Summary and Background
The gastrointestinal (GI) tract plays an important role in regulating the body’s inflammatory response and immune function, in addition to the absorption of nutrients. In critical illness, patients can experience a massive pro-inflammatory response from the gut, leading to oxidative tissue damage, apoptosis, and an impaired immune response towards infectious pathogens. Additionally, increased mucosal permeability can occur, increasing the risk of infection via bacterial translocation into the bloodstream. 30-50% of ICU patients are malnourished upon admission, a factor that can further predispose patients to these consequences of GI impairment.
Early initiation of enteral nutrition (EN) can be greatly beneficial in supporting proper GI function in critically ill patients. Providing as little as 20% of a patient’s total nutritional goals enterally can lower inflammation, reduce oxidative stress, support the humoral immune response, restore microbiome composition, and decrease insulin resistance. The 2016 ASPEN/SCCM guidelines state, “In setting of hemodynamic compromise or instability, EN should be withheld until patient is fully resuscitated and/or stable,” due to the risk of nonocclusive bowel necrosis (NOBN). The largest study supporting the concern for NOBN stems is the NUTRIREA-2 study that investigated 2410 mechanically ventilated patients requiring vasopressor support, randomized to early enteral nutrition or parenteral nutrition. Patients in the enteral nutrition group experienced increased bowel ischemia over the parenteral nutrition group. Of note, the study’s patient population had an elevated mean vasopressor requirement of 0.53 ug/mg/min of norepinephrine.
The effect of vasopressors on gut perfusion and the risk of NOBN seems to be dose-related. Thus, recommendations for a safe dose range and vasopressor selection for initiation of enteral nutrition would be of utility. These guidelines seek to increase the administration of early enteral nutrition in appropriate clinical scenarios, as well as provide guidance in higher-risk situations where enteral nutrition should be restricted to a reduced rate or withheld.
Prior to initiation of EN, assess patient for resuscitation and hemodynamic stability markers:
-Lactate normalized (≤ 2.0) or correcting rapidly
-Mean arterial pressure (MAP) maintained >65 (with or without vasopressors)
-Vasopressor requirements decreasing or stable (e.g.: Norepi @ 0.2mcg/kg/min with other stable parameters listed here)
-Fluid requirements stabilizing (patient is not actively requiring boluses for blood pressure maintenance)
-No ongoing or active bleeding
-The primary team will initiate the tube feeding based on resuscitation and hemodynamic stability markers and using the guidelines below (Table 1)
-The RD will be responsible for completing a Nutrition Evaluation note with tube feeding recommendations within 24 hr of the placement of the Nutrition Consult order
References
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November 29, 2020 (K Fedder/B Woodward/A Bernard); Reviewed 12-15-23
