Should we be checking gastric residuals?

What is a VAP?

We won’t dive into too much detail here, but VAP is considered hospital-acquired pneumonia that has occurred 48 hours after a patient has been intubated. VAP can be suspected when a patient develops a new infiltrate on CXR, increased ventilator settings, increased tracheal secretions, leukocytosis, new fever, and clinical judgment of the LIP. 

Gastric Physiology

The stomach is ultimately a reservoir, and this reservoir allows slow emptying into the small bowel. The slow emptying of the stomach occurs at 5-15 cc and is designed to help with absorption in the gut. We must remember that endogenous and exogenous factors go into the gastric volume (food, water, medications, bile, etc.). During any given meal, the stomach can expand upwards of 1,000 cc. After 1,000 cc, pressure can increase, causing distention and discomfort. Complete emptying after a meal can occur around 3-4 hours. During a fasting state, the stomach can secrete upwards of 500-1,500 cc of bile and content alone, and in a fed state upwards of 2,500 cc. This is a lot of mixed secretions and bile content that the body needs that can be contributing to our “high residuals.”

Show them the studies?

The REGANE study compared the effects of increasing gastric residual volume and receiving an adequate amount of nutrition. Montejo et al. studied 329 mechanically ventilated patients using a diet volume ratio (diet received/diet prescribed) and compared this to GI complications, VAP, days on mechanical ventilator, and ICU length of stay. Results were that there were no essential differences in a residual limit of 500 cc vs. 200 cc. In addition, the higher limit of 500 cc was not associated with an increase in GI complications, VAP, mechanically ventilated days, and ICU LOS. 

The CRICS group study took whether VAP had a higher association with higher residual gastric volume. This study was a randomized multicenter trial in nine French ICUs that enrolled 449 patients. Two groups in this study were no monitoring of gastric residual vs. routine (Q. 4hr with a cut off of 250 cc) checks in patients receiving mechanical ventilation. Outcomes that they measured were patients with at least one VAP episode. Reignier et al. showed no significant difference between study groups in mechanically ventilated days, ICU LOS, ICU acquired infections, or mortality rates. 

There are numerous other studies (Nutrirea1 trial, Poulard, McClave, and Yasuda) with similar findings. You can look at these further yourself, but I won’t bore you with any more studies. 

The newest American Society of parenteral and enteral nutrition (ASPEN) guidelines recommend NOT using gastric residual volumes as a part of routine care for those patients receiving enteral nutrition in the ICU. This is due to the fact that frequent checking of gastric residuals can lead to a hold on enteral nutrition related to “high residuals”. This causes patients to not reach their caloric goals, thereby a possible worsening in outcomes for your patient. In summary patients who do not get their total caloric needs show worse outcomes.

If there are clinical signs of intolerance such as abdominal distention, constipation, and/or pain, the bedside warrior can ask for further evaluation. This evaluation includes KUB or CT scan, and maybe the addition of prokinetic medications and a bowel regimen to help with emptying.

Early nutrition

Some studies have looked at early enteral/parenteral nutrition vs. delayed nutritional intake. What we have found is that early administration of nutrition reduced mortality and pneumonia compared to delayed administration. In addition, critical care medicine released a meta-analysis in 2018 that showed improvement in clinical outcomes when early nutrition was established. Improvements are related to preserved gut integrity, leading to fewer infections, fewer organ failures, and a reduction in sepsis occurrences. Preventing any number of these complications can only help improve survival and reduce hospital length of stay.