VASGBI Trainee Research Development Grants

There are approximately 60,000 vascular operations (surgery relating to problems of veins and arteries) every year in the UK. Patients who have problems with their blood vessels often have other medical problems such as heart or lung disease which increases their risk of becoming unwell after an operation. Currently, doctors predict this risk by asking patients about medical problems and how these impact on how active they are able to be. Investigations such as a heart scan or breathing tests can give further information. If an operation is very high risk, a patient may undergo cardiopulmonary exercise testing (CPET) where the patient rides an exercise bike to maximum effort (exhaustion) whilst their heart and lung function is measured. This gives the doctor specific numbers which can be discussed with the patient about the risk of complications after surgery. CPET however is not widely available and some patients are unable to perform the test due to painful joints or poor circulation. By using a portable heart rate monitor placed on the skin we aim to produce a new measure of a patient's fitness for surgery which can be easily performed at clinic without needing to exercise to maximum effort (submaximal). This measure looks at how quickly heart rate slows again after submaximal exercise, called heart rate recovery (HRR).

Aim
To assess whether HRR is a valid measure of a vascular patient's risk of postoperative complications.

Method
With their consent, 80 patients undergoing vascular surgery will be asked routine questions and blood tests will be taken. Patients will be asked to perform a HRR assessment. A small external device will be placed on the patient and heart rate recorded. This will be done sitting at rest and whilst walking until 50% of their predicted maximum heart rate is reached. The patient will walk for a further minute and then rest until heart rate is back to baseline.
Additionally, patients at UHH will undergo CPET as routine. After the operation, blood tests indicating whether the heart has been under strain will be taken on days one and two and the presence of postoperative complications will be recorded by survey. Data regarding their length of hospital stay will also be collected. This data will be analysed to see how well HRR predicts postoperative complications and how well it agrees with the predictive measures doctors currently use.

Expected outcome and implications
HRR tests will predict postoperative complications in vascular patients and will prove a valid measure compared to current practice. HRR could be used as part of a doctor's toolkit to predict the operative risk of vascular surgical patients. Future studies will investigate whether HRR can be improved with exercise, so could therefore be targeted to improve patients' fitness for surgery. Patients identified as high risk could be offered interventions to reduce their risk and therefore improve patient outcomes after surgery.

Platelets are cells that help blood to clot. This process may become abnormal and the clots formed by platelets may block off important blood vessels, resulting in strokes and heart attacks. This is more common in patients who are older and who have high blood pressure or diabetes. As a result, many of these patients are prescribed antiplatelet medications, such as aspirin and clopidogrel. These drugs prevent formation of dangerous blood clots but may increase the risk of bleeding when a person undergoes an operation.

Many patients who require major operations of the blood vessels (vascular surgery) are also taking antiplatelet medications. On the day of surgery, they may require an epidural for pain relief. An epidural is an injection in your back that blocks the nerves carrying pain from the vessels and organs that are being operated on. It is generally a safe procedure which provides excellent pain relief. One very rare risk is bleeding into the injection site, which can have potentially devastating complications such as paralysis or death. Fortunately it is rare and thought to occur in 1 in every 150,000 cases. The risk is thought to be slightly higher in patients who are on antiplatelet medications and therefore guidelines recommend stopping antiplatelet medications for between 5 and 7 days before an epidural injection. However, this is not based on high-quality research and stopping these medications, even for a brief period, can result in patients experiencing strokes or heart attacks.

For patients in whom the risks of stopping antiplatelet medications before surgery are deemed too high, epidural analgesia is unfortunately not an option. However, little is also known about how each person responds individually to these medications. Some research suggests that antiplatelet medications may not work in up to 32% of patients. Epidural analgesia may be a suitable option for these patients. Expert committees have called for more research on identifying these patients.

The aim of our study is to better understand the true effects that antiplatelet medication has on circulating platelets in the blood. We will use novel methods of analysing platelet function. We will aim to recruit 80 patients who are scheduled to undergo major vascular surgery at the John Radcliffe Hospital, Oxford. We will require two to three teaspoons of blood from patients who have agreed to take part. This would be done during routine pre-operative assessment clinic visits and on the day of surgery. There are no drugs that will be given as part of the study and the remainder of the study data can be collected from routine healthcare records.

This study will help us to design a larger study to see if we can change treatment plans for patients taking antiplatelet drugs so we can offer them epidural analgesia whilst also reducing the risk of bleeding and having a heart attack or stroke around the time of surgery. We will work with patient and public members to publicise our findings through newsletters, social media and journal publications.