AMBULANT MONITORING OF HEPARIN AND HAEMOSTASIS DURING VASCULAR SURGERY

Heparin has been used to prevent thranbotic events in vascular surgery for more than 45 years. Heparin-activity monitoring has been advocated, but is not usually performed routinely. A direct method for measuring heparin anti-Xa activity with a chromogenic substrate is difficult to perform during surgery for logistic reasons or lack of suitable equipment. The use of this assay, however, could give us a better insight in the kinetics of heparin during vascular surgery. To use this heparin-activity assay during vascular surgery in ccmbinatian with clotting assays and a antithrcmbin III-assay, one should be able to perform both kinetic and end-point methods in a rapid, simple and reproducable manner. Therefore, in this study we tested the FP-910 coagulation analyser (Labsysterns), in which both methods can be assayed. It was used during 20 consecutive abdominal aorta reconstruction operations, in which a standard dose of 4-5,000 IU heparin was given intravenously. Bloodsairples were taken at several intervals, APTT, PT, ThT, fibrinogen, AT-III and heparin could be assayed within 30 min. after a bloodsanple was taken, with good intravariations (1.8%, 3.3%, 3.9%, 7.5%, 4.9% and 5.0%, ersp.) and intervariations (5.0%, 4.5%, 3.8%, 11%, 8.9% and 6.1%, resp.). Heparin activity alone could be measured within 10 min. The preoperative sanples shewed no abnormalities. Heparin activity response 5 min. after injection showed a wide variation (0.2-2.8 IU/ml) and this was also seen in the individual heparin elimination rates. In one case a thranbotic complication occured during a period of low heparin activity (0.1 IU/ml). In another patient a combined decrease of fibrinogen and AT-III, to 30% and 37% resp, of the initial value was seen. These results showed that, during vascular surgery, a close monitoring of heparin activity with a anti-Xa activity assay, together with other haemostasis parameters is necessary, and possible in a rapid and simple way, using the FP-910 coagulation analyser.