positive nuclei were observed only in the outer nuclear layer beginning on day 2. The nuclei spread throughout the outer nuclear layer by the end of day 3. No TUNEL-positive nuclei were observed in other layers throughout the experimental period. Analysis of DNA, extracted from the retinas by electrophoresis on agarose gel, revealed a typical ladder pattern of internucleosomal DNA cleavage in the experimental eyes. CONCLUSIONS: Apoptosis occurred during photoreceptor cell death at the early phase of iron-induced retinopathy in these rats. Like photic injury, iron-induced apoptosis was limited to the outer nuclear layer.

Animals↗
PubMed1997

A new classification system predicting keratomalacia after trauma in vitamin A deficiency: sodium citrate does not prevent disease progression.

PURPOSE: The purpose of this study was to develop a classification system to predict keratomalacia after trauma in vitamin A-deficient eyes and to determine whether citrate impedes polymorphonuclear leukocyte infiltration into the cornea, thus preventing keratomalacia. METHODS: Preliminary classification studies showed that a 7.0-mm corneal epithelial scrape, before clinical findings of corneal xerosis, did not induce keratomalacia. Primary studies were conducted concurrently on the same animals to develop the classification system and test the effect of citrate in vitamin A deficiency. A 7.0-mm corneal epithelial scrape was performed on vitamin A-deficient eyes in various stages of corneal xerosis and treated as follows. Experiment 1: group 1, 10% citrate drops; group 2, phosphate buffer solution (PBS) drops; experiment II: group 3, drops and subconjunctival injection of 10% citrate; group 4, drops and subconjunctival injection of PBS. RESULTS: Corneal abrasion in eyes with 2+ corneal xerosis yielded keratomalacia in 50% of cases; the remainder healed with xerotic epithelium. Eighty-three percent of eyes with > 2+ xerosis developed keratomalacia after corneal abrasion, whereas only 7.1% of eyes with < 2+ xerosis advanced to this stage. In experiment I, 27% of citrate-treated eyes and 38% of PBS-treated eyes developed keratomalacia (not significant). In experiment II, two of six citrate-treated eyes perforated and one eye developed keratomalacia. One of six control PBS eyes perforated and four developed keratomalacia. CONCLUSION: We correlated the degree of corneal xerosis with the occurrence of keratomalacia after corneal trauma. This led to the development of a classification scale that is of research and clinical significance. Additionally, citrate did not significantly reduce keratomalacia or perforation in the vitamin. A-deficient eye.

Animals↗