Anticoagulants and Noncardiac Surgery
Full-dose anticoagulation is discouraged perioperatively because of the harmful effect on the ability to control surgical blood loss.
Risk of perioperative bleeding must be weighed against thromboembolic risk.
Patients on oral vitamin K antagonists can undergo noncardiac surgery when the INR is <1.5.
For patients with AF and normal renal function undergoing elective major surgery, spine surgery, and epidural catheterization, discontinuation of anticoagulants for >48 hours is suggested.
For patients with a mechanical mitral valve, regardless of the absence of additional risk factors for thromboembolism, or patients with an aortic valve and >1 additional risk factor (such as AF, previous thromboembolism, LV dysfunction, hypercoagulable condition, or an older-generation prosthetic aortic valve), bridging therapy may be appropriate.
Risk factors of thromboembolic events include: —
Patients with such risk factors require preoperative bridging therapy with unfractionated heparin UFH or low molecular weight heparin LMWH.
The last dose of LMWH should be administered no later than 12 hours before surgery.
Depending on the type of Vitamin K antagonists, it is recommended to stop therapy 3 - 5 days before surgery.
For urgent reversal of vitamin K antagonists, vitamin K low-dose (2.5–5.0 mg) intravenous or oral vitamin K is recommended and FFP or the prothrombin complex concentrate (PCC) can be given.
The effect of vitamin K on INR will first be apparent after 6–12 hours.
Vitamin K is not routinely recommended for reversal because the effect is not immediate and the administration of vitamin K can significantly delay the return to a therapeutic level of anticoagulation once vitamin K antagonists have been restarted.
In patients on IV UFH and requiring reversal - cessation of therapy is sufficient, because coagulation is usually normal 4 hours after cessation.
For subcutaneous UFH ,the anticoagulant effect is more prolonged. For immediate reversal, the antidote is protamine sulphate. The dose of protamine sulphate for reversal of a heparin infusion is 1 U per 1 U of heparin sodium.
In patients who are receiving LMWH, the anticoagulant effect may be reversed within 8 hours of the last dose.
If immediate reversal is required, IV protamine sulphate can be used, but anti-Xa activity is never completely neutralized (maximum 50%).
Non-vitamin K antagonist oral anticoagulants (NOACs) -
Classified by mode of action: dabigatran is a direct thrombin inhibitor, while rixaroxaban, apixaban and edoxaban target coagulation factor Xa.
It is recommended to discontinue NOACs for 2-3 times their respective half-lives before surgery with average risk of bleeding, and for 4-5 times their biological half-lives before surgery with high risk of bleeding. When severe bleeding complications occur under the influence of NOACs, symptomatic treatment should be initiated
Due to their well-defined “on” and “off” action, preoperative bridging therapy with UFH or LMWH is usually not required.
Factor Xa inhibitors – given for prevention of stroke in AF. They are not recommended for long-term anticoagulation of prosthetic valves because of an increased risk of thrombosis when compared with warfarin.
They do not have a reversible agent. Prothrombin complex concentrates can be given.
Oral anticoagulant ( dabigatran, rivaroxaban) agents are not acutely reversible. Haemodialysis - eliminates dabigatran from circulation but does not help when a direct factor Xa inhibitor has been used
Monitoring activated partial thromboplastin time APTT for dabigatran and prothrombin time PT for apixaban and rivaroxaban may be helpful.