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Biomedical subjects

Y H Tam

Publications and source records attributed to Y H Tam.

At least 19 recordsLinked to original sources
PubMed2006

Seven-day is more effective than 4-day ranitidine bismuth citrate-based triple therapy in eradication of Helicobacter pylori in children: a prospective randomized study.

BACKGROUND: Helicobacter pylori infection is common in paediatric population. To date, there is still no universally accepted recommendation on the treatment of this infection in children. Ranitidine bismuth citrate-based triple therapy has been shown to be effective in H. pylori eradication in adults but its use has rarely been validated in children. AIM: To investigate the efficacy of ranitidine bismuth citrate-based triple therapy in eradication of H. pylori in children and to determine the shortest duration of treatment required. PATIENTS AND METHODS: We conducted a prospective randomized study comparing ranitidine bismuth citrate plus amoxicillin plus clarithromycin given for 4 days vs. 7 days in H. pylori-infected children diagnosed by (13)C-urea breath test. Eradication was evaluated by repeat (13)C-urea breath test at 6 weeks after treatment. RESULTS: A total of 206 children were recruited (median age 12 years, 97 boys and 109 girls). Ninety-eight (47.6%) and 108 (52.4%) children were randomized to receive 7-day and 4-day regimen respectively. The eradication rate of 4-day treatment arm was 77.8% (both intention-to-treat and per protocol) compared with 88.8% (intention-to-treat, P = 0.036) and 89.7% (per protocol, P = 0.022) of 7-day regimen. There was no statistical difference in terms of side effects between the two groups. CONCLUSIONS: Seven-day ranitidine bismuth citrate-based triple therapy is an effective and well-tolerated treatment for eradication of H. pylori in children.

Adolescent↗
PubMed2003

Short-term postural reflexes in diabetic patients with autonomic dysfunction.

AIMS/HYPOTHESIS: Assessment of autonomic dysfunction provides prognostic data in diabetic patients. Clinical tests are limited to heart rate variability and blood pressure measurements. We investigated whether a detailed analysis of postural reflexes of patients during short-term head-up tilting and standing erect (both for 3 min) would provide useful clinical data. METHODS: We studied 14 control subjects and 56 patients with Type 2 diabetes, stratified into four matched groups: uncomplicated, micro-albuminuria, macro-albuminuria and autonomic neuropathy, who were tilted 55 degrees three times and were standing erect. Non-invasive finger plethysmography blood pressure measurements, using the Portapres, and impedance cardiac output measurements, using the RheoCardioMonitor, were continuously recorded throughout the study. Wavelets of the response to tilting and standing were drawn. The wavelets for the three tilts were combined to improve definition. The degree of autonomic dysfunction was quantified by calculating the baroreflex sensitivity index from the heart-rate and blood-pressure variability data. RESULTS: Baroreflex sensitivity data confirmed that autonomic dysfunction increased as diabetic complications worsened (p<0.001). Both standing and tilting resulted in an initial decrease in blood pressure followed by recovery, an increase in heart rate which was more pronounced with standing and a decrease in stroke volume. Characteristic and incremental changes in these responses were noted as the complications of diabetes worsened (p<0.001). These were a greater decrease in blood pressure with loss of the recovery phase, a reduced heart-rate response and paradoxically an increase in stroke volume. CONCLUSION/INTERPRETATION: Non-invasive blood-pressure and stroke-volume measurements recorded during short-term tilting and standing promises to be useful in assessing diabetic autonomic dysfunction.

Adult↗
PubMed2001

Retroperitoneoscopic dismembered pyeloplasty for pelvi-ureteric junction obstruction in infants and children.

OBJECTIVE: To report our initial experience of endoscopic dismembered pyeloplasty through a retroperitoneal approach in infants and children with pelvi-ureteric junction (PUJ) obstruction. PATIENTS AND METHODS: Thirteen infants and children with PUJ obstruction underwent retroperitoneoscopic dismembered pyeloplasty (mean age at operation 2.7 years, range 0.25-10). Nine patients presented with complications secondary to PUJ obstruction, including urinary tract infection, pyonephrosis and increasing hydronephrosis with impairment in renal function. The other four patients had recurrent loin pain secondary to intermittent PUJ obstruction. The patient was placed in semi-prone (for left-sided) or a semilateral position (for right-sided PUJ obstruction). The retroperitoneal space was entered via a 1-cm incision over the mid-axillary line and further developed using a glove balloon. Video-retroperitoneoscopy was undertaken using a 5-mm laparoscope. Dismembered pyeloplasty was carried out with the pelvi-ureteric anastomosis fashioned using fine polydioxanone sutures over a double-pigtail ureteric stent. RESULTS: The retroperitoneoscopic dismembered pyeloplasty was successful in 12 patients, while one with previous percutaneous nephrostomy drainage for pyonephrosis required open conversion because of difficulties in developing the retroperitoneal space. The mean (range) operative duration was 143 (103-235) min. All patients had a rapid and uneventful recovery. The drainage was satisfactory in all 12 patients on a follow-up scan. CONCLUSIONS: Retroperitoneoscopic dismembered pyeloplasty is effective and safe in infants and young children giving a good early outcome, although the long-term results await further studies.

Anastomosis, Surgical↗
PubMed2001

Laparoscopic excision of prostatic utricles in children.

OBJECTIVE: To report our experience of laparoscopic excision of symptomatic prostatic utricles in children. PATIENTS AND METHODS: Prostatic utricles were excised laparoscopically in four boys (mean age 6.3 years, range 1.5-17). Cysto-urethroscopy and cannulation of the prostatic utricle was initially undertaken with a cystoscope that was left in situ inside the prostatic utricle to facilitate subsequent identification and mobilization during the laparoscopic procedure. Laparoscopy was conducted via a 5-mm port inserted through a supra-umbilical incision. Two more 5 mm working ports were inserted at the right and left mid-abdomen. The prostatic utricle was easily identified with the guidance of cystoscopic transillumination. Dissection was further facilitated by lifting and counter-traction of the prostatic utricle using the indwelling cystoscope. The prostatic utricle was completely mobilized and divided at its confluence with the urethra using an ultrasonic scalpel. RESULTS: Laparoscopic excision of the prostatic utricle was successful in all four patients. The urethral defect was closed by intracorporeal suturing in three patients while the defect was small enough to be adequately closed by ultrasonic coagulation in one. One patient also had a nonfunctioning dysplastic kidney associated with an ectopic ureter joining into the prostatic utricle, and underwent nephroureterectomy at the same setting. The mean (range) operative duration was 148 (105-225) min. All four patients recovered uneventfully with no complications. CONCLUSIONS: Laparoscopic excision under cystoscopic guidance is effective for symptomatic prostatic utricles, offering a good surgical view and allowing easy dissection in a deep and narrow pelvic cavity.

Adolescent↗
PubMed2000

The use of laparoscopy in the management of adnexal pathologies in children.

BACKGROUND: The authors' experience of using laparoscopy in the management of 23 girls (mean age: 8.9 years; range: 3 months-15 years) with various adnexal pathologies over a 3-year period is reviewed. METHODS: Of the 23 patients, seven were evaluated for congenital gonadal pathologies, 15 presented with abdominal pain and one patient had an antenatally diagnosed adnexal mass. Detailed laparoscopic examination of the pelvic cavity and laparoscopic gonadectomy were successfully performed in all seven patients with congenital gonadal pathologies: mosaic Turner's syndrome (n = 2), gonadal dysgenesis (n = 3) and testicular feminization syndrome (n = 2). Of 15 patients presenting with abdominal pain, 11 had an adnexal mass, two had acute appendicitis and two had pelvic inflammatory disease. RESULTS: Laparoscopic excision of the adnexal masses were successfully performed in 10 of 11 patients. Conversion to open surgery was required in one patient with a huge teratoma. Laparoscopic appendicectomy was successfully performed in both patients with acute appendicitis while diagnostic laparoscopy was the only procedure required in the two patients with pelvic inflammatory disease. Laparoscopy in the infant with an antenatally diagnosed adnexal mass confirmed this to be an omental cyst, which was successfully excised. All patients recovered without complications and good cosmetic result was universally achieved. CONCLUSION: Laparoscopy is safe and effective in both diagnosis and treatment of adnexal pathologies in children.

Adnexa Uteri↗
PubMed2000

Laparascopy for definitive diagnosis and treatment of gastrointestinal bleeding of obscure origin in children.

BACKGROUND/PURPOSE: Gastrointestinal bleeding (GIB) in children with no identifiable source found after upper endoscopy and colonoscopy or GIB of obscure origin can pose a great management problem for pediatric surgeons. The recent advent of laparoscopy in children has provided a useful solution. METHODS: The authors reviewed their experience of using laparoscopy in the management of 17 children (13 boys) with GIB of obscure origin over an 8-year period. The mean age was 9.8 years (range, 3 to 17 years). RESULTS: In all patients, upper endoscopy and colonoscopy results did not show a bleeding source. Pertechnetate technetium Tc 99m scan showed positive uptake in 6 patients. Of these, 4 were found on laparoscopy to have a Meckel's diverticulum, 1 had intestinal duplication, and the remaining patient had nodular lymphoid hyperplasia at the terminal ileum. Ten patients had a negative pertechnetate scan. Of these, 3 had a Meckel's diverticulum, 1 had lymphoid hyperplasia, 1 had intestinal duplication, 1 had vascular enteritis, and 4 had normal findings on videolaparoscopy. Pertechnetate scan was not performed in 1 patient and, on laparoscopy, it turned out to be Meckel's diverticulum. Laparoscopic-assisted small bowel resection was performed successfully in all patients with Meckel's diverticulum, intestinal duplication, and nodular hyperplasia. Conversion to open surgery was required in the patient with extensive ileal vascular enteritis secondary to Henoech Scholein purpura. All patients, including the 4 with normal findings on laparoscopy, had made uneventful recovery without further episode of bleeding. CONCLUSION: Laparoscopy is a useful diagnostic as well as therapeutic tool in children with GIB of obscure origin.

Adolescent↗
PubMed1999

A new management algorithm for impalpable undescended testis with gadolinium enhanced magnetic resonance angiography.

PURPOSE: We evaluated the diagnostic accuracy of preoperative localization of impalpable undescended testis using ultrasound and gadolinium (Gd) enhanced magnetic resonance angiography (MRA). MATERIALS AND METHODS: Ultrasound and Gd-MRA were performed prospectively in 21 boys (23 impalpable testes) with cryptorchidism before laparoscopy and surgical exploration. Gd-MRA was done using a 1.5 Tesla magnetic resonance scanner with a turbo field echo technique after bolus intravenous injection of 0.4 mmol./kg. body weight of Gd diethylenetriaminepentaacetic acid. A total of 10 dynamic scans were acquired during 15 minutes after Gd injection to cover the early arterial and delayed venous phases. All patients subsequently underwent diagnostic laparoscopy and definitive surgery. RESULTS: Ultrasound correctly localized 9 of 10 intracanalicular testes but failed to reveal any intra-abdominal or vanishing testes. In contrast, Gd-MRA correctly localized 4 intra-abdominal, all 10 intracanalicular and 8 canalicular vanishing testes. In 1 patient with an intra-abdominal vanishing testis ultrasound and Gd-MRA failed to make the diagnosis. When correlated with the findings of subsequent laparoscopy and surgical exploration, Gd-MRA had a diagnostic sensitivity of 96% and a specificity of 100% for localizing impalpable undescended testes. Based on Gd-MRA and ultrasound findings laparoscopy could have been avoided in 18 of 23 cases (78%). No adverse effect was associated with Gd use in this study. CONCLUSIONS: Gd-MRA accurately diagnoses vanishing testes and reliably differentiates intraabdominal from intracanalicular impalpable testes, allowing definite preoperative planning of the surgical approach and avoiding unnecessary laparoscopy. A new management algorithm for impalpable testis in patients with cryptorchidism is proposed based on ultrasound and Gd-MRA findings.

Algorithms↗
PubMed1999

Laparoscopy as the investigation and treatment of choice for urinary incontinence caused by small 'invisible' dysplastic kidneys with infrasphincteric ureteric ectopia.

OBJECTIVE: To report our experience of using laparoscopy for the accurate location and simultaneous removal of small dysplastic kidneys with ectopic ureteric insertion causing urinary incontinence and that were not detected by conventional imaging modalities. PATIENTS AND METHODS: Seven girls (mean age 7.9 years, range 3.5-13) presented with urinary leakage occurring between normal voids. Imaging studies including ultrasonography, renal scintigraphy, intravenous urography, computed tomography and/or magnetic resonance imaging in six of the seven patients revealed a single normal functioning kidney, but failed to detect the contralateral nonfunctioning dysplastic kidney. All patients were examined under anaesthesia, followed by transperitoneal laparoscopy for the simultaneous localization and removal of the dysplastic kidneys under the same setting. RESULTS: Laparoscopy in all seven patients revealed a small dysplastic kidney that could always be easily located by first finding the draining ureter over the iliac vessels and then following it upwards. Four dysplastic kidneys were found in the renal fossa (two left, two right). One kidney was found at the left iliac fossa just above the pelvic brim, one at the left lumbar region, and the other at the right iliac fossa. Laparoscopic nephroureterectomy was successful in all seven girls and the patients were discharged 48 h after surgery. The follow-up (mean 2.7 years, range 3 months-5.4 years) showed excellent cosmetic results and all the patients have remained completely dry. CONCLUSIONS: In patients with a classical picture of urinary incontinence caused by infrasphincteric ureteric ectopia associated with a small nonfunctioning kidney, video-laparoscopy, with its magnifying effect, can reliably confirm the diagnosis, locate the dysplastic kidney and allow its removal in the same setting. We propose that laparoscopy should be considered the investigation and treatment of choice in such patients, and should be undertaken without delay even if the dysplastic kidney or the ectopic ureteric orifice cannot be identified with all other conventional means.

Adolescent↗
PubMed1997

Computer-controlled infusion of propofol for long neurosurgical procedures.

This study evaluated the performance of a computer-controlled infusion (CCI) system for propofol during long neurosurgical procedures. Anesthesia was induced and maintained in 15 patients using a CCI of propofol. The initial target concentration was set at 3 micrograms/ml, and this was then titrated according to the clinical situation. A total of 284 blood samples were taken for propofol assay. The performance of the system during anesthesia, assessed using the median performance error (MDPE), median absolute performance error (MDAPE), wobble, and divergence, were -5.3%, 20.6%, 9.0%, and 0.3%/h, respectively. MDPE and MDAPE during the first 20 min after stopping the infusion were -38.7% and 39.0%, respectively. The CCI system did not show significant changes in predictive ability, with time during anesthesia lasting up to 12 h. Changes in the measured blood concentration were in the same direction as changes in the target concentration.

Adolescent↗
PubMed1996

Prospective evaluation of pharmacokinetic model-controlled infusion of propofol in adult patients.

We have tested prospectively the algorithm of White and Kenny for pharmacokinetic model-controlled infusion of propofol in 40 healthy Oriental adults. Anaesthesia consisted of a target-controlled infusion of propofol, 70% nitrous oxide and an infusion of alfentanil. For the first 20 patients studied, median performance error was -5%, median absolute performance error 19%, divergence -9% and wobble 6%. The model was revised to minimize the prediction error of the variable set and tested prospectively in another 20 patients. There was a deterioration in performance of the revised model. Performance statistics for the original model in all 40 patients were: median performance error 2% (range -34 to 69%), median absolute performance error 21% (6-69%), divergence -17% (-92 to 49%) and wobble 7% (2-34%). The algorithm was found to perform adequately in our Oriental patient population.

Adult↗
PubMed1996

Pharmacokinetics and concentration-effect relationship after propofol infusion.

BACKGROUND: We investigated the pharmacokinetics (PK) and concentration-effect relationship after an infusion of propofol in order to obtain a model which can predict the time to eye opening. METHODS: Anaesthesia was induced and maintained with propofol in 34 patients using a Computer Controlled Infusion Pump. Arterial blood samples were taken during recovery and a new model describing the PK was derived. The model was then used to predict the concentration of propofol at the time of eye opening to command. RESULTS: The central volume of distribution was 0.228 L/kg, and the inter-compartment transfer rate constants (min-1) were: k10 0.166, K12 0.091, k13 0.124, k21 0.045, and k31 0.0098. The predicted concentration at which 50% of the patients responded to command was 0.98 microgram/ml. CONCLUSIONS: PK parameters predicting propofol concentration during anaesthesia differ from those describing recovery. The PK of propofol during recovery following an infusion are similar to those following a bolus dose. Real time estimation of blood propofol concentration serves as a useful additional monitor of recovery from anaesthesia.

Adult↗
PubMed1995

Superimposed inspiratory work of the Siemens Servo 300 ventilator during continuous positive airway pressure.

OBJECTIVE: To compare the superimposed inspired work of breathing (SIW) of the Siemens Servo 300 ventilator with the Siemens Servo 900 C ventilator. DESIGN: Comparisons made at continuous positive airway pressure (CPAP) levels of 0, 4, and 8 cmH2O, and at trigger sensitivities of -1 and -2 cmH2O, and flow triggering. SETTING: General intensive care unit in a University teaching hospital. PATIENTS: 7 patients receiving CPAP. At all levels of CPAP, the SIW was significantly less with the Siemens Servo 300 ventilator as compared to the Siemens Servo 900 C ventilator despite similar trigger sensitivities. No significant difference was found in the SIW of the Servo 300 ventilator when comparing trigger sensitivities of -1 cmH2O, -2 cmH2O, and flow triggering. Different levels of CPAP had no effect on SIW. CONCLUSIONS: The Siemens Servo 300 ventilator entails less superimposed inspiratory work of breathing than the Siemens Servo 900 C ventilator.

Adult↗
PubMed1995

Pressure support ventilation during isoflurane anaesthesia.

We have studied the respiratory effects of 5 and 10 cmH2O pressure support ventilation during anaesthesia with 1.5% end-tidal concentration of isoflurane in nine healthy, spontaneously breathing, adult patients. Some of the patients demonstrated an irregular respiratory pattern with periods of apnoea and we therefore went on to study a further seven patients with a continuous 500 s recording of airflow. Pressure support ventilation augmented mean (SD) tidal volume from 212 (56) ml to 360 (88) ml at 5 cmH2O and to 509 (108) ml at 10 cmH2O (n = 16, p < 0.05). Mean (SD) respiratory rate decreased from 26 (6) min-1 to 22 (6) min-1 at 5 cmH2O and 17 (5) min-1 at 10 cmH2O pressure support (n = 16, p < 0.05). Mean (SD) inspiratory work of breathing decreased from 1.77 (0.70) J. min-1 to 0.31 (0.36) J.min-1 at 5 cmH2O and 0.16 (0.26) J.min-1 at 10 cmH2O pressure support ventilation (n = 9, p < 0.05). Analysis of the respiratory rhythm in the second group of seven patients revealed an oscillating respiratory pattern in four patients at 5 cmH2O and six of the seven patients at 10 cmH2O pressure support ventilation. The metabolic advantage of the decreased work of breathing during pressure support ventilation during anaesthesia is unlikely to balance the disadvantage of an oscillating respiratory rhythm.

Adolescent↗
PubMed1994

A prospective evaluation of pharmacokinetic model controlled infusion of propofol in paediatric patients.

We have tested a published algorithm for pharmacokinetic model controlled infusion of propofol to supplement 67% nitrous oxide for general anaesthesia in Chinese children aged 4-10 yr. Initially we studied 10 children undergoing minor procedures with spontaneous ventilation; mean duration of surgery was 38 min and mean propofol infusion rate 497 micrograms kg-1 min-1. The precision of the model was 24.8% and bias -18.5%. The model was revised using an iterative linear least squares regression procedure and the revised model tested prospectively in another 20 children. The precision of the revised model was 21.5% (range in individuals 8.4-43.1%) and bias -0.1% (range -30 to 42%). Mean propofol infusion rate required to maintain anaesthesia was 474 micrograms kg-1 min-1 (range 125-737 micrograms kg-1 min-1). The mean blood concentration required for satisfactory anaesthesia was 6.6 micrograms ml-1 (range 3-11 micrograms ml-1) and the mean blood concentration at the time of waking, which occurred 40 min after switching off the infusion, 0.86 microgram ml-1 (range 0.40-1.45 micrograms ml-1). Our patient population required different pharmacokinetic variables from those in the previous study. Recovery was slow because of the high infusion rates required to maintain satisfactory anaesthesia and large difference between the blood concentration required for anaesthesia and that at which waking occurred.

Algorithms↗
PubMed1994

Midazolam and flumazenil pharmacokinetics and pharmacodynamics following simultaneous administration to human volunteers.

Resedation after antagonism of midazolam sedation with flumazenil may occur because some individuals have rapid elimination of flumazenil but slow elimination of midazolam. To determine whether there are parallel or divergent rates of elimination of the two drugs between individuals, the pharmacokinetic profiles of midazolam and flumazenil were studied simultaneously in 12 adult male volunteers. Free drug concentration data for the two drugs were incorporated into a receptor occupancy model and psychomotor testing was performed and correlated with receptor occupancy. Variation was found between individuals in the pharmacokinetics of the two drugs. There were significant correlations between Cltot (P < 0.01) but not in t1/2 alpha, t1/2 beta, Vc, or VDss. In individuals, midazolam elimination half-life ranged from less than half that of flumazenil to more than three times that of flumazenil. There was a relatively poor, although statistically significant linear correlation found between calculated receptor occupancy and critical flicker fusion frequency, r = 0.50, P < 0.01, and linear analogue scales of sedation r = 0.56, P < 0.005; and anxiolysis, r = 0.54, P < 0.005. There is divergence in the disposition and elimination of midazolam and flumazenil in some individuals. A benzodiazepine receptor occupancy model is useful for predicting the consequent differences in clinical effect when the drugs are given together.

Adult↗
PubMed1993

Bedside measurement of work of breathing.

This paper describes the technique of measuring work of breathing, presented at the 13th International Symposium on Computers in Clinical Medicine and Anaesthesiology, Rotterdam, June 1992. Measuring work of breathing has clinical uses in the Intensive Care Unit. Oxygen consumption does not truly reflect work of breathing. Mechanical work of breathing can be measured by recording continuous pressure and flow and integrating the resultant power. This method is facilitated at the bedside with the use of a PC computer and a spreadsheet program. It is further simplified by software to measure the area under the inspiratory pressure: volume loop.

Anesthesiology↗