Bleeding and thrombotic complications in ECMO patients
Research type
Research Study
Full title
Retrospective cohort study of bleeding and thrombotic complications in patients receiving Extracorporeal Membrane Oxygenation (ECMO)
IRAS ID
244283
Contact name
Stephane Ledot
Contact email
Sponsor organisation
Royal Brompton and Harefield NHS Foundstion Trust
Duration of Study in the UK
0 years, 5 months, 18 days
Research summary
Bleeding and development of blood clot (thrombosis) are the main causes of morbidity and mortality in patients receiving an intervention called extracorporeal membrane oxygenation (ECMO). ECMO uses a machine to take over the work of the lungs and sometimes the heart. The part of the machine referred to as the “artificial lungs,” carries out Membrane Oxygenation. This puts oxygen into the blood and removes carbon dioxide, mimicking the effect of normal lung function. When the machine is used to support severe lung disease this is called ven-venous ECMO (VV-ECMO), and when used in severe heart disease this is called veno-arterial ECMO (VA-ECMO).
Patients on ECMO are acutely unwell and likely to suffer from many complications during their treatment. To prevent blood clots from forming while on the machine, a blood thinning medication (Unfractionated heparin (UFH)) is given as a continuous drip into the ECMO circuit. Low platelet count (Thrombocytopenia) can be a common finding in patients receiving ECMO for many reasons. An allergic reaction which is immune mediated, called Heparin induced thrombocytopenia (HIT), is one of the very important cause of low platelet count in patients receiving ECMO treatment. HIT can also cause blood clots (thrombosis) in any blood vessel (venous or arterial) or organ of the body in these patients
Patients requiring ECMO typically need ongoing blood transfusion support, which means they are likely to receive multiple transfusions over the course of the ECMO treatment. However, blood product transfusion protocols are not currently evidence-based in most centres, but rather are based on clinical experience, historical literature, and clinical guidelines. Thresholds for the transfusion of red cells vary between centres and by type of patient. Our current transfusion trigger is a haemoglobin of <70 g/L in patients requiring VV-ECMO and in patients on VA-ECMO, although depending on any additional cardiac risk we may keep haemoglobin at a slightly higher level
Many ECMO centres use a blood test called the activated partial thromboplastin time (APTT) for monitoring the effect of UFH. We use a test called heparin anti-Xa to monitor the actual amount of heparin in the blood, which gives an accurate measurement of the level of anticoagulation. We believe that the APTT may not accurately monitor the amount of heparin present in these acutely ill patients. This is a retrospective cohort on patients who received ECMO at the Royal Brompton & Harefield NHS Foundation Trust from January 2016 to June 2018.
We aimed to determine the frequency of low platelet count (thrombocytopenia), the development of the allergic reaction called HIT, blood clot formation (thrombosis) and bleeding complications in adult patients receiving ECMO compared to patients on cardiopulmonary bypass (CPB). CPB is a technique in which a machine temporarily takes over the function of the heart and lungs during surgery, maintaining the circulation of blood and the oxygen content of the patient's body. The CPB pump itself is often referred to as a heart–lung machine or "the pump".
In addition, we aimed to assess the following; whether the reliability of standard pre-test probability 4Ts score (which is an assessment tool for predicting the presence of the allergic reaction to heparin, HIT) can identify ECMO patients developing HIT compared to patients received CPB; the usefulness of APTT in monitoring heparin in patients receiving ECMO and the correlation of the APTT with bleeding and blood clot formation; and an assessment of transfusion requirements and clinical outcomes. Patients who received VV-ECMO or VA-ECMO will be assessed separately.
The information gained from this retrospective study, will help us to design a prospective study to improve the care for patients receiving ECMO.REC name
North West - Preston Research Ethics Committee
REC reference
19/NW/0474
Date of REC Opinion
24 Jul 2019
REC opinion
Favourable Opinion