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Biomedical subjects

H K Tan

Publications and source records attributed to H K Tan.

At least 37 records · Page 2Linked to original sources
PubMed2001

Early and intensive continuous hemofiltration for severe renal failure after cardiac surgery.

BACKGROUND: The aim of this study was to test whether early and intensive use of continuous venovenous hemofiltration (CVVH) achieved a better than predicted outcome in patients with severe acute renal failure undergoing cardiac operations, and whether a simple and yet accurate model could be developed to predict their outcome before starting CVVH. METHODS: Medical record analysis with collection of demographic, clinical, and outcome information was used. RESULTS: Sixty-five consecutive patients were treated with early and intensive CVVH (mean operation to CVVH time, 2.38 days; pump-controlled ultrafiltration rate, 2 L/h) after coronary artery bypass grafting (56.9%), single valve procedure (16.9%), or combined operations (26.2%). In 32.3% of patients, intraaortic balloon counterpulsation was required and 20% of patients were emergencies. Sustained hypotension despite inotropic and vasopressor support occurred in 40% of patients and prolonged mechanical ventilation in 58.5%. Using an outcome prediction score specific for acute renal failure, the predicted risk of death was 66%. Actual mortality was 40% (p = 0.003). Using multivariate logistic regression analysis and neural network analysis, patient outcome could be predicted with good levels of accuracy (receiver operating characteristic 0.89 and 0.9, respectively). CONCLUSIONS: Early and aggressive CVVH is associated with better than predicted survival in severe acute renal failure after cardiac operations. Using readily available clinical data, the outcome of such patients can be predicted before the implementation of CVVH.

Acute Kidney Injury↗
PubMed2001

Prevalence of gestational thyrotoxicosis in Asian women evaluated in the 8th to 14th weeks of pregnancy: correlations with total and free beta human chorionic gonadotrophin.

OBJECTIVES: The prevalence of gestational transient thyrotoxicosis (GTT) in Europeans evaluated during the 8th to 14th weeks of pregnancy is 2-3%. However, there is evidence that GTT may be more common in some Asian populations. The aims of this study were to evaluate the prevalence of thyroid hormone abnormalities in Asian women in their 8th to 14th weeks of pregnancy using highly sensitive free T4 and TSH assays and to correlate these with total and free beta-hCG levels. DESIGN AND PATIENTS: One hundred and eighty-four consecutive unselected Asian (Singaporean) pregnant women seen at ante-natal clinics for the first time and who were in their 8th to 14th weeks of pregnancy were tested. MEASUREMENTS: Serum free T4, free T3, TSH, total beta-hCG and free beta-HCG levels were measured on the Vitros ECi system (Johnson & Johnson Ortho-Clinical Diagnostics, Amersham, UK) which employs chemiluminescent immunochemical technology. This free T4 assay is free of biases related to serum binding capacity. The TSH assay used was a third generation assay. Thyrotrophin-receptor antibody (TRAb) levels were measured using LUMItest TRAK (BRAHMS Diagnostica, Berlin, Germany). RESULTS: Two subjects (1.1%) were found to have Graves' disease. Elevated free T4, free T3, total T3 and suppressed TSH were seen in 14.8%, 3.3%, 26.4% and 33.0% of the remaining 182 pregnant women, respectively. Total and free beta-hCG correlated negatively with TSH (r = -0.30, P < 0.0001 and r = -0.29, P < 0.0001, respectively), positively with fT4 (r = 0.283, P < 0.001 and r = 0.253, P < 0.001) and fT3 (r = 0.273, P < 0.001 and r = 0.204, P < 0.01). 11.0% of cases had gestational thyrotoxicosis (GT) defined as elevated free T4 (> 19.1 pmol/l), suppressed TSH (< 0.36 mIU/l) and TRAb levels within the reference interval (0-0.9 U/l). The prevalence of GT was significantly higher in patients tested at 8-11 weeks compared to those evaluated at 12-14 weeks (14.4% vs. 4.7%, P < 0.05). Total beta-hCG (P = 0.0002), free beta-hCG (P < 0.0001) and free T4 (P = 0.02) levels were higher and TSH levels (P = 0.01) lower in patients tested at 8-11 weeks. Significant positive correlations between both total and free beta-hCG with free T4 were seen at 8-11 weeks but not in patients tested at 12 weeks or later. TT3 levels were similar in the two groups. CONCLUSIONS: Using sensitive assays, the prevalence of gestational thyrotoxicosis in Asian women was found to be 11.0% and was significantly higher in subjects at 8-11 weeks of gestation than at 12-14 weeks. The positive correlation between hCG and free T4 seen in patients tested at 8-11 weeks was absent in patients tested at later stages of the first trimester. Future studies investigating the entity of gestational thyrotoxicosis, at least in Asian patients, should focus on patients at earlier stages of gestation than currently practised.

Chorionic Gonadotropin, beta Subunit, Human↗
PubMed2001

Phosphatemic control during acute renal failure: intermittent hemodialysis versus continuous hemodiafiltration.

BACKGROUND: Achieving "adequacy of dialysis" includes the maintenance of normal serum phosphate concentrations and is an important therapeutic goal in the treatment of acute renal failure (ARF). It is unknown whether this goal is best achieved with intermittent or continuous renal replacement therapy. METHODS: We compared the effects of continuous veno-venous hemodiafiltration (CVVHDF) and intermittent hemodialysis (IHD) on serum phosphate concentrations using daily morning blood tests in 88 consecutive intensive care patients half of which were treated with IHD and half with CRRT RESULTS: Mean patient age was 54+/-14 years for IHD and 60+/-14 years for CVVHDF (NS). However, patients who received CVVHDF were more critically ill (mean APACHE II scores: 24.4+/-5.1 for IHD vs. 29.2+/-5.7 for CVVHDF, p<0.003). Before treatment, the serum phosphate concentration was 2.04+/-0.16 mmoll L for IHD and 1.96+/-0.17 mmoll L for CVVHDF (NS), with abnormal values in 79.4% of IHD patients and in 64.8% of CVVHDF patients (NS). During treatment, CVVHDF induced a greater reduction in serum phosphate (p=0.02) during the first 48 hours and conferred superior subsequent control of hyperphosphatemia (achieved in 64.6% of observations during CVVHDF vs. 41.8% during IHD; p<0.0001). The serum phosphate concentration was also more likely to be within the normal range during CVVHDF (55.3% vs.36.2%; p<0.0001). There was a trend toward more frequent hypophosphatemia (9.3% vs. 5.6%; P<0.1) during CVVHDF CONCLUSIONS: Abnormal serum phosphate concentrations are frequent in ARF patients before and during renal replacement, however, normalization of phosphatemia is achieved more frequently with CVVHDF.

APACHE↗
PubMed2000

Airway foreign bodies (FB): a 10-year review.

A retrospective chart review of children who had airway foreign body removed via direct laryngoscopy and bronchoscopy (DLB) from 1987-1997 was conducted in Children's Hospital, Boston. Patient characteristics noted included age, sex, and clinical presentation. Pre-operative radiographic findings, reason for delay in evaluation, DLB findings, length of procedure, reason for repeat DLB, and types of foreign body etc. were recorded. Serious complications from aspirated foreign bodies such as severe airway obstruction and death tend to occur in infants and younger children because of their small airway size. A history compatible with foreign body aspiration dictates diagnostic endoscopy with or without radiologic confirmation. Chest and airway radiographs supplemented by fluoroscopy can increase the ratio of correct and early diagnosis. Fluoroscopy should be universally accepted as an initial diagnostic technique in airway foreign body evaluation. Fluoroscopy is not a worthwhile investigation if a preceeding chest radiograph suggests the presence of a foreign body. Long-standing airway foreign bodies are associated with considerable morbidity, and early diagnosis remains the key to successful and uncomplicated management of foreign body aspiration. Education aimed at increasing diagnostic acumen of the physicians and heightening of public awareness are the most important steps needed to reduce the morbidity and mortality. Parents should be instructed to abstain from feeding nuts and seeds to young children and to keep small, potentially ingestible objects out of their reach.

Age Distribution↗
PubMed2000

Nasopharyngeal carcinoma in children.

Nasopharyngeal carcinoma (NPC) is rare in children. We report two cases from KK Women and Children's Hospital in Singapore, who presented with advanced locoregional disease. The various aspects of NPC in children are discussed. It is more common in males and black adolescents. The etiology is probably different from that in adult. Undifferentiated NPC or lymphoepithelioma is the commonest variety. Confusing symptoms like cervical lymphadenopathy and unilateral otitis media with effusion (OME) are among the commonest presentations. When children present with both conditions simultaneously, it is imperative to manage them like adult patients and perform nasendoscopy to rule out NPC. The disease stage at presentation is often more advanced compared with adults. These tumors are, however, associated with a higher cure rate as they are most radiosensitive. Radiotherapy with neo-adjuvant chemotherapy is currently the treatment of choice. Both cases achieved satisfactory control of the disease and are presently under close follow-up.

Anti-Bacterial Agents↗
PubMed2000

Continuous veno-venous hemofiltration without anticoagulation in high-risk patients.

OBJECTIVE: To study the safety and operative efficacy of continuous veno-venous hemofiltration (CVVH) without anticoagulation in patients at high risk of bleeding. DESIGN: Prospective cohort study and comparison to control group. SETTING: Tertiary, multidisciplinary intensive care unit. PATIENTS: Forty hemofiltration circuits in 12 patients with severe acute renal failure (ARF) deemed at high risk of bleeding. Forty control circuits in 14 patients treated with low-dose pre-filter heparin infusion. INTERVENTIONS: CVVH at 21/h of pump-controlled ultrafiltration without anticoagulation or saline flush in patients at high risk of bleeding. Collection of data at the bedside. MEASUREMENTS AND MAIN RESULTS: Mean circuit life was 32 h (95% CI: 20-44.4) in patients receiving CVVH without anticoagulation. Forty-three per cent of filters lasted longer than 30 h. Circuit lifespan did not correlate with international normalized ratio (INR), activated partial thromboplastin time (APTT) or platelet count. There were no bleeding complications and azotemic control was not compromised by lack of circuit anticoagulation with a mean serum urea of 16.0 mmol/l (95% CI: 14.9-18.1) during treatment. A control group of consecutive similarly ill patients not at high risk of bleeding received low-dose pre-filter heparin (mean dose 716 IU; 95% CI: 647-785). Their mean filter life was 19.5 h (95% CI: 14.2-23.8), significantly shorter than in the study patients (p = 0.017). CONCLUSIONS: Critically ill patients at high risk of bleeding who require continuous renal replacement therapy (CRRT) can be safely managed without circuit anticoagulation. This strategy minimizes bleeding risks and is associated with an acceptable filter life. CRRT without anticoagulation should be strongly considered in high-risk patients.

Acute Kidney Injury↗
PubMed2000

A prospective study of thromboelastography (TEG) and filter life during continuous veno-venous hemofiltration.

Anticoagulants are commonly used to prolong circuit life during continuous hemofiltration. However, a clear correlation between routinely performed blood coagulability tests and circuit life has not been demonstrated. This lack of correlation may derive from the limited ability of such tests to describe the likelihood of in vivo clotting. We hypothesized that thromboelastography (TEG), which derives its variables from a closer reproduction of in vivo coagulation, would significantly correlate with filter life. Accordingly, we conducted a prospective pilot study of the correlation between filter life and TEG-derived variables in 21 hemofilters used in 6 critically ill patients admitted to a tertiary intensive care unit. It involved the performance of TEG during steady state anticoagulation, measurement of circuit life, and of routine coagulation variables. The results showed that the mean circuit life was 20.7+/-4.0 h despite an average aPTT of 67.7+/-12.8 s and a mean heparin dose of 472.5+/-96.2 IU/h. The mean INR was 1.4+/-1 and the mean platelet count was 118+/-16 x 10(3)/mm3. Although several TEG variables correlated with heparin dose (p < 0.03), no correlation was found between any of the routine coagulation variables or any of the TEG variables and circuit life. In conclusion, no significant correlation between TEG derived variables or routinely measured coagulation variables and circuit life could be demonstrated. These findings suggest that such tests are not useful indicators of circuit anticoagulation adequacy and that factors other than blood coagulability may play a role in circuit failure.

Anticoagulants↗
PubMed2000

Restoring the vertical dimension of mandibular incisors with bonded ceramic restorations.

Mandibular incisors are difficult to restore with conventional anterior crowns due to their small axial diameters. Crown preparation risks pulp exposure and results in a thin core of dentine. An experiment was designed to determine if increasing the thickness of ceramic to restore incisal edges affects the load at the point of restoration failure. Forty-eight mandibular incisors were randomly divided into four groups. The incisal edges of the teeth in three groups were reduced so that the coronal height was 7.5 mm (Group A), 6.5 mm (Group B), and 5.5 mm (Group C). Group D was designated as the experimental control. A fifth group (Group E), independent of the random sample, was introduced to the study for discussion purposes and was characterized by each of the incisors having an intact incisal edge of enamel. Groups A, B and C were prepared in a standard fashion for ceramic veneer restorations that were constructed to restore the vertical height of each tooth to 8.5 mm. Prior to cementation, the preparation surfaces were analysed and the relative surface areas of enamel and dentine were calculated. The ceramic restorations were cemented using a resin luting agent. The teeth were then thermocycled prior to loading at 135 degrees C until failure. The mean fracture load was 305 N (SD 134 N) for Group A, 403 N (SD 101 N) for Group B, 515 N (SD 296 N) for Group C, 587 N (SD 187 N) for Group D and 395 N (SD 129 N) for Group E. As determined by analysis of variance followed by a Sheffè multiple comparison test there was a significant difference (p < or = 0.01) between Group A and Group D. There were no significant correlations of load at failure with the percentage of exposed dentine, enamel surface area, total preparation surface area, and the incisal surface area. The patterns of failure of the fractured specimens were also analysed. There were significantly (p < or = 0.05) greater fractures of the ceramic restorations when they were bonded with the minimum incisal thickness of ceramic.

Analysis of Variance↗
PubMed2000

Otogenic lateral sinus thrombosis--a case report.

INTRODUCTION: We portray and discuss a case of lateral sinus thrombosis following acute otitis media and mastoiditis. CLINICAL PICTURE: The patient presented with otorrhoea, otalgia, neck pain, fever and chills. TREATMENT: Cortical mastoidectomy was performed. Intravenous antibiotics and heparin were administered. OUTCOME: The patient had a complete recovery with no sequelae. CONCLUSIONS: Neurotologic complications of suppurative otitis media like meningitis, cerebral abscess, extradural abscess and dural sinus thrombosis are rare in the antibiotic era. Hence, doctors today have to maintain extra vigilance and a high index of suspicion for such complications.

Adolescent↗
PubMed2000

Inhaled foreign bodies in children--anaesthetic considerations.

Many anaesthetic problems and hazards exist in children with inhaled foreign bodies. Careful, stepwise and detailed consideration of clinical history, examination and investigations cannot be over-emphasised. Special consideration has to be given to the fragile paediatric cardiopulmonary status especially in the presence of airway foreign body. The small paediatric airway is frequently shared for anaesthesia and endoscopy. Complete cooperation and good communication between the endoscopist and the anaesthetist is paramount in achieving an optimal outcome.

Anesthesia↗
PubMed1999

Unfused hypoplastic tongue in a newborn.

Malformations of the tongue are rare. There are < 50 cases of tongue hypoplasia reported in the literature since the first case described by de Jussieu in 1718. These are usually associated with the hypoglossia-hypodactaly syndrome. We describe a newborn with a hypoplastic anterior tongue unfused to the posterior tongue and airway obstruction. Its embryology, theories of pathogenesis, treatment and clinical course are discussed.

Diagnosis, Differential↗
PubMed1999

Necrotizing fasciitis of the pharynx following adenotonsillectomy.

Necrotizing fasciitis is a rare clinical entity in the head and neck region. We report a case of necrotizing fasciitis following adenotonsillectomy in a previously healthy 2-year-old girl. The child presented in a septic state with impending airway compromise. Computed tomography (CT) showed massive soft tissue widening with air in the retropharyngeal, parapharyngeal and retromandibular spaces. Intraoperative exploration showed necrosis of the posterior pharyngeal wall from the skull base to the cricoid, with extension into the parapharyngeal and retropharyngeal spaces. Cultures from the debrided tissues grew two aerobes and three anaerobes. Management involved airway support, surgical debridement, broad spectrum antibiotic coverage and nutritional support. The patient ultimately developed nasopharyngeal and oropharyngeal stenosis requiring tracheostomy and gastrostomy tube placement. This case report highlights an extremely rare complication of adenotonsillectomy.

Adenoidectomy↗
PubMed1999

Outcome of tunnelled central venous haemodialysis catheters inserted by radiologists.

Radiologists have only recently been involved in the percutaneous placement of tunnelled central venous haemodialysis catheters. We report our initial experience with our first 60 catheters. All catheters were successfully inserted. Immediate complications encountered included puncture site haemorrhage in 3 patients (5%) and puncture of the left brachiocephalic vein in 1 patient (1.7%). These were managed conservatively without any clinical sequelae. About 80% of the catheters were uncomplicated and removed electively. Slightly more than 80% of the catheters were in place for more than 30 days. Infection and blocked catheters were the most common short-term complications. Ten catheters (17%) were infected resulting in premature removal of 9. There was 1 death from presumed line sepsis. Mean duration before the onset of infection was 53 days; the rate of infection was 0.28 episodes per 100 catheter days. Five catheters (8%) were blocked or had poor flow. The mean duration before the onset of blockage was 39 days and the rate of blockage was 0.14 episodes per 100 catheter days. A higher proportion of catheters inserted from the left encountered complications. In conclusion, percutaneous insertion of tunnelled haemodialysis catheters by radiologists is safe and effective. The right internal jugular vein should be the preferred access site. Precautions should be taken to avoid infectious complications given the high rate of catheter removal amongst infected catheters.

Catheters, Indwelling↗
PubMed1997

Cervical ectopic pregnancy--a case report.

Mdm LLG, a 28-year-old Chinese, a gravida 2 para I, presented at 9 weeks of pregnancy with painless vaginal bleeding. Ultrasound examination showed features of a cervical pregnancy. Hysterectomy was employed for treatment. Various recent conservative and surgical treatment modalities employed for this condition are discussed.

Adult↗
PubMed1996

Fragmented, distorted cricoid cartilage: an acquired abnormality.

This paper reports the identification of the fragmented, distorted cricoid cartilage. The laryngeal findings in four patients with this acquired abnormality are presented. The postmortem whole organ serial section of their larynges is described and illustrated with horizontal sections from the Laryngeal Development Laboratory in Chicago. The histopathologic sequence, pathogenesis, and clinical relevance are elucidated.

Child↗
PubMed1996

Removable partial denture design in Alberta dental practices.

Studies published in the dental literature have found, all too frequently, that dentists do not pay adequate attention to the design of cast removable partial denture frameworks. This study investigated removable partial denture design in Alberta dental practices. The authors considered various issues related to surveying, partial denture design, and provider education, as well as the possible collaboration of clinical dentistry with denturism in removable partial denture treatment. Although the study found that a significant proportion of Alberta's dentists get involved in designing the cast framework, relatively few undertake surveying. Instead, surveying tends to be deferred to dental technicians. As was the case in other studies, no clear reason for this trend emerged, and it appeared to be unrelated to remuneration or time utilization issues. Responding dentists perceived that their undergraduate education was adequate for providing removable partial denture care. The study also identified a need for small, hands-on continuing education courses. About half of the respondents indicated that it is appropriate for dentists to collaborate with denturists on complete denture care. However, very few respondents considered it appropriate to refer to, or collaborate with, denturists in removable partial denture care.

Alberta↗