November 2012 e-journal Club

 

Greetings,

We do not host a training program in November, but we have been busy with our state ASPEN chapter meeting (VASPEN), dietetic interns starting their nutrition support rotations with us, and preparing to study the effects of turkey and pumpkin pie ingestion on the efficiency of nutrition support practitioners... :)

Our journal club this month is an observational study that examines the potential of intra-abdominal pressure monitoring to help predict enteral nutrition tolerance.

November Citation:

Bejarano N, Navarro S, Rebasa P, et al.  Intra-abdominal Pressure as a Prognostic Factor for Tolerance of Enteral Nutrition in Critical Patients.  JPEN J Parenter Enteral Nutr. 2012 Oct 15. [Epub ahead of print]

Summary: 

This was a single-center, observational study of 72 mixed medical-surgical adult ICU patients with an expected ICU stay of > 72 hours.  All patients had their intra-abdominal pressure (IAP) checked every 8 hours, which is done by measurement of bladder pressure via an indwelling urinary bladder catheter.  A number of physiologic variables, several different scoring methods of injury and illness severity, need for mechanical ventilation, medications and fluid balance were recorded.  The goal of the study was to develop a model using IAP and other clinical variables that would predict, in advance, who would tolerate enteral nutrition (EN)

EN tolerance was defined as meeting nutrition goals within 72 hours of starting the study.  EN intolerance was defined as at least 1 of the following:  abdominal pain or distention, emesis/regurgitation, pulmonary aspiration, diarrhea, constipation or a gastric residual volume (GRV) ≥ 200 mL.  GRVs were checked every 6 hours.  Calorie needs were estimated by the Harris-Benedict equation and feedings were started at 1/3 of the goal rate and advanced by 1/3 every 8 hours until goal feeding was reached.  The authors defined “absolute intolerance” as a GRV ≥ 400 mL (after treating known potential causes), “or considering parenteral nutrition (PN) or small bowel feedings.”

Inclusion and Exclusion Criteria were:

Inclusion criteria:

Patients admitted to the ICU with postoperative care following abdominal surgery (elective or emergency), abdominal trauma in the context of polytrauma, medical pathology with shock (hypovolemic or septic), or severe acute pancreatitis with an expected ICU stay of > 72 hours and receiving EN.

Exclusion criteria:

Patients with previous surgery on the bladder, neurogenic bladder, inability to apply a transurethral bladder catheter, hepatic ascites, pregnancy, or those who otherwise could not have monitoring of IAP.

Major Results reported by authors:

Simple between group comparisons identified the following as associated with EN intolerance: need for muscle relaxants, need for motility stimulants, SOFA score, APACHE II score, baseline IAP, and water balance.  Multiple logistic regression modeling identified only 2 variables deemed predictive of EN tolerance: baseline IAP and APACHE II score.  The authors reported that the results demonstrated that “patients with a median APACHE score of 13–14 as well as an IAP of around 14mm Hg prior to the initiation of the diet have a high probability of intolerance, whereas those with an IAP below 11 mm Hg will tolerate the diet.”  The sensitivity for the formula was 92.2%, with a specificity of 52.4%, a positive predictive value of 82.5%, and a negative predictive value of 73.3%.

Author’s Conclusions:

“In critically ill patients, there is a relation between IAP values and the tolerance of EN. The IAP prior to the start of the EN along with the APACHE II score can predict the tolerance of EN.”

Evaluation:

Intra-abdominal hypertension and abdominal compartment syndrome can occur when abdominal contents expand beyond the normal capacity of the abdominal cavity, which can compromise abdominal organ perfusion, and may increase risk for necrotic bowel during EN.  Capillary leakage during fluid resuscitation, decreased abdominal wall compliance, increased intraluminal contents and increased peritoneal cavity contents are all believed to be factors that contribute to increased IAP.  The concept of increased IAP as a potential risk factor for EN intolerance is logical.

However, there are a number of limitations to this article that we identified.  Most importantly, the definition of feeding intolerance was very conservative. This study used a physiologically normal amount of gastric fluid (200 mL of GRV), diarrhea and constipation as indicators of feeding intolerance, which are not valid indicators of clinical intolerance to EN.  The use of non-validated indicators as a surrogate for feeding intolerance limits the clinical significance of this study.  A second major limitation is that there were only 21 patients with feeding intolerance in the entire study, which is a very small number for predictive models on a mixed medical, trauma and surgical population.  Other issues that the group discussed were the limited number of obese patients (may limit the generalizability to a US population), the possibility of an increased IAP in the obese, and the limited specificity of the model.

Our Take Home Message (s)

1)   There may be a link between feeding intolerance and intra-abdominal hypertension in critically ill adult patients, however larger studies that utilize clinical outcomes of feeding intolerance are required.

Other News on the UVAHS GI Nutrition Website: (www.ginutrition.virginia.edu):

Upcoming Webinars 2012/2013:

--Tuesday, December 4:  Information Mastery:  Evidence-Based Medicine in the Real World--David Slawson, MD

--Tuesday, January 15:  Outpatient PEGs & the “Stat RD Consult--Carol Parrish, MS, RD

Check out What’s New:

--“Nutrition Support Blog”  

--“ Resources for the Nutrition Support Clinician

Latest Practical Gastroenterology article:

--Sansaricq, FC, Petronic-Rosic V. Dermatitis Herpetiformis: What Practitioners Need to Know.  Practical Gastroenterology 2012;XXXVI(11):39.

 

Joe Krenitsky MS, RD

Carol Rees Parrish MS, RD

 

PS – Please feel free to forward on to friends and colleagues.