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Biomedical subjects

J Wong

Publications and source records attributed to J Wong.

At least 361 records · Page 20Linked to original sources
PubMed1997

Adaptive radiation therapy.

Adaptive radiation therapy is a closed-loop radiation treatment process where the treatment plan can be modified using a systematic feedback of measurements. Adaptive radiation therapy intends to improve radiation treatment by systematically monitoring treatment variations and incorporating them to re-optimize the treatment plan early on during the course of treatment. In this process, field margin and treatment dose can be routinely customized to each individual patient to achieve a safe dose escalation.

Confidence Intervals↗
PubMed1997

Comparison of hand-sewn and stapled esophagogastric anastomosis after esophageal resection for cancer: a prospective randomized controlled trial.

OBJECTIVE: The objective of this study was to compare the hand-sewn and stapled methods in esophagogastric anastomosis. SUMMARY BACKGROUND DATA: After esophageal resection for cancer, the relative merits of the hand-sewn and the stapled methods of esophagogastric anastomosis, especially regarding leakage and stricture rates, have not adequately been studied. METHODS: A prospective randomized controlled trial was undertaken in 122 patients with squamous cell cancer of the thoracic esophagus who underwent a Lewis-Tanner esophagectomy. Patients were stratified according to esophageal size, based on the diameter of the divided esophagus (< or > or = 30 mm) and then were randomized to have either a hand-sewn or a stapled anastomosis. RESULTS: The mean total operating times (standard error of the mean) when the hand-sewn and the stapled methods were used were 214 (4) minutes and 217 (3.4) minutes, respectively (p = not significant [NS]). The respective in vivo proximal resection margins (standard error of the mean) were 8 (0.4) cm and 7.6 (0.4) cm (p = NS). Leakage rates were 1.6% and 4.9% (p = NS). Excluding hospital deaths, patients with leakage or anastomotic recurrence, and those who received radiation therapy to histologically infiltrated resection margin, anastomotic stricture was found in 5 (9.1%) of 55 patients in the hand-sewn group and 20 (40%) of 50 in the stapler group (p = 0.0003). The difference in stricture rates was significant in small as well as large esophagi. Anastomotic recurrence developed in only one patient in each group. CONCLUSIONS: The authors conclude that both methods were safe, but the stapled technique resulted in more stricture formation.

Aged↗
PubMed1997

Adult-to-adult living donor liver transplantation using extended right lobe grafts.

OBJECTIVE: The authors report their experience with living donor liver transplantation (LDLT) using extended right lobe grafts for adult patients under high-urgency situations. SUMMARY BACKGROUND DATA: The efficacy of LDLT in the treatment of children has been established. The major limitation of adult-to-adult LDLT is the adequacy of the graft size. A left lobe graft from a relatively small volunteer donor will not meet the metabolic demand of a larger recipient. METHODS: From May 1996 to November 1996, seven LDLTs, using extended right lobe grafts, were performed under high-urgency situations. All recipients were in intensive care units before transplantation with five having acute renal failure, three on mechanical ventilation, and all with hepatic encephalopathy. The median body weight for the donors and recipients was 58 kg (range, 41-84 kg) and 65 kg (range, 53-90 kg), respectively. The body weights of four donors were less than those of the corresponding recipients, and the lowest donor-to-recipient body weight ratio was 0.62:1. The extended right lobe graft was chosen because the left lobe volume was <40% of the ideal liver mass of the recipient. RESULTS: Median blood loss for the donors was 900 mL (range, 700-1600 mL) and hospital stay was 19 days (range, 8-22 days). Homologous blood transfusion was not required. Two donors had complications (one incisional hernia and one bile duct stricture) requiring reoperation after discharge. All were well with normal liver function 5 to 10 months after surgery. The graft weight ranged from 490 g to 1140 g. All grafts showed immediate function with normalization of prothrombin time and recovery of conscious state of the recipients. There was no vascular complication, but six recipients required reoperation. One recipient died of systemic candidiasis 16 days after transplantation and 6 (86%) were alive with the original graft at a median follow-up of 6.5 months (range, 5-10 months). CONCLUSIONS: When performed by a team with experience in hepatectomy and transplantation, LDLT, using an extended right lobe graft, can achieve superior results. The technique extends the success of LDLT from pediatric recipients to adult recipients and opens a new donor pool for adults to receive a timely graft of adequate function.

Acute Kidney Injury↗
PubMed1997

Prospective evaluation of Pringle maneuver in hepatectomy for liver tumors by a randomized study.

OBJECTIVE: To evaluate whether vascular inflow occlusion by the Pringle maneuver during hepatectomy can be safe and effective in reducing blood loss. SUMMARY BACKGROUND DATA: Hepatectomy can be performed with a low mortality rate, but massive hemorrhage during surgery remains a potentially lethal problem. The Pringle maneuver is traditionally used during hepatectomy to reduce blood loss, but there is a potential harmful effect on the metabolic function of hepatocytes. There has been no prospective randomized study to determine whether the Pringle maneuver can decrease blood loss during hepatectomy, improve outcome, or affect the metabolism of hepatocytes. METHODS: From July 1995 to February 1997, we studied 100 consecutive patients who underwent hepatectomy for liver tumors. The patients were randomly assigned to liver transection under intermittent Pringle maneuver of 20 minutes and a 5-minute clamp-free interval (n = 50), or liver transection without the Pringle maneuver (n = 50). The surface area of liver transection was measured and blood loss during transection per square centimeter of transection area was calculated. Routine liver biochemistry, arterial ketone body ratio (AKBR), and the indocyanine green (ICG) clearance test were done. RESULTS: The two groups were comparable in terms of preoperative liver function and in the proportion of patients having major hepatectomy. The Pringle maneuver resulted in less blood loss per square centimeter of transection area (12 mL/cm2 vs. 22 mL/cm2, p = 0.0001), a shorter transection time per square centimeter of transection area (2 min/cm2 vs. 2.8 min/cm2, p = 0.016), a significantly higher AKBR in the first 2 hours after hepatectomy, lower serum bilirubin levels in the early postoperative period, and, in cirrhotic patients, higher serum transferrin levels on postoperative days 1 and 8. The complication rate, the hospital mortality rate, and the ICG retention at 15 minutes on postoperative day 8 were equal for the two groups. CONCLUSION: Performing the Pringle maneuver during liver transection resulted in less blood loss and better preservation of liver function in the early postoperative period. This is probably because there was less hemodynamic disturbance induced by the bleeding.

Adult↗
PubMed1997

A discharge scoring system for patients with total hip replacement.

Total hip replacement is a common and expensive procedure. Any attempt to shorten the length of hospital stay safely is desirable. Proposes a scoring system specifically designed for this patient population, to determine the optimal timing of safe discharge and postacute care placement. Discusses its implications for the quality of patient care.

Arthroplasty, Replacement, Hip↗
PubMed1997

Hippocampal volumetry with magnetic resonance imaging: a cost-effective validated solution.

PURPOSE: The clinical utility of hippocampal volumetry is well documented, but the materials and techniques required to perform the procedure are not widely available outside major research centers. We describe a personal computer-based method of volumetric data analysis. METHODS: Using a 1.0-T scanner, we obtained 2-mm-thick tilted coronal MPRAGE magnetic resonance imaging (MRI) scans of 20 healthy volunteers aged 20-38 years. We used an inexpensive utility program to extract image information and an NIH Image for image analysis. The hippocampal formations were traced with a graphics tablet and landmarks described by Watson et al. (Neurology 1992;42:1743-50). Overlays of individual observers' tracings were used to fine tune the selection of landmarks and boundaries. Filled-in silhouette pairs generated from these "training tracings" were compared to determine how well observers could visually quantify area differences. RESULTS: Visual detection of asymmetry of silhouette pairs was sensitive, but the magnitude of asymmetry was underestimated. We achieved intraobserver coefficients of variation of right/left volume ratios between 0.82 and 3.16 and an interobserver range of volume ratios of 6%. In 20 healthy controls aged 20-38 years, the mean right and left hippocampal volumes were 2,911 mm3 and 2,836 mm3, respectively. The lower limits of normal were 2,217 mm3 for the right and 2,178 mm3 for the left. The mean right/left hippocampal ratio was 1.03, and the limits of normal (3 SD) for this were 0.95 to 1.10. CONCLUSIONS: Hippocampal volumetry can be performed reliably and economically. Our methodology makes it possible for different observers to generate consistent and comparable measurements.

Adult↗
PubMed1997

Are clinical laboratories in California accurately reporting vancomycin-resistant enterococci?

In order to determine whether hospital-based clinical laboratories conducting active surveillance for vancomycin-resistant enterococci in three San Francisco Bay area counties (San Francisco, Alameda, and Contra Costa counties) were accurately reporting vancomycin resistance, five vancomycin-resistant enterococcal strains and one vancomycin-susceptible beta-lactamase-producing enterococcus were sent to 31 of 32 (97%) laboratories conducting surveillance. Each strain was tested by the laboratory's routine antimicrobial susceptibility testing method. An Enterococcus faecium strain with high-level resistance to vancomycin (MIC, 512 microg/ml) was correctly reported as resistant by 100% of laboratories; an E. faecium strain with moderate-level resistance (MIC, 64 microg/ml) was correctly reported as resistant by 91% of laboratories; two Enterococcus faecalis strains with low-level resistance (MICs, 32 microg/ml) were correctly reported as resistant by 97 and 56% of laboratories, respectively. An Enterococcus gallinarum strain with intrinsic low-level resistance (MIC, 8 microg/ml) was correctly reported as intermediate by 50% of laboratories. A beta-lactamase-producing E. faecalis isolate was correctly identified as susceptible to vancomycin by 100% of laboratories and as resistant to penicillin and ampicillin by 68 and 44% of laboratories, respectively; all 23 (74%) laboratories that tested for beta-lactamase recognized that it was a beta-lactamase producer. This survey indicated that for clinically significant enterococcal isolates, laboratories in the San Francisco Bay area have problems in detecting low- to moderate-level but not high-level vancomycin resistance. Increasing accuracy of detection and prompt reporting of these isolates and investigation of cases are the next steps in the battle for control of the spread of vancomycin resistance.

Ampicillin↗
PubMed1997

Multicenter evaluation of the MicroScan Rapid Gram-Negative Identification Type 3 Panel.

The accuracy and performance of the revised MicroScan Rapid Gram-Negative Identification Type 3 Panel (Dade MicroScan Inc., West Sacramento, Calif.) were examined in a multicenter evaluation. The revised panel database includes data for 119 taxa covering a total of 150 species, with data for 12 new species added. Testing was performed in three phases: the efficacy, challenge, and reproducibility testing phases. A total of 405 fresh and stock gram-negative isolates comprising 54 species were tested in the efficacy phase; 96.8% of these species were identified correctly in comparison to the identification obtained either with the API 20E system (bioMérieux Vitek, Hazelwood, Mo.) or by the conventional tube method. The number of correctly identified isolates in the challenge phase, including new species added to the database, was 221 of 247, or 89.5%, in comparison to the number correctly identified by the conventional tube method. A total of 465 isolates were examined for intra- and interlaboratory identification reproducibility and gave an agreement of 464 of 465, or 99.8%. The overall reproducibility of each individual identification test or substrate was 14,373 of 14,384, or 99.9%. The new Rapid Gram-Negative Identification Type 3 Panel gave accurate and highly reproducible results in this multiple-laboratory evaluation.

Evaluation Studies as Topic↗
PubMed1997

The changing epidemiology of recurrent pyogenic cholangitis.

Recurrent pyogenic cholangitis is prevalent in Hong Kong and East Asia. While the recent influx of Asian immigrants has resulted in more cases appearing in the West, over the past three decades, the overall incidence in East Asia has been in decline. The experience of the Queen Mary Hospital and other hospitals in the region has been confirmed by comprehensive surveys. The decline in incidence has been attributed to the improved economic situation and living standards with the associated westernisation of diet.

Journal Article↗
PubMed1997

Pyloroplasty and pyloromyotomy in gastric replacement of the esophagus after esophagectomy: a randomized controlled trial.

BACKGROUND: Drainage methods for the gastric conduit after esophagectomy for carcinoma have been controversial. STUDY DESIGN: In a randomized controlled trial, 92 patients with esophageal carcinoma were randomized to have pyloroplasty or pyloromyotomy as a drainage procedure for the gastric conduit used for esophageal replacement. Only patients who underwent Lewis- Tanner operation or esophagogastrectomy and who had normal pyloroduodenal regions were included. RESULTS: The mean postoperative daily nasogastric output (SEM) were 164 mL (17 mL) in the pyloroplasty group and 179 mL (21 mL) in the pyloromyotomy group (p = not significant). No leakage occurred at the pyloroduodenal region in either group. In both groups, the anastomotic leakage rate was 2 percent, and the in-hospital mortality rate was 7 percent. No significant difference was found in postoperative morbidity and mortality. Gastric outlet obstruction developed in only two patients who underwent pyloromyotomy, and both required reexploration. One died of malignant obstruction of the gastric outlet and aspiration pneumonia. Scintigraphy performed 6 months after operation showed that the median half-life (interquartile range) for gastric emptying was 19 minutes (10 to 24 minutes) in the pyloromyotomy group and 8 minutes (5 to 19 minutes) in the pyloromyotomy group (p = 0.04). Long-term follow-up up to 5 years, however, did not reveal significant differences between the two groups in the type and quantity of food consumed. The incidence of other symptoms such as regurgitation, diarrhea, bile reflux, and dumping, also was no different. CONCLUSIONS: Pyloroplasty and pyloromyotomy were effective and safe drainage procedures for the gastric conduit used for esophageal replacement. The choice depends on the preference and experience of the surgeon. Most patients adapted to their new conduit with time.

Anastomosis, Surgical↗
PubMed1997

Evaluation of preoperative hepatic function in patients with hepatocellular carcinoma undergoing hepatectomy.

BACKGROUND: Postoperative hepatic failure is the leading cause of hospital mortality following hepatectomy for hepatocellular carcinoma (HCC). This prospective study was performed to identify the best test for assessment of the adequacy of hepatic functional reserve in patients with HCC before hepatectomy. METHODS: Between April 1989 and June 1993, 127 patients with HCC underwent hepatectomy. Each patient was evaluated before operation with the indocyanine green (ICG) clearance test, the aminopyrine breath test and the amino acid clearance test. RESULTS: Fourteen patients (11 per cent) died after hepatectomy. ICG retention at 15 min showed significant differences between patients who survived or died. By discriminant analysis, the safety limit of ICG retention at 15 min for major hepatectomy was 14 per cent and the relative risk of hospital mortality was 3. CONCLUSION: The ICG clearance test, expressed as the percentage of ICG retained at 15 min, is the best discriminating preoperative test for evaluating hepatic functional reserve in patients with HCC before hepatectomy.

Adult↗
PubMed1997

Ozone, cloud, solar and UV-B levels at a low pollution, Southern Hemisphere, sub-tropical site for winter/spring 1995.

This paper analyses daily ozone, cloud cover, solar radiation and broadband UV-B data for winter/spring at a low pollution Southern Hemispheric sub-tropical site (27.80 degrees S). The average ozone concentration for the period was 290 DU. An anti-correlation is presented between the ozone and UV-B data over a 5 day period during winter. An ozone deficiency of 45 DU was calculated for the cloud free day on the 16th July, 1995, in which the UV-B level exceeded the clear sky envelope by about 6%. Part of this increase may be attributed to a decrease in cloud cover. In winter, the July average of the daily integrated UV-B irradiance was 29.0 kJ/m2, (a level which is comparable to that observed in Japan during the summer months).

Air Pollution↗
PubMed1997

Management of fulminant hepatic failure at Queen Mary Hospital.

OBJECTIVE: To evaluate the strategy of the management of patients with fulminant hepatic failure at Queen Mary Hospital. METHODS: In the period 1994 through 1996, 30 patients with fulminant hepatic failure were managed by active supportive treatment in the Intensive Care Unit in preparation for liver transplantation. Liver transplantation was performed in 14 patients (aged 17-47), 3 of whom received liver grafts from brain-stem dead donors and 11 received live-related grafts from family members. The median duration from admission to liver transplantation was 3 days (range: 1-6 days). RESULTS: Thirteen patients (93%) survived the liver transplantation and are well after a median period of follow-up of 7 months. The only mortality was in a patient with pre-exiting renal transplantation and hepatitis B infection, who died from intra-abdominal candidiasis. CONCLUSION: The strategy of active supportive treatment and early liver transplantation using live-related liver graft is probably the key to the success of the management of fulminant hepatic failure in our series.

Adolescent↗
PubMed1997

The roles of multimodality treatment and lymphadenectomy in the management of esophageal cancer.

PURPOSE: To review the current status of multimodality treatment and lymphadenectomy in the management of esophageal cancer. DATA SOURCES: Literature review. STUDY SELECTION: Multimodality treatment and lymphadenectomy in esophageal cancer. DATA EXTRACTION: Results in research papers published selected by literature search. RESULTS: Numerous studies have been carried out attempting to define the roles of various neoadjuvant or adjuvant regimens in the treatment of esophageal cancer. These included the use of radiotherapy or chemotherapy alone or in different combinations, with or without surgical resection. Randomized trials have failed to show significant improvement compared with surgical resection alone, although downstaging of disease and benefits on subgroups of patients could be demonstrated. Whether the extent of resection can influence outcome was tested by varying the surgical approach, and by increasing the extent of lymphadenectomy. Although indirect evidence exists suggesting more extensive resection may improve long term prognosis, definitive proof is lacking. CONCLUSIONS: More well organized randomized controlled trials are needed to further elucidate the roles of these approaches in the treatment of esophageal cancer.

Combined Modality Therapy↗
PubMed1996

Functional characterization of a mutant thyroid hormone receptor in Xenopus laevis.

Thyroid hormone plays a causative role during frog metamorphosis, and its effect is mediated by thyroid hormone receptors (TRs). To investigate the function of Xenopus TRs, we have recently developed a thyroid hormone dependent in vivo transcription system by introducing TRs and RXRs (9-cis-retinoic acid receptors) into Xenopus oocytes. Interestingly, using this system, we have found that the TRalphaB cloned previously is defective in transcriptional activation compared with TRalphaA. In vitro DNA binding experiments show that TRalphaB.RXR heterodimers have drastically reduced affinity for a thyroid hormone response element. Site-directed mutagenesis shows that two of the seven amino acid residues that differ between TRalphaA and TRalphaB are responsible for the defect in TRalphaB function. These two residues affect the DNA binding by both TR.RXR heterodimers and TR homodimers. In contrast, heterodimer formation with RXRs is not affected as demonstrated by coimmunoprecipitation and dominant-transcriptional inhibition experiments. By cDNA and genomic DNA sequence analysis, we have demonstrated that the residues, which affect TRalphaB function when mutated, are identical between the wild type TRalphaB and TRalphaA. Thus, our experiments have discovered the first amphibian TR mutant. The DNA binding and transcription activation functions of the mutant are discussed in relation to the recently published TR crystal structure.

Amino Acid Sequence↗
PubMed1996

Mood disorders: rural/urban differences in prevalence, health care utilization, and disability in Ontario.

This study examines whether rural Ontario differs from urban Ontario in mood disorder prevalence, health service use and concomitant disability. An epidemiologic community survey of 9953 individuals was conducted, with rural/urban status defined by population-density-related criteria. Overall, Ontario prevalence rates for depression, manic episode, and dysthymia were similar to previous studies, but rural rates were unexpectedly no different from urban ones. Nearly half of mood disorder subjects used no services, and one-third reported significant disability. Rural individuals with mood disorders were similar to their urban counterparts in service use and disability.

Adolescent↗