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Biomedical subjects

S T Tan

Publications and source records attributed to S T Tan.

At least 19 recordsLinked to original sources
PubMed2006

The clinical implication of the vocal cords-carina distance in anaesthetized Chinese adults during orotracheal intubation.

BACKGROUND: Previous studies have identified no strong correlation between patients' height and tracheal length in anaesthetized patients. We have attempted to compare vocal cords-carina distance (VCD) in Chinese patients with the dimensions of five commonly used tracheal tubes. In addition, we attempted to find a surface anatomy measurement that would identify patients with 'short tracheas'. METHODS: We measured VCD in 130 anaesthetized Chinese patients with a fibreoptic bronchoscope. Also measurements were obtained of the distal ends of five commonly used tracheal tubes. We undertook various surface anatomy measurements on the patients' chest and neck region to predict those patients with short tracheas. RESULTS: VCD averaged 12.6 (SD 1.4) cm. In seven patients (5%) this distance was particularly short (between 8.8 and 10.4 cm). Many of the commonly used tracheal tubes would be placed close to or beyond the carina when the black intubation guide mark(s) is (are) at the level of the vocal cords. The VCD of <or=11 cm (short trachea) could be predicted by patient height of <or=167.5 cm and a thyrosternal distance of <or=28.5 cm with limited reliability. CONCLUSIONS: A significant number of patients with short VCD in our study group could be at risk of endobronchial intubation with many of the tracheal tubes. Patient height and thyrosternal distance can be useful in predicting short tracheas.

Adolescent↗
PubMed2006

Parotid metastasis--an independent prognostic factor for head and neck cutaneous squamous cell carcinoma.

BACKGROUND: Metastatic parotid cutaneous squamous cell carcinoma (SCC) is the most common parotid gland malignancy in New Zealand and Australia. The current AJCC TNM staging system does not account for the extent of nodal metastasis. A staging system that separates parotid (P stage) from neck disease (N stage) has been proposed recently. AIM: To review the outcome of patients with metastatic head and neck cutaneous SCC treated at our multidisciplinary Head and Neck Service using the proposed staging system. METHOD: Consecutive patients were culled from our Head and Neck/Skull Base Database, 1990-2004. These patients were restaged according to the proposed staging system: P stage: P0 = no disease in the parotid (i.e., neck disease only); P1 = metastatic node < or = 3 cm; P2=metastatic node > 3 cm and < or =6 cm, or multiple nodes; and P3 = metastatic node > 6 cm, or disease involving the facial nerve or skull base. N stage: N0=no disease in the neck (i.e., parotid disease only); N1 = single ipsilateral metastatic node < or = 3 cm; and N2 = multiple metastatic nodes, or any node > 3 cm, or contralateral neck involvement. Loco-regional recurrence and disease-specific survival were calculated using the Kaplan-Meier method and comparison of graphs made with the log-rank test. Multivariate analysis using the Cox regression model was carried out to assess the impact of various parameters. RESULTS: Sixty-seven patients with metastatic head and neck cutaneous SCC were identified. Thirty-seven patients had parotid metastasis (of whom 13 also had neck disease) while 21 had neck metastasis alone. Nine patients had dermal or soft tissue metastasis. These nine patients were excluded from this series, and data analysis was carried out on the remaining 58 (46 men, 12 women, mean age 71 years) patients. Sixty-seven percent of the patients underwent post-operative adjuvant radiotherapy. The five-year disease-specific survival rate was 54%. Among 56 patients followed up to disease recurrence or for a minimum period of 18 months, the loco-regional recurrence rate was 52%. The presence of parotid disease was an independent prognostic factor on survival (p < 0.01), and P3 fared significantly worse than P1 and P2. Those patients who had both parotid and neck disease fared worse than those who had parotid or neck disease alone (p = 0.01). N2 had a significantly poorer outcome compared with N1 (p < 0.01). Immunosuppression (p = 0.01) and a positive surgical margin (p < 0.01) were significant adverse prognostic factors for survival. Adjuvant radiotherapy, extracapsular spread, and perineural and vascular invasion did not influence survival. Our study demonstrates that the extent of parotid disease is an independent prognostic factor for metastatic head and neck cutaneous SCC.

Aged↗
PubMed2006

Malignant peripheral nerve sheath tumour of the cervical vagus nerve in a neurofibromatosis type 1 patient.

One serious complication of neurofibromatosis type 1 (NF1) is the development of malignant peripheral nerve sheath tumours (MPNSTs). These malignancies often develop within pre-existing plexiform neurofibromas and their development is now thought to be associated with both tumour suppressor gene mutations and dysregulated growth factor signalling. Recent work demonstrates that the lifetime risk of malignant transformation is significantly greater than previously thought. Ionising radiation, a long-standing disease, particularly the presence of a large number of plexiform neurofibromas from an early age, are suggested risk factors. We present an NF1 patient who developed an MPNST of the cervical vagus nerve which was successfully treated with surgery. Close monitoring of patients with NF and a high level of suspicion towards rapidly enlarging and painful swellings is merited as these features may signify malignant transformation. Whether a positive history of MPNST in other affected family members predisposes the individual to a higher risk of malignant transformation is unclear.

Adult↗
PubMed2006

Evaluation of the new Viewmax laryngoscope in a simulated difficult airway.

BACKGROUND: In this study, we evaluated the learning curve and performance of the Viewmax laryngoscope during simulated difficult laryngoscopy in an intubation manikin (Laerdal Airway Management Trainer). METHODS: To determine the learning curve, 25 anaesthesiologists without previous experience with the Viewmax laryngoscope performed 10 successive intubations in an intubation manikin with a normal airway. Time to intubation and failed intubation attempts were recorded. Another manikin was modified to enable comparison of the Viewmax laryngoscope with Macintosh and McCoy laryngoscopes. The time to intubation, number of failed intubation attempts, modified Cormack and Lehane (MCL) laryngeal view grading, percentage of glottic opening (POGO score), use of gum elastic bougie and subjective rating of degree of difficulty were recorded. RESULTS: The learning curve for the Viewmax laryngoscope showed a progressive decrease in time to successful intubation and reached a plateau at the sixth attempt. In simulated difficult laryngoscopy, the Viewmax laryngoscope demonstrated significantly better laryngeal view than the Macintosh and McCoy laryngoscopes in terms of MCL grading (Macintosh, P = 0.01; McCoy, P < 0.01) and POGO score (Macintosh, P < 0.01; McCoy, P < 0.01). The time required for intubation in simulated difficult laryngoscopy for the Viewmax laryngoscope was significantly longer than that for the Macintosh (P = 0.02) and McCoy (P < 0.01) laryngoscopes. There was no significant difference in the degree of difficulty, number of failed intubations and use of gum elastic bougie. CONCLUSION: When compared with the Macintosh and McCoy laryngoscopes in a manikin, the Viewmax laryngoscope appears to improve the view of the larynx but requires a longer time for tracheal intubation.

Clinical Competence↗
PubMed2004

Pulsed dye laser therapy for rosacea.

Rosacea is a chronic and progressive inflammatory skin disorder affecting the facial convexities for which no curative measure is currently available. Forty consecutive patients with rosacea were treated with the Cynosure PhotoGenica V pulsed dye laser. The improvement following laser therapy was assessed according to a sliding scale: 1 (worse after treatment), 2 (no improvement), 3 (slight improvement), 4 (moderate improvement), 5 (marked improvement). Following an average of 2.4 (range 1-10) laser treatments, a mean score of 4.4 and 4.3 for overall improvement was achieved as judged by the patients and independently assessed by a family member or a close friend of the patients, respectively. The response of erythema and telangiectasia to laser therapy, evaluated by an independent panel of 10 members, showed a mean score of 3.7. Three patients experienced an exacerbation of rosacea during the treatment period requiring antibiotic therapy. During the follow-up period of 6.0-55.5 (mean, 23.3) months after completion of laser therapy, no patient (including 13 patients in whom papulation and pustulation which were amongst the presenting symptoms) required medical treatment. Six patients developed post-inflammatory hyper-pigmentation necessitating skin bleach but no other complication such as scarring was observed. Three patients reported that the residual erythema had progressed after an initial improvement during follow-up periods of 52.4, 15.8 and 6.0 months. All patients felt that laser therapy was worthwhile. We conclude that pulsed dye laser therapy is a useful treatment for rosacea.

Adolescent↗
PubMed2003

Effects of five commonly used glucocorticoids on haemangioma in vitro.

1. High-dose systemic or intralesional steroids are the first-line pharmacological treatments for haemangioma. However, the mechanism of action of steroids is unknown. Using the in vitro model developed by us, the present study examined some of the effects of five commonly used glucocorticoids on haemangioma biopsies taken from two patients. 2. At 12 micro mol/L, triamcinolone and dexamethasone consistently exhibited capillary growth inhibition, whereas methylprednisolone displayed an inhibitory effect during the first 7 days of culture. At this concentration, inhibition of capillary growth was observed in betamethasone-treated cultures derived from one patient but not in those derived from the other. However, hydrocortisone had a negligible effect on capillary growth. 3. Transcription of various factors considered important for haemangioma development were studied by reverse transcription-polymerase chain reaction. Neither vascular endothelial growth factor nor fibroblast growth factor-2 played a vital role in steroid-induced inhibition of capillary growth. All glucocorticoids induced a marked decrease of interleukin (IL)-6 transcripts. 4. Capillary growth inhibition in cultures treated with all glucocorticoids, except triamcinolone, was associated with an increased transcription of clusterin/apolipoprotein J (clust/apoJ), an apoptotic gene. There was increased transcription of mitochondrial cytochrome (cyt) b in the inhibited cultures resulting from triamcinolone, dexamethasone or methylprednisolone treatment that was associated with capillary growth inhibition, suggesting an important role of mitochondria in glucocorticoid-induced regression of haemangioma. 5. Our results indicate that glucocorticoids may modulate haemangiogenesis via an upregulation of cyt b, clust/apoJ and/or IL-6. The variable effects of different glucocorticoids on one or more of these factors may explain the interindividual variation in the in vivo response of haemangioma to the steroids.

Analysis of Variance↗
PubMed2003

Acute-on-chronic subdural haematoma: a rare complication after spinal anaesthesia.

An 88-year-old woman with an undiagnosed chronic subdural haematoma underwent emergency repair of a femoral hernia under spinal anaesthesia. The patient complained of headache postoperatively, and a subsequent computed tomography brain scan showed an acute-on-chronic subdural haematoma, with midline shift and impending coning. The patient recovered completely after surgical decompression. The difficulty in diagnosing chronic subdural haematoma in the elderly patient with no history of trauma is discussed, along with the differential diagnosis of headache following spinal anaesthetic in this age-group.

Acute Disease↗
PubMed2001

Altered mitochondrial cytochrome b gene expression during the regression of hemangioma.

Hemangioma is a primary tumor of microvasculature. Its development typically exhibits a proliferative phase followed by an involuting phase that continues into the involuted phase. Although apoptosis has been reported, the mechanisms regulating the spontaneous regression of hemangioma are largely unknown. The authors recently demonstrated up-regulation of the mitochondrial cytochrome b gene in hemangioma associated with steroid-induced regression. The present study investigated whether a similar change occurred during spontaneous regression. Biopsy material was obtained from 11 patients with hemangiomas at different phases of development. In one of these patients, a biopsy was taken from the proliferative, involuting, and involuted areas of the hemangioma. In another patient, a biopsy was taken before and 5 weeks after the intralesional administration of steroids. From each tissue specimen, RNA was isolated and subjected to reverse transcriptase-polymerase chain reaction analysis by use of specific primers for the human mitochondrial cytochrome b gene. Semiquantitative reverse transcriptase-polymerase chain reaction analysis revealed that the strongest expression of the mitochondrial cytochrome b transcripts was in specimens taken from hemangiomas in the involuting phase compared with those from the proliferative and involuted phases. The authors concluded that mitochondrial cytochrome b is associated with both the spontaneous and the steroid-induced regression of hemangioma, probably by regulating apoptosis.

Apoptosis↗
PubMed2000

A novel in vitro human model of hemangioma.

Hemangioma, the most common tumor of infancy, is characterized by a proliferation of capillary endothelial cells with multilamination of the basement membrane and accumulation of cellular elements, including mast cells. The initial rapid growth is followed by an inevitable but slow involution. The currently available therapies are empirical and unsatisfactory because what is known of the cellular and molecular basis of hemangioma development is rudimentary. Advances in the understanding of its programmed biologic behavior has been hampered by the lack of a valid human model. We report here a novel in vitro culture system that is a useful human model of hemangioma. A small fragment of hemangioma biopsy is embedded in fibrin gel in a well of culture plates and incubated in a serum-free, buffered-salt, minimal medium. A complex network of microvessels grows out from the tissue fragments. Biopsies taken from all three phases of hemangioma development were cultured successfully; proliferative phase samples developed microvessels in 1 to 4 days, involuting phase in 5 to 7 days, and involuted phase in 7 to 12 days. The relative growth rates of the microvessels in the culture of biopsies taken from different stages of hemangioma development reflect the growth patterns seen clinically. This model has been validated using histochemistry, immunohistochemistry, and reverse transcriptase-polymerase chain reaction. Comparison of the number, localization, and phenotype of endothelial and mast cells and the distribution of basement membrane constituents (type IV collagen, perlecan, and laminins) and growth factors (basic fibroblast growth factor, vascular endothelial growth factor, transforming growth factor-betas) in the biopsy and the tissue after culture shows that many of the characteristics of the original tissues were retained in culture. This in vitro human model of hemangioma overcomes some of the deficiencies associated with earlier models. It offers an opportunity for studying the precise cellular, biochemical, and molecular basis of hemangioma It may also help to elucidate the mechanisms of action of existing therapies and may lead to the identification of novel treatments for hemangioma.

Biomarkers, Tumor↗
PubMed2000

Clusterin/apoJ expression during the development of hemangioma.

Hemangioma is the most common tumor of infancy. This vascular tumor is characterized by an initial rapid proliferation followed by an inevitable regression. The life cycle of hemangioma is divided into proliferative, involuting, and involuted phases. The cellular and molecular mechanisms responsible for controlling the biological behavior of hemangioma are largely unknown. Differential display analysis using mRNA isolated from biopsy specimens representative of the 3 different phases showed increased expression of clusterin/apoJ (clust/apoJ) in the involuting samples. Clust/apoJ is a multifunctional glycoprotein that has been associated with apoptosis. Reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry showed that both the transcription and protein expression of clust/apoJ were increased in hemangioma as the tumor progressed from the proliferative to the involuting and involuted phases. This suggests that clust/apoJ is involved in regulating apoptosis during the spontaneous regression of hemangioma. It has been suggested that mast cells (MC) play a role in the regression of hemangioma. The increase in the number and proportion of clust/ apoJ-positive MC with progression of hemangioma, along with the localization of clust/apoJ to MC granules, supports this hypothesis. We suggest that MC may be synthesizing/releasing this apoptotic modulator, leading to the regression of the tumor. Better understanding of the pathogenesis of hemangioma by identification of the relevant factors involved in its regression such as clust/apoJ will result in the development of novel therapies for this condition and tumors that do not undergo spontaneous regression.

Biopsy↗
PubMed2000

Paralysis of the marginal mandibular branch of the facial nerve: treatment options.

Isolated paralysis of the marginal mandibular branch of the facial nerve results in an asymmetrical smile with elevation of the lower lip on the affected side. We discuss the surgical options for its correction and present a series of 26 patients who underwent either botulinum toxin injection, anterior belly of digastric transfer or free extensor digitorum brevis transfer as treatment. Botulinum toxin injection provided satisfactory results although these were temporary. Anterior belly of digastric transfer was the surgical procedure of choice. It yielded superior cosmetic results, less donor-site morbidity and required a shorter operating time. In more complex congenital facial hypoplastic syndromes, or following extensive surgery in the digastric triangle, the anterior belly of the digastric muscle may be absent or damaged. Extensor digitorum brevis transfer is the preferred option in these cases.

Adolescent↗
PubMed2000

Cellular and extracellular markers of hemangioma.

Several cellular and extracellular markers that distinguish the phases of the hemangioma life cycle have been described previously. However, details of the phenotypic changes of; the various cellular elements during hemangioma development have not been fully reported, and the extracellular matrix composition, especially in the vicinity of the proliferating endothelial cells, is poorly described. This study examined the expression of cellular and extracellular molecules and cytokines in the proliferative, involuting, and involuted phases of hemangioma. Paraffin-embedded hemangioma specimens, four from each phase, were examined histochemically and immunohistochemically. Throughout the three phases, vascular endothelial cells stained positive for CD31 and von Willebrand factor, although in the involuted phase, not all vessels in the tissue expressed these endothelial markers. Proliferating cell nuclear antigen was expressed by the majority of endothelial cells and pericytes in the proliferative and early involuting phases, but its expression was negligible in the involuted phase. In addition to finding that the total number of mast cells was highest in the involuting phase, the authors observed that the proportion of chymase-positive mast cells decreased with the progression of hemangioma and that virtually all mast cells expressed the biogenic amine phenotype throughout the hemangioma life cycle. The localization of vascular endothelial growth factor predominantly to the pericytes and endothelial cells during the proliferative phase and of basic fibroblast growth factor to the endothelial cells in both the proliferative and early involuting phases is consistent with previous reports, although the latter growth factorwas also observed in mast cells. Type IV collagen and the beta chain of laminin and perlecan were detected in the basement membranes in all phases. Interestingly, collagen types I, III, and V were present in basal membranes throughout the phases and with increasing density in the stromal areas with involution, although type I collagen was less prominent during the proliferative phase. Short-chain collagen type VIII was localized extracellularly throughout the development of hemangioma but, during the early proliferative phase, it was also detected within mast cells. The expression of specific cytokines and cellular and extracellular markers may help distinguish the different clinical phases of the hemangioima life cycle. These results provide further insight into the biology of hemangioma.

Antigens, Nuclear↗
PubMed2000

Steroid therapy of a proliferating hemangioma: histochemical and molecular changes.

OBJECTIVES: Hemangioma is a primary tumor of the microvasculature in which angiogenesis is initially excessive, followed by regression of the newly formed vessels. Intervention is necessary in up to 20% of cases, high-dose systemic or intralesional steroids being the first-line treatment. As the mechanism of action of steroids is unknown, we undertook an investigation of the cellular and molecular effects of their action. STUDY DESIGN: A unique opportunity to study the effect of steroid treatment was presented when biopsy material was obtained from an infant with an ulcerated proliferating hemangioma before and after intralesional triamcinolone injection, which resulted in an accelerated regression of the lesion. Histochemical quantitation of mast cells, molecular analysis by reverse transcriptase-polymerase chain reaction (RT-PCR) for 7 growth factor transcripts and differential display RT-PCR (DD RT-PCR) were conducted. RESULTS: After steroid therapy, the mast cell number increased (untreated = 2.22 +/-.27 [standard error of the mean ¿SEM¿]; treated = 8.7 +/-.71 [SEM] mast cells per field, respectively; P <.0001; n = 40 fields for each group), and the transcriptional expression of cytokines: platelet-derived growth factor-A and -B; interleukin-6; transforming growth factor-beta1 and -beta3 decreased, while that of basic fibroblast growth factor (bFGF) and vascular endothelial cell growth factor remained unaltered. Elevated urinary bFGF levels noted in cases of proliferating hemangioma, persisted even after steroid treatment. Using DD RT-PCR an amplicon that shared 100% sequence homology with the human mitochondrial cytochrome b gene was detected in the hemangioma biopsy after steroid treatment. CONCLUSIONS: The regression of this hemangioma subsequent to steroid therapy was accompanied by a significant increase in mast cell density, reduced transcription of several cytokines, and an enhanced expression of the mitochondrial cytochrome b gene.

Anti-Inflammatory Agents↗
PubMed1999

Anomalous extensor muscles of the hand: a review.

Anomalous extensor muscles of the hand are not uncommon. Well-recognized anomalies anomalous extensor indicis proprius, extensor digitorum brevis manus, extensor medii proprius, and extensor indicis et medii communis are reviewed and discussed in detail. Anomalous extensor indicis proprius and extensor digitorum brevis manus may occasionally give rise to dorsal wrist pain and the diagnosis is often confused especially in the presence of other pathologic findings such as a ganglion. An analysis of the embryologic development of the extensor muscle mass with phylogenetic comparisons between species of the animal kingdom is presented to underscore the clinical relevance of these anomalous extensors.

Decompression, Surgical↗
PubMed1999

Pulsed dye laser therapy for viral warts.

Twenty-eight patients with 103 recalcitrant and 20 simple viral warts were treated with the Cynosure PhotoGenica V pulsed dye laser at 585 nm, and fluencies of 6.0-9.0 J/cm(2). An eradication rate of 92% for recalcitrant warts after an average of 2.1 (range 1-7) treatments and 75% for simple warts after an average of 1.6 (range 1-2) treatments was achieved with a mean follow-up period of 7.2 (range 3-15) months. Mild hypopigmentation was noted in one patient and superficial infection in another. Unlike ablative treatment modalities, with pulsed dye laser therapy, no wound was created thus avoiding prolonged postoperative pain, disability and scarring. Treatment was well tolerated by patients, most of whom returned to work or normal activities immediately postoperatively. Pulsed dye laser is an effective treatment for both recalcitrant and simple warts. It is the treatment of choice for these lesions in cosmetically sensitive areas.

Adolescent↗
PubMed1999

Modified Antia-Buch repair for full-thickness upper pole auricular defects.

Various reconstructive techniques have been described for repair of full-thickness upper pole auricular defects. The wedge excision commonly used for treatment of upper pole tumors allows excision and reconstruction in a single stage. However, this technique suffers from major deficiencies. We apply the concept of crescentic scaphal excision and the Antia-Buch advancement-rotation flap principle to repair various full-thickness upper pole auricular defects resulting from excision of skin lesions in eight consecutive patients. The technique achieves a natural auricular shape in three dimensions with minimal disruption of the anatomic landmarks and avoids conspicuous scars. It has several advantages over the original Antia-Buch repair and other techniques used for reconstruction of full-thickness upper pole auricular defects.

Aged↗
PubMed1998

Hormone responses to stress in patients with major burns.

The responses of the plasma stress hormones corticotrophin (ACTH), vasopressin (AVP), cortisol and corticotrophin releasing hormone (CRH) have been studied in seven consecutive patients aged between 15 and 65 years who suffered from burns of 15-95% total body surface area. There was a distinct peak in AVP (up to 100 pmol/l) and ACTH levels well above the upper limit of normal in all except one patient within 24 h of burn injury. Following the initial rise, AVP and ACTH tended to fall. Plasma CRH with one exception remained within the normal range. Concurrent measurement of plasma renin activity (PRA), haemoglobin (Hb), haematocrit (Hct) and plasma sodium (Na), to assess hydration, showed that PRA was increased in all except one patient during the first 4 days of hospital admission. The correlation between ACTH and cortisol was highly significant (P < 0.001), as was the correlation between ACTH and AVP, AVP and Na, PRA and Hb, and Hct and Na. Other significant correlations were ACTH and Hct (P = 0.023), ACTH and Na (P = 0.017), AVP and Hct (P = 0.029), CRH (P = 0.018), CRH and Hb (P = 0.001). No significant correlation could be demonstrated between CRH and ACTH or AVP. Our findings suggest that AVP plays a role in the hypercortisolaemia which accompanies major burns. The possible detrimental effect of very high levels of AVP leading to progression of burn depth and reduction of skin graft take by its potent vasoconstrictive action and water retention effect (resulting in oedema) deserves further study. As AVP has the potential to reduce tissue perfusion, the possible use of antagonists in major burns merits further consideration. Persistently raised PRA levels, despite normal biochemical and haematological parameters, may indicate that volume expansion therapy may not be adequate, and that both hypovolaemia and stress may contribute to the AVP response. Stress hormone monitoring may lead to better treatment and a reduction in burn stress.

Adolescent↗