SummaryThe objective of the study was to investigate possible diurnal rhythms in coagulation tests during a continuous intravenous infusion of unfractionated heparin. Six volunteers participated in the study, which was divided in a treatment (500 U heparin/h for 30 h) and a control experiment. Under basal conditions, no rhythm was found in coagulation tests. During heparin treatment, APTT, thrombin clotting time and anti-Xa activity showed a greater anticoagulant effect at night, with a striking decrease in the morning.In a search for the explanation of this phenomenon we looked for diurnal variations in the urinary excretion of heparin, in the plasma concentrations of antithrombin III and platelet factor 4, and in the effect of heparin added to the plasma samples in vitro. None of these studies provided the explanation.

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A continuous intravenous infusion of unfractionated heparin has a maximum anticoagulant effect between 04.00 and 8.00 hours and a minimum effect at noon. For individual patients the moment of minimum and maximum effect varies widely. Because the most impressive changes occur between 06.00 and 08.00 hours, laboratory control can best be performed at fixed times, e.g. at 10.00 and at 22.00 hours.

We report the case history of a 35-year-old male patient with lymphoblastic non-Hodgkin's lymphoma who acquired a systemic infection with Fusarium nygamai during the granulocytopenic phase of cytostatic treatment. The patient survived this infection after haematological recovery and treatment with intravenous amphotericin B (total dose 543 mg). Subsequent chemotherapy courses were not complicated by fungal infections. A recent trip to Egypt and severe chemotherapy-induced mucositis were probably the major causes of this severe infection.