ASPEN-SCCM Guidelines on Nutrition
There is recommendation of the use of the Nutrition Risk Screening(NRS)/NUTRIC score for all patients who are expected not to be able to have sufficient volitional intake. Of all the other scores used these are the only ones that determine both nutrition status and disease severity.
NRS score >3 is a patient at ‘risk’ and those at ‘high risk’ with an NRS score equal to or greater than 5.
If interleukin 6 is measured this value would be greater than 6 in the NUTRIC score. However as there are rarely the facilities to measure this value then a value of 5 or greater indicates ‘high risk in the NUTRIC score also.
It is anticipated that ultrasound will emerge as a useful tool in measuring muscle mass and determine changes in muscle tissue and even CT scans of the skeletal muscle could be done. Both of these will not be too common currently due to cost and lack of trained personnel, however it is an aspiration towards the future. The same could be said of indirect calorimetry measurements which are also recommended.
Where there is an absence of indirect calorimetry then energy requirements should be calculated using published predictive equations or simplistic weight based equations. Even where indirect calorimetry is available it is prone to error in the ICU due to presence of air leaks or chest tubes, supplemental oxygen, ventilator settings and renal replacement therapy.
However calculated energy expenditure should be reevaluated at least once per week.
There is also an emphasis on the provision of protein, being the most important macronutrient for healing wounds, supporting immune function and maintaining lean body mass.
Initiating Enteral Nutrition
Enteral Nutrition (EN) should be initiated within 24-48 hours. The specific reasons for providing EN are to:
- maintain gut integrity
- modulate stress
- modulate the systemic immune response
- attenuate disease severity
Studies have shown a significant reduction in mortality with the introduction of early EN. There is also a recommendation to use EN rather than parenteral nutrition (PN). Studies have shown a reduction in infectious morbidity and ICU LOS when comparing EN to PN.
There is no need to wait for overt signs of bowel activity i.e. bowel sounds. These indicate only contractility and do not relate to mucosal integrity, barrier function or absorptive capacity.
On most critically ill patients it is acceptable to initiate NG feeding whilst those at risk of aspiration should have feeding initiated lower down the GI tract. If small bowel access is difficult then feeding should be initiated in the stomach rather than wait.
EN can be given to those stable patients on low dose vasopressors but should be withheld on patients who are hypotensive, have catecholamine agents or who are requiring escalating doses to maintain stability.
For patients on vasopressors any sign of gut intolerance:
- abdominal distension
- increasing NG output
- decreased passage of stool and flatus
- hypoactive bowel sounds
- increasing metabolic acidosis
then the EN should be with held.
Dosing of EN
Patients at low risk with normal baseline nutrition and low disease severity (NRS less than or equal to 3 or NUTRIC less than or equal to 5) who cannot maintain volitional intake do not require specialised nutrition therapy. They should be offered oral intake and reassessed daily.
Trophic or full EN is appropriate for patients with ALI or ARDS and those expected to have a ventilation period greater than 72 hours.
In the high-risk patient, efforts should be made to provide greater than 80% of target within 48-72 hours. Studies have shown that greater than 50-60% of goal energy may be required to prevent increases in intestinal permeability and systemic infection in burn and bone marrow patients, promote faster cognitive return in head injury patients and to reduce mortality in high-risk hospitalised patients.
Monitoring Tolerance and Adequacy of EN
For me, this is one of the main points to come out of this document.
So some facts first!
- 97% of nurses assess tolerance by gastric residual volumes (GRVs) alone.
- The most frequently cited thresholds for withholding feed were 200 and 250mls.
- Less than half of patients ever reach their target goal energy intake during their ICU stay
- Cessation of EN occurs in >85% of patients for an average of 8%-20% of the infusion time
Raising the cutoff value for GRVs from a lower number of 50-150ml to a higher number of 250-500ml DOES NOT increase the incidence of regurgitation, aspiration or pneumonia.
Use of GRVs leads to:
- enteral access clogging
- inappropriate cessation of EN
- consumption of nursing time
- may adversely affect outcomes through reduced volume of EN delivered.
So the recommendation is that GRVs should NOT be used and, if they are used, the cut off should be 500mls.
The patient should be monitored for other signs of intolerance (see above).
Another area which drew my attention especially was the recommendation that there should be a volume based feeding protocol which should be ICU or nurse-driven. These protocols would:
- define goal EN infusion rate
- designate more rapid start-ups
- provide specific orders for handling GRVs, frequency of flushes and conditions under which EN may be adjusted or stopped.
Such strategies have been shown to increase the overall percentage of energy provided.
These are the free to access references that are used….go have a read and see what you think…
The aim of these protocols is to empower nurses to increase feeding rates to make up for volume lost while EN is held.
Aspiration is always of great concern in the Intensive Care patient and the guidelines acknowledge this.
Patients should be assessed for risk of aspiration which may be identified by a number of factors:
- inability to protect the airway
- presence of a Naso enteric enteral access device
- mechanical ventilation
- age > 70 years
- reduced level of consciousness
- poor oral care
- inadequate nurse:patient ratio
- supine positioning
- neurologic deficits
- gastroesophageal reflux
- transport out of ICU
- use of bolus intermittent EN
….phew! That covers a lot of my patients!
Where there is a risk of aspiration the patient should be feed beyond the pylorus, so NJ feeding, they should not be fed by bolus EN and there should be the use of prokinetics, and those prokinetics would include metoclopramide and erythromycin. Whilst not improving long-term ICU outcomes these drugs have been shown to improve gastric emptying.
Nursing measures, such as head elevation between 30-45 degrees and the use of chlorhexedine mouth washes, are recommended. Other steps to decrease aspiration risk include reducing the level of sedation/analgesia when possible and minimising transport out of the ICU for diagnostic tests and procedures (although I think we only ever take patients for these tests when absolutely necessary).
Enteral feeding should not be discontinued due to the presence of diarrhoea until other causes have also been investigated. These could include:
- type and amount of fibre in formula.
- osmolality of formula
- delivery mode.
- glucose-lowering agents
- infectious etiologies including C Diff.
Assessment of diarrhoea should then include abdominal examination, quantification of stool, stool culture for C Diff, serum electrolytes and review of medications.
When to Use Parenteral Nutrition (PN).
In the low nutrition risk patient, where early EN is not feasible, then PN should be witheld for the first seven days whereas in the patient at high nutrition risk in the same circumstances then PN should be started as early as possible.
In the patient where EN is not meeting greater than 60% of their needs then PN should be started after 7-10 days.
Nutrition Support in Particular Conditions.
Speciality high fat/low carbohydrate formulations designed to manipulate the respiratory quotient and reduce carbon dioxide production are not recommended in ICU patients with acute respiratory failure.
Recommendation is made for the use of fluid restricted energy dense formulations in this group of patients and also that the serum phosphate levels should be monitored closely. Phosphate is crucial in the synthesis of ATP and 2,3-DPG which are both crucial for normal diaphragmatic contractility and optimal pulmonary function.
Guidelines for the management of tracheal intubation in critically ill adults
Having read the guidelines I made these infographics. They are FREE. Just click on the button below.