January 2017 E-Journal Club
Although we have had a smattering of brisk days, overall we have been rather shamelessly spoilt here in Virginia by our very mild winter (thus far). With no snow to shovel, we are deep in the midst of updating talks for our spring Weekend Warrior program, mentoring dietetic interns and preparing for trainees to visit in March. No doubt, that will be when the snow arrives!
Our article this month deals with one of our favorite topics: gastric residuals. Just when Carol Parrish thought we were done checking, thinking, or talking about gastric residuals, the topic has zombied back in a new way.
Sharma V, Gudivada D, Gueer R, Bailitz J. Ultrasound-Assessed Gastric Antral Area Correlates With Aspirated Tube Feed Volume in Enterally Fed Critically Ill Patients. Nutrition in Clinical Practice, Online First, December 16, 2016.
This was a pilot study of mechanically ventilated adult ICU patients which investigated the feasibility of using ultrasound to estimated gastric antral dimensions to determine gastric residual volume. A convenience sample of 19 patients was utilized, with a total of 57 attempts to image the antrum using the aorta as a landmark and 57 using the IVC as a landmark.
Ultrasound images were obtained just prior to measurement of gastric residuals with a 50 mL syringe, and after no further material could be aspirated, the stomach was scanned again to ensure complete emptying.
All ultrasound measurements were performed at 30 degrees head up, in the supine position. The median BMI of the patients was 26 kg/m2 (IQR: 17-41).
Gastric antral area was determined by assessing anteroposterior (AP) and craniocaudal (CC) diameters of the gastric antrum. Simple linear regression analysis was used to assess correlations between gastric antral dimensions and aspirated residual volume.
Inclusion and Exclusion Criteria:
Mechanically ventilated adult ICU patients with a nasogastric, orogastric, or percutaneous gastrostomy tube in place, Tube feeds ongoing or planned to continue, Tip of tube in stomach on most recent X-ray.
Feeds being delivered by nasojejunal tube, Tip of gastric tube not in the stomach in most recent X-ray, Prisoners, Intestinal obstruction, Gastrointestinal perforation, No feeding planned for prolonged duration, GRVs not being monitored regularly, Pregnant women, Patient deemed inappropriate for study enrollment by either attending/registered nurse or investigator for any reason
Ultrasound visualization of the gastric antrum using the aorta as a landmark was unsuccessful (due to overlying bowel gas or intragastric air) in 21% of the attempts, while visualization of the gastric antrum using the IVC as a landmark was not successful in 42% of the attempts.
Gastric cross-sectional area (CSA) using IVC as a landmark (R2 = 0.92, P < .0001) and aorta as a landmark (R2 = 0.86, P < .0001) correlated with aspirated volume. Craniocaudal diameter of the stomach measured using the aorta as a landmark correlated with aspirated volume and increased linearly with increasing GRV (R2 = 0.78, P < .0001). A craniocaudal diameter alone of <10 cm using the aorta as a landmark predicted a gastric volume of <500 mL and a craniocaudal diameter using the aorta as a landmark of <5 cm predicted GRV <150 mL.
“…gastric ultrasound can accurately estimate gastric volume among critically ill patients being enterally fed in a medical ICU setting. The ultrasound appearance of the empty or nearly empty stomach is defined, allowing for confident titration of feeds or institution of aggressive bolus feeding, especially when there is a “need to know” the gastric volume. Ultrasonographically assessed CC diameter of the gastric antrum <10 cm using the aorta as a landmark is a simple test to predict gastric volume <500 mL. Nursing staff may be able to use bedside ultrasound as an alternative to radiographic studies to assess gastric volume in patients with ETF intolerance..”
This was only a small pilot/feasibility type study, but the use of ultrasound to determine the volume of gastric contents appears to hold promise as a clinically useful tool. One of the limitations of traditional syringe aspiration of gastric contents is that there is no way to know the position of the tube’s feeding ports relative to the pool of fluid. The feeding tube ports could potentially be near the top (or above) the fluid pool and give a false impression of gastric emptying, even though the patient might have a large volume of retained feeding formula and endogenous secretions. If ultrasound could provide a simple, accurate way to assess actual gastric volume, then it might be a useful tool for reducing the incidence of regurgitation or emesis during EN.
Unfortunately, although there was correlation between ultrasound and aspirated residual measurement, and craniocaudal diameter < 10 was a reasonable predictor of gastric volume < 500 mls, visualization of the gastric antrum using the aorta as a landmark was unsuccessful in 1 out of 5 attempts (21%). The inability to visualize the antrum is some patients may ultimately limit the clinical usefulness at the bedside.
Additionally, it would have been helpful to learn more about the number of any false negatives/false positive measurements that occurred (with both ultrasound and syringe aspiration) during this study.
Most importantly, there is also a need for further study to determine if ultrasound monitoring during EN in the ICU allows any improvements in clinical outcome (less emesis, less pneumonia). Considering the limited clinical utility of syringe aspiration to measure gastric residuals, and the cost of providing easier access to ultrasound in all the ICUs, we need further data before ultrasound assessment during EN becomes routine.
Our Take Home Message(s)
- When ultrasound visualization of the stomach is successful, ultrasound assessment of gastric cross sectional area correlates with aspiration of gastric contents via syringe in adult ICU patients.
- There is a need for further studies to evaluate if ultrasound monitoring of the abdomen during EN results in improvements in clinical outcomes that matter.
Other News on the UVAHS GI Nutrition Website: (www.ginutrition.virginia.edu):
Upcoming Webinars 2017:
March 7: Clinicians Guide to Gastric Versus Jejunal Feeding
April 19: Nutrition Support Cases
May 10: Blenderized Enteral Feeding
Latest Practical Gastroenterology article:
The Use of Medium-Chain Triglycerides in Gastrointestinal Disorders
Joe Krenitsky MS, RDN
PS – Please feel free to forward on to friends and colleagues.