Anti-Coagulants Flashcards
How long do anti-coagulants need to be withheld before surgery?
The following table outlines how long anticoagulants need to be withheld before surgery:
Dabigatran 1-2 days with creatinine clearance >50ml/min
Rivaroxaban 1 day if creatinine clearance >90 ml/min
Apixaban 1-2 days if creatinine clearance >60
Fondaparinux 36-48 hours
LMWH 12 hrs for prophylactic dose, 24 hours for therapeutic dose
Warfarin 1-8 days, check INR
UFH IV 4-6 hrs, SC 12-24 hrs
Anti-coagulants and surgery - Example Question
You are the medical registrar on call. The surgical registrar contacts you for a patient he has just seen in clinic who requires an elective cholecystectomy. The patient is a 65-year-old woman who has atrial fibrillation for which she takes rivaroxaban. The patient is otherwise well. The bloods performed in clinic that day are as follows:
Hb 131 g/l
Platelets 352 * 109/l
WBC 5.5 * 109/l
INR 1.5
Na+ 137 mmol/l
K+ 3.6 mmol/l
Urea 3.2 mmol/l
Creatinine 67 µmol/l
The surgical registrar would like to know how long the patient should omit their anticoagulation before the procedure?
> 1 day 2 days 3 days 5 days 7 days
The new oral anticoagulant drugs (NOACs) are being used increasingly in patients who require anticoagulation. They have the advantage of once or twice daily dosing regimes, oral formulation and do not require therapeutic monitoring like warfarin. They are particularly useful in patients that may have issues with warfarin compliance or those with erratic international normalised ratio (INR) readings. NOACs have been shown to convey equivalent efficacy to warfarin in most contexts the main exception being anticoagulation in patients with prosthetic heart valves where NOACs were not as effective as warfarin.
Rivaroxaban is one of the most commonly used agents. It acts as a direct factor Xa inhibitor. It is absorbed from the gut and has maximum factor Xa inhibition four hours post dose. It is indicated for anticoagulation in atrial fibrillation and in the treatment of venous thromboembolism. It has a half-life of 7-9 hours and is metabolised in the liver. Factor Xa levels do not return to normal for just over 24 hours so once daily dosing is appropriate.
GI Bleeding on NOAC: Example Question
A 55-year-old lady is seen in the Emergency Department with haematemesis. She developed upper abdominal pain yesterday and began vomiting dark brown material about an hour ago. She has also passed some loose stools today. She recalls having a couple of similar episodes of abdominal pain over the last 2 months but much less severe and not associated with vomiting.
Her past medical history includes hypertension, high cholesterol, type 2 diabetes, atrial fibrillation and chronic back pain. Her medications are bisoprolol, ramipril, atorvastatin, metformin, sitagliptin, apixaban, paracetamol and codeine. She also admits to taking some other over-the-counter pain relief for her back in recent months. She took her regular morning medication 10 hours ago but has not had any since.
On examination her heart rate is 105 beats per minute and blood pressure is 112/88 mmHg. She looks clammy and pale. She is very tender in the epigastric region with guarding and normal bowel sounds. There is malena on rectal examination.
Bloods have been sent but are not yet available, though a haemoglobin on venous gas is 96 g/l.
She is started on fluids and an urgent endoscopy is requested. Which medication should be given to help control the bleeding?
Activated charcoal and prothrombin complex concentrate Activated charcoal and tranexamic acid > Prothrombin complex concentrate and tranexamic acid Vitamin K and prothrombin complex concentrate Vitamin K and fresh frozen plasma
This lady has major bleeding on apixaban. Consensus guidelines suggest that this should initially be managed with tranexamic acid, with consideration of prothrombin complex concentrate if there is insufficient response.
In cases where apixaban has been ingested within 6 hours, activated charcoal can be administered but this would be inappropriate in a gastrointestinal bleed.
There is no evidence to support the use of fresh frozen plasma to reverse the effects of novel anticoagulants such as apixaban.
Vitamin K is used to reverse warfarin (as warfarin inhibits vitamin K dependent clotting factor synthesis) but it does not affect the function of direct factor Xa inhibitors such as apixaban.
Major Bleeding on NOAC - Mx
Consensus guidelines suggest that this should initially be managed with tranexamic acid, with consideration of prothrombin complex concentrate if there is insufficient response.
In cases where apixaban has been ingested within 6 hours, activated charcoal can be administered but this would be inappropriate in a gastrointestinal bleed.
Warfarin - Mx of High INR
The following is based on the BNF guidelines, which in turn take into account the British Committee for Standards in Haematology (BCSH) guidelines. A 2005 update of the BCSH guidelines emphasised the preference of prothrombin complex concentrate over FFP in major bleeding.
Situation Major bleeding: Stop warfarin Give intravenous vitamin K 5mg Prothrombin complex concentrate - if not available then FFP*
INR > 8.0 Minor bleeding Stop warfarin Give intravenous vitamin K 1-3mg Repeat dose of vitamin K if INR still too high after 24 hours Restart warfarin when INR < 5.0
INR > 8.0
No bleeding
Stop warfarin
Give vitamin K 1-5mg by mouth, using the intravenous preparation orally
Repeat dose of vitamin K if INR still too high after 24 hours
Restart when INR < 5.0
INR 5.0-8.0 Minor bleeding Stop warfarin Give intravenous vitamin K 1-3mg Restart when INR < 5.0
INR 5.0-8.0
No bleeding
Withhold 1 or 2 doses of warfarin
Reduce subsequent maintenance dose
*as FFP can take time to defrost prothrombin complex concentrate should be considered in cases of intracranial haemorrhage
Major Bleeding on Warfarin - Example Question
A 77-year-old man with known atrial fibrillation is admitted following an upper gastrointestinal haemorrhage. His atrial fibrillation is managed using bisoprolol and warfarin. Since his admission, he has had four large episodes of haematemesis. You, the emergency department doctor, request the patient’s INR to be checked as one of a series of investigations. The haematology laboratory phone through and inform you his INR is 8.5. He is currently hypotensive (90/45 mmHg) and tachycardic (120 beats per minute). You begin resuscitation using 0.9% saline, and send a cross match, group and save. What is the most appropriate treatment of this patients INR?
Fresh frozen plasma + stop warfarin Vitamin K + stop warfarin Prothrombin complex concentrates > Prothrombin complex concentrates + vitamin K + stop warfarin Stop warfarin
The nub of this question is the emergency management of haemorrhage in patients on warfarin. This patient has an INR greater than 8 and is actively bleeding. Therefore the answer is 4.
Patients on warfarin have reduced levels of Factor X, IX, VII and II. Rapid correction is most effectively achieved through administration of prothrombin complex concentrates.
The British Journal of Haematology states that: ‘Emergency anticoagulation reversal in patients with major bleeding should be with 2550 u/kg four-factor prothrombin complex concentrate and 5 mg intravenous vitamin K’
Mx of High INR on Warfarin - Example Question
You receive a phone call requesting advice from a GP. A patient who is on long term warfarin for atrial fibrillation has been found to have an INR of 10.0 following a recent course of antibiotics. She is not bleeding and only has long standing senile purpura on her arms with no new bruising. What is the most appropriate advice to give?
Admit for intravenous vitamin K and monitoring Give oral vitamin K and continue warfarin at usual dose > Give oral vitamin K and stop warfarin until INR < 5 Give oral vitamin K and stop warfarin until INR < 3 Stop warfarin and restart when INR < 3
