Peripheral Revascularisation Clinical Trial
Official title:
A Pilot Study on the Influence of an Optimized Heparin Regimen on the Hemostatic Environment Downstream From the Surgical Clamp in Major Vascular Surgery.
Hypothesis: Optimal anticoagulation defined as an Activated Clotting Time (ACT) of 300 to
350 seconds obtained by weight-adjusted doses of unfractionated heparin (UFH) will improve
the hemostatic environment downstream from the vascular clamp, provide better blood flow in
the distal bed following peripheral revascularization surgery.
Objectives: This study is designed to assess the effects of an optimized regimen of UFH on
the hemostatic environment downstream from the vascular clamp in major vascular surgery.
Peripheral revascularization surgery is usually performed in high-risk patients, suffering
from major comorbidities. Complications associated with vascular surgery include coronary
problems, arrhythmias, failure of revascularization and thrombosis. In order to prevent
these complications and possible re-interventions it is essential to optimize the
intraoperative path.
Unfractionated heparin is commonly used during arterial vascular surgery to prevent
thrombosis and accumulation of thrombi at the surgical site. UFH is administered before
clamping and blood flow interruption. However, the best heparin regimen to achieve optimal
anticoagulation for peripheral revascularization remains unknown, with current
recommendations based on data from the coronary literature and guidelines. Few studies have
assessed the effect of vascular clamping and blood flow interruption on the anticoagulation
in the distal vascular bed.
Perioperative monitoring of coagulation is important to diagnose potential causes of
hemorrhage and guide hemostatic therapies. Routine laboratory-based coagulation tests such
as prothrombin time (PT), International Normalized Ratio (INR), activated partial
thromboplastin time (aPTT) and platelet count are used to assess the patient's coagulation
status. However, the value of these tests has been questioned in the acute perioperative
setting for the following reasons: substantial delays between blood sampling and results,
tests performed on plasma rather than whole blood and lack of information on platelet
function.
The activated clotting time (ACT) is used to monitor anticoagulation and, indirectly,
concentrations of UFH. The ACT is measured on whole blood in cuvettes containing high
concentrations of activators, typically celite or kaolin. Modern methods are completely
automated. ACT measurement with point-of-care devices is used during procedures requiring
anticoagulation, such as cardiopulmonary bypass, interventional cardiology and hemodialysis.
In vascular surgery, the target ACT is not clearly defined and therefore not systematically
monitored.
Thromboelastography (TEG) is a bedside coagulation test that enables evaluation of all
components of hemostasis. An advantage of TEG over conventional tests of hemostasis is that
it is performed on whole blood, taking into consideration the role of interacting blood
elements. The TEG can also be adapted to different clinical situations. Activators such as
tissue factor, celite and thrombin can be added to whole blood to accelerate the analysis.
TEG cups coated with heparinase can also be used to degrade heparin without affecting other
coagulation parameters.
Ankle-brachial (ABI) and toe-brachial (TBI) indexes are currently used to evaluate patients
with peripheral arterial disease. These non-invasive tests provide information about
peripheral blood flow. The ankle-brachial index is the ratio of the systolic blood pressure
at the ankle to that measured at the brachial artery. The diagnostic limits of the ABI have
been confirmed in several large-scale studies. Conditions associated with medial
calcifications, such as diabetes, chronic kidney disease or advanced age, can lead to false
results due to vessel stiffness. The toe vessels are less susceptible to vessel stiffness,
which makes the TBI useful.
Methods:
Monitoring and postoperative analgesia will be left to the discretion of the attending
anesthesiologist. Surgery will be performed under general or regional anesthesia. For safety
reasons, patients under regional anesthesia will automatically be assigned to receive a
fixed dose of heparin.
UFH will be administered 2 minutes prior to vascular clamping according to randomization.
Blood samples will be collected at the following time points for ACT and TEG analysis:
following induction of anesthesia, 30 minutes after heparin administration, and on arrival
in the recovery room. Heparin will be neutralized with protamine if needed.
Intraoperative blood losses will be recorded. Administration of crystalloids, colloids and
blood products during surgery will be noted. Blood samples to assess cardiac troponin levels
will be collected in the recovery room and on the day following surgery. Ankle-brachial and
toe-brachial indexes will be measured preoperatively and postoperatively in the recovery
room. The occurrence of cardiovascular complications will be noted during the hospital stay.
The incidence of vascular re-interventions will be noted 30 days following surgery.
;
Allocation: Randomized, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Subject, Caregiver), Primary Purpose: Treatment
| Status | Clinical Trial | Phase | |
|---|---|---|---|
| Completed |
NCT02388867 -
Matrix Metalloproteinases in Patients With Critical Limb Ischemia Undergoing Surgical Revascularization
|
N/A |