Regional Anaesthesia in Patients Receiving Anti-Thrombotic Therapy

Abstract

Anaesthetists are often faced with the question of whether the risks of regionalanaesthetic techniques are increased when performed on patients withabnormalities of coagulation and, if so, whether they are so increased thatthe techniques should be modified or avoided. This is not only because thepopularity of regional anaesthesia is on the rise but also because the use ofanticoagulant drugs in the prevention of venous thromboembolism isexpanding, as is the number of different drugs in use. So, concise guidelines are presented to relate abnormalities of coagulation as a result of the administration of drugs to the consequent haemorrhagic risks associated with neuraxial and peripheral nerve blocks. To apply the regional anaesthetic technique in patients receiving anti-thrombotic therapy, a good perception of the neuranatomy and the vascularity in the area of the regional anaesthesia performance, beside the physiology of haemostasis and the pharmacological action of each anti-thrombotic drug have to be taken in mind by the anaesthesiologist. Also the optimum technique to apply the regional anaesthesia has to be chosen according to its efficacy to perform the block with minimal risk of vascular injury and according to its availability in the operation theatre. These regional anaesthesia techniques include: field block technique, purely anatomical technique, nerve stimulation technique and ultrasound guided technique. The anti-thrombotic drugs are classified into: antiplatelets, anticoagulants and fibrinolytic agents. Each of them has several types of drugs that affect the coagulation through different ways and variable durations. The antiplatelets affect the platelet functions by inhibiting specific receptors or enzymes, and it’s classified into thromboxane A2 inhibitors, P2Y12 receptor antagonists, phosphodiesterases inhibitors and glycoprotein IIb/ IIIa antagonists. The anticoagulants affect mainly the coagulation cascade by inhibiting the action or decreasing the formation of one or more of the coagulation factors. Heparins and Warfarin are the most commonly used anticoagulants while low-dose Aspirin and Clopidogrel are the most commonly used antiplatelets. That’s why every drug as a special guidelines while taking it perioperatively. Also many long-acting anti-thrombotic drugs have to be bridged by other short-acting anti-thrombotic medications to decrease the incidence of thrombus formation in high risk patients of thrombosis, and this bridging therapy has also its guidelines. Although the regional anaesthesia is contraindicated with fibrinolytic agents, guidelines were put to minimize the risk of bleeding if the fibrinolytic agents have to be taken before or after applying the block or catheter specially in the emergency situation as pulmonary embolism. The major complications during applying regional anaesthesia while taking anti-thrombotic therapy is haematoma formation. Haematoma must be detected and managed as early as possible to prevent permanent or fatal affection as in spinal haematoma or haemothorax.