Changes of activated partial thromboplastin time during constant intravenous and fixed intermittent subcutaneous administration of heparin.

Marked circadian variations in the activated partial thromboplastin time (APTt) during continuous heparin infusions for thromboembolic episodes have been reported in a French study. The aim of the present study was to test if these variations could be reproduced in a Swedish population. The frequency spectrum variations in APTt values were analysed with the Prony and the statistical Pearson product momentum correlation coefficient methods. In seven patients with pulmonary embolism, APTt was checked every fourth hour during 48 h of continuous, constant heparin treatment. In only one patient was a distinct circadian variation of APTt values seen. In six patients with venous leg thromboses, treated with s.c. heparin, marked variations in APTt were noticed over periods of 12 h. These variations paralleled the regular s.c. injections of heparin every twelfth hour. The results of the present study could not confirm the marked circadian variations in APTt reported in an earlier French study during continuous heparin infusions, except in one patient.