Simon Howell | University of Leeds, UK
OBTAIN: The Occurrence of Bleeding and Thrombosis during Antiplatelet Therapy In Non-cardiac surgery
Managing antiplatelet therapy in patients who have undergoing coronary artery stenting and now require non-cardiac surgery is a major dilemma for anaesthetists. On the one hand, there is good evidence from the cardiology literature that the premature discontinuation of antiplatelet therapy is associated with an increased risk of coronary stent thrombosis and myocardial infraction; on the other the continuation of dual antiplatelet therapy through the intraoperative period carries a significant risk of bleeding.1 OBTAIN is a major international multicentre study run by the ESA Clinical Trials Network designed the address the question of whether patients who have undergone percutaneous coronary intervention (PCI) and now require non-cardiac surgery should receive single or dual anti-platelet therapy in the perioperative period.
The steering committee of OBTAIN brought together colleagues from a number of disciplines. Anaesthetic expertise was provided by the chief investigator Dr. Simon Howell (Leeds, UK) and Professor Andreas Hoeft (Bonn, Germany). Methodological and epidemiological direction came from Dr Sanne Hoeks (Rotterdam, The Netherlands). Cardiological input was provided by Professor Stephen Wheatcroft (Leeds, UK) and statistical expertise by Professor Robert West (Leeds, UK)
OBTAIN is an observational study. It was recognised from the outset that there would be substantial challenges for a randomised controlled trial and that many anaesthetists, cardiologists and surgeons would be reluctant to randomise patients to single or dual anti-platelet therapy. The study team therefore choose a prospective observational cohort design. Patients who had undergone PCI and now required non-cardiac surgery were recruited into the study. The management of antiplatelet therapy through the perioperative period was at the discretion of the clinical team. Data were collected on cardiac risk factors and drugs and the prescription of antiplatelet agents. Patients were followed up in hospital after surgery and major cardiac and bleeding events were recorded. The statistical technique of propensity matching was used data analysis. This allowed us to compare outcomes from patients on single and dual antiplatelet therapy whilst making a robust statistical adjustment for the clinical indication for dual antiplatelet therapy.
OBTAIN was open to recruitment from March 2011 to December 2013 with the follow up of patients continuing until the end of January 2014. Forty-one centres across twelve European countries entered patients into the study, with many centres recruiting twenty or more patients. Data cleaning took place from April 2014 to February 2015. The study steering committee are grateful to colleagues across Europe both for the large number of patients recruited into the study and the energy and efficiency with which they responded to data queries. A total of 917 patients were recruited into the OBTAIN. 847 patients with were included in our initial analysis data which we presented in Stockholm at Euroanaesthesia 2014 in Stockholm. This was simple unadjusted analysis conducted whilst data cleaning was in progress. It suggested that intraoperative dual antiplatelet therapy in non-cardiac surgery patients who have undergone previous PCI does not protect from cardiac events but is associated with an increased risk of bleeding. A detailed propensity score analysis conducted following the completion of data cleaning is being prepared for publication and supports these findings.
The results of OBTAIN and other studies suggest that there is a need to review current advice on antiplatelet therapy in surgical patients. We are currently conducting a meta-analysis of studies of the use of anti-platelet agents in surgical patients who have undergone PCI which will inform this discussion.
OBTAIN could not have gone forward without the support of the funding of the ESA, the support of the excellent ESA-CTN secretariat , most of all the dedication, of the members of the ESA in recruiting patients and collecting data. We are very grateful to all for their support for this project which we believe will contribute to the perioperative care of patients across Europe.
Kristensen SD, Knuuti J, Saraste A, et al. 2014 ESC/ESA Guidelines on non-cardiac surgery: cardiovascular assessment and management: The Joint Task Force on non-cardiac surgery: cardiovascular assessment and management of the European Society of Cardiology (ESC) and the European Society of Anaesthesiology (ESA). Eur J Anaesthesiol 2014; 31: 517-573.