Pre‐habilitation (i): aggregation of marginal gains

“The whole principle came from the idea that if you broke down everything you could think of that goes into riding a bike, then improved it by 1%, you will get a significant increase when you put them all together” 1. Questioned during a BBC interview following the astounding success of his riders in the 2012 Olympics, this was the unexpectedly simple explanation offered by a modest Dave Brailsford, performance director of British Cycling. Even those less enamoured with cycling can appreciate the ten Olympic gold medals obtained by a dominant British team in the London velodrome. The performance had left their international opposition dumbfounded and commentators simply asking ‘how’? Based on these comments, fields outside of elite sport, including business and education, have clamoured to investigate potential value in applying the ‘marginal gains theory’ (outlined by Brailsford) to their own circumstances. What Brailsford described is the principle of multiple, seemingly miniscule, improvements throughout any given process, collectively achieving a far superior output. Whilst the British Olympic cycling team and the British professional cycling team, Team Sky, are the highest-profile contemporary examples of marginal gains in action, the 19th century Austrian world chess champion, Wilhelm Steinitz, first introduced the concept. Steinitz is credited with initially describing the gradual gain of advantages that are not decisive individually but collectively may be so 2. Boiled down, marginal gains can be thought of as sweating over seemingly insignficant detail. Indeed, much has been made in the media of the lengths to which Team GB cyclists went in their pursuit of excellence: taking their own pillows when moving training sites to ensure consistently good sleep; employing cutting-edge ‘skin suits’; and endlessly refining their riding position to make tiny improvements to their aerodynamic efficiency. Even surgical hand washing techniques have reportedly been implemented in an attempt to minimise episodes of minor illness that disrupt athletes’ training 1. Whilst the methods may seem extreme to some, it is difficult to argue with the results. For healthcare professionals in multidisciplinary surgical teams, it may seem a significant leap from skin-tight suits to improved peri-operative patient care. By definition, application of marginal gains must begin with the breaking down and identification of every tiny step and component of the larger process. Considering that Brailsford and his team identified hundreds of individual elements to refine in the allegedly straightforward process of pedalling a bicycle, translation into the complex field of peri-operative patient management appears, at first glance, intimidating. On closer inspection, however, it is clear that a thorough overhaul of peri-operative patient management is already underway, with the marginal gains theory truly embedded in the process. In the UK, the enhanced recovery care pathway is now firmly established across a broad range of elective surgical practice 3, with the latest consensus statement from the National Enhanced Recovery Partnership acknowledging the parallels with GB cycling 4. The programme breaks the entire peri-operative patient journey into seven broad phases, each scoured to remove redundancy and facilitate efficient, safe progress from pre-operative assessment to discharge and rehabilitation. Management of patients during the pre-operative, admission, operative and postoperative phases is now well established in many NHS institutions. Examples of this include: appropriate patient selection during the pre-operative phase; carbohydrate loading and goal-directed fluid therapy in the operative period; and multi-modal analgesia and early mobilisation postoperatively. Although a substantial, and still debated, evidence base exists for several of these key components 5-12, limited published research exists for other individual elements. Despite this, when analysed collectively, the package appears to achieve clear improvements in surgical outcomes from both clinical and economic standpoints 13-15. This finding maps well against the concept of marginal gains in action. With many enhanced recovery interventions relevant to the immediate peri-operative period now widely established in clinical practice, focus turns towards the days, weeks and months that precede surgery – within the primary care setting. Here, in the extended pre-operative phase, a wealth of opportunity exists to implement a marginal gains approach in the active, structured optimisation of patients before surgery. This concept is increasingly recognised as ‘pre-habilitation’ in the medical literature. The literature supports significant improvements in outcome in patients with many conditions that may be optimised in the pre-operative period. These include: identification and correction of anaemia 16; optimisation of underlying medical co-morbidities in an evidence-based manner 17; and smoking cessation 18. These factors are already accepted as part of the enhanced recovery programme. Alongside the beneficial pre-operative interventions already identified within the programme, others are emerging. First, compelling evidence is now available across several specialities that a lack of prerequisite aerobic fitness in the peri-operative period has an adverse impact on high-risk surgical outcomes 5, 19, 20. The concept of short-term pre-operative exercise interventions, enabling significant improvements in aerobic fitness, is therefore appealing. Despite the lack of definitive outcome studies in this area, our group has published findings 21 demonstrating that a six-week, cycle-based, continuous exercise intervention of moderate intensity in patients with abdominal aortic aneurysm disease (under surveillance) resulted in a mean improvement in aerobic fitness of 10%. Tew et al. demonstrated more substantial fitness improvements, in the same patient population, consequent to a 12-week, moderate but continuous cycle-based intervention 22. Although these results are encouraging, it is vital to recognise that any future research should deliver evidence of time-efficient, substantial and safe improvements in fitness, thereby facilitating minimal delay in surgery whilst improving outcome. High-intensity interval training (HIT) shows much promise in this respect. When compared with moderate continuous exercise training in high-risk cardiac populations, HIT has delivered significantly superior fitness improvements and is more enjoyable to participating individuals 23, 24. The low absolute risk of complications with HIT has also been well established in these studies. Encouragingly, we are aware of two National Institute for Health Research-funded feasibility studies presently underway examining the benefits of HIT before abdominal aortic aneurysm repair 25 and colorectal cancer surgery 26. Second, pre-operative physical frailty is increasingly recognised as an independent surgical risk factor 27, 28. Assessment of frailty is increasingly being undertaken in pre-operative assessment clinics, but little appears underway to facilitate its partial correction (if possible) in this setting. It appears a rational concept, that pre-operative musculoskeletal conditioning and mobilisation strategies implemented in appropriately identified individuals may translate to or facilitate improved surgical outcome. This intervention may be beneficial in tandem with aerobic fitness training in the pre-operative period: outcome studies are awaited in this area. Third, the recognition of pre-operative nutritional deficiency as a negative prognostic indicator 29, 30 suggests that gains may be made from improving patients’ nutrition over the longer pre-operative term, in addition to established carbohydrate loading immediately before surgery. It is also important to recognise the importance of optimisation of nutritional status in obese individuals before surgery, although to some degree being overweight/obese may confer ‘paradoxical’ protection with improved surgical outcomes 31. Combining all of these variables in a marginal gains approach or ‘pre-habilitation package’ appears to have significant potential in an effort to improve outcome following major surgery. Integrated optimisation of anaemia, aerobic fitness, nutrition, frailty, smoking cessation and medication for individual patients will undoubtedly create a complex challenge across several healthcare disciplines, with a high degree of collaborative support required. The ideal scenario would be to look towards providing ‘one-stop’ regional facilities centred within primary care, with all available infrastructure and expertise available on site. Referrals could be initiated in tandem with referrals to surgeons so as to avoid unnecessary delays or redundant time within the process. Anaesthetists would be ideally placed to run/co-ordinate such facilities, given our diverse knowledge and expertise in all these areas. Integration with primary care physicians would be a pivotal part of any process. Once the approach has been applied to elective cases, the next (and arguably bigger) challenge would be to introduce broader pre-habilitation concepts to the population at large, to prepare them for emergency surgery 32. It remains unlikely that widespread commissioning and adoption of such a sea change in pre-operative management will be implemented, however, without further development of the current evidence base. Awaiting robust outcome evidence from trials of separate individual components of the package is likely to be fruitless; first, it might never occur, and second, it runs contrary to the spirit of the concept of aggregation of marginal gains. Very large trials would be required to define precisely the effect of some individual components, and these isolated effects might not be clinically significant in their own right, in any case. Therefore it might be more appropriate to design future research interventions with all the putative marginal gains components in place from the outset. Such trials would involve an example of a ‘complex intervention’, containing several interacting components and presenting challenges for design, implementation, and evaluation 33. The scale and expense of a definitive trial of the aggregation of marginal gains obligates a focus on both effectiveness (does it work?) and mechanisms (how does it work?). Regarding the second question, however, any crude evaluation based on the decomposition of a complex intervention into its constituent parts reduces a complex intervention to a simple one – a complex intervention is more than the sum of its parts 34. In designing a trial of aggregation of marginal gains, a sine qua non is to produce, a priori, a robust causal diagram linking the intervention to the outcome, and including all putative mechanism variables (mediators), and other relevant covariates 35. This process will help decide the set of covariates to adjust for in the data analysis to reduce bias, and to tease out the mechanisms underlying any overall beneficial effect 36. There is a lot of evidence available within the field of sports science, some of which is transferrable into clinical practice and, we hope, improved patient outcomes. Although significant challenges exist in producing high-quality definitive outcome studies within the current NHS financial climate, this should not represent a barrier to moving forwards. Alternatively, we could recommend that patients bring their own pillows and skin-tight pyjamas to hospital with them in a bid to improve outcome! No external funding and no competing interests declared.