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Biomedical subjects

K K Tan

Publications and source records attributed to K K Tan.

At least 37 records · Page 2Linked to original sources

Acute epiglottitis in the tropics: is it an adult disease?

Acute epiglottitis has traditionally been described as a paediatric disease in reports from temperate countries. There have been very few reports from tropical countries. This is a retrospective review of 32 cases of acute epiglottitis from Singapore over an eight-year period from 1992 to 1999. There were 31 adults and only one child. In Singapore, Haemophilus influenzae Type b (Hib) immunization in not routine, and thus the increased prevalence in adults cannot be attributed to Hib immunization. Eleven patients required airway intervention, of whom nine had endotracheal intubation and two had a surgical airway. Significant predictors for airway intervention included the sex of the patient, stridor, presence of airway compromise on examination and a "thumb sign" on the lateral neck radiograph. In adults, selective airway intervention is recommended as those without airway compromise at presentation recover very well with medical treatment alone.

Acute Disease↗

Physics-based approach to color image enhancement in poor visibility conditions.

Degradation of images by the atmosphere is a familiar problem. For example, when terrain is imaged from a forward-looking airborne camera, the atmosphere degradation causes a loss in both contrast and color information. Enhancement of such images is a difficult task because of the complexity in restoring both the luminance and the chrominance while maintaining good color fidelity. One particular problem is the fact that the level of contrast loss depends strongly on wavelength. A novel method is presented for the enhancement of color images. This method is based on the underlying physics of the degradation process, and the parameters required for enhancement are estimated from the image itself.

Journal Article↗

Sphenochoanal polyps in Singapore: diagnosis and current management.

Sphenochoanal polyp is a rare form of choanal polyp. If unrecognised, they can be mistaken for an antrochoanal polyp. This will result in unnecessary exploration of the maxillary sinus, and a failure to remove the sphenoidal component of the sphenochoanal polyp. Adequate preoperative evaluation with computed tomography or magnetic resonance is mandatory to ascertain the correct diagnosis, and to facilitate the planning of the appropriate surgical procedure. We present two patients with sphenochoanal polyp and a review of the literature.

Adult↗

Pneumonia presenting as acute abdomen in children: a report of three cases.

From 10th September 1998 till 5th June 1999, the Paediatric and Cardiothoracic Surgery Units of Sultanah Aminah Hospital Johor Bahru managed three children with lung collapse secondary to pneumonia. The dominant initial clinical presentation in all three cases was acute abdominal pain. Basal pneumonia was diagnosed in two cases post-operatively after surgical contributory causes were excluded intra-operatively. Thoracotomy, evacuation of infected debris and decortication of the collapsed lung was done in all three cases. In children presenting with acute abdominal pain, basal pneumonia should be considered as a possible contributory cause.

Abdomen, Acute↗

Spontaneous subarachnoid haemorrhage and outcome--results from Tan Tock Seng Hospital, Singapore.

AIM OF STUDY: To ascertain the number of cases of spontaneous (aneurysmal) subarachnoid haemorrhage presenting to Tan Tock Seng Hospital, Singapore, over a one year period, the demographics of the patients involved, their treatment and their eventual outcome. METHOD: A retrospective study from June 1995 to June 1996. RESULTS: There were 62 patients admitted over this period with an average of 5 patients per month. Their ages ranged from 9 to 85 years with a mean of 54 years. All 62 patients underwent 4-vessel cerebral angiograms. Forty-three patients (69%) underwent clipping of their aneurysms. Twelve patients (19%) had negative angiograms. Four patients (6%) underwent coiling of their aneurysms via interventional neuroradiology techniques. Patients with subarachnoid haemorrhage of Grades 1 to 3 on the WFNS (World Federation of Neurological Surgeons) grading had a favourable outcome (Glasgow Outcome Score of 4 and 5) in 85% of the cases. The overall mortality rate for the operated group (all grades) was 11%. However for the group with good WFNS grading, namely the Grade 1 to 2 groups, there were no deaths. Twenty-four percent of patients developed clinically symptomatic vasospasm. Eighteen percent of patients required ventriculo-peritoneal shunting for hydrocephalus secondary to the subarachnoid haemorrhage. The overall management mortality (operated and non-operated cases) was 14% for proven aneurysmal and angiographically-negative spontaneous subarachnoid haemorrhage. These results are comparable to that of other reputable centers reported in the literature.

Adolescent↗

Differential localisation of the metabotropic glutamate receptor mGluR1a and the ionotropic glutamate receptor GluR2/3 in neurons of the human cerebral cortex.

Specimens of human cerebral cortex were obtained during neurosurgical operations and studied by immunocytochemistry and electron microscopy, using antibodies to the metabotropic glutamate receptor subunit mGluR1a and the ionotropic glutamate receptor GluR2/3. A small number of non-pyramidal neuronal cell bodies were labelled for mGluR1a. Double immunolabelling with mGluR1a and GluR2/3 showed that most pyramidal cell bodies were labelled for GluR2/3 but not for mGluR1a. Despite the non-colocalisation of these two receptor subtypes in cell bodies, however, many dendrites and dendritic spines were double-labelled for mGluR1a and GluR2/3 at electron microscopy. As there is evidence that most neurons positive for GluR2/3 are pyramidal cells, this suggests that mGluR1a is present in dendrites of pyramidal neurons, despite absent or low levels of immunoreactivity in their cell bodies.

Adolescent↗

A study on the efficacy of intraventricular urokinase in the treatment of intraventricular haemorrhage.

Twenty-one patients with intraventricular haemorrhage were randomized to two treatment groups. Both groups had bilateral external ventricular drains inserted, but only the treatment group received 50,000 IU urokinase instilled into the ventricles. The clinical and radiological progress, and 1- and 6-month outcomes were compared. The group that received urokinase treatment was shown to have an improved outcome, with a lower mortality and a lower incidence of hydrocephalus requiring shunt insertion. No haemorrhagic complications were seen in either group, although the treatment group had a slightly increased rate of drain-related ventriculitis.

Adult↗

A prospective review of laparoscopic cholecystectomy in Brunei.

Brunei has a small population and a unique medical setup: The number of laparoscopic cholecystectomies (LCs) performed in our institution represents the total number of cases performed in this country. A prospective analysis of all the LCs performed in Brunei is presented. All 220 LCs performed between February 1, 1992, and November 30, 1996, were prospectively recorded on a detailed protocol. Analyses were made with respect to preoperative patient demography, intraoperative complications, and postoperative morbidity and mortality. Symptomatic gallstone disease was found to be common among the ethnic Nepalese population. In this series, nine patients required conversion to open surgery (4%). Acute cholecystitis comprised 21% of cases, and the mean operating time was longer in these cases (144.1 min) than in elective cases (101.2 min; P = 0.002). The overall morbidity was 5% with one ductal injury (0.5%). The mortality rate in this series was 0.5%. Our results of LC are favorable and comparable with those of published series. We conclude that LC has been successfully introduced into our institution. This study also represents an unofficial audit of the state of development of LC in Brunei.

Acute Disease↗

Otitis externa--the clinical pattern in a tertiary institution in Singapore.

Otitis externa is a common condition in the tropics. Most of the data related to the condition have arisen from Western sources. Locally, the aetiology and the pathogens identified have not been systematically studied. A prospective study involving 107 patients was conducted. Otomycosis was frequently encountered. Coagulase negative Staphylococcus and Aspergillus niger were the most common bacteria and fungus cultured respectively. Gentamicin and polymyxin B were the most effective topical agents against Pseudomonas aeruginosa. Self-cleaning of the ears was the most common predisposing factor.

Adolescent↗

Subclavian-oesophageal fistula as a complication of foreign body ingestion: a case report.

Foreign bodies in the upper aerodigestive tract are very common. In the local community, the commonest foreign body encountered in the oesophagus is the fish bone. Impaction in the thoracic oesophagus can lead to perforation and the subsequent formation of an arterial-oesophageal fistula. Such fistulae are inevitably aorto-oesophageal in nature. A subclavian-oesophageal fistula is described in this patient.

Animals↗

Outcome of patients with traumatic brain injury managed on a standardised head injury protocol.

A standardised protocol in the management of severe head injury in our hospital enables pre-determined critical care-paths and consistent treatment regimes to be instituted. In Singapore there has been no previously reported data on the outcome of severely head injured patients. Over a 6-month period, 48 consecutive patients who were enrolled in our severe head injury protocol were prospectively studied. In addition to demographic and outcome data, physiologic measurements obtained from a computerised patient information system (Carevue Hewlett-Packard 9000) were analysed to determine the mean cerebral perfusion pressure (CPP) and intracranial pressure (ICP) achieved throughout the protocol period. Median Glasgow Coma Score for all patients on admission to the protocol was 6 (range 4 to 8). The mean age was 34.46 +/- 15.03 years with a male to female ratio of 43:5. The average duration of treatment on the protocol was 110.73 hours. Initial ICP measured was 25.5 +/- 19.68 mmHg. Outcome was measured at 6 months post-injury using the Glasgow Outcome Score. Favourable outcome (GOS 4-5) was seen in 29 of 48 patients (60.4%) while 12 out of 48 (25%) had an unfavourable outcome. There was a mortality of 14.6% (7 of 48 patients). Patients who survived had a higher mean CPP (P = 0.00005), a lower initial ICP and a mean ICP (P = 0.007 and 0.0009). The use of a protocol with standardised treatment goals in the management of traumatic brain injury allows for the optimal use of limited resources and provides consistency in treatment. Good outcome is related to early aggressive resuscitation to prevent hypotension and hypoxia, prompt evacuation of surgical mass lesions and the maintenance of an adequate cerebral perfusion pressure. Our results are comparable with that reported in other established neurotrauma systems.

Accidents↗

An immunocytochemical study of calpain II in the hippocampus of rats injected with kainate.

The distributions of the kainate/DL-alpha-amino-3-hydroxy-5-methylisoxazolepropionic acid (KA/ AMPA) receptors GluR1 and calcium-activated neutral protease II (calpain II) in the hippocampus of normal and kainate-lesioned rats were studied by immunocytochemistry. There was a reduction in GluR1 immunoreactivity and a slight increase in calpain II immunoreactivity on the dendrites of pyramidal neurons in CA fields affected by the kainate at 18 h postinjection. Calpain II immunore-activity was associated with amyloid fibrils at electron microscopy. These fibrils were most often intracellular, in membrane-bound profiles, some of which were contacted by axon terminals and were identified as degenerating dendrites. There was extensive destruction of mitochondrial membranes in degenerating profiles, and accumulations of amyloid fibrils were often localised in mitochondria in a calpain-positive profile. This was unlike other, calpain-negative degenerating profiles, that contained tubulovesicular profiles or multilamellar bodies, where mitochondrial membranes were preserved. Many more calpain-positive profiles were observed at electron microscopy 6 days after kainate injection. The enzyme was present in macrophages and astrocytes in lesioned areas.

Animals↗

The Singapore swing.

The use of a rotation pedicled flap, entitled the 'Singapore Swing', comprising temporalis fascia and mastoid periosteum, is presented as a new method of promoting healing in 'open' mastoid surgery for chronic ear discharge. Cadaver studies show that the main blood supply of the flap is derived from a branch of the postauricular artery which enters the pedicle near the mastoid tip. A review of the first 14 operations showed complete healing with dry ears and intact tympanic membranes in all instances, three cases requiring secondary grafting of residual perforations. We consider the results sufficiently encouraging to merit an extended trial of the technique.

Cholesteatoma↗

Successful closure of a recto-prostatic fistula.

Recto-prostatic fistula is a rare complication of prostatic surgery, occurring usually because surgical planes are not appreciated. We describe a combined abdomino-perineal approach for the repair of a large recto-prostatic fistula with the interposition of omentum and gracilis without formally closing the fistula in layers.

Aged↗

Pseudomyopia in a patient with blocked ventriculo-peritoneal shunt--a case report.

Accommodative spasm usually encompasses a classical triad of pseudomyopia, esodeviation and pupillary constriction. Accommodative spasm is most often psychogenic in nature; however, it may be associated with other organic diseases of which a rare cause is that of intracranial catheter complications. We report a case of dorsal midbrain syndrome with pseudomyopia in a patient with a blocked ventriculo-peritoneal shunt inserted for aqueductal stenosis. Clinical presentation was unusual in this patient as pseudomyopia occurred with exodeviation and without pupillary constriction.

Adult↗

Pharmacodynamics of cyclosporine in heart and heart-lung transplant recipients. I: Blood cyclosporine concentrations and other risk factors for cardiac allograft rejection.

We have attempted to determine the optimal clinical use of cyclosporine during the first 3 months after heart transplantation. We used multiple logistic regression to quantify how blood cyclosporine concentrations and other potential risk factors influence the risk of histologically confirmed acute rejection in 111 heart transplant recipients. A 50% increase in cyclosporine concentration was associated with a 15% reduction in risk of rejection in the subsequent 5 days (P=0.002). Increasing oral corticosteroid dose also protected against rejection (P=0.01). Rejection was over 2.5 times more likely during the first 20 postoperative days, and patients with 2 HLA-DR mismatches who were transplanted for cardiomyopathy or who had multiple previous rejection episodes were predisposed to further rejection (P<0.01). High short-term variability in cyclosporine concentrations was weakly associated with risk of rejection (P=0.1). Investigation of threshold levels for the cyclosporine concentration-effect relationship suggested that concentrations above 375 microgram L(-1) provide optimal protection against acute cardiac allograft rejection. This result yields an objectively defined therapeutic threshold for targeting early cyclosporine concentrations following heart transplantation, although the upper end of the range will depend on the individual's susceptibility to nephrotoxicity and infection.

Analysis of Variance↗

Pharmacodynamics of cyclosporine in heart and heart-lung transplant recipients. II: Blood cyclosporine concentrations and other risk factors for lung allograft rejection.

We have attempted to quantify the optimal clinical use of cyclosporine during the first 3 months after heart-lung transplantation. We used multiple logistic regression to investigate the influence of blood cyclosporine concentrations and other potential risk factors on histologically confirmed acute lung rejection in 50 heart-lung transplant recipients. A 50% increase in cyclosporine concentration was associated with a 25% reduction in risk of rejection in the subsequent 5 days (P=0.008). Increasing oral corticosteroid dose also protected against rejection (P=0.006). Rejection was over 4 times more likely to occur during the first 20 postoperative days (P=0.002). After 20 days, an FEV1 < or = 70% of the age-, sex-, and height-adjusted expected score was associated with a 4-fold increase in risk of rejection (P=0.01). Patients who had multiple previous rejection episodes were also predisposed to further rejection (P=0.005). An investigation of threshold levels for the cyclosporine concentration-effect relationship suggested that cyclosporine concentrations above 500 microg L(-1) provide optimal protection against acute lung allograft rejection. This result provides an objectively defined therapeutic threshold for targeting early cyclosporine concentrations following heart-lung transplantation.

Adult↗