Guidelines for the Provision and Assessment of Nutrition Support Therapy in the Adult Critically Ill Patient: Society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition (ASPEN)
This is an update and expansion of the previous nutrition guidelines and this is a summary of the some of the key points. I discussed this particular document at the Intensive Care Society State of the Art 2016 with Danielle Bear (@Danni_dietician), Ella Segaran (@ESegaran), Roger Harris (@RogerRdHarris) and Dr Todd Rice and that will be available as a podcast very soon so that you can listen to the discussion. When it is I will make sure I include the link on this page.
Nutrition Support in Particular Conditions.
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.
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
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.
Selection of Appropriate Enteral Formulation and Adjunctive Therapy
There is a recommendation to start with standard feed when initiating EN as there has been no clear benefit shown to using speciality formulas in areas such as the surgical ICU or medical ICU. They also do not recommend the use of immune modulation formulations.
They make no recommendations around the use of fish oils, borage oil and antioxidants in patients with ARDS and ALI due to conflicting data.
Consideration needs to be given to the use of a mixed fibre formulation in those patients with persistent diarrhoea. Such a formulation is not recommended for routine use in the patient to promote bowel regularity.
There is no recommendation as to the use of probiotics in the general ICU population. The use of probiotics would seem theoretically sound but there has not been a consistent benefit demonstrated. Antioxidants (vitamin E and C) and trace minerals might be useful especially in burns, trauma and critical illness requiring mechanical ventilation.
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.
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.
Renal and Hepatic Failure
Patients in ARF or AKI should be put onto a standard formula. If significant electrolyte disturbances occur then formulations designed for renal failure should be considered. Those patients on CRRT should receive increased protein as significant amino acid loss is associated with CRRT.
A dry weight should be used instead of actual weight in the patient in hepatic failure when determining energy and protein requirements. This then accounts for the possibly significant ascites and oedema they may be suffering.
EN should be used in preference to PN in the patient with liver failure and a standard formulation should be used.
Disease state may change quickly in this condition so frequent reassessment is needed. For those patients with a mild acute pancreatitis specialised nutritional therapy is not recommended but an effort to work towards normal oral intake instead.
For those with moderate to severe pancreatitis an NG tube should be inserted and there should be efforts made to advance to goal within 24-48 hours after admission.
Standard formula should be used in the severe pancreatitis patient and EN is preferred to PN as it has been shown in several studies and meta-analysis to reduce mortality, LOS and surgical interventions.
In moderate to severe patients who have an intolerance to EN measures should be taken to reduce the intolerance such as:
- starting EN as early as possible to minimise the period of ileus.
- diverting level of EN more distally.
- change to a formula that contains small peptides or one that is nearly fat-free.
- switch from bolus to continuous.
Probiotics should be added for this type of patient.
EN therapy should be introduced within 48 hours from diagnosis when resuscitation is complete and the patient is haemodynamically stable.
In the acute phase, where possible, EN should be used exclusively.
A recommendation is made for trophic feeding for the initial phase of sepsis advancing to 80% within the first week and there should be delivery of 1.2-2g protein/kg/day.
Chronically Critically Ill
Defined as those with persistent organ dysfunction requiring ICU LOS greater than 21 days.
They should be managed with aggressive high protein EN therapy. In a series of studies, patients demonstrated chronic inflammation and a maladaptive immune response that contributed to secondary nosocomial infections and severe protein catabolism.
Obesity in Critical Illness
Early EN should start within 24-48 hrs. There is no difference between this type of patient and those that are not obese. 57% of hospitalised patients with a BMI of greater than 25 show signs of malnutrition! A couple of quotes are needed here I feel to reinforce a couple of key points:
The reasons for the surprisingly high rate of malnutrition in obese patients may stem in part from unintentional weight loss early after admission to the ICU and a lack of attention from clinicians who misinterpret the high BMI to represent additional nutrition reserves that protect the patient from insult.
The obesity paradox may contribute to clinicians’ illusion that obese patients do not need nutrition therapy early in their ICU stay. The mortality curve for BMI is U-shaped, with the mortality highest in class III severely obese patients with BMI >40 and in people with BMI <25. Mortality is lowest in subjects with BMI in the range of 30–40 (class I and II obesity). This protective effect of moderate obesity is the obesity paradox.
This section of the paper highlights a number of the problem the obese patient will have in the ICU such as:
- technical difficulties of management
- vascular access
- performing tracheostomy
- interpreting radiologic images
- altered drug metabolism
- Predisposition to heart failure
- Respiratory abnormalities
- Liver pathology
- nonalcoholic fatty liver
- steatosis- accumulation of fat in the liver
- Compared lean counterparts:
- increased morbidity
- greater incidence of infection
- prolonged hospital and ICU LOS
- increased risk of organ failure
- Longer duration mechanical ventilation
As a consequence of all of these factors there is a recommendation for the nutrition assessment of the obese patient to focus on evidence of central adiposity, metabolic syndrome, sarcopenia (loss of skeletal muscle mass), SIRS and other comorbidities that correlate with higher obesity-related risk for cardiovascular disease and mortality.
There is a recommendation for high protein hypocaloric feeding to preserve lean body mass, mobilise adipose stores and minimise the metabolic complications of overfeeding.
Promotion of weight loss is achieved by aiming for 60-70% of target energy requirements. Some degree of weight loss may increase insulin sensitivity, facilitate nursing care and reduce risks of comorbidities.
Due to the intentional permissive underfeeding of the obese patient, there should be additional monitoring to assess for worsening of:
- Fluid overload
- Hepatic fat accumulation
It is very important to restate that these are guidelines only. Each patient should be assessed individually and care should be taken to take account of the units they are being nursed in and the resources that are available, both financial and personnel.
These are very extensive guidelines and if you want to read more or see the many references then go to this site here.
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