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Biomedical subjects

H R Doyle

Publications and source records attributed to H R Doyle.

At least 19 recordsLinked to original sources
PubMed2003

Changes in serum electrolytes during treatment of patients in liver failure with molecular adsorbent recirculating system.

PURPOSE: To study the effect of MARS on serum electrolytes during liver failure. DESIGN: Twenty-three patients admitted to a quaternary health care facility from September 2000 to May 2002, 22 adults and 1 child, 11 males (48%) and 12 females (52%), age 15-70 (median 53), treated with MARS for: 12 acute-on-chronic liver failure (52%); 4 fulminant hepatic failure (17%); 3 intractable pruritus (13%); 2 primary-non-function (9%); 2 following major liver resection (9%). PROCEDURES: Sodium, potassium, chloride, phosphorus, calcium, and magnesium were measured in the serum, ultrafiltrate and albumin circuit before and after MARS. STATISTICAL METHODS: A comparison of electrolyte concentrations, before and after MARS, was performed using a paired t test. MAIN FINDINGS: Serum electrolyte concentrations before and after MARS, while statistically significant in some cases, were very small, and of no clinical relevance. CONCLUSION: MARS exchanges potassium, chloride, calcium, and magnesium by ultrafiltration; sodium by the albumin dialysis.

Adolescent↗
PubMed2001

The impact of liver dysfunction on outcome in patients with multiple injuries.

Multiple organ dysfunction syndrome (MODS) is the leading cause of late deaths after traumatic injury. The relative importance of dysfunction of individual organ systems in determining outcome from MODS has not been clearly defined. Some studies have suggested that hepatic dysfunction associated with MODS increases mortality, whereas others have suggested that it contributes little to outcome in trauma patients. To clarify the role of the hepatic dysfunction after traumatic injury we retrospectively reviewed all trauma patients with an Injury Severity Score > or = 14 admitted from January 1, 1994 through June 30, 1997 for the presence of hepatic dysfunction defined as a serum bilirubin > or = 2.0 mg/dL. Of the 1962 patients who met the entry criteria 154 developed hepatic dysfunction during their hospital stay. Patients with hepatic dysfunction were older (46 +/- 2 versus 41 +/- 1 years), were more severely injured (Injury Severity Score 31.5 +/- 0.9 versus 23.3 + 0.2), and had a lower prehospital blood pressure (102 +/- 3 versus 117 +/- 1 mm Hg) compared with patients who did not develop hepatic dysfunction. Patients with hepatic dysfunction were more likely to present with shock as reflected in a lower initial emergency room blood pressure (109 +/- 3 versus 128 +/- 1 mm Hg) and base deficit (-6.9 +/- 0.6 versus -3.5 +/- 0.1 mEq/L). Patients who developed hyperbilirubinemia had longer lengths of stay in the intensive care unit (15.8 +/- 1.2 versus 3.4 +/- 0.2 days) and the hospital (27.4 +/- 1.7 versus 11.1 +/- 0.2 days) and a higher in-hospital mortality (16.2% versus 2.5%). These data demonstrate that the development of hepatic dysfunction reflects the severity of injury and is associated with a significantly worse outcome after traumatic injury.

Adult↗
PubMed2001

Malignant fibrous histiocytoma of the gallbladder: case report and review of the literature.

Malignant fibrous histiocytoma is a soft tissue sarcoma of mesenchymal origin. It can rarely present as a primary gallbladder tumor with only five cases having been reported to date in the English literature. Here we report the sixth documented case of malignant fibrous histiocytoma of the gallbladder, and we review all other cases reported. The outcome of the visceral sarcomas is poor when compared with tumors arising from the soft tissues. The treatment of primary malignant fibrous histiocytomas of the gallbladder is surgery. However, tumor recurrence is the norm even if wide clean margins are obtained. In contrast to tumors arising from the extremities the role of adjuvant radiotherapy and chemotherapy is less clear in the case of retroperitoneal and visceral sarcomas. Our patient is still alive and free of disease 46 weeks after surgery. The fact that this is the longest survival reported to date underscores the dismal prognosis of this disease.

Aged↗
PubMed2001

Recurrent neural networks for predicting outcomes after liver transplantation: representing temporal sequence of clinical observations.

OBJECTIVES: This paper investigates a version of recurrent neural network with the backpropagation through time (BPTT) algorithm for predicting liver transplant graft failure based on a time series sequence of clinical observations. The objective is to improve upon the current approaches to liver transplant outcome prediction by developing a more complete model that takes into account not only the preoperative risk assessment, but also the early postoperative history. METHODS: A 6-fold cross-validation procedure was used to measure the performance of the networks. The data set was divided into a learning set and a test set by maintaining the same proportion of positive and negative cases in the original set. The effects of network complexity on overfitting were investigated by constructing two types of networks with different numbers of hidden units. For each type of network, 10 individual networks were trained on the learning set and used to form a committee. The performance of the networks was measured exhaustively with respect to both the entire training and test sets. RESULTS: The networks were capable of learning the time series problem and achieved good performances of 90% correct classification on the learning set and 78% on the test set. The prediction accuracy increases as more information becomes progressively available after the operation with the daily improvement of 10% on the learning set and 5% on the test set. CONCLUSIONS: Recurrent neural networks trained with BPTT algorithm are capable of learning to represent temporal behavior of the time series prediction task. This model is an improvement upon the current model that does not take into account postoperative temporal information.

Adult↗
PubMed1998

Matching donors and recipients.

This study identifies the major risk factors associated with outcome after liver transplantation, showing that candidates for this surgery can be stratified into differential risk categories at the time of the actual surgery. All the livers used were flushed with University of Wisconsin solution. The study is a retrospective multivariate analysis of 2376 consecutive transplantations performed on 2019 recipients between November 1, 1987, and December 31, 1993. Donor variables studied were age, sex, blood type, cause of death, intensive care unit length of stay, body mass index, use of pressors (dopamine infusion > 10 micrograms/kg/min or continuous infusion of epinephrine or norepinephrine), use of pitressin, cardiopulmonary resuscitation, terminal transaminase levels, serum sodium level at procurement, and total ischemia time. Recipient variables studied were age; sex; blood type; indication for liver transplantation; history of liver transplantation or upper abdominal surgery; United Network for Organ Sharing urgency status; need for mechanical ventilation; primary immunosuppression; and preoperative bilirubin level, prothrombin time, and creatinine level. The variables independently associated with outcome were donor age, female donor sex, ischemia time, recipient age, prior liver transplant, preoperative mechanical ventilation, preoperative bilirubin level, preoperative creatine level, indication for transplantation and primary immunosuppression used. The results of this study not only give us insight into the probable outcomes of individual patients, but also show that this stratification can be useful when comparing results across different groups or in helping to choose the best donor-recipient combination based on the calculated probability of a favorable outcome.

Adult↗
PubMed1998

Reducing the length of stay after kidney transplantation--the intensive outpatient unit.

The need to reduce the costs associated with the initial hospitalization for kidney transplantation has led to the development of outpatient facilities in which patients can be seen on a daily basis. The implementation of a kidney transplant intensive outpatient unit (IOPU) is described. Prior to the opening of the IOPU, the median and mean lengths of stay after kidney transplantation in our program were 14.0 and 18.9 d, respectively. Subsequent to the opening of the IOPU, the median and mean lengths of stay after kidney transplantation have gradually decreased and are currently 5.0 and 7.5 d, respectively. The median inpatient cost of transplantation, excluding organ acquisition charges, has decreased by 54%, from $25516 to $11616. Patient satisfaction has exceeded 80%. The IOPU represents an effective means of reducing the cost associated with transplantation, without sacrificing the quality of care.

Cost Savings↗
PubMed1996

Hepatic Retransplantation--an analysis of risk factors associated with outcome.

Hepatic retransplantation is controversial because the results are inferior to primary transplants and organs are so scarce. To determine the factors that are associated with poor outcome within the first year following retransplantation, we performed a multivariate analysis, using stepwise logistic regression, of 418 hepatic retransplantations performed at a single institution from November 1987 to December 1993. The minimum follow-up was 1 year. Seven variables were found to be independently associated with subsequent graft failure (defined as either patient death or retransplantation): donor age (odds ratio 2.2 for each 10-year increase over age 45, 95% CI 1.3 to 3.7), female donor sex (odds ratio 1.7, 95% CI 1.05 to 2.7), recipient age (odds ratio 1.6 for each 10-year increase over age 45,95% CI 1.2 to 2.8), need for preoperative mechanical ventilation (odds ratio 1.8, 95% CI 1.1 to 2.9), pretransplant serum creatinine (odds ratio 1.24 for each increase of 1 mg/dl, 95% CI 1.1 to 1.4), pretransplant total serum bilirubin (odds ratio 1.4 for each 10-mg/dl increase over 15 mg/dl, 95% CI 1.1 to 1.8), and the primary immunosuppressant, using tacrolimus as the reference category (odds ratio for cyclosporine-based immunosuppression 3.9, 95% CI 2.3 to 6.8). Although not part of the logistic regression model, the timing of retransplantation was also found to be important, with the overall probability of failure increasing from 0.58 on day 0 to a peak of 0.8 on day 38 and decreasing slowly after that. The implications of these results regarding the appropriateness of retransplantation are discussed.

Adult↗
PubMed1996

A high incidence of native portal vein thrombosis in veterans undergoing liver transplantation.

The incidence of native portal vein thrombosis (PVT) in liver transplant recipients has been reported to range from 2.1 to 13.8%. We have identified an inordinately high incidence of PVT in a consecutive series of U.S. veterans receiving liver transplants. Between October 1989 and February 1994, 88 consecutive U.S. veterans received 99 orthotopic liver transplants under primary Tacrolimus (Prograf, formerly FK506) based immunosuppression. A number of clinical features were examined in an effort to identify risk factors for PVT and outcome was compared to patients without PVT. Native PVT was present in 23/88 (26%) patients. All of these patients were male U.S. veterans with a mean age of 47 years. When compared to the 65 patients without PVT, we found no significant difference with respect to underlying liver disease, age, Childs-Pugh score (mean = 12), UNOS status as defined prior to April 1995 (95% UNOS 3 or 4), previous abdominal surgery, or liver volume. Median blood loss for patients with PVT (21 units of packed red blood cells) was greater than for those without PVT (14 units, P = 0.04). Portal thrombectomy was performed in 11 patients, 11 patients required mesoportal jump grafts, and 1 patient had an interposition graft. Standard veno-venous bypass was used in 10 patients with single bypass utilized for the remainder. Actuarial patient survival for all patients at 1, 2, and 4 years was 88, 85, and 79%, respectively. There was no significant difference in patients with or without PVT. Patients with PVT had poorer graft survival than patients without PVT (86% vs 65%, 1 year; 81% vs 65%, 2 years; 81% vs 61%, 4 years; P = 0.03); however, this was not related to technical problems with the portal venous inflow. PVT occurred in 26% of U.S. veterans undergoing liver transplantation. These patients had significantly higher operative blood loss and poorer graft survival. The high incidence of postnecrotic cirrhosis in a predominantly male group of patients with advanced disease, as is evident by the high mean Childs-Pugh score and UNOS status, perhaps accounts for our observations.

Female↗
PubMed1996

Multisolutional clustering and quantization algorithm (MCQ).

We have developed a novel clustering and quantization algorithm that allows the user to create multiple one-to-one correspondences between the actual data and its transformed (clustered and quantized) values, based on the user's hypothesis regarding the nature of the classification task. The types of problems for which the algorithm can be beneficial are discussed. We report experiments employing simulated and real data that suggest the proposed algorithm may be useful in neural network analysis of various phenomena in medicine and biology.

Algorithms↗
PubMed1996

Assessing risk in liver transplantation. Special reference to the significance of a positive cytotoxic crossmatch.

OBJECTIVE: The authors determined the impact of a positive cytotoxic crossmatch on the outcome of liver transplantation. SUMMARY BACKGROUND DATA: Liver allografts rarely undergo hyperacute rejection, but transplants performed across a positive cytotoxic crossmatch tend to follow a different clinical course, with higher intraoperative blood use, postoperative graft dysfunction, and, in some cases, graft loss. How this affects overall graft survival has not been determined. METHODS: The authors provide a retrospective analysis of 1520 liver transplants performed between November 1989 and December 1993, with a minimum follow-up of 1 year. All cases had a cytotoxic crossmatch using serum pretreated with dithiothreitol. RESULTS: There were 1390 negative crossmatch and 130 positive crossmatch cases. There was no difference in overall graft survival, although early survival rates were lower in the positive crossmatch group, with the maximum difference at 6 months: 0.76 (95% confidence interval, 0.74-0.78) for a negative crossmatch versus 0.68 (95% confidence interval, 0.61-0.77) for a positive crossmatch. These differences become negligible by the 2-year mark. Using stepwise logistic regression, the authors identified seven variables independently associated with outcome: 1) donor age, 2) donor gender, 3) prior liver transplant, 4) medical urgency status, 5) ischemia time, 6) indication for transplantation, and 7) primary immunosuppressant. CONCLUSIONS: The cytotoxic crossmatch is not statistically associated with overall graft survival after liver transplantation. However, early failure rates are higher in the positive crossmatch cases, a difference that disappears by the second year.

Adult↗
PubMed1996

Orthotopic liver transplantation in U.S. veterans under primary tacrolimus immunosupression.

The evolution and refinement of surgical techniques, per ioperative patient care, and immunosuppression hav~ estab~ished orthoto~ic li~er transplantation (OLTX) as a ~ighly successful therapeutic modality for patients wrth end-stage hver disease. In February 1989,Tacrohmus (Prograf®, formerly FK 506)was first used successfully at the University of Pittsburgh Medical Center to treat patients with rejection refractory to cyclosporine-based immunosuppression." Clinical trials utilizing Tacrolimus in solid organ transplantation followed, and in April of 1994 it was approved for use by the Food and Drug Administration,

Journal Article↗
PubMed1996

Risk factors and predictive indexes of early graft failure in liver transplantation.

A retrospective analysis of 462 consecutive liver transplantations has been carried out. These were divided into two groups, according to whether they failed within 90 days (Group I) or survived longer than 90 days (Group II). Twenty-five donor and recipient variables were analyzed. In the univariate analysis, the only donor variable that was significantly different between the two groups was age (45.3 +/- 16.9 years in Group I vs 37.9 +/- 15.4 years in Group II, p < 0.001). There were five recipient variables significantly associated with early graft failure: history of previous liver transplantations (p < 0.0001), United Network for Organ Sharing 4 status (p = 0.003), primary diagnosis (p = 0.001), preoperative serum creatinine (1.97 +/- 1.5 mg/dL in Group I vs 1.46 +/- 1.2 mg/dL in Group II, p = 0.005), and preoperative total serum bilirubin (13.5 +/- 14.4 mg/dL in Group I vs 8.4 +/- 11.4 mg/dL in Group II, p = 0.003). In the multivariate analysis, only three variables were independently associated with outcome: donor age greater than 45 years, abnormal (> 1.5 mg/dL) recipient preoperative creatinine, and a history of previous liver transplantation.

Adult↗
PubMed1995

Long-term results after liver transplantation for primary hepatic epithelioid hemangioendothelioma.

BACKGROUND: Hepatic epithelioid hemangioendothelioma (PHEHE) is a multifocal, low-grade malignant neoplasia characterized by its epithelial-like appearance and vascular endothelial histogenesis. The outcome of 16 patients treated with orthotopic liver transplantation (OLT) is the subject of this report. METHODS: A retrospective study of 16 patients with HEHE (7 men, 9 women) with ages ranging from 24 to 58 years (mean 37 +/- 10.6 years). Follow-up intervals ranged from 1 to 15 years (median of 4.5 years). RESULTS: Actual patient survival at 1, 3, and 5 years was 100, 87.5, and 71.3%, respectively. Disease-free survival at 1, 3, and 5 years was 81.3, 68.8, and 60.2%, respectively. The 90-day operative mortality was 0. Involvement of the hilar lymph nodes or vascular invasion did not affect survival. The 5-year survival of HEHE compares favorably with that of hepatocellular carcinoma at the same stage (stage 4A): 71.3 versus 9.8% (p = 0.001) CONCLUSIONS: The long-term survival obtained in this series justifies OLT for these tumors even in the presence of limited extrahepatic disease.

Adult↗
PubMed1995

Effect of donor age and sex on the outcome of liver transplantation.

We correlated donor and recipient factors with graft outcome in 436 adult patients who underwent 462 liver transplants. Donor variables analyzed were age, gender, ABO blood group, cause of death, length of stay in the intensive care unit, use of pressors or pitressin, need for cardiopulmonary resuscitation, terminal serum transaminases, and ischemia time. Recipient variables analyzed were age, gender, primary diagnosis, history of previous liver transplant, ABO blood group, cytotoxic antibody crossmatch, United Network for Organ Sharing (UNOS) status, and waiting time (except for the cross-match results, they were all known at the time of the operation). The endpoint of the analysis was graft failure, defined as patient death or retransplantation. Using multivariate analysis, graft failure was significantly associated with donor age, donor gender, previous liver transplantation, and UNOS 4 status of the recipient. The effect of donor age became evident only when they were older than 45 years. Livers from female donors yielded significantly poorer results, with 2-year graft survival of female to male 55% (95% CI, 45% to 67%); female to female, 64% (95% CI, 54% to 77%); male to male, 72% (95% CI, 66% to 78%); and male to female, 78% (95% CI, 70% to 88%). The only donors identified as questionable for liver procurement were old (> or = 60 years) women in whom the adverse age and gender factors were at least additive. However, rather than discard even these livers, in the face of an organ shortage crisis, their individualized use is suggested with case reporting in a special category.

Adult↗
PubMed1995

Building clinical classifiers using incomplete observations--a neural network ensemble for hepatoma detection in patients with cirrhosis.

One objective of liver transplant evaluation is to identify patients that harbor a hepatoma, but standard screening techniques are not sensitive enough. We trained neural network ensembles to predict the presence of hepatoma in patients with cirrhosis, based on information collected at the time of transplant evaluation. Network architecture and training were modified to handle missing observations. Three ensembles were trained: ensemble A using the subset with no missing observations (528 patients); ensemble B using the complete set, which included missing observations (853 patients); and ensemble C using the smaller subset, originally with complete data, but after a fixed number of observations were deleted (i.e., made "missing"). Ensemble performance on testing sets was very good. The areas under the ROC curves were 0.91, 0.89, and 0.90, for ensembles A, B, and C, respectively. Neural networks can successfully perform this classification task, and strategies can be developed that allow use of incomplete observations.

Adult↗