July is often a busy month because we welcome new interns, residents and fellows to our facility. Although I occasionally have to answer some of the same questions each year, at least I am getting better at the answers! The waterfall picture is from one of Joe’s summer adventures: if you look closely you can see an RD pictured near the falls for scale (right in the middle of the photo).
Our journal club article was about one of our favorite topics – gastric residuals!
Hamada SR, Garcon P, Ronot M, et al. Ultrasound assessment of gastric volume in critically ill patients. Intensive Care Med. 2014;40(7):965-972.
This was a prospective observational study that examined the feasibility and validity of using ultrasound to estimate the gastric volume (GV) of 55 critically ill adult patients. Ultrasound estimation of GV (antral cross-sectional area) by ICU physicians at the bedside was compared with contrast-enhanced CT scan measurement of GV.
The primary endpoint of the study was the validity of ultrasound to estimate GV, compared to GV measured on CT scan. Secondary endpoints were the feasibility of ultrasound at the bedside in terms of how many were good versus low quality images and to compare ultrasound estimation of GV by ICU physicians compared with measurements by a radiologist in terms of being able to distinguish an empty stomach from an “at-risk” stomach (defined as 0.8 mL/kg fluid).
Inclusion and Exclusion Criteria:
Consecutive patients admitted to an ICU and scheduled to have an abdominal contrast-enhanced CT scan.
Age < 18 years, pregnancy, history of upper GI surgery.
There were 55 patients included in the study, with major trauma as the reason for admission in 49% of the patients. The abdominal CT was performed within 44 minutes after ultrasound measurements in all patients. Only 25% of the patients were receiving enteral nutrition support (EN) , with 62% of the patients reportedly taking oral intake and 13% fasting.
The ultrasound quality was rated as good in 65% of patients, poor in 29% and impossible in 6% of patients due to ileus and “gas screen” impairing penetration.
There was not a strong correlation between ultrasound and CT measurement of total GV in all patients (rs = 0.39), and only minor improvement even when only the “good” studies were considered (rs = 0.43). Correlations between intensivist and radiologist ultrasound measurements were acceptable in studies rated as good (rs= 0.94), but not acceptable in the poor studies.
“Antral cross-sectional area measured by ultrasound is feasible in the majority of critically ill patients. Antral CSA is positively correlated with GV and allows qualitative assessment of GV with clinically acceptable accuracy.”
This is an interesting study, because one of the limitations of checking gastric residuals during EN is the inherent inaccuracy of the measurement. It is possible that the feeding tube port (s) may not even be in the pool of gastric fluid! The concept of a non-invasive and non-yucky method of accurately assessing GV might let us finally pin down the volume of gastric fluid during EN that is usually safe, and what is too much.
It is important to remember that this was a feasibility study with a modest number of patients. Inclusion into the study was dictated by those patients who required an abdominal CT scan, thus it is possible that these results may not translate directly to some other patient groups. The average BMI of these patients was 23.9 kg/m2 (range 21 -26), so it is possible that these results may also not apply to a more obese population.
Our group discussed the study definition of an “at-risk stomach” defined as gastric fluid volume of 0.8 mL/kg. This small volume (55 mL GV for a 68 kg reference patient) was based on animal studies of the volume of hydrochloric acid that would cause pneumonia when instilled into the pulmonary system. We know that critically ill adults routinely tolerate a much higher gastric volume during EN without increasing the risk of aspiration pneumonia. Based on the graphs, there appeared to be only 10 patients that actually had an increased gastric residual during the CT scan. From a practical standpoint, ultrasound may be a more practical tool to differentiate “doing fine” from “hold the feeding” than this study might suggest.
We also discussed that GV could change in 44 minutes on the way down to CT scan – especially if patients are turned on their right side during transfers. The lack of correlation between CT scan and ultrasound (in patients with limited fluid in the stomach) does not necessarily mean that ultrasound would not be useful at the bedside.
Our Take Home Message (s)
- Ultrasound may be a feasible method to assess gastric volume in many adult ICU patients.
- There is a need for larger studies of ultrasound measurement of gastric volume, with more diverse patients during EN, including studies that measure clinical outcomes (i.e., does measurement of GV matter?).
- We would be very interested in evaluating a “nutrisonic” device that would allow us to assess muscle mass for nutrition assessment and also monitor gastric volume during EN.
Other News on the UVAHS GI Nutrition Website: (www.ginutrition.virginia.edu):
Upcoming Webinars 2014:
–Fall webinar topics will include: Nutrition Support in Gastroparesis, Feeding the Critically Ill Obese Patient, and Issues in Long Term Enteral Feeding. Details to be posted shortly.
Check out What’s New:
–“Nutrition Support Blog”
Latest Practical Gastroenterology article:
–Krenitsky J. The Calorie Requirement Conundrum Practical Gastroenterology 2014;XXXVIII(7):12.
Joe Krenitsky MS, RD
Carol Rees Parrish MS, RD
PS – Please feel free to forward on to friends and colleagues.