Periopertative management of the anticoagulated acute surgical patient

There is an apparent dilemma in managing the patient with anticoagulation and antithrombotic treatment. The indications for anticoagulation are sometimes absolute – as in the treatment of patients with mechanical heart valves – and in many instances strongly indicated as in patients with atrial fibrillation. The anaesthesiologist and surgeon strive to optimize haemostasis and to reduce perioperative bleeding. In the acute patient the opposite priorities will surface and an integrated approach is needed to ensure the optimal patient treatment. Stopping or reversing the effective anticoagulation can lead to disaster with thrombosis of mechanical valves or thromboembolism. A rebound effect from abrupt cessation of therapy can increase the tendency to thrombosis. Bridging of antithrombotic therapy prior to surgery is substituting oral anticoagulant therapy with heparin or low-molecular-weight heparin (LMWH) until full anticoagulation can be resumed. Such bridging will often be necessary but may promote bleeding. The anaesthesiologist will have to decide whether to use regional anaesthesia or other means of perioperative pain relief. Risk of thromboembolism. An anticoagulated patient coming for surgery should undergo a thorough evaluation of the risk of thromboembolism. An overview of the potential for thromboembolism respective to preoperative conditions is given in table 1. This evaluation will determine the perioperative treatment. The different antithrombotic and anticoagulant agents have different pharmacology and different effects on haemostasis and should therefore be addressed individually. Warfarin is the preferred vitamin-K antagonist agent (VKA) for patients having mechanical heart valves and for the prevention of thromboembolic episodes in certain dysrrhythmias, cerebral arteriosclerosis and thrombosis- prone patients. The VKA can be stopped 2-4 days before elective surgery depending on the INR level. A close overview of the INR values is mandatory to avoid thromboembolic problems and excessive bleeding during surgery. A bridging regimen means that another and more manageable anticoagulant is substituted for the VKA in the perioperative period. This must be in place before surgery. Proposed INR values before surgery as well as bridging regimens are given in the Norwegian Guidelines (table 2). Platelet inhibitory agents. Acetyl salicylic acid (ASA) inhibits the platelet function irreversibly. It is in widespread use for prevention of attacks from coronary heart disease and for peripheral arterial disease. The effect on platelet activity is well documented. Despite its half-life of only 15-20 minutes, the effect lasts for 7 to 10 days after administration. Four to five days of stopping ASA will result in normalized function in more than 50% of the platelets. Thus, it is not surprising that ASA increases perioperative bleeding. Recent trends are to maintain the ASA up to the time of surgery in order to avoid vascular problems. Tranexamic acid (30 mg/kg i.v.) has been shown to limit the haemorrhage in cardiac surgery and also local application of tranexamic acid have been shown to reduce bleeding in minor surgery such as in dental procedures (Pleym et al. 2003, Douketis et al 2008). Clopidogrel (Plavix) has a half-life of 8 hours and inhibits irreversibly the adenosine diphosphate receptor-mediated platelet activation and aggregation. It therefore has an effect on coagulation for 7-10 days in order to restore the platelet pool. Its effects lead to significantly increased bleeding and is best stopped for at least a week before surgery. Clopidogrel is often indicated after coronary stenting. This aspect is important since stopping the drug can lead to coronary occlusion and myocardial infarction. A close cooperation between surgeon, anaesthesiologist, cardiologist and haematologist should be in place when these patients are coming for surgery.