ICU Nutritional Management – Insights from the frontline
By Dr Timothy Eden, RD with contributions from Shane McAuliffe, RD and edited by Professor Sumantra Ray, RNutr
Insights from the frontline as NNEdPro Global Innovation Panel (GIP) member Dr Tim Eden RD shares his own experience of the challenges faced in the nutritional management of COVID-19 patients in ICU: https://twitter.com/TimothyEdenRD/status/1245634083012505602
With a high rate of COVID-19 patients in the overweight/obese category as well as those with Type-2 Diabetes, this can present a significant challenge when estimating and fulfilling these individualised nutritional requirements. Looking specifically at obese patients, there has historically been an attitude of underfeeding in intensive care, but this cohort is equally at risk of becoming malnourished (rapid, significant and unplanned weight loss) when nutritional requirements are not met for prolonged periods, and this can be a predictor of poorer clinical course and outcomes (1). The following narrative is not intended to replace clinical guidelines but is designed to highlight some key aspects relevant to nutritional assessment in ICU when treating patients with COVID-19.
Estimating Nutritional Requirements:
Anthropometry:
- Obtaining accurate/actual weight can be difficult when patients are often haemodynamically unstable and susceptible to acute desaturation on repositioning early in the COVID-19 clinical course.
- It is advisable to obtain weight when utilising time spent with physiotherapy and/or at times of hoisting.
- Equally height is often estimated and remains very variable due to individual bias and limitations on movement/measurements; accurate heights are useful two-fold to help better estimate BMI/weight but also for ventilator settings (manipulating tidal volumes) therefore ulnar measures may be acceptable (2).
- From anecdotal experience a significant proportion of patient’s requiring level 3 care have BMI >25 or are in the obese category defined as BMI >30.0kg/m2.
- If BMI>30kg/m2 then opt for Adjusted Ideal Bodyweight or Ideal Body Weight (IBW)
- Ideal body weight can be calculated based on the patient’s height calculated to BMI = 25kg/m2 (2) – this is more realistic and time efficient.
- Limited ideal energy equations in obesity whereby current evidence opts for hypocaloric high protein feeding (so factor this in when implementing feeding regimes).
Energy Requirements:
- There are a number of suitable predictive equations used on ICU (3,5,6).
- PENN State & Mifflin St Jeor: These equations account for temperature and ventilation settings (3,5,6) – although it should be appreciated these fluctuate daily and therefore the additional effort spent may not provide significant clinical gain.
- A more practical and time efficient approach to adopt can be the ESPEN/ASPEN equations using kcal/kg.
o ASPEN recommend 11-14kcal/kg/actual bodyweight in the BMI range of 30-50kg/m2 or 22-25kcal/IBW when BMI >50kg/m2 (7).
o ESPEN recommending 20-25kcal/kg or 25-30kcal/kg in the Ebb and Flow phase respectively for ABW in the non-obese (3).
- It is important to note many patients in ICU are ventilated (requiring respiratory support) and having an awareness of the type of ventilation can help gauge the level of support and severity of their respiratory needs e.g. mandatory through to spontaneous modes.
- Assessing ongoing temperatures and extremes of febrile states will influence your estimates of insensible losses.
- We have seen many patients receive a maximum of approx. 70% of feed in a 24h period due to issues such as proning, aspiration risk, tube placement delays which has been reported elsewhere (8,9,11).
- It is therefore important to prioritise tolerance and build up energy/protein provision as able – protocol for nursing staff enable ongoing increments without the need of ongoing dietetic review (3,7).
Protein Requirements:
- ASPEN recommend 2g/kg IBW in patients with BMI 30-40kg/m2 and 2-2.5g/kg/IBW if BMI>40 kg/m2 (7).
- Reaching these high targets may require additional protein supplementation (e.g. Prosource TF), particularly in the presence of tolerance issues or when feed volume is restricted (5,6).
- An important consideration is for patients on temporary renal replacement therapy (RRT) whereby the timeframe of continuous filtration will vary greatly
- For patients ‘on-filter’ or receiving RRT, aim for 1.5-2g/kg (10).
- For patients ‘off-filter’, although potentially still with signs of kidney damage (AKI/ CKD/ low eGFR), aim for 1-1.2g/kg (10).
- Fluid balance is closely controlled in COVID-19 patients, along with increased use of diuretics (e.g Furosemide) to aid respiratory function. This can increases the risk of renal dysfunction and electrolyte abnormalities (10). Low volume/electrolyte feeds may be most suitable in these circumstances (5).
Factors affecting feed choice:
Sedation:
- It has been observed that the younger cohort of patients require higher levels of sedation (e.g. Fentanyl/Propofol) and these are also a source of calories, approx. 1kcal/ml should be factored in when using propofol doses of ≥200mg/h.
Fluid Balance:
- Due to close fluid balance control targets could well be negative 500ml to 1L, meaning high energy, concentrated feeds to help meet energy requirements (1.5-2kcal/ml) (5,11).
- Close attention should be paid to time on and off filtration (RRT) as fluid restrictions will be influenced by medical interventions available i.e. be aware of the term ‘filter holiday’ as when off filter, a tighter restriction may be implemented.
GI Issues:
- This in itself can be a symptom of COVID-19, but is also contributed by high levels of medication (analgesia/sedatives/noradrenaline), which can result in delayed gastric emptying.
- Early prokinetics (e.g. Metoclopramide/Erythromycin) can be effective in counteracting this issue and close monitoring instigated to help remove the burden of polypharmacy (5,6).
- Hydrolysed (or partially broken down) feeds can also improve digestibility and GI tolerance.
- Proning is often associated with poorer feed tolerance – be aware of local guidance for pre-proning advice and set protocols when patient is in prone positon(described below).
Proning:
- This refers to the adjustment of a patient from a supine (lying back down) into the prone (lying face/chest down), as a means of improving ventilation in patients with acute respiratory distress syndrome (ARDS) (12).
- This technique is commonly employed in (up to 70% of) ventilated COVID patients (5).
- This generally occurs in cycles, 16 hours on (prone) and 8 hours off (supine) which can contribute to interruptions in feeding (5).
- This will require adjusting feeding rate, based on GI tolerance. Starting with a concentrated feed at approx. 20ml/hr and increasing in slow increments is generally good practice.
- It is important to monitor gastric residual volumes (GRV’s) or ‘aspirates’ to assess tolerance, and consider reducing rate as these approach 300ml (max). These should be checked every 4-8 hours if possible (5,11).
- Persistent intolerance of feed may require post-pyloric feeding although in practice there has been limited clinical need for this so far (5,11).
Novel Therapies:
- High does Vitamin C has been suggested as an adjunctive therapy to support the immune system during ARDS, however this has not been demonstrated in a recent trial (13) and may warrant further investigation in COVID specific patients.
- Low carbohydrate feeds are rarely used in UK practice and few enteral feeds have been shown to exceed glucose oxidation rate (GOR) and therefore this is not likely to impact ventilation settings, but low CHO feeds could impact negatively on energy provision.
- Fish oils rich in omega-3 fatty acids possess anti-inflammatory properties (14). This has led to suggestions that they may play a role in mediating the severe inflammatory response observed in critically ill patients with COVID-19, having previously been associated with favourable outcomes in ARDS (15). This may warrant further investigation in COVID-19 patients.
- The potential antioxidant effect of specific micronutrients remain contentious and unsubstantiated. There is a high risk of suboptimal micronutrient status in COVID-19 patients based on demographic (16), disease pathology (17) and also certain treatment practices (10). Certain micronutrients have been suggested to play a role in mediating the inflammatory process in critically ill patients (18,19,20), particularly when used to correct suboptimal status.
- Suboptimal vitamin D status associates with poorer outcomes in ARDS, and a number of viral infections and may warrant assessment/replacement in high risk patients appreciating the timing of year of this pandemic (post winter) and low risk intervention (21).
- Consideration of the role of micronutrient status in COVID-19 risk and recovery may also warrant further investigation.
Summary:
The nutritional management of patients presenting with COVID-19 in the critical care setting remains complex and evolving. However, we have a wealth of resources to aid our nutritional assessment and to help implement feeding plans. As with all management plans, we must be able to adapt and adjust our clinical management accordingly in line with standard clinical and dietetic review processes.
Simplistic equations and utilising feed protocols for varying scenarios may be a pragmatic method to ensure consistency across departments whilst aiding AHPs to manage increased caseloads. Excellent communication with nursing, medical and other healthcare staff who form part of the care process is key to help implement and monitor interventions and identify any acute issues impacting management. Those with doubts or questions, are not alone. Voicing questions within a department as collective thinking will ultimately serve in the best interest of patients whilst recognising we are all navigating uncharted territory. That said each day is a learning curve!
Future work
As the role of nutritional management in COVID-19 is being elucidated, further research in this field will help to shape specific nutrition guidelines. A key point of interest is the baseline nutritional status for patients presenting with COVID-19 and how this may impact the clinical course. For example measures of anthropometry e.g. weight/BMI have drawn much attention associating with poorer outcomes but also direct nutritional measures such as vitamin D status and other micronutrient panels may be of significant interest. It is well documented in other respiratory viruses that vitamin D plays a role at mediating viral inflammation of the respiratory tract whilst having other roles in immune function. This at present has attracted wide research interest noting that coming out of a winter whereby across the general population vitamin D levels are likely to be suboptimal. It could also be linked to the disproportionate impact to the BAME (Black, Asian and Minority Ethnic) community which has been evident in London but is reflective across the UK and more widely (22).
Research groups and clinicians continue to work quickly to help further identify patterns which may lead to therapeutic interventions to combat COVID-19. As a junior doctor in a West London Intensive Care Unit, together with colleagues, we are seeking to address early unanswered questions by assessing nutritional status on admission and tracking morbidity and mortality. The principal aim is to identify a clinical panel of nutritional markers and assess outcomes to begin identifying those groups of patients who may in turn benefit from more targeted nutritional care as we progress through this pandemic.
Notes:
TE is both a Licensed Medical Doctor as well as a Registered Dietitian working in NHS Intensive Care; SM is a Registered Dietitian working in the NHS; SR is both a Licensed Medical Doctor as well as a Registered Nutritionist (Public Health) working as a Medical Academic.
Recently Tim Eden spoke to James Bradfield about his experiences during the COVID-19 pandemic. Links to the podcast below:
TE, Minha Rajput-Ray and SR are co-authors of the chapter on Micronutrient and vitamin physiology and requirements in critically ill patients. Textbook of Nutrition in Critical Care. Cambridge University Press (2014).
References:
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