Update: How Many Calories

regarding updated literature on feeding critically ill patients

In the previous post, I discussed relying heavily on the Penn State Equation to assess energy needs and compare to calories/kg. Also, assessing energy needs daily when a patient is ventilated and a minute ventilation is available. I am also a dietitian that likes to get my patients fed! This article begs me question myself “am I being too gung ho?” when I am recommending feeding patients. I am always looking for ways to improve care or make sure I am following best practice. Some really good new assessment ideas of how we should feed critically ill patients is available. Most of the ideas are not new but have been made more concrete!

According to “Early Feeding in Critical Care – Where Are We Now?” (Which I will be referencing for this blog)

Mette M. Berger, MD, PhD^a [email protected] ∙ Annika Reintam Blaser, MD, PhD^b,c ∙ Orit Raphaeli, PhD^d ∙ Pierre Singer, MD^e,f

we should be concentrating on “slow rolling” feeding advancement on patients who are critically ill, and paying more attention to where they are in the metabolic phase. Also the importance of energy balance cannot be ignored. . It appears that a cumulative deficit of ~4000 cals has been shown to have few detrimental affects, but the progression of up to 6000-8000 kcal deficit, patients begin to show increasing mortality ,VAP, wound dehiscence, sepsis infection, renal failure and pressure sores.

Overfeeding:

Overfeeding is detrimental to critically ill patients and should be avoided. Using predictive equations can often times lead to over feeding because they generally overestimate energy needs. Indirect calorimetry is the gold standard, but most facilities do not have access to this.

Another reason patients are overfed is because of elevated endogenous glucose production, which is present during the early phases of inflammation in critical illness. It is not picked up by IC and is not repressed if the patient is being fed endogenously. “It is indirectly reflected by high insulin requirements and high VCO2.” In one example of young trauma patients who were not being fed for 3 days, it was estimated that EGP generated as much as 1200 calories per day, which depleted muscle stores by gluconeogenisis. Partially fed, older patients saw some similarity, with making ~720 calories per day from EGP, even when being partially fed. One of the issues, is that feeding patients with tube feeding or PN does not seem to suppress this pathway, so full feeding from an exogenous source will actually represent overfeeding these patients. This can lead to such things as hyperglycemia, further insulin resistance, renal failure, non obstructive mesenteric ischemia and Ogilvie’s Syndrome.

Refeeding syndrome is also common in critically ill patients, which is another reason to slowly increase feeds to goal. That will be a topic for another day.

Enteral Feeding Intolerance:

Another interesting concept is that enteral feeding intolerance (EFI), is indicative that the body is too ill to be fed. EFI can include, gastric overfilling, intestinal dilation and or diarrhea. Management of these issues may depend on the phase and underlying illness. Defining the target of enteral nutrition according to where the patient is appears to be helpful to the patient. It is also advantageous to know where in the phase the patient is to help define what monitoring is being done. Being able to define triggers to stop enteral nutrition when it appears detrimental is key. For example, if a patient is early in critical illness and is not tolerating enteral feeds due emesis, abdominal distention, elevated gastric residuals, stopping or trickle feeds may be helpful versus starting pro kinetic agents because their body may be telling us it is not ready for enteral nutrition. If, the patient is stable and still having issues, the above options are more suitable.

Early Feeding Strategy:

According to this article, we should be doing the following with our critical care patients:

1. Start early EN; 10-20 ml/hr with in 48 hours, Assess for gi tolerance, assess for refeeding.
2. Increase progressively to 20-25 kcal/kg/day.
3. Measure EEN if patient is stable.
4. Reach 100% of EEN with 4-7 days.
5. Reassess target and monitor response to feeding.
6. If by day 4-7, patient is not tolerating enteral feeds, consider PN.

Estimating energy needs::

If there is no Indirect Calorimetry available, consider an integrated VCO2 measurement using the Weir Equation. This is has been used for personalized IC tools that appear fairly accurate. It would be interesting to assess how they align with other predictive equations.

The formula for the Weir Equation is; RMR = 1.440 × (3.94 × VO2 + 1.11 × VCO2).

In summary, I would recommend downloading the above article, it is a good read! There were many other areas discussed that I did not mention but are worthy of review.

Also, if you have an interest in critical care nutrition and you are not following Dr. Paul Wischmeyer on Instagram, you should be. He always has amazing , up to date articles and great graphics!

https://www.threads.net/@paulwischmeyermd?xmt=AQGzPjYXhPV_55mqQhRAkI2zya4uydyW1FNjfnDDFRpnyUM

Anyway, hope this was interesting, please feel free to leave a comment!