Urokinase activity after freezing: implications for thrombolysis in intraventricular hemorrhage

The retention of urokinase activity after frozen storage was studied. Urokinase powder was reconstituted aseptically in sterile water for injection or preservative-free 0.9% sodium chloride injection to a final concentration of 5000 IU/mL. Samples were stored in 5-mL plastic syringes at -20 or -70 degrees C for up to six months. Samples containing urokinase 25,000 IU/mL were similarly prepared by using sodium chloride injection as the diluent and were stored frozen at the same temperatures for up to 93 days. Urokinase activity was measured with a chromogenic assay at each test interval. Samples were also cultured after thawing to evaluate their potential to support microbial growth. The activity of urokinase at either concentration did not change appreciably during the study period. The method of thawing-at room temperature or in a refrigerator-had no effect on urokinase activity. No microbial growth was observed. Urokinase 5000 IU/mL did not show any changes in activity when reconstituted with sterile water for injection or 0.9% sodium chloride injection and frozen for up to six months. Urokinase 25,000 IU/mL in sodium chloride injection was also stable after 93 days of frozen storage.

Prospective double-arm study of fibrinolysis in surgical patients

BACKGROUND

During surgery, the balance between thrombosis and fibrinolysis is altered. Methods reported to increase fibrinolysis, such as compression devices, may reduce venous thrombosis. However, there are no prospective studies comparing methods and the effect on fibrinolysis.

MATERIALS AND METHODS

In a prospective study, general surgical patients were randomized to either sequential compression devices (Group 1) or subcutaneous heparin (Group 2), and fibrinolysis factors were measured in order to determine the effect on the fibrinolysis system. Blood samples were drawn at a similar time of the day with the tourniquet off. Specifically, t-PA antigen, plasminogen activator inhibitor-1 (PAI-1), and D-dimer were measured preoperatively (preop) and on Postoperative Days (POD) 1 and 7 by the ELISA method. Fibrinolysis factors were reported as the mean +/- SD and as percentage change from preoperative values. Noninvasive vascular studies were performed preop, and on POD 1, 7, and 30, by an examination of the infrainguinal venous system and external iliac veins in bilateral lower extremities. Nonambulatory patients were excluded from the study and DVT prophylaxis methods were initiated at surgery and used through POD 2.

RESULTS

For the 136 patients in the study, there were no differences in clinical characteristics such as age, surgical time (all > 60 min), anesthesia type (general or spinal), type of surgical procedure, or other risk factors for DVT. Two DVTs occurred at POD 1 and 30 (both Group 2), and one pulmonary embolism in each group (POD 7 for Group 1; POD 1 for Group 2). For subjects without thrombosis, D-dimer changes were parallel for both groups, increasing through POD 7. Similarly, t-PA antigen levels rose from baseline on POD 1 in both groups, with a return toward baseline by POD 7. The PAI-1 levels increased on POD 1 in both groups, but severalfold more in Group 1 (compression devices). The elevation in PAI-1 decreased by 50% in Group 1 by POD 7, while values returned to normal in Group 2. These changes were not significant using the Mann-Whitney test. Only three patients had thrombotic episodes so that data on changes in fibrinolysis factors are difficult to compare with the larger group.

CONCLUSIONS

This is the first report of a prospective, randomized comparison of fibrinolysis factors using sequential compression devices in comparison to low dose unfractionated heparin in general surgical patients, and comparing postoperative values to preop. Both groups showed an enhanced fibrinolysis by elevation in t-PA antigen and D-dimer on POD 1, as expected when fibrinolysis occurs. While PAI-1 and t-PA work in parallel, the marked elevation of PAI-1 on POD 1 (although only slightly above reference values) and continuing into POD 7 for subjects using compression devices requires further inquiry. The elevation of PAI-1 in the face of elevated t-PA and D-dimer has been reported, but the comparison between patients using sequential compression devices and mini-dose heparin has not been reported. The reason for the elevation requires additional study into other influences on the synthesis, secretion, and/or function of PAI-1 that do not affect t-PA.