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Biomedical subjects

G A Porter

Publications and source records attributed to G A Porter.

At least 19 recordsLinked to original sources
PubMed2006

Obesity and lifestyle risk factors for gastroesophageal reflux disease, Barrett esophagus and esophageal adenocarcinoma.

The aim of this study was to examine the association of obesity with esophageal adenocarcinoma, and with the precursor lesions Barrett esophagus and gastroesophageal reflux disease (GERD). This case-control study included cases with GERD (n = 142), Barrett esophagus (n = 130), and esophageal adenocarcinoma (n = 57). Controls comprised 102 asymptomatic individuals. Using logistic regression methods, we compared obesity rates between cases and controls adjusting for differences in age, gender, and lifestyle risk factors. Relative to normal weight, obese individuals were at increased risk for esophageal adenocarcinoma (Odds Ratio [OR] 4.67, 95% Confidence Interval [CI] 1.27-17.9). Diets high in vitamin C were associated with a lower risk for GERD (OR 0.40, 95% CI 0.19-0.87), Barrett esophagus (OR 0.44, 95% CI 0.20-0.98), and esophageal adenocarcinoma (OR 0.21, 95% CI 0.06-0.77). For the more established risk factors, we confirmed that smoking was a significant risk factor for esophageal adenocarcinoma, and that increased liquor consumption was associated with GERD and Barrett esophagus. In light of the current obesity epidemic, esophageal adenocarcinoma incidence rates are expected to continue to increase. Successful promotion of healthy body weight and diets high in vitamin C may substantially reduce the incidence of this disease.

Adenocarcinoma↗
PubMed2002

Evolution and critical appraisal of anastomotic technique following resection of esophageal adenocarcinoma.

The aim of this study was to critically evaluate acute and long-term complications of hand-sewn and semimechanical cervical esophagogastric anastomosis following resection of primary esophageal adenocarcinoma. Between February 1991 and 2001, 91 consecutive patients underwent subtotal esophagectomy (transthoracic, n=49; transhiatal, n=42), transposing a gastric tube based on the right gastroepiploic artery. All esophagogastric anastomoses were performed in the left neck using a hand-sewn technique (n=53) and, from September 1997, a side-to-side semimechanical technique (n=38). Outcomes evaluated were anastomotic leak rates, length of stay, and development of strictures. Postoperative mortality was 4.4% (all cardiopulmonary causes). Fifty-eight patients (63.7%) had an uncomplicated postoperative course, with a median postoperative length of stay of 10 days (vs. 20 days with associated morbidity; P </= 0.001). Anastomotic leaks were the leading cause of postoperative morbidity (16.5%, 15/91), and were classified into four types based on severity. The semimechanical anastomotic technique was associated with a reduced leak rate compared with the hand-sewn technique (7.9%, 3/38 vs. 22.6%, 12/53; P=0.08), although different patterns of anastomotic failure were seen following semimechanical anastomoses, with increased mediastinal and pleural sepsis. Anastomotic strictures developed in nine (17.0%) hand-sewn and three (7.9%) semimechanical anastomoses. Our conclusion was that a semimechanical technique for cervical esophagogastrostomy is associated with reduced anastomotic leak rates compared with hand-sewn anastomoses, resulting in a shorter postoperative stay. Patterns of anastomotic failure varied between each technique, possibly as a consequence of a longer cervical esophageal segment required for construction of a semimechanical anastomosis. The association between anastomotic technique and stricture development was not clear from this study.

Adenocarcinoma↗
PubMed2001

Significance of plasma cytokine levels in melanoma patients with histologically negative sentinel lymph nodes.

INTRODUCTION: Although sentinel lymph node (SLN) status is the most powerful predictor of prognosis in patients with clinically localized melanoma, a proportion of melanoma patients with histologically negative SLNs will still recur. It is hypothesized that tumor response may be altered or mediated by specific cytokines. We therefore investigated whether levels of IL-4, IL-6, IL-10, TNF-alpha, or IFN-gamma would predict disease recurrence in melanoma patients with histologically negative SLNs. METHODS: This prospective cohort study involved 218 patients with clinically localized melanoma who underwent a histologically negative SLN biopsy. Preoperative plasma cytokine levels were determined by enzyme-linked immunosorbent assay on these patients, as well as on 90 healthy controls. Kaplan-Meier life tables were constructed, and Cox proportional hazards analyses were performed to assess predictors of disease-free survival (DFS). RESULTS: At a median follow-up of 43 months, 33 of 218 patients (15%) had suffered disease recurrence. Melanoma patients had significant elevations of IL-4, IL-6, and IL-10 compared to healthy controls; levels of IFN-gamma were less elevated in melanoma patients compared to controls. Despite this, melanoma patients with detectable IFN-gamma levels were at significantly higher risk for recurrence compared to patients with undetectable levels (5-year DFS 70% vs. 86%, P = .03). On multivariate analysis including standard melanoma prognostic factors, only tumor thickness (P = .004) and the presence of detectable IFN-gamma levels (P = .05) were significant independent prognostic factors for disease-free survival. CONCLUSIONS: Among melanoma patients with clinically localized disease who have undergone a histologically negative SLN biopsy, presence of a detectable plasma level of IFN-gamma is an independent predictor of disease recurrence. Elevated levels of IFN-gamma may identify a group of early-stage melanoma patients who are more likely to have recurrence of disease and who may benefit from adjuvant therapies, including immunotherapies.

Adolescent↗
PubMed2001

Ontogeny of humoral heart rate regulation in the embryonic mouse.

Catecholamines, acetylcholine, and adenosine are known to influence cardiac function, yet the effects of these agents on mammalian embryonic myocardium are largely unknown. To address this issue, we compared the chronotrophic effects of adenosinergic, adrenergic, and muscarinic agents on cultured murine embryos from postcoital day (PC) 8.0, when the fusing heart tubes first begin to beat, to PC 14, when cardiogenesis is essentially complete. At PC 8.0 and older, A(1)-adenosine receptor (A(1)AR) activation significantly decreased heart rates. Adrenergic stimulation caused modest increases in heart rates (145-155% of baseline) beginning at PC 9.0. Muscarinic activation decreased heart rates only after PC 13. When receptor gene expression was examined, A(1)ARs and beta(1)ARs were expressed in isolated hearts as early as PC 9.0, and beta(2)ARs and m(2)-muscarinic receptor genes were expressed at PC 11.0. These results identify the adenosinergic system as the earliest and most potent regulator of embryonic cardiac function and show that prenatal responsiveness to catecholamines and acetylcholine develops at later embryonic stages.

Adenosine↗
PubMed2000

Significance of multiple nodal basin drainage in truncal melanoma patients undergoing sentinel lymph node biopsy.

BACKGROUND: Although previous studies have demonstrated that truncal site is associated with an adverse prognosis, explanations for such risk are lacking. In addition, the number of nodal basins as well as the number of lymph nodes containing regional metastases are important prognostic factors in these patients. Because the lymphatic drainage pattern of truncal melanoma often includes more than one basin, we designed a study to evaluate (1) whether patients with multiple nodal basin drainage (MNBD) were at an increased risk of lymph node metastases identified by sentinel lymph node (SLN) biopsy, and (2) whether the histological status of an individual basin reliably predicted the status of the other draining basins in patients with MNBD. METHODS: The records of 295 consecutive truncal melanoma patients who were managed primarily with intraoperative lymphatic mapping and SLN biopsy, between 1991 and 1997, were reviewed. All patients underwent preoperative lymphoscintigraphy, which established the number and location of draining nodal basins. Univariate and multivariate analyses of relevant clinicopathological factors were performed to assess which factors may predict the presence of a pathologically positive SLN. RESULTS: At least one SLN was identified in 281 patients. MNBD was present in 86 (31%) patients, and a pathologically positive SLN was found in 56 (20%) patients. By multivariate analysis, the presence of MNBD (relative risk = 1.9; P = .03), tumor thickness (P = .007), and tumor ulceration (relative risk = 2.4; P = .01) were significant independent risk factors for the presence of at least one pathologically positive SLN. SLN pathology in one basin did not predict the histology of other basins in 19 (22%) of 86 patients with MNBD. CONCLUSIONS: MNBD is independently associated with an increased risk of nodal metastases in truncal melanoma patients. Because the histological status of an individual basin did not reliably predict the status of the other draining basins in patients with MNBD, it is important to adequately identify and completely assess all nodal basins at risk, as defined by lymphoscintigraphy, in truncal melanoma patients.

Biopsy↗
PubMed2000

Outcomes research in surgical oncology.

BACKGROUND: There have been significant developments and advances in the area of outcomes research in the past 25 years. Unfortunately, many surgical oncologists may not have a clear concept of outcomes research and the methodology involved. METHODS: A literature-based review article was done that included an overview of outcomes research, and study design and types, outcome measures, outcome instruments, and sources of outcome data were examined. In addition, we reviewed small area variation/volume outcome analysis as well as quality-of-life studies and their applications in surgical oncology clinical investigation. Specific examples from surgical oncology were identified. RESULTS: As the costs of health care have increased, so has the emphasis on measuring outcomes of medical and surgical care to determine the quality and appropriateness of care. Marked variations in a variety of outcomes after oncological procedures have been attributed to individual surgeon and institution characteristics. Because much of the clinical surgical oncology literature deals only with the traditional mortality and morbidity outcomes, a more comprehensive examination of patient outcomes is required to fully evaluate the impact of patient management decisions. Health-related quality of life can be measured and analyzed in several ways and decisions regarding the use of such methodology are dependent on multiple factors. CONCLUSIONS: Surgical oncologists should recognize that the true value of their interventions requires systematic and comprehensive examination of patient outcomes.

Decision Making↗
PubMed2000

Cost and utilization impact of a clinical pathway for patients undergoing pancreaticoduodenectomy.

BACKGROUND: When implemented in several common surgical procedures, clinical pathways have been reported to reduce costs and resource utilization, while maintaining or improving patient care. However, there is little data to support their use in more complex surgery. The objective of this study was to determine the effects of clinical pathway implementation in patients undergoing elective pancreaticoduodenectomy (PD) on cost and resource utilization. METHODS: Outcome data from before and after the development of a clinical pathway were analyzed. The clinical pathway standardized the preoperative outpatient care, critical care, and postoperative floor care of patients who underwent PD. An independent department determined total costs for each patient, which included all hospital and physician costs, in a blinded review. Outcomes that were examined included perioperative mortality, postoperative morbidity, length of stay, readmissions, and postoperative clinic visits. RESULTS: From January, 1996 to December, 1998, 148 consecutive patients underwent PD or total pancreatectomy; 68 before pathway development (PrePath) and 80 after pathway implementation (PostPath). There were no significant differences in patient demographics, comorbid conditions, underlying diagnosis, or use of neoadjuvant therapy between the two groups. Mean total costs were significantly reduced in PostPath patients compared with PrePath patients ($36,627 vs. $47,515; P = .003). Similarly, mean length of hospital stay was also significantly reduced in PostPath patients (13.5 vs. 16.4 days; P = .001). The total cost differences could not be attributed solely to differences in room and board costs. Cost and length-of-stay differences remained when outliers were excluded from the analysis. Despite these findings, there were no significant differences between PrePath and PostPath patients in terms of perioperative mortality (3% vs. 1%), readmissions within 1 month of discharge (15% vs. 11%), or mean number of clinic visits within 90 days of discharge (3.3 vs. 3.4 visits). CONCLUSIONS: The establishment of a clinical pathway for PD patients dramatically reduced costs and resource utilization without any apparent detrimental effect on quality of patient care. These findings support the implementation of clinical pathways for PD patients, as well as investigation into pathway care for other complex surgical procedures.

Aged↗
PubMed2000

How many lymph nodes are enough during sentinel lymphadenectomy for primary melanoma?

BACKGROUND: Sentinel lymph node (SLN) biopsy has been shown to reliably identify nodal metastases and the subsequent need for further surgical and adjuvant therapy in patients with cutaneous melanoma. Although SLN identification rates have improved with the addition of radioactive colloid to the blue dye technique, it remains unclear how many lymph nodes should be removed to accurately determine the histologic status of the nodal basin. The objective of this study was to determine the optimal extent of SLN biopsy in these patients. METHODS: The records of 633 consecutive patients with melanoma (765 nodal basins) whose primary treatment included SLN biopsy with the use of a combination of blue dye and technetium Tc 99 labeled sulfur colloid were reviewed. SLN biopsy consisted of the removal of all of the blue-stained nodes and all nodes with radiotracer uptake activity of at least twice background. RESULTS: SLN biopsy was successful in 765 of 772 basins (99%). A mean of 1.9 SLNs (median, 2 SLNs) per basin were excised. At least 3 SLNs were removed in 176 basins (23%). The overall histologic status of a basin was always established by the first or second SLN harvested (ie, in no patient was the third or subsequent SLN positive when 1 of the first 2 was not). Of the 124 basins containing lymphatic metastases, the SLN that contained the maximal radiotracer uptake (hottest) and/or stained blue was pathologically positive in 118 basins (95%). In only 6 of the 124 positive basins (5%) was the sole evidence of occult nodal metastases identified in an SLN that was neither blue-stained nor the hottest. All but 1 of these SLNs had counts that were at least 66% of the hottest node in the basin. CONCLUSIONS: With a combined modality approach to SLN biopsy, removal of more than 2 SLNs did not provide information that upstaged any patient with primary melanoma. Removal of additional nonblue SLN(s) that contained radioactive counts of at least twice background but lower than two thirds of the SLNs with maximal radiotracer uptake affected patient management in less than 0.2% of all cases. These findings may be helpful in minimizing the extent of surgery and perhaps in reducing the costs and resource use associated with operating room time and pathologic examination.

Biopsy↗
PubMed2000

Limitations of size as a criterion in the evaluation of adrenal tumors.

BACKGROUND: Size has been considered to be the single best predictor of malignancy in adrenal neoplasms that have been identified incidentally. However, small adrenal cortical cancers have been reported from multiple centers. METHODS: We retrospectively evaluated the value of tumor size and other clinical parameters in the prediction of the presence of adrenal malignancy. RESULTS: The records of 117 patients who underwent evaluation for tumors of the adrenal gland were reviewed. The median tumor size of the adrenal cortical carcinomas (n = 38 carcinomas) was 9.2 cm (range, 1.7-30 cm); 5 cancers (13.5%) were smaller than 5.0 cm. The median overall size of the benign tumors, excluding pheochromocytomas, was 4.0 cm (n = 38 carcinomas); 10 benign tumors (26%) were larger than 5.0 cm. The imaging features of 4 of 5 small adrenal cancers predicted malignancy; the remaining patients had hormonally functioning tumors. The imaging features of 7 of 10 large benign adrenal tumors predicted benign histologic features, including 5 of 5 myelolipomas. CONCLUSIONS: Although size remains a good predictor of the histologic features and clinical behavior of adrenal neoplasms, both small adrenal cortical cancers and large benign tumors occur with measurable frequency. High-quality imaging studies may be helpful in the identification of relatively small adrenal cancers and of characteristic benign lesions that may be selectively followed.

Adolescent↗
PubMed2000

Long term follow up of the utility of troponin T to assess cardiac risk in stable chronic hemodialysis patients.

Thirty long-term, stable hemodialysis patients were followed 24 months to identify any predictable relationship between elevated serum cTnT values and the diagnosis of coronary artery disease and/or the occurrence of a cardiac death. Patients with a baseline cTnT value of >0.1 microg/L were at high risk for life-threatening cardiac events during the 2 years follow-up. With regard to predicting a cardiac event, cTnT has a specificity of 93.75% and sensitivity of 81.8% compared to cTnI whose specificity was 87.5% but sensitivity of between 9.1 and 18.2%. CK-MB was the most specific at 100% but had a low sensitivity of 9.1%. The hemodialysis process, while causing an increase in the serum levels of all the markers studied except CK, the increase only proved significant for cTnT. The only markers whose stratification remained consistent over the 2 years where cTnT and CK-MB, for all others a gain or lose was registered. Baseline stratification using cTnT with a cut-off value of >0.1 microg/L offers opportunities to select at risk hemodialysis patients for corrective cardiovascular intervention.

Adult↗
PubMed1999

Laparoscopic splenectomy in patients with hematologic malignancies.

BACKGROUND: Although laparoscopic splenectomy (LS) for benign hematologic disease is well accepted, its role in hematologic malignancies is not clearly defined. This study examined the efficacy and feasibility of LS for hematologic malignancies. METHODS: Records were reviewed from patients who underwent LS at two university hospitals. Charts from 77 open splenectomies for malignancy (OM) during the same period were also reviewed. RESULTS: Fifty-three patients underwent LS, 22 for hematologic malignancies (LM) and 31 for benign hematologic disorders (LB). Median splenic weight was greater in the LM group (930 g) than in the LB group (164 g, P = 0.001). LM was associated with longer operations and greater blood loss than was LB. LM had a 41% conversion rate. Morbidity, mortality, and transfusion rates were similar. Median hospital stay was shorter for LM (4 days) than for OM (6 days, P = 0.001). CONCLUSIONS: LS is feasible in hematologic malignancies but is associated with increased operative time and blood loss and a high conversion rate. Morbidity and mortality, however, was similar. Shorter hospital stays for LM compared with OM may translate into earlier recovery and initiation of antineoplastic therapy.

Adult↗
PubMed1998

Surgeon-related factors and outcome in rectal cancer.

OBJECTIVE: To determine whether surgical subspecialty training in colorectal surgery or frequency of rectal cancer resection by the surgeon are independent prognostic factors for local recurrence (LR) and survival. SUMMARY BACKGROUND DATA: Variation in patient outcome in rectal cancer has been shown among centers and among individual surgeons. However, the prognostic importance of surgeon-related factors is largely unknown. METHODS: All patients undergoing potentially curative low anterior resection or abdominoperineal resection for primary adenocarcinoma of the rectum between 1983 and 1990 at the five Edmonton general hospitals were reviewed in a historic-prospective study design. Preoperative, intraoperative, pathologic, adjuvant therapy, and outcome variables were obtained. Outcomes of interest included LR and disease-specific survival (DSS). To determine survival rates and to control both confounding and interaction, multivariate analysis was performed using Cox proportional hazards regression. RESULTS: The study included 683 patients involving 52 surgeons, with > 5-year follow-up obtained on 663 (97%) patients. There were five colorectal-trained surgeons who performed 109 (16%) of the operations. Independent of surgeon training, 323 operations (47%) were done by surgeons performing < 21 rectal cancer resections over the study period. Multivariate analysis showed that the risk of LR was increased in patients of both noncolorectal trained surgeons (hazard ratio (HR) = 2.5, p = 0.001) and those of surgeons performing < 21 resections (HR = 1.8, p < 0.001). Stage (p < 0.001), use of adjuvant therapy (p = 0.002), rectal perforation or tumor spill (p < 0.001), and vascular/neural invasion (p = 0.002) also were significant prognostic factors for LR. Similarly, decreased disease-specific survival was found to be independently associated with noncolorectal-trained surgeons (HR = 1.5, p = 0.03) and surgeons performing < 21 resections (HR = 1.4, p = 0.005). Stage (p < 0.001), grade (p = 0.02), age (p = 0.02), rectal perforation or tumor spill (p < 0.001), and vascular or neural invasion (p < 0.001) were other significant prognostic factors for DSS. CONCLUSION: Outcome is improved with both colorectal surgical subspecialty training and a higher frequency of rectal cancer surgery. Therefore, the surgical treatment of rectal cancer patients should rely exclusively on surgeons with such training or surgeons with more experience.

Adenocarcinoma↗
PubMed1998

Troponin T, a predictor of death in chronic haemodialysis patients.

Of the 10 chronic haemodialysis patients whose serum TnT levels exceeded the threshold value of 0.1 microg.L(-1) at entry into the study, four were dead at 1 year and three others had a diagnosis of CAD. Of the 20 chronic haemodialysis patients with normal serum TnT levels at entry, one died and none had CAD. All five deaths were cardiac related, either arising from acute myocardial infarction or by sudden death. When serum TnT levels were compared with accepted predictors of death in chronic haemodialysis patients, such as serum creatinine, serum albumin and haematocrit, in the present study serum TnT proved to be more accurate and had excellent sensitivity and specificity. Serum TnT was also superior to serum TnI, which proved to be no more discriminating than the non-specific muscle marker, aldolase.

Adult↗
PubMed1997

Two populations of beta-spectrin in rat skeletal muscle.

We use immunoblotting, immunoprecipitation, and centrifugation in sucrose density gradients to show that the product of the erythrocyte beta-spectrin gene in rat skeletal muscle (muscle beta-spectrin) is present in two states, one associated with fodrin, and another that is not associated with any identifiable spectrin or fodrin subunit. Immunofluorescence studies indicate that a significant amount of beta-spectrin without alpha-fodrin is present in the myoplasm of some muscle fibers, and, more strikingly, at distinct regions of the sarcolemma. These results suggest that alpha-fodrin and muscle beta-spectrin associate in muscle in situ, but that some muscle beta-spectrin without a paired alpha-subunit forms distinct domains at the sarcolemma.

Animals↗