Where ICU meets sports nutrition

Where ICU overlaps with sports nutrition

Isn’t it bizarre how trivial conversations or moments can stick in your head? I often think back to such a moment in September 2019…

Despite having promised to myself in 2013 that my life in academia was finally over, having qualified as a Registered Dietitian, there I was in the classroom again, ready for Exercise Physiology – the first module of my Applied Sports Nutrition postgrad.

Most of the students on my side of the course had a nutrition background of some description (while the other side had a sports background), including a sprinkling of dietitians with differing levels of clinical experience. I was the only one coming from a critical care (ICU) background though, and this caused a few eyebrows to raise. At least two or three of my new coursemates asked ‘why would an ICU dietitian be interested in sports nutrition’ or stated that ‘you couldn’t pick two more different ends of the dietetic spectrum’. I knew that this wasn’t the case, but I could also see why someone who didn’t work in critical care might make these assumptions…and no doubt there are others visiting my website who will be thinking the same. So these conversations stayed with me, and I’ve been meaning to write this blog ever since.

I make no secret of the fact that I specialise in critical care and endurance sports nutrition (plus plant-based nutrition, but I’ve covered that in lots of other blogs so won’t mention here), and I feel lucky to have found two areas of nutrition that I feel so passionate about. Importantly though, there are huge areas of overlap that mean that, far from being totally separate entities, a greater understanding in one really benefits my practice in the other.

  1. Precision nutrition

ICU is all about numbers, data, and precision – or at least the pursuit of precision – and this is certainly part of the appeal. This is true for everything from biochemistry to ventilation settings, and certainly for nutrition too. Patients are generally fed via enteral feeding tube or intravenously, and every ml of delivered nutrition is documented. That’s not to say that how we set our nutrition targets is without some controversy, nor that feeding always goes to plan (there are always interruptions and unexpected breaks in feed), but as long as everything is accurately documented and analysed, we can monitor and react to those individual nutritional ‘balances’ (comparing feed prescription to delivery), as we seek to optimise that patient’s nutritional status.

The same can be said for sports nutrition. As with ICU, there may never be absolute consensus on how we calculate athletes’ nutrition requirements, but as the evidence base continues to grow (and it’s my job to stay on top of this), there is now undoubtedly greater precision and specificity in the guidelines. Through electronic food diaries, we can then quantitively track a client’s progress against these targets and be extremely precise in our recommendations. In my experience, this is what clients want, and it’s great to be able to provide this with confidence.

  1. Periodisation

In a similar vein to the point above, there is a broad acceptance that nutrition advice on critical care needs to be periodised, adjusting for different stages in a patient’s journey from early acute illness (where substrate utilisation is impaired) through to the late acute and then chronic and rehab phases, when physiology and metabolism shifts dramatically.

A major outstanding question in critical care nutrition is how to recognise the flow between these different phases. Fortunately, this is not a problem in sports nutrition, where the evidence and guidelines allow for nutrition advice to be neatly periodised around far more clearly defined phases, both on a ‘macro’ level in terms of training seasons and race build-ups, but also on a ‘micro’ level, in terms of key nutrient intake windows around individual sessions and rest days: essential to getting the best adaptation from all that hard work in training.

  1. Body under stress

I mentioned earlier the acute phase of critical illness and how this impacts on nutrition. Critical illness puts a huge amount of stress on the body, and, certainly in its earliest stages at least, induces a hypoxic and catabolic state where the metabolism of glucose, fatty acids and amino acids is all likely to significantly altered.

The same is true in sports, of course, where we push ourselves to the limit and induce physiological stress, albeit deliberately! We deprive our working muscles of adequate oxygen to respire aerobically, tipping us into and beyond our anaerobic or lactate thresholds. We also need to remember that exercise alone (whether resistance or cardio) is catabolic, and it only becomes an anabolic (i.e. muscle-building) process when combined with adequate nutrition. I’ve often come across statements such as ‘one day on ICU is like running a marathon’, and this is all rooted in the massive overlap here in terms of stress on the body.

I look out for rising blood lactate, electrolyte depletion and reduced oxygen saturation in all my ICU patients. It’s no coincidence that these are all also key elements  of exercise physiology and performance nutrition!

  1. Rehab and recovery

As ICU medical management improves, so do patient survival rates. And with this being the case, in recent years there has been an ever-increasing emphasis on achieving far more than just ‘survival’. Post Intensive Care Syndrome (PICS) is a dreadful but all-too-common combination of cognitive, psychological and physical impairments that persist for months, if not years, after ICU. One benefit of the current pandemic has been the increased media attention (and clinical funding) that post-ICU has received, but the reality is that this is not an issue specific to COVID-19.

We have the most fantastic post-ICU MDT recovery clinic at my hospital, where patients have access to a consultant, nurse, physio, occupational therapist, psychologist, pharmacist, and of course, a dietitian – me! I feel very privileged to be able to guide these incredibly vulnerable patients through their rehabilitation and recovery, as they deal with a bewildering mix of symptoms and changes in appetite, intake and body composition.

The language overlap with sports nutrition in terms of ‘rehab’, ‘recovery’, and ‘muscle wasting’ is immediately obvious, and in fact, this is another area where the evidence base in critical care rehab nutrition lags behind and actually borrows from the comparably well-defined guidance for sports and performance nutrition. Logic suggests, for example, that the ‘muscle full effect’ of protein dosing and timing that is so well described in performance nutrition should also apply to the rehabilitating post-ICU patient. I do therefore often adopt a similar strategy in my post-ICU clinic, but the reality is we don’t yet have the data in this population to confirm the theory. Watch this space, hopefully…

The other benefit of working in the post-ICU clinic is that I get to actually speak to my patients (!), many of whom have no idea that my colleagues and I were also providing their nutritional care when they were sedated, mechanically ventilated and tube-fed on the ICU a few months earlier. Given that all of my sports clients are awake (hopefully), it’s probably no bad thing that I’ve been keeping up my clinic skills, not least negotiating goals that work around individual patient lifestyles and schedules.

  1. Holistic physiology

Working on a mixed medical and surgical ICU means that every patient that comes through the door is completely different, and critical care dietitians, perhaps more than any other, need to be experts on the body as a whole. Organ systems don’t fail in isolation; a patient might have respiratory, kidney and GI failure simultaneously, for example, and each of these has nutritional implications that we interpret and respond to. It’s sometimes incredibly complicated and may mean prioritising one component over another, but coming from a biology background, I relish the opportunity to think so holistically.

Once again, this really benefits my work in sports nutrition, where it’s all about different organ systems working together. Of course, there are the fundamental and overlapping roles of the working muscles, lungs and heart. But we also need to consider, for example, the complex relationship between exercise and the GI tract, and the massive impact of the central nervous system on performance. All of these can be influenced by or impact on an athlete’s nutrition and hydration strategy, and this is what usually occupies my mind when I’m running (genuinely!), and certainly when I’m advising clients.

Hopefully I’ve managed to convince you that, far from being alien ends of the nutrition spectrum, there is a HUGE overlap between the wonderful worlds of critical care and sports nutrition, and that expertise in one massively benefits the other.


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