Perfusion 24(5) 295 © The Author(s) 2009 Reprints and permission: http://www. sagepub.co.uk/journalsPermission.nav DOI: 10.1177/0267659109358491 http://prf.sagepub.com Editorial Evidence-based medicine or instinct-based medicine? “Trust the instinct to the end, though you can render no reason” Ralph Waldo Emerson, American poet, lecturer and essayist – 1803 -1882 I am delighted to confirm Professor Ken Taylor’s contin- ued association with “Perfusion” as Editor Emeritus. As some of you may be aware, Ken’s contribution since inception has been instrumental and, simply put, the journal would not exist if he and some of you had not decided to start “Perfusion”. Ken was invited to deliver the Honored Guest address to the AATS in Boston 1998. 1 As his guest, I was impressed, like many, with his simplistic, yet in depth, thorough and serendipitous, approach and association with him since the mid 1990s has imbibed in me both evidence and instinct. We all follow evidence-based medicine; however, I am sure each one of us has made decisions based on evi- dence and instinct. You have probably heard the saying “good instincts usually tell you what to do long before your head has figured it out”. Definitions of instinct (15th century: latin : instinctus meaning impulse) vary, but the most commonly accepted definition is “a largely inheritable and unalterable ten- dency of an organism to make a complex and specific response to environmental stimuli without involving reason or behaviour and that is mediated by reactions below the conscious level”. Are instinctive reactions actually evidence-based in their own way? Surely instinct is a synthesis of perceptive experience and collective knowledge. Thomas Bayes (1702 – 1761), British mathematician and Presbyterian minister, formulated Bayes’ Theroem, often called Bayes’ Law or Bayes’ Rule. This is a simple mathematical formula used for calculating conditioning probabilities. It figures prominently in subjectivist or Bayesian approaches to epistemology statistics and inductive logic. Subjectivists, who maintain that rational belief is gov- erned by the laws of probability, lean heavily on conditional probabilities in their theories of evidence and their mod- els of empirical learning. Bayes’ Theorem is central to these enterprises, both because it simplifies the calcula- tion of conditional probabilities and because it clarifies significant features of subjectivist position. Indeed, the theorem’s central insight – that hypothesis is confirmed by any body of data that its truth renders probable – is the cornerstone of all subjectivist methodology. So, in practice, does this not mean that hypothesis will change too? Is it not that instincts are quick Bayesian responses emerging as pieces of evidence are collected and, finally, is it as good as other more formal evidence? Biancari et al. are to be congratulated on getting the evidence for safe time limits of aortic cross-clamping and cardiopulmonary bypass in adult cardiac surgery. On the same theme, Marcoux et al. compare five coated CPB circuits versus an uncoated control group and also share their experience of CPB-assisted aortic valve replacement in a pregnant 27 year old with endocarditis. Hussaini evaluates blood components exposed to coated arterial filters in extracorporeal circuits and Tyree and Walker assess ECMO by correlating brain tissue oxygen tension with cerebral near-infrared spectroscopy and mixed venous oxygen saturation as well as calculating mixed venous saturation during veno-venous ECMO, and, finally, Myers investigates the effect of diprivan on phosphorylcholine surfaces during CPB I hope you agree the articles provide further proof that instinct is being used to gather evidence and together an attempt to achieve clinical excellence is pursued. “Instinct is untaught ability” Alexander Bain, Scottish philosopher and education ana- lyst, 1818 - 1903 Mr Prakash P Punjabi Editor-in-Chief Perfusion Reference 1. A Practical Affair. K M Taylor, JTCVS, 118: 399 – 403, 1999.