Haemostasis Management of Patients Undergoing Abdominal Aortic Procedures Associated With High Bleeding Risk

Despite the fact that interventional therapy of vascular lesions (endovascular and hybrid procedures) is becoming more and more common, angioplasties involving major vessels have to be still managed as surgical procedures associated with extreme high demand for transfusion, this applies especially to acute rupture of aortic aneurysm, aortic dissection, aortobifemoral bypass and certain elective procedures where conventional open surgery is the only therapeutic option. Due the generalised atherosclerosis typical for most vascular surgical patients as well as the vulnerability of vessel wall, major blood loss has to be taken in account even during elective surgeries with minimally invasive techniques. In the event that excessive bleeding would occur, conversion to open surgery may be necessary, for this reason the preparation and perioperative care of patients undergoing interventional surgery have to be performed in the same manner as its is prescribed for open aorta operations.

The bleeding risk associated with the above surgical procedures is increased by the fact that the majority of patients affected are on a single or in some cases on double antiplatelet therapy, and/or receive prolonged anticoagulation treatment. Discontinuation of the treatments is expensive and, in case of indication for acute surgery, may not always be carried out.

Previous bleeding history, current drug therapy, evaluation of coagulation status (prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen) and blood count screening using conventional laboratory tests are part of preoperative preparations. Control of platelet function is always indicated in case of positive anamnesis (inherited or acquired thrombocytopathy, anamnestic information on bleeding complication, skin symptoms suggesting haemophilia), but is not performed routinely. Preoperative normalization of possible abnormalities as well as optimalization of drugs affecting haemostasis, so the reduction of bleeding risk to the minimum are of essential importance, however, we do not always have enough time for it. In cardiovascular surgery, withdrawal of aspirin and/or clopidogrel therapy increases the risk of thrombosis; continuation of aspirin and/or clopidogrel therapy increases the risk of bleeding. In our own practice, in case of elective vascular surgical procedures, aspirin therapy will be continued, but clopidogrel will be stopped 5-7 days prior to surgery, according to the European recommendations. When a patient with prolonged anticoagulant therapy is at high risk for embolism, his medication will be switched to low molecular weight heparin. In case the surgery is performed under ongoing antiplatelet therapy, transfusion of thrombocyte concentrate may also be necessary.

In the European guidelines, the application of transfusion algorithms and protocols incorporating predefined intervention triggers to guide haemostatic intervention during preoperative bleeding are recommended, as well as viscoelastic point-of-care tests (POCT). In lack of the latter, the Hungarian recommendation suggests the application of conventional monitoring assays, however, they give an poor assessment picture with associated with significant time delay, therefore have to be considered inadequate in case of excessive bleeding.

At first, it has to be definitely cleared whether the blood loss is caused by haemostatic or surgical source. In the meantime, however, maintenance of normothermia, prevention of acidosis and normalisation of ionized calcium level are of significant importance. In case of active bleeding the targeted value of systolic blood pressure is 80-100 mmHg, that of haemoglobin concentration 7-9 g/dl. The restrictive transfusion strategy is aimed at decreasing the number of allogeneic transfusions which are regarded as a form of tissue transplantation to the possible minimum.