Ralf Knöfler

Clinical importance of prothrombotic risk factors in pediatric patients with malignancy--impact of central venous lines.

Abstract To evaluate the role of inherited thrombophilia in the development of central venous line (CVL)-related thrombosis, the following parameters were determined in 77 pediatric-oncologic patients with CVL: activated protein C (APC)-ratio, factor V (FV) G1691A and prothrombin G20210A mutation, protein C, protein S, antithrombin, coagulation factor XII, lipoprotein (a) and homocysteine. An inherited prothrombotic risk factor was found in 17 patients (23%). Four out of 14 patients with a single defect (hyperlipoproteinemia, heterozygous FV G1691A and prothrombin G20210A mutation, protein C deficiency type I) and all three patients with combined defects (heterozygous FV G1691A mutation combined with heterozygous prothrombin G20210A variant, protein S deficiency or hyperlipoproteinemia) suffered from CVL-related thrombosis. In 11 out of 77 patients (14%) a CVL-related thrombosis was detected. In 2 children thrombosis occurred a few days after asparaginase therapy and in another three thrombosis was associated with CVL-related septicemia caused by Staphylococcus epidermidis. After removal of CVL, thrombosis was detected in 5 children, in 2 without clinical symptoms but in the presence of inherited prothrombotic risk factors. Conclusion The present study demonstrates the clinical importance of CVL in combination with inherited thrombophilia in the development of thrombosis in pediatric-oncologic patients. Before or shortly after insertion of CVL, patients should be tested for the presence of factor V G1691A mutation, prothrombin G20210A variant and increased lipoprotein (a) values.

Release of adenosine triphosphate by adenosine diphosphate in whole blood and in erythrocyte suspensions.

In whole blood samples from thrombocytopenic patients, large amounts of ATP were released by ADP, exceeding the level obtained with samples from normal persons by far. Because we suspected that the high potential of ATP in erythrocytes would be the main source for this phenomenon, the release of ATP by ADP was measured in whole blood samples from normal, thrombocytopenic, and leukocytopenic persons and in suspensions of washed erythrocytes. The release was recorded by a Whole Blood Lumi‐Aggregometer type 500 VS (Chrono‐Log Corporation, Havertown, PA) using the luciferin‐luciferase system. Not only in samples from thrombocytopenic persons but also with normal platelet count, increasing amounts of ATP were released with increasing ADP concentrations, finally exceeding the ATP releasable from thrombocytes by thrombin. The amounts of ADP required to match the ATP release of thrombin were closely correlated with the platelet counts in the samples. With lower platelet counts, the release mechanism from erythrocytes could be stimulated more easily by low concentrations of ADP. The binding of ADP to platelets occurred with ostensibly higher affinity. The phenomenon of overshooting ATP release was also observed in samples from extremely leukocytopenic patients. A very large release of ATP was also achieved in suspensions of washed erythrocytes. In this way our hypothesis of ATP release from erythrocytes by ADP was confirmed again. The mechanism of the release from erythrocytes remains unclear. We speculate that its purpose is to regulate extracellular nucleotides in the circulating blood. Am. J. Hematol. 56:259–265, 1997.

CRITICAL EVALUATION OF THE QUANTIFICATION OF ATP RELEASE REACTION IN WHOLE BLOOD

The influence of erythrocyte and thrombocyte content on the release of adenosine triphosphate (ATP) in whole blood was tested. Citrated blood from 39 healthy persons was diluted gradually. The release reaction was induced by arachidonic acid (1.25 mM), adenosine diphosphate (ADP; 30 microM) and collagen (1.0 and 5.0 micrograms/ml). The peak of the obtained curves was transformed into percent values of the maximal deflection by the undiluted sample (PEAK IN RELATION) and into ATP concentrations (ABSOLUTE PEAK). By rising dilution an increase of the peak in relation with all inducers was observed which was mainly due to the luminescence-optical effect. As expected the absolute peak decreased but only under arachidonic acid and collagen. Under ADP despite of the rising dilution constant amounts of ATP were released suggesting an additional release from other blood cells. High ATP release curves in response to ADP were observed in patients with pancytopenia and with thrombocytopenia when compared to health persons. ADP seems not to be suited for the measurement of ATP release reaction in whole blood. Collagen at a final concentration of 1.0 micrograms/ml was found as the optimal inducer. The ATP standard is essential for the quantification of release reaction.

Duodenocolonic Fistula As A Rare Complication of Intestinal Burkitt Lymphoma in a Three-Year-Old Boy

BACKGROUND Burkitt lymphoma (BL) in children often presents with abdominal localization. Intestinal perforations have been described mainly during treatment. We report on a three-year-old patient with abdominal BL who was diagnosed with a duodenocolonic fistula. CASE REPORT A three-year-old boy presented with diarrhea, crampy abdominal pain, and a four-week history of loss of appetite and weight. Ultrasound and MRI detected a colonic tumor forming a duodenocolonic fistula which was verified by gastroduodenoscopy. A surgical biopsy revealed BL. The stage III BL with low LDH was treated with four courses of BFM-type short-pulse chemotherapy. After two courses of chemotherapy the patient developed a mechanic ileus. A segmental resection of a short segment of the colon at the right flexure carrying the residual tumor mass with cicatricial stenosis and fistula followed by colonic end to end anastomosis and covering of the fistula by omentum major were carried out without complication. 15 days after surgery, two additional courses of chemotherapy could be administrated and the boy is in ongoing remission and free of any symptoms with a follow-up interval of 18 months. CONCLUSIONS Duodeonocolonic fistula at presentation in a child with abdominal BL is extremely rare. Delayed surgery after size of the tumor bulk has been reduced by chemotherapy might represent a risk adapted approach. However, due to limited experience with duodenocolonic fistulas even in larger pediatric lymphoma trials any decision has to be based on the problems to be faced in individual cases.

Endothelin-1 as One of the Mediators of the Interaction between Endothelium and Platelets in Humans

Endothelin-1 (ET-1) is an endothelium-derived peptide with multiple functions affecting the cardiovascular, renal, neuroendocrine, pulmonary and gastrointestinal system1,2. Elevated plasma levels of ET-1 were found in diseases associated with the activation of platelets, e.g. myocardial infarction, disseminated intravascular coagulation and diabetes. These findings prompted us to investigate the ET-1 effect on platelet aggregation in human whole blood and in platelet rich plasma (PRP).