The Risk of Stroke after a Hip or Knee Surgery


The risk of stroke following hip or knee surgery was recently discussed on Radio 4’s Today programme in March.

Stroke Risks following surgery

Around a 160,000 people in the UK will have a new hip or knee this year and while complications like infection and blood clots are well recognised, the link with stroke is not so well established. New research suggests that stroke is one of the major hazards faced during the recovery period and that taking daily aspirin is an effective way of preventing it.

Cyrus Cooper, Professor of Rheumatology at the Universities of Southampton and Oxford was one of the lead authors of the international study, which followed over 60,000 people after they had hip replacement surgery.

Prior to the study it was known that there is an increased risk of stroke in patients who have hip replacement surgery and that the risk is as high as 1 in 30 people.

Professor Cooper’s study demonstrated that the increased risk occurs quite soon after the operation, during and within 6 weeks after the operation.

A lot of people going in for orthopaedic hip and knee surgery of this type will already be given anti-clotting agents in the form of injections - heparin - to prevent deep vein thrombosis, and Professor Cooper’s study has shown that over and above that low dose of heparin, those patients that were using aspirin also had a 70% reduction in the risk of stroke following their hip replacement operation.

The precise mechanism why patients get an increased risk of stroke after a hip replacement operation is not completely identified, but there seem to be 2 major pathways. The first is that as part of any operation you'd get a reduction in the blood flow through the vessels of the brain and that predisposes the blood to travel a bit more slowly and be a bit more prone to clotting. The second is that as part of the operation on the bone bits of marrow, particularly fatty bits of marrow, may flick out and go and lodge in the small vessels of the brain. The aspirin would certainly help the first of these 2 pathways, we don't really know that it might really help the second.

Approximately 4 in 5 strokes are caused by a clot, but as many as 1 in 5 may be from bleeding. Whilst we would normally expect aspirin to increase the risk of a bleeding type of stroke the study found no evidence for that. However, this would need to be confirmed in future research but at the present time the balance of benefit seems to outweigh the risk of that bleeding type of stroke.

Therefore the study has clearly shown that aspirin should not be stopped for fear of a bleeding stroke and that patients that are on the aspirin are going to reap benefit from it in terms of their risk of a clotting type of stroke.

However, whilst the risk of stroke is well known it is sometimes the case that doctors simply fail to recognise symptoms that are consistent with stroke or recurrent transient ischaemic attacks, or they may fail to correctly interpret blood results that indicate a high risk of thromboembolism, or fail to administer an appropriate dose of heparin or a similar agent, if at all.

Such mistakes can be costly, resulting in severe disability, leaving the victim requiring 24-hour care and supervision for the remainder of their life.

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