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Biomedical subjects

K M Ho

Publications and source records attributed to K M Ho.

At least 37 records · Page 2Linked to original sources
PubMed2004

Use of Sengstaken-Blakemore tube to stop massive upper gastrointestinal bleeding from Dieulafoy's lesion in the lower oesophagus.

Massive upper gastrointestinal bleeding from Dieulafoy's lesion in the gastrointestinal tract is uncommon. The use of the Sengstaken-Blakemore tube in acute gastrointestinal bleeding has become less common since endoscopic sclerotherapy and banding procedures have become widely available. The successful use of a Sengstaken-Blakemore tube to control acute massive upper gastrointestinal bleeding from a Dieulafoy's lesion in the lower oesophagus in an elderly man with severe coronary artery disease and heart failure is described.

Acute Disease↗
PubMed2004

Withholding and withdrawal of therapy in New Zealand intensive care units (ICUs): a survey of clinical directors.

Withdrawing and withholding life-support therapy in patients who are unlikely to survive despite treatment are common practices in intensive care units (ICUs). The literature suggests there is a large variation in practice between different ICUs in different parts of the world. We conducted a postal survey among all public ICUs in New Zealand to investigate the pattern of practice in withholding and withdrawal of therapy. Nineteen ICUs responded to this survey and they represented 74% of all the public ICU beds and 83% of the annual ICU admissions. The percentage of ICU admissions with therapy withdrawn or withheld was less than 10% in most ICUs. Only a small percentage (21%) of ICUs had a formal policy in withholding and withdrawal of therapy. The timing of making the decision to withhold or withdraw therapy was very variable. The patient and/or the family, the primary medical team consultant, two or more ICU consultants, and ICU nurses were usually involved in the decision making process. ICU nurses were more commonly involved in the decision making process in smaller ICUs (5 beds vs 10 beds, P = 0.03). The patient's pre-ICU quality of life, medical comorbidities, predicted mortality, predicted post-ICU quality of life, and the family's wishes were important factors in deciding whether ICU therapy would be withheld or withdrawn. Hospice ward or the patient's home was the preferred place for palliative care in 32% of the responses.

APACHE↗
PubMed2004

Performance evaluation of hybrid and conventional sequencing batch reactor and continuous processes.

Bench-scale systems, using conventional and compact hybrid activated sludge configurations, were set up to evaluate the systems' nitrification-denitrification performance, operating sludge age/MLSS concentration and sludge settleability at a Hong Kong municipal STW. Configurations tested were the continuous clarifier modified Ludzack Ettinger (MLE) and the sequencing batch reactor (SBR) with and without hybrid suspended biofilm carriers. Results demonstrated that the hybrid SBR and MLE systems consistently achieved close to complete nitrification (effluent NH4-N = 2.4 and 6.9 mg/L) and 75% and 67% removal of nitrogen (N) (effluent NO3-N < 10 mg/L) with an overall hydraulic retention time of only 7.5 hours, operating sludge age as short as 5.2 days, and mixed liquor suspended solids concentration of approximately 1,300 mg/L with a sludge volume index of 109 and 229 mL/g, respectively. The most sensitive and slowest growing nitrifiers attached to the hybrid biofilm carriers. This allowed the hybrid processes to be operated at a sludge age shorter than the critical nitrifying sludge age while still retaining near complete nitrification. In contrast, to achieve complete nitrification, the conventional MLE system needed to be operated at 1.5 to 2.5 times the critical sludge age. These results indicate that the hybrid MLE configuration is a suitable process for use in upgrading existing conventional works for N removal and for increasing hydraulic capacity of existing N removal works, without major civil works modifications, in Hong Kong. For new works, consideration might be given to the use of the hybrid SBR, which shows a more stable N removal performance than the MLE process due to its inherent in-basin equalization capacity and better reaction conditions for nitrification in terms of higher initial NH4-N level. It was also observed that the conventional SBR produced better nitrification performance than the hybrid MLE process tested. Design parameters and operating conditions of the hybrid systems should be subjected to further full-scale trial for higher hydraulic capacity and N removal performance.

Ammonia↗
PubMed2003

Heat-induced transformation of nanodiamond into a tube-shaped fullerene: a molecular dynamics simulation.

Heat-induced structural transformation in nanodiamond of diameter approximately 1.4 nm is investigated by tight-binding molecular dynamics simulations using the environment-dependent tight-binding carbon potential. The nanodiamond is found to transform into a tube-shaped fullerene via annealing. Three interesting mechanisms for promoting inner carbon atoms of the nanodiamond into the surface carbon atoms of the tubular structure are observed. The "flow-out" mechanism prevails at temperatures lower than 2500 K and the "direct adsorption" and "push-out" mechanisms are observed at higher temperatures.

Journal Article↗
PubMed2003

Use of odds ratios on anaesthesia related studies.

In line with other medical journals, odds ratios are increasingly being reported in anaesthesia literature. The frequency of the use of odds ratio and how well it relates to the relative risk when it is interpreted as relative risk remains unknown. We investigated the use of odds ratio, and its relationship to relative risk and the incidence of outcome in this study. We identified 60 meta-analyses and 87 original articles that reported odds ratios. While relative risk could have been reported in 79% of the studies, only a small proportion (3%) of these studies have estimated and reported the relative risk in addition to the odds ratio. There is a significant bias if odds ratio is interpreted as relative risk, especially so when the incidence of outcome is high. While odds ratio is a valid measure of treatment effect in its own right, anaesthetists and investigators should be careful not to interpret odds ratio as equivalent to relative risk.

Anesthesia↗
PubMed2003

Withholding and withdrawal of therapy in patients with acute renal injury: a retrospective cohort study.

The incidence of withholding and withdrawal of therapy in the setting of multi-organ failure in critically ill patients has increased. Epidemiological data on the decision-making process of withholding or withdrawal of therapy from Australian and New Zealand intensive care units is sparse. We examined the clinical and electronic records of 179 consecutive patients, admitted to the ICU between 1st January 2000 and 31st December 2001, who had acute renal injury. Acute renal replacement therapy was offered in 11.2% of patients. Therapy was withheld or withdrawn in 21.2% of patients. The levels of supportive care were comparable between those who had therapy withheld or withdrawn and those who had full intensive care therapy until such a decision was made. Predicted mortality (OR 1.04, 95% CI: 1.01-1.08, P = 0.03) and age (OR 1.04, 95% CI: 1.00-1.08, P = 0.03) were independently associated with the decision to withhold or withdraw therapy. The mean ICU stay of those with withdrawal or withholding of therapy was much shorter than those with full therapy (2.5 vs 5.7 days). This was likely to be due to an older age of our cohort, rapid progressive nature of the acute disease, a different clinical approach to treating critically ill elderly patients, or a combination of these factors. This pattern of practice was quite different from those reported from ICUs in other parts of the world. A prospective multi-centre observational study will clarify the pattern of practice in this important area of intensive care practice in Australasia.

Acute Kidney Injury↗
PubMed2003

Use of intravenous tranexamic acid to reduce allogeneic blood transfusion in total hip and knee arthroplasty: a meta-analysis.

Total hip or knee arthroplasty is associated with significant blood loss. Techniques such as the use of antifibrinolytics or desmopressin, or normovolaemic haemodilution have been used to reduce the need for allogeneic blood transfusion. Tranexamic acid has been used to reduce blood loss and transfusion requirement for total hip and knee arthroplasty, with variable results. This meta-analysis aims to evaluate whether intravenous tranexamic acid, when compared with placebo, reduces blood loss and transfusion requirement in total hip and knee joint replacement surgery and whether it might increase the risk of thromboembolic complications. The literature search was based on MEDLINE, EMBASE, Cochrane Controlled Trials Register, and information from the pharmaceutical company that produces tranexamic acid (Pharmacia-Upjohn). We identified 15 clinical trials and 12 were considered suitable for detailed data extraction. Tranexamic acid reduces the proportion of patients requiring allogeneic blood transfusion (OR 0.16, 95% CI: 0.09-0.26), total amount of blood loss (WMD 460 ml, 95% CI: 274-626 ml), and the total number of units of allogeneic blood transfused (WMD 0.85 unit, 95% CI: 0.36-1.33). Tranexamic acid does not increase the risk of thromboembolic complications such as deep vein thrombosis, pulmonary embolism, thrombotic cerebral vascular accident, or myocardial infarction (OR 0.98, 95% CI: 0.45-2.12). Intravenous tranexamic acid appears effective and safe in reducing allogeneic blood transfusion and blood loss in total hip and knee arthroplasty.

Antifibrinolytic Agents↗
PubMed2003

Lack of ageing cohort effect among sexually acquired HIV infections in Hong Kong.

We studied HIV rate in different age populations and whether there has been on-going new infections in Hong Kong, by examining the age characteristics and their temporal trend of reported HIV infections. It was found that people in the age group 25-34 were worst hit by the local epidemic. Ageing cohort effect was not apparent for the age pattern of sexually-acquired infections reported from 1987 to 2000, with the annual median ages ranged from 31.5 to 36 years (regression coefficient 0.14, 95% confidence interval -0.14 to 0.42, P = 0.295). Similar temporal age patterns were observed for individual subgroups of homo-/bisexuals, heterosexuals and female heterosexuals. The findings suggested the occurrence of new HIV infections over the years in Hong Kong, despite maintenance of a low prevalence. Albeit capturing largely prevalent infections, reported HIV/AIDS data could be tapped for understanding the evolving epidemic pattern to better evaluate and target current prevention programmes.

Adult↗
PubMed2003

Clinical predictors of acute renal replacement therapy in critically ill patients with acute renal impairment.

OBJECTIVE: To investigate the early predictors of acute renal replacement therapy (RRT) in critically ill patients with acute renal impairment. METHODS: A retrospective study of the clinical and laboratory records of all critically ill adult patients with acute renal impairment admitted to a 6-bed multidisciplinary intensive care unit of a general teaching hospital between 1 January 2000 and 31 December 2001 were reviewed to determine risk factors for RRT. Acute renal impairment was defined as an acute increase in plasma creatinine of > 0.12 mmol/L and urea of > 8 mmol/L or an increase in plasma creatinine of > 0.06 mmol/L from the baseline level in patients who had chronic renal impairment. RESULTS: A cohort of 179 critically ill patients with acute renal impairment were identified. The mean APACHE II score was 23.4 and RRT was required in 11.2% of patients. The final logistic regression model showed that the requirement for noradrenaline (OR 29.0; 95% CI: 1.92 - 436.4, p = 0.015) was a positive risk factor and an increase in the average hourly urine output after intravenous frusemide (post-frusemide average hourly urine output/pre-frusemide average hourly urine output, OR 0.08; 95% CI: 0.02 - 0.32, p = 0.0004) was a negative risk factor for the requirement of RRT (area under the ROC curve = 0.88, 95% CI: 0.82 - 0.94, p = 0.001). CONCLUSIONS: After adequate fluid resuscitation, poor urinary output response to intravenous frusemide coupled with requirement for noradrenaline predicted the requirement for RRT in critically ill patients with early acute renal impairment in our intensive care unit.

Journal Article↗
PubMed2002

All-metallic three-dimensional photonic crystals with a large infrared bandgap.

Three-dimensional (3D) metallic crystals are promising photonic bandgap structures: they can possess a large bandgap, new electromagnetic phenomena can be explored, and high-temperature (above 1,000 degrees C) applications may be possible. However, investigation of their photonic bandgap properties is challenging, especially in the infrared and visible spectrum, as metals are dispersive and absorbing in these regions. Studies of metallic photonic crystals have therefore mainly concentrated on microwave and millimetre wavelengths. Difficulties in fabricating 3D metallic crystals present another challenge, although emerging techniques such as self-assembly may help to resolve these problems. Here we report measurements and simulations of a 3D tungsten crystal that has a large photonic bandgap at infrared wavelengths (from about 8 to 20 microm). A very strong attenuation exists in the bandgap, approximately 30 dB per unit cell at 12 microm. These structures also possess other interesting optical properties; a sharp absorption peak is present at the photonic band edge, and a surprisingly large transmission is observed in the allowed band, below 6 microm. We propose that these 3D metallic photonic crystals can be used to integrate various photonic transport phenomena, allowing applications in thermophotovoltaics and blackbody emission.

Journal Article↗
PubMed2002

The impact of sea water flushing on biological nitrification-denitrification activated sludge sewage treatment process.

The process performance of the two largest activated sludge processes in Hong Kong, the Sha Tin and the Tai Po Sewage Treatment Works (STW), deteriorated in the initial period after the introduction of seawater flushing in 1995 and 1996, respectively. High effluent ammonia nitrogen (NH4-N) and total suspended solids (TSS) in excess of the discharge standards resulted from incomplete nitrification and changes in floc characteristics. A desktop study on the inhibitory effects of salinity, particularly on nitrification, was subsequently conducted using the Tai Po STW operating data. To assist the upgrade of the Sha Tin STW a five-month extensive bench-scale investigation on a simple but flexible modified Ludzack-Ettinger configuration with bio-selector was conducted to quantify the inhibitory effects due to the saline concentration. The Sha Tin STW upgrade consists of restoration of its original design capacity (conventional process) of 205,000 m3/day from its currently much reduced capacity as a Bardenpho process. Only the volume of the existing biological process and clarifier is to be utilized. The saline concentration ranges from 3,500 up to 6,500 mg Cl-/L, both daily and seasonally. High and greatly fluctuating saline concentrations have been known to inhibit nitrification. Design consideration should also be given to the peak daily and seasonal TKN loading of up to three times the average. Although the nitrifiers maximum specific growth rate was significantly reduced to a low 0.25 day(-1), the inhibition was considered to be tolerable with effluent NH4-N and NO3-N consistently at < 1 and < 6 mg/L. The bio-selector was demonstrated to be efficient in control of sludge foaming and bulking with SVI consistently < or = 125 mL/g. Results from the IAWO Model No. 1 and the hydraulic model of the secondary clarifiers allowed overall process capacity maximization. With an anoxic mass fraction of 25-30%, operating sludge age of 9-14 days and SVI < or = 125 mL/g, both the design requirements and the effluent discharge standards could be met. Without these investigations, an unnecessarily large reaction basin and secondary clarifier volume, and hence capital investment, would have resulted.

Ammonia↗
PubMed2001

Porphyria cutanea tarda and melioidosis.

Porphyria cutanea tarda is a metabolic disorder in the haem biosynthetic pathway. It includes a heterogeneous group of conditions, which may be inherited or, more commonly, acquired. Although porphyria cutanea tarda presents with cutaneous lesions only, it is often associated with systemic disease. A 64-year-old Chinese patient, who developed sporadic porphyria cutanea tarda 1 year after the diagnosis of pulmonary melioidosis, is discussed. The patient presented with a history of recurrent photosensitive vesicles, blisters, and skin fragility on the sun-exposed areas of both forearms and hands, 6 months after commencing doxycycline and amoxycillin. Both the histological and biochemical findings were characteristic of porphyria cutanea tarda. All the lesions subsided after cessation of these antibiotics. The patient was free of further lesions at follow-up 6 months later. The association seen in this case between porphyria cutanea tarda and melioidosis is unlikely to be coincidental, because these two diseases are both very rare in Hong Kong. In addition, the temporal relationship between the antibiotic therapy and the clinical course of skin lesions in this patient suggests that the drugs were a trigger factor, precipitating their appearance.

Anti-Bacterial Agents↗
PubMed2001

Epidemiology and detection of human immunodeficiency virus among pregnant women in Hong Kong.

OBJECTIVES: To determine the epidemiology of human immunodeficiency virus infection among pregnant women and the neonatal outcomes in Hong Kong. DESIGN: Retrospective observational study composed of two parts: record review of pregnant women and unlinked anonymous screening of cord blood from neonates. SETTING: Two human immunodeficiency virus clinics and the Government Virus Unit. PARTICIPANTS: Female patients attending the two clinics who became pregnant and neonates who underwent routine metabolic screening by the Government Virus Unit between 1992 and 1999. MAIN OUTCOME MEASURES: The outcomes of neonates born to women who had human immunodeficiency virus infection during pregnancy. RESULTS: Forty-one human immunodeficiency virus-related pregnancies were recorded among 32 infected women. Fifteen pregnancies were terminated, of which 14 were in women who knew their infection status before conception. Twenty-six pregnancies continued to term, resulting in 26 live births. Twelve babies were born to women who knew their infection status before delivery. One baby was confirmed to be infected. Six women were given zidovudine for prophylaxis against vertical transmission and none of the babies were infected at birth. Of the remaining 14 human immunodeficiency virus-related pregnancies, the mothers' status became known only at a later date and nine (64.3%) babies were confirmed to be infected at the age of 18 months or older. The rate ratio of giving birth to an infected baby was 8.18 from mothers who did not know their status antenatally. Unlinked anonymous screening showed that the seroprevalence rate for human immunodeficiency virus in pregnant women was 0.032% (1/3125) in Hong Kong in 1999. CONCLUSIONS: Human immunodeficiency virus-related pregnancy is not rare in Hong Kong and the majority of infected mothers were not identified and treated. Detection of these pregnancies will be invaluable for the prevention of mother-to-child transmission. Universal antenatal screening of human immunodeficiency virus antibody is proposed as an effective strategy.

AIDS Serodiagnosis↗
PubMed2000

Unique dynamic appearance of a Ge-Si ad-dimer on Si(001).

We carry out a comparative study of the energetics and dynamics of Si-Si, Ge-Ge, and Ge-Si ad-dimers on top of a dimer row in the Si(001) surface, using first-principles calculations. The dynamic appearance of a Ge-Si dimer is distinctively different from that of a Si-Si or Ge-Ge dimer, providing a unique way for its identification by scanning tunneling microscopy (STM). Its "rocking" motion, observed in STM, actually reflects a 180 degrees rotation of the dimer, involving a piecewise-rotation mechanism. The calculated energy barrier of 0.74 eV is in good agreement with the experimental value of 0.82 eV.

Journal Article↗
PubMed2000

Laser-induced graphitization on a diamond (111) surface.

We report an atomistic simulation study of laser-induced graphitization on the diamond (111) surface. Our simulation results show that the diamond to graphite transition occurs along different pathways depending on the length of the laser pulse being used. Under nanosecond or longer laser pulses, graphitization propagates vertically into bulk layers, leading to the formation of diamond-graphite interfaces after the laser treatment. By contrast, with femtosecond (0.2-0.5 ps) laser pulses, graphitization of the surface occurs layer by layer, resulting in a clean diamond surface after the ablation. This atomistic picture provides an explanation of recent experimental observations.

Journal Article↗
PubMed2000

Studies of the pathophysiology of idiopathic detrusor instability: the physiological properties of the detrusor smooth muscle and its pattern of innervation.

PURPOSE: Idiopathic detrusor instability (IDI) is a common cause of lower urinary tract storage symptoms, such as urgency, frequency and urge incontinence. We have investigated the in vitro properties and pattern of innervation of the detrusor from patients with this condition. MATERIALS AND METHODS: Full thickness bladder specimens were obtained perioperatively from 14 patients with IDI and from 14 cadaveric controls undergoing transplant organ retrieval. Isolated detrusor smooth muscle strips were mounted in organ baths for isometric tension recording. Frequency-response curves to electrical field stimulation (EFS) (1 Hz to 50 Hz) and concentration response curves for carbachol (10(-7) M to 5 x 10(-4) M) and potassium (12 mM to 120 mM) were constructed. Acetylcholinesterase histochemistry and immunohistochemistry for both phosphorylated and non-phosphorylated neurofilaments was carried out on frozen sections of control and IDI bladders. RESULTS: IDI strips developed greater spontaneous tone (0.25 gm./mg. versus 0.12 gm./mg.; p <0.0001) and more spontaneous fused tetanic contractions (16.8% versus 6.8%; p <0.005) during an initial 90 minutes equilibration period. The IDI strips were less responsive than controls to nerve stimulation (max. response to EFS 0.79 gm./mg. versus 1.23 gm./mg.; p <0.0001) and were supersensitive to potassium (EC50 39.7 mM versus 45.7 mM; p = 0.003) but not to carbachol (EC50 7.3 x 10(-6) M versus 6.6 x 10(-6) M; p = 0.48). Morphometric studies revealed reduced staining of presumed cholinergic nerves, with 34.7% of IDI smooth muscle bundles appearing denervated compared with 1.5% of controls (p <0.0001). CONCLUSIONS: Our study supports the notion that there is a fundamental abnormality in IDI at the level of the bladder wall, with evidence of altered spontaneous contractile activity consistent with an increased electrical coupling of cells, a patchy denervation of the detrusor and a potassium supersensitivity.

Adult↗