Haemostasis Management of Abdominal Aortic Procedures
Haemostasis Management of Abdominal Aortic Procedures
Comparative study on efficacy of haemostatic therapy guided either by standard laboratory
 coagulation parameters or point-of-care testing in patients undergoing vascular surgical
 procedures. We investigate the amount of perioperative bleeding and the number of blood
 product used.

 Inclusion criteria Patients scheduled for elective and acute open aorta surgery or undergoing
 acute aorta surgery with minimally invasive techniques and were provided treatment in the
 operating theatre and/or ICU attached to perioperative care, they must be at least 18 years
 of age and written informed consent was obtained from the patient or his/her legal
 representative.

 Randomisation technique Patients will be randomly assigned to each of two treatment groups
 using sealed envelopes. In group 1 (G1) haemostasis strategy guided by conventional
 coagulation tests, while in group 2 (G2) transfusion algorithms guided by point-of-care (POC)
 tests will be carried out.

 Sampling techniques and measurements

 For assessment of monitored parameters shall be used arterial or venous blood depending on
 the catheter placed preoperatively. In case of the above mentioned vascular surgical
 procedures, all patients will receive arterial cannula routinely, and, depending on the
 extension of procedure, as appropriate, a central venous catheter will be inserted as well.
 Sampling in the patient groups shall be performed as follows:

 -  pre- and postoperative evaluation of standard laboratory parameters in all patients

 -  evaluation of standard laboratory parameters and arterial Astrup test during and after
 surgery in group 1, if the blood loss volume reaches 1,5 ml/kg/minute during 20 minutes

 -  in case of elective surgery: thromboelastometry and arterial Astrup test during and
 after surgery in group 2 if the blood loss volume reaches 1,5 ml/kg/minute during 20
 minutes

 -  in case of acute surgery: thromboelastometry and arterial Astrup test before, during and
 after surgery in group 2

 -  in case of positive anamnesis, preoperative platelet aggregation test in both groups
 Besides the above samplings, routine lab tests (blood gas, blood count, sodium (Na),
 potassium (K), parameters of renal and liver function, clotting and inflammation, lactic
 acid, blood sugar) will be performed every day as usual during intensive therapy.
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.

 The first step for optimal restoration of the function of haemostasis system has to be the
 regulation of the concentration of fibrinogen in the blood plasma, using either conventional
 laboratory tests or point-of-care testing. Fibrinogen is synthesized in the liver and will
 not be stored; it has the highest concentration among all coagulation factors (3 g/l). During
 blood loss, its concentration decreases and reaches the crucial level (<2 g/l) most rapidly.
 It is essential that besides erythrocyte (RBC) concentrate fresh frozen plasma (FFP) has also
 to be given (RBC:FFP=2:1) in a timely manner, in a fixed proportion. In case of excessive
 blood loss and transfusion, administration of thrombocyte concentrate is also necessary.

 Aim of the study Comparative study on efficacy of haemostatic therapy guided either by
 standard laboratory parameters or point-of-care testing in patients undergoing vascular
 surgical procedures.

 Study design Prospective randomised clinical trial

 Patients Inclusion criteria Patients scheduled for elective and acute open aorta surgery or
 undergoing acute aorta surgery with minimally invasive techniques and were provided treatment
 in the operating theatre and/or ICU attached to perioperative care, they must be at least 18
 years of age and written informed consent was obtained from the patient or his/her legal
 representative.

 Randomisation technique:

 Patients will be randomly assigned to each of two treatment groups using sealed envelopes:

 -  Patient group 1: haemostasis strategy guided by conventional coagulation tests.

 -  Patient group 2: transfusion algorithm guided by viscoelastic POC tests and algorithms.

 Exclusion criteria:

 -  patients under 18 years of age

 -  informed consent not provided

 -  congenital coagulation factor deficiency

 -  congenital thrombocytopathy

 Discontinuation criteria:

 -  death of patient

 -  withdrawal of consent by the patient or his/her relative

 Assessment of parameters Conventional coagulation laboratory tests In the preanalytical phase
 consisting of steps within and outside the laboratory we have to face a great number of
 influence factors which can be of critical importance concerning the result of the lab test
 (e.g. quality of blood sampling tube, method of sampling, appropriate amount of sample,
 haemolysis, lipaemia). The time-consuming nature of these tests may cause problems primarily
 in case of massive bleeding. It is not the same blood that circulates in the patient's
 organism by the time we receive the result. Another disadvantage is that only a few steps of
 coagulation cascade are investigated. The tests are performed using the plasma separated by
 centrifugation of blood. Information regarding reactions on the surface of activated
 platelets, fibrin polymerisation, clot firmness and fibrinolysis cannot be obtained.

 Routinely monitored parameters:

 -  Prothrombin time (PT)/ International normalized ratio (INR): extrinsic coagulation
 pathway and final common pathway.

 -  Activated partial thromboplastin time (aPTT): intrinsic coagulation pathway and final
 common pathway.

 -  Thrombin Time (TI): reflects the speed of conversion of fibrinogen to fibrin.

 -  Fibrinogen: amount of fibrinogen in the blood plasma.

 -  Blood count (platelet number ) Point-of-care methods Point-of-care tests using whole
 blood provide information within a short time, including the patient's haemostatic
 status. These benefits are associated with many advantageous features such as small
 place demand, simply use, no need of maintenance; centrifugation is not required, the
 reagents are ready to use, some tests can be stored at room temperature.

 Viscoelastic tests Viscoelastic tests used for global haemostasis assays are
 thromboelastography (TEG) and rotational thromboelastometry (ROTEM). The original method has
 been developed by Harter in 1948 in Heidelberg, initially for analysis of not anticoagulated
 blood. Viscoelastic tests provide information on primary haemostasis (platelet adhesion and
 aggregation), thrombin generation, thrombus formation and fibrinolysis, thus, on every steps
 of haemostasis. Informative analysis in case of patients who are on prolonged heparin therapy
 can also be accomplished.

 Disadvantages of viscoelastic coagulation POC tests include indirectly obtained information
 on the platelet function, furthermore, the role of endothelium is not recognizes and the
 characteristics of blood flow are disregarded.

 During TEG/ROTEM analysis a pin is dipped into a sample of whole blood - to be given in a
 cuvette of not physiological surface - and the coagulation becomes activated. Cuvette and
 sensor move relative to each other. In TEG, the movement is initiated from the cup, in ROTEM
 the pin is oscillated and the cuvette remains fixed. Increasing viscosity of blood and
 enhancing stability of clot being formed induce a change of elasticity. This process affects
 the motion of the sensor that is detected by light reflection changes. The two methods are
 equivalent and can be considered as mutual alternatives.

 The tested parameters provide information on the starting time of clotting process, the clot
 formation, stabilisation and quality as well as fibrinolysis.

 The efficacy of viscoelastic POC tests have been confirmed by several clinical studies,
 primarily in the field of cardiac surgery, liver transplantation, and traumatology. As per
 the published data, the number of allogeneic transfusions and postoperative blood loss
 decreased significantly.

 Parameters of ROTEM analysis:

 -  Clotting time (CT): Time elapsed from beginning of test until the starting time of
 clotting.

 -  Clot formation time (CFT): Time to reach 20 mm amplitude from the starting time of
 clotting.

 -  Maximum clot firmness (MCF): Provides information on firmness of clot.

 -  Maximum lysis (ML): Provides information on loss of clot firmness.

 Analysis of platelet aggregation Platelet aggregation inhibitors (e.g. aspirin
 [acetylsalicylic acid], ticlopidine, clopidogrel), significantly decrease the aggregation
 ability of platelets or may even completely terminate it. During examination, several
 platelet aggregation agents will be added to the platelet-rich plasma prepared appropriately
 and the aggregation induced this way will be measured using an impedance aggregometer. The
 device measures the change of electric resistance between the two electrodes dipped into the
 blood sample in relation to time.

 Most commonly it is applied for adjustment of antiplatelet therapy and monitoring the
 efficacy of the substance. It is suitable for highly sensitive detection of aspirin,
 clopidogrel, prasugrel and IIb/IIIa-receptor antagonists.

 Now there are literary data also in respect of its efficacy in respect of predicting the
 probability of coronary stent thrombosis, as well as that of bleeding and the need of
 transfusion in cardiac surgery. Still, it is not recommended to routinely use this device in
 the perioperative care of any and all patients. At the same time, however, in case of
 patients at risk (e.g. positive bleeding anamnesis, treatment with platelet-aggregation
 inhibiting drugs) it is able to identify and to help diagnose a possible platelet
 disfunction.

 Routinely monitored parameter:

 • Area Under the Curve (AUC): Indication of platelet activity. The results calculated by the
 software are the mean values of data of the several curves.
Inclusion Criteria:

 -  patients scheduled for elective and acute open aorta surgery or undergoing acute aorta
 surgery with minimally invasive techniques and were provided treatment in the
 operating theatre and/or ICU attached to perioperative care

 -  they must be at least 18 years of age

 -  written informed consent was obtained from the patient or his/her legal
 representative.

 Exclusion Criteria:

 -  patients under 18 years of age

 -  informed consent not provided

 -  congenital coagulation factor deficiency

 -  congenital thrombocytopathy