Key Points
- The DOACs are oral anticoagulants that are an alternative to vitamin K antagonists (warfarin) and heparins. They include dabigatran (a direct thrombin inhibitor), rivaroxaban, edoxaban and apixaban (direct Xa inhibitors). The DOACs do not affect the results of coagulation tests (PT, INR, APTT, anti-Xa) in a predictable or linear fashion, unlike warfarin.
- It is more important to focus on the time of the last dose of DOAC than on the laboratory results, as the clotting times do not correlate with bleeding risk, but normal clotting times are more reassuring than those that remain prolonged, particularly if there is uncertainty about the time of the last dose.
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Abbreviations
Summary
The DOACs are oral anticoagulants that are an alternative to vitamin K antagonists (warfarin) and heparins. They include dabigatran (a direct thrombin inhibitor), rivaroxaban, edoxaban and apixaban (direct Xa inhibitors). The DOACs do not affect the results of coagulation tests (PT, INR, APTT, anti-Xa) in a predictable or linear fashion, unlike warfarin.
Standard coagulation assays will not predict the degree of anticoagulation in a given patient but abnormalities of APTT (dabigatran) and PT (rivaroxaban, edoxaban and apixaban) indicate possible ongoing presence of the anticoagulant and hence increased bleeding risk.
It is more important to focus on the time of the last dose of DOAC than on the laboratory results, as the clotting times do not correlate with bleeding risk, but normal clotting times are more reassuring than those that remain prolonged, particularly if there is uncertainty about the time of the last dose.
Good communication between the geriatric, orthopaedic, anaesthetic and eventually haematology teams is vital to coordinate optimal time of surgical intervention. It’s important to balance the benefit of early surgery (reduction of complications like delirium, pain,
pressure ulcers, reduction of the length of stay, targeting of the BPT criteria of surgery within 36 hours) and safety issues mainly related to safe spinal anaesthesia and surgery.
Recent literature and the AAGBI Proximal Neck of Femur Guidelines emphasise the need to consider the very small but serious risk of Vertebral Canal haematoma against the common and proven risks of delaying surgery beyond 36 hours.
Ideally the emergency surgery should be started at least 1-2 elimination half-lives after the last dose of anticoagulant if possible. The European Society of Anaesthesiologist (ESA) recommends that 2 elimination half- lives need to elapse between administration of the last dose of the drug and the performance of the neuraxial block. The estimated half- life varies according to the creatinine clearance (CrCl).
Incorporating these time intervals, a pragmatic guideline approach, based on creatinine clearance, would be:
*Dabigatran:
Consider use of Praxbind, a specific antidote to dabigatran available in blood bank, active in 30 min/1 hour. This will neutralise the anticoagulant effect of dabigatran after approximately 1 hour when it is safe to proceed. Needs discussion between a senior member of orthopaedic or geriatric team (registrar, associate specialist, consultant) with on call haematologist consultant for authorisation.
Consider the use of tranexamic acid 1 gram, to be administered upon induction by anaesthetist.
Postoperative resumption of DOACs: restart pre-op dose
The DOACs need to be restarted postoperatively cautiously once haemostasis is secure; be aware that the onset of action is far quicker than for warfarin. LMWH prophylaxis post- operatively can be considered until full anticoagulation is surgically safe if there is significant delay in restarting DOAC.
Restart pre-op dose: Administration of drug while spinal or epidural catheter in place is Not recommended
Antiplatelet medications
Any single antiplatelet medication (including aspirin, clopidogrel, ticagrelor, prasugrel) is not a contraindication to spinal anaesthesia for acute hip fracture surgery, if this is the best option for an individual patient. This should be discussed with the patient.
Whilst dual antiplatelet therapy (e.g., aspirin and clopidogrel) is not an absolute contraindication to central neuraxial block in the context of acute hip fracture surgery, there would need to be good reason not to proceed with a general anaesthetic on a risk/benefit basis.
All high-risk patients should be monitored for signs of vertebral canal haematoma in the postoperative period (back pain, numbness, motor weakness, bladder/bowel incontinence).
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