Anti-platelet factor 4/heparin antibodies in patients with impaired graft function after liver transplantation

BACKGROUND

Heparin, the standard perioperative anticoagulant for the prevention of graft vessel thrombosis in patients undergoing liver transplantation (LT), binds to the chemokine platelet factor 4 (PF4). Antibodies that are formed against the resulting PF4/heparin complexes can induce heparin-induced thrombocytopenia. LT is a clinical situation that allows the study of T-cell dependency of immune responses because T-cell function is largely suppressed pharmacologically in these patients to prevent graft rejection.

OBJECTIVES

To investigate the immune response against PF4/heparin complexes in patients undergoing LT.

PATIENTS AND METHODS

In this prospective cohort study, 38 consecutive patients undergoing LT were systematically screened for anti-PF4/heparin antibodies (enzyme immunoassay and heparin-induced platelet aggregation assay), platelet count, liver function, and engraftment.

RESULTS

At baseline, 5 (13%) of 38 patients tested positive for anti-PF4/heparin IgG (non-platelet-activating) antibodies. By day 20, an additional 5 (15%) of 33 patients seroconverted for immunoglobulin G (two platelet-activating) antibodies. No patient developed clinical heparin-induced thrombocytopenia. Two of six patients with graft function failure had anti-PF4/heparin IgG antibodies at the time of graft function failure. Graft liver biopsy samples from these patients showed thrombotic occlusions of the microcirculation.

CONCLUSIONS

Anti-PF4/heparin IgG antibodies are generated despite strong pharmacologic suppression of T cells, indicating that T cells likely have a limited role in the immune response to PF4/heparin complexes in humans.

[Diagnosis and surgical treatment of pancreatic cancer]

Despite sustained efforts, intensive research has not been proven successful to reveal risk factors, which relevantly influence early diagnostics or effective treatment of pancreatic carcinoma. Principally, it must be noted, that currently no ideal tumor marker exists for the (early) detection of pancreatic carcinoma. The most important imaging modalities are high-resolution computed tomography, abdominal ultrasound, and endosonography. Surgical procedures in therapy have become more and more standardised and lead to a decrease in morbidity and mortality on the one hand and to an increase in resectability on the other hand. Pylorus-preserving partial pancreaticoduodenectomy is the treatment of choice for a tumor of the pancreatic head, whereas resection of the left pancreas (including splenectomy) is the standard therapy for carcinomas of the pancreatic tail. In all cases, a local systematic lymphadenectomy is mandatory; hence the prognostic gain of an extended lymphadenectomy remains indeterminate. An infiltration of mesenteric and portal veins does not prevent respectability, as long as by venous resection an R0 status can be achieved. However arterial involvement in general excludes resection. Patients with marginally resectable or locally non-resectable tumors should be recruited into neoadjuvant radiochemotherapy trials since one third of these patients could be considered for potentially curative resection. However the majority of pancreatic cancer patients show locally unresectable or metastasized disease and therefore palliative treatment concepts are needed. Both, endoscopic or percutaneous stenting procedures and operative bypass surgery, are safe and reach high success rates.

[Unresectable pancreatic cancer--palliative interventional and surgical treatment]

In most cases pancreatic cancer appears in a non-curatively resectable stage at time the diagnosis is made. Thus, palliative treatment concepts come to the fore in these patients. Patients without metastases, but presenting with marginally resectable or locally non-resectable tumours should not be treated in a palliative therapeutic scheme. These patients should be enrolled in neoadjuvant radiochemotherapy trials. After finishing treatment and restaging, a potentially curative resection can be achieved in approximately one-third of these patients. Within the scope of the best possible palliative care, excision of metastases together with resection of the primary cancer represents a therapeutic option to be contemplated in selected cases. For distinct locally unresectable or metastasised advanced pancreatic cancer, treatment of bile duct or duodenal obstruction is an essential part of the comprehensive palliative therapy. However, both endoscopic / percutaneous stenting procedures and surgical bypass makeshifts constitute safe and highly effective therapeutic alternatives in this context. In the case of operative drainage of the biliary tract the prophylactic creation of a gastro-intestinal bypass (double bypass) is recommended. The decision on a surgical versus an endoscopic procedure for palliation depends considerably on the tumour stage and the estimated prognosis and has to be determined interdisciplinary and individually in each case.

Liver transplantation in the rat: single-center experience with technique, long-term survival, and functional and histologic findings

OBJECTIVE

Orthotopic liver transplantation (OLT) in rats is frequently used as an experimental model. Numerous surgical techniques have been developed that enable the investigator to conduct clinically relevant studies. The objective of this study was to develop a rat model of acute and chronic rejection, to explicitly study technical modifications of vascular anastomoses with precision, and to examine histopathologic and functional changes in the graft.

MATERIALS AND METHODS

With DA-(RT1av1) rats as donors and Lewis-(RT1) rats as recipients, arterialized OLT was performed using a combined suture, cuff, and splint method. Recipients were divided into 5 groups: syngeneic control rats (group 1), allogeneic control rats (group 2), allogeneic OLT rats with low-dose tacrolimus (FK506) immunosuppression (group 3), allogeneic OLT rats with high-dose tacrolimus immunosuppression (group 4), and allogeneic OLT rats with high-dose tacrolimus immunosuppression and retrograde reperfusion via the infrahepatic caval vein (group 5). After OLT, serum parameters were determined and hepatic biopsy specimens were sampled. We examined the effects of acute rejection with or without immunosuppression therapy at histopathologic evaluation.

RESULTS

Liver grafts in syngeneic and allogeneic rats (groups 1, 2, 4, and 5) demonstrated normal serum parameters and histopathologic findings at 10 days after OLT, and 93% survival at 3 months. The simplified technique using 1 suture and 2 cuff anastomoses provided the best short- and long-term survival after OLT in all groups. Retrograde perfusion via the infrahepatic caval vein resulted in lower postoperative liver enzyme values.

CONCLUSION

The present model is feasible, enabling comprehensive preclinical experimental research on liver transplantation. Furthermore, we provide helpful instructions for learning this surgical technique.

[Middle segmental pancreatic resection: an organ-preserving option for benign lesions]

Benign and low malignant tumors of the middle pancreatic segment can be resected by extended pancreaticoduodenectomy or distal pancreatic resection. Both procedures involve unavoidably extensive loss of normal pancreatic parenchyma, leading to deteriorated endocrine and exocrine pancreatic function. Segmental pancreatic resection represents an organ-preserving surgical procedure. Normal pancreatic tissue can be preserved as only the tumor with a pancreatic segment is resected. Several reports confirm lower mortality and minimal risk of postoperative endocrine or exocrine insufficiency than with standard pancreatic resections. The indication should be limited exclusively to benign or low malignant pancreatic tumors, metastases from other tumors, and focal chronic pancreatitis, as this type of resection cannot be deemed oncologic. Segmental pancreatic resections are technically more demanding and therefore should be performed in experienced centers.

Nitric oxide inhibition and consecutive Aspisol application show a prolonged survival of orthotopic transplanted livers in a rat model

BACKGROUND

It is generally accepted that nitric oxide (NO) plays a crucial role in acute rejection caused by inflammatory responses. Therefore, the purpose of this study was to investigate the effect on survival following arterialized orthotopic rat liver transplantations (o-RLTx) of NO inhibition and consequent blockade of platelet aggregation by application of Aspisol.

MATERIALS AND METHODS

Inbred LEWIS-(RT(1)) rats underwent arterialized o-RLTx under ether anesthesia with DA-(RT1av1) rats as organ donors. After liver transplantation, serum parameters were determined and hepatic biopsy specimens were sampled on postoperative days 5, 8, 10, 30, and 90. Sixty-one rats were divided into 5 groups: syngenic controls (group I, n = 12); allogenic controls (group II, n = 11); allogenic with FK506 immunosuppression (group III, n = 12); allogenic with AGH-treatment (group IV, n = 13); and allogenic with AGH/low- dose Aspisol treatment for 5 days after liver transplantation (group V, n = 13) (Bayer, Leverkusen, Germany).

RESULTS

Rats of group V with AGH/low-dose Aspisol treatment showed significantly longer graft survival (18.2 days +/- 1.8 days) compared with group II rats with untreated grafts (11.3 days +/- 1.7 days) the allogenic group IV with AGH treatment (11.2 days +/- 1.8 days; P < .05). Histological examination revealed moderate graft rejection among the AGH-treated group IV; however, marked platelet aggregation in sinusoids was present, which was not observed in the AGH/low-dose Aspisol-treated animals (group V).

CONCLUSION

Our data suggested that simultaneous treatment with AGH/low-dose Aspisol leads to a significant increase in survival and inhibition of platelet aggregation in the graft after orthotopic liver transplantation.

High-risk constellation in living renal transplantation

There is only limited information about recipient risk factors for graft survival in living- donor kidney transplantation. This study aimed to investigate prognostic factors and their impact on living-related and unrelated renal transplant recipients. From October 2000 until October 2004, 81 adult living-related renal transplantations were performed at our institution. Using multivariate analysis, the association of the following variables with kidney graft outcome was studied: ages of donors and recipients, gender and body mass index, cold and warm ischemia, HLA mismatches, identity and compatibility of blood group, duration of dialysis, cytomegalovirus (CMV) status, recipient original disease, surgical and general complications, and status of retransplantation. Multivariate analysis revealed significant reduction of graft function and graft survival in recipients with retransplantation, more than 4 mismatches, and a high body mass index. Thus, living-donor kidney transplantation can be regarded as a safe and standardized operation relating to surgical technique, but further consideration of the recipient body mass index and the number of mismatches are recommended during the preparation for transplantation.