Topic 5 Preoperative anticoagulation
Mrs B is 70 years old. She is for total right knee replacement. You will be seeing her today in the preoperative clinic. In passing, the nursing staff mentions to you that she is on warfarin. How do you manage this?
Introduction
You will come across patients who are on anticoagulation in the preoperative clinic. This is a challenging area. Stopping anticoagulation places the patient at an increased risk of thromboembolism, but at the same time, being on anticoagulation perioperatively increases the risk of surgical bleeding.
Therefore, a balance needs to be struck between risk of thromboembolism and risk of surgical bleeding. Whilst it would be nice for a ‘one size fits all’ approach, unfortunately this does not exist. The preoperative management of anticoagulation is therefore individualized.
Estimation of bleeding risk
The type and urgency of surgery impacts on bleeding risk.
High bleeding risk procedures includes: colectomy, coronary artery bypass surgery, nephrectomy
Low bleeding risk procedures includes: teeth extraction, skin cancer excision, cataract surgery
Patient’s past medical history should also be evaluated (eg Haemophillia, Liver failure).
HAS-BLED is a risk assessment score that can be used. It uses the clinical variables of stroke, liability of INR, hypertension, abnormal liver or kidney function, age, alcohol and antiplatelet drugs. A HAS-BLED score of 3 or more indicates high bleeding risk.
Estimation of thromboembolic risk
The most common conditions associated with high thromboembolic risk are:
atrial fibrillation
prosthetic heart valves
recent thromboembolism (in the past 3 months).
In patients who have a high thromboembolic risk, it is very important that the duration of anticoagulation suspension, is as short as possible.
Atrial fibrillation
Clinical factors which are associated with higher bleeding risk in patients with AF are:
age
high blood pressure
heart failure
diabetes
past stroke.
CHA2DS2-VASC is a scoring system that can provide a risk assessment score on the thromboembolic risk for patients with atrial fibrillation. This scoring system incorporates the clinical factors described above.
You can access this through: https://clincalc.com/Cardiology/Stroke/CHADSVASC.aspx
Prosthetic heart valve
Simply put, there are 2 types of prosthetic heart valves. They are mechanical and biological heart valves.
Mechanical valve requires strict lifelong anticoagulation, commonly in the form of warfarin. They are structurally more vigorous.
Biological valve does not require strict anticoagulation regime. At most, 3 to 6 months of anticoagulation is required. However, they are structurally less vigorous.
Patients with mechanical heart valves, are at the highest risk for thromboembolic events, when anticoagulation is stopped. The type, location, and number of prosthetic heart valves, needs to be taken into account when formulating a preoperative plan.
Surgery should ideally be postponed in patients who have undergone valve replacement or repair in the first 3 months.
However, good quality data to guide the preoperative management of anticoagulation in patients with prosthetic heart valve is lacking. American College of Cardiology/American Heart Association recommend considering bridging anticoagulation on an individualized basis in patients with mechanical heart valve. The risk of surgical bleeding versus the risk of thromboembolism needs to be carefully weighed.
#TIP This is a complicated area. If you encounter a patient with prosthetic heart valve for surgery, you will need to escalate this to your Senior.
Thromboembolism
In both Venous (PE and DVT) and Arterial thromboembolism, the greatest risk for further thromboembolic events is within the first 3 months after the initial event. Therefore, in patients with recent venous or arterial thromboembolism should have their surgery ideally postponed.
Bridging anticoagulation
Bridging anticoagulation is the use of a short-acting anticoagulant agent, whilst the patient’s normal anticoagulant agent is suspended. Bridging anticoagulation is considered when the patient is assessed to be at a high thromboembolic risk (eg mechanical heart valve and recent stroke) and for patients who are also on warfarin. For patients on Direct Oral Anticoagulant agent, bridging anticoagulation is not required.
The use of Bridging anticoagulation means that the duration of time without anticoagulation is minimized, thus in turn reducing perioperative thromboembolic risk. Low-molecular weight heparin (enoxaparin) is normally used, as enoxaparin is easy for the patient to use, has more predictable pharmacodynamics and no monitoring is required.
BRIDGE trial found that in patients with AF undergoing surgery, the use of Bridging therapy (dalteparin) did not reduce the rate of thromboembolic events. Additionally, the Bridging therapy group also had more bleeding complications.
This means that in patients with AF, careful consideration needs to be given to determine whether Bridging therapy is required. British Journal of Haematology Peri-operative management of anticoagulation and antiplatelet therapy Guideline do not recommend Bridging therapy in patients with AF who have CHADS2 score<4 and no stroke in the past 3 months.
Making the final decision
The decision on whether to hold anticoagulation or not, is made after determining the thromboembolic and surgical bleeding risks. This decision, ultimately, is a clinical one.
Generally speaking:
Anticoagulation should be held in situations where the risk of surgical bleeding is HIGH
Anticoagulation can be considered to continue, in situations where the risk of surgical bleeding is LOW
In patients, who have a high risk of surgical bleeding, but also have a high thromboembolic risk, strategies to manage this are:
Bridging therapy
Minimizing the duration of holding anticoagulation to as short as possible
Postponement of surgery, in order to lower thromboembolic risk (eg if patient had a recent stroke in the past 3 months)
Duration of holding anticoagulation agent
Warfarin- Omit 5 days before surgery
Direct Oral Anticoagulant (Apixaban, Dabigatran, Rivaroxaban)
Low risk surgery- HOLD one day before surgery
High risk surgery- HOLD two days before surgery.
Conclusion- Step by step algorithm
This is an algorithm of the thought processes you should have, when you encounter a patient presenting to the preadmission clinic on anticoagulation.
A1 What is the indication for anticoagulation (sometimes, you might find there is not one!)
A2 What is the patient’s surgical bleeding risk?
A3 What is the patient’s thromboembolic risk?
If the clinical decision is made to suspend anticoagulation
B1 Does the surgical bleeding risk outweigh the thromboembolic risk?
B2 How many days do I suspend anticoagulation for?
B3 Is bridging therapy required?
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