RETURN PATIENTS : ADVICE ON WARFARIN THERAPY

IMPLICATIONS OF WARFARIN THERAPY

Spontaneous bleeding risks

In general, individuals on warfarin are at increased risk of bleeding compared with the general population. However, studies have shown that warfarin therapy is safe provided that it is closely monitored to avoid overdosing. One large study ¹ showed that over 2011 patient-years of follow-up, bleeding complications occurred in 7.6 per 100 patient-years. Out of those, 0.25 per patient-years were fatal from brain haemorrhages, 1.1 were major (e.g. bleeding in the brain, eyes, abdomen, joints or bleeding requiring an operation or a blood transfusion), 6.2 were minor. 

Bleeding from injuries

Warfarin increases the extent of bleeding or bruising resulting from any wounds or physical injury. The risk would depend on the mechanism of injury, the force and site of impact and the INR at the time. It is difficult to quantify precisely. The following are some examples:

Superficial injuries

• Lacerations or superficial wounds from sites where compression could be applied readily e.g. extremities or any external skin surfaces.
• Minor blunt injuries e.g. a kick on the shin, slap on the face
• Minor fall (no head injury, no fall from height, minor grazes to the skin or bruises)

These injuries are non-serious. They may be increased bleeding/bruising as a result of warfarin therapy but the risk of serious damage is very low.

Serious injuries

• Blunt trauma to the chest, severe enough to result in extensive bruising, rib fractures or coughing up blood.
• Blunt trauma to the abdomen, severe enough to result in extensive bruising, passing blood in urine, signs of internal bleeding e.g. abdominal swelling, abdominal pain and drop in blood count.
• Involvement in road traffic accidents
• Fall from height
• Fractures
• Penetrating injuries leading to serious bleeding and possible internal damage

These injuries are serious and the extent of bleeding would be potentiated by warfarin therapy. Prompt medical attention is required.

Head injury

Patients on warfarin are at greater risk of intracranial (inside the skull) haemorrhage following a head injury even if they are classified as being in the low risk category (e.g. no skin lacerations, no skull fractures, no loss of consciousness, mild symptoms only). The NICE guidelines² on the management of head injury recommend that all patients on warfarin sustaining a head injury should be referred to Accident and Emergency for assessment. Urgent CT scanning is required if there is any loss of memory or loss of consciousness since injury. Other factors determining the risk of intracranial haemorrhage applicable to the general population are the presence of a skull fracture, dangerous mechanism of injury (such as fall from >1m or 5 stairs, a pedestrian in road traffic accidents or a passenger ejected from the vehicle), altered consciousness, seizures, vomiting or focal weakness or loss of sensation in the face/limbs after injury.

ALTERNATIVES TO WARFARIN

At present, warfarin is the only oral anticoagulant for available for clinic use. Several other oral agents are under development by different drug companies. Two furthest on in development are dabigatran and rivaroxaban. Their advantages over warfarin are that there are no drug or food interactions and INR monitoring is not required. Their efficacy and safety in preventing blood clots in orthopaedic surgery and strokes in patients with atrial fibrillation (irregular heart rhythm) is being evaluated in clinical trials. It may take another 2-3 years for them to be in clinical use. They are also associated with bleeding risks like warfarin. Data on their safety profile compared with warfarin are awaited.

RECOMMENDATIONS

There is no absolute limitation to her daily activities as a result of warfarin therapy, but the risk of increased bleeding from any injury needs to be borne in mind especially in the context of potential head injury. The general advice would be to avoid any contact sports where there is a significantly increased risk of injury. The obvious examples are boxing and rugby, but other sport activities such as skiing are also associated with the potential risks of injury. The risks should be minimised by wearing protective garment and ensuring that INR is within the desired range. It is up to the individual to take part if he or she finds the risks acceptable. With respect to employment, there are no published guidelines by the British Society for Haematology or American Society of Haematology on employment restrictions related to warfarin therapy.

FURTHER INFORMATION

Websites that may be useful are:

www.patient.co.uk

www.b-s-h.org.uk

www.hematology.org

References

1.    Bleeding complications of oral anticoagulant treatment: an inception-cohort, prospective collaborative study (ISCOAT). Italian Study on Complications of Oral Anticoagulant Therapy. Lancet. 1996 Aug 17; 348 (9025):423-8.

2.    Triage, assessment, investigation and early management of head injury in infants, children and adults. NICE Clinical Guideline (September 2007).