We have just concluded another great traineeship week. This month our trainees were from opposite ends of the Appalachian Trail – Maine and Georgia. We all went out for South American cuisine on Wednesday night, and had a great time there too.
Our article this month is from the April issue of Intensive Care Medicine and deals with a somewhat controversial topic – enteral feeding in hypotensive patients receiving “pressors”.
Rokyta R Jr, Matejovic M, Krouzecky A, Senft V, Trefil L, Novak I. Post-pyloric enteral nutrition in septic patients: effects on hepato-splanchnic hemodynamics and energy status. Intensive Care Med. 2004 Apr;30(4):714-7.
This study was designed to study the effects of low-dose post-pyloric enteral nutrition on splanchnic blood flow, metabolic response and gastric mucosal PCO2 in septic patients. Data was collected from ten mechanically ventilated patients with sepsis in a medical ICU on the 2nd to 5th day of ICU admission. The subjects received a semi-elemental, 1 calorie/ml formula (Survimed OPD) via a post-pyloric feeding tube. The feeding was provided as a 40ml bolus, then 40ml/hr for two hours, then the feedings were held for two hours for further data collection.
In order to gauge intestinal perfusion all subjects had a catheter placed into the hepatic vein via the internal jugular, and hepato-splanchic blood flow estimated with “primed continuous indocyanine green”. In addition gastric mucosal PCO2 was measured with gastric tonometry. Arterial and hepatic blood lactate and pyruvate, blood gasses, blood glucose, heart rate, cardiac index, and indirect calorimetry were measured before, during and after the feedings.
The authors reported that hepato-splanchnic blood flow significantly increased during enteral feeding, and returned to baseline after feedings were stopped. The splanchnic lactate, pyruvate and mucosal PCO2 did not change during the feedings. The authors conclusion was that “enteral nutrition during sepsis may not be harmful even in patients requiring norepinephrine.”
This study is important because there is such a limited body of data on the safety of feeding the hypotensive patient. Several case studies have been published in which small bowel ischemia was believed to be associated with enteral feeding in hemodynamically unstable patients. In the current study, each patient served as their own control as feedings were started and then held again. Eight of the 10 patients were receiving norepinephrine at the time of the feedings, and none of the patients had any signs of compromised luminal blood flow during the study.
There are, however, a number of limitations to this study that limit it’s relevance to the patient’s that we deal with. One of which was the small “n”. Patients who were deemed to be hemodynamically unstable, or who had a cardiac index less than 2.5 L/min were excluded from the study. Those patients who were included were able to have their blood pressure controlled with a modest dose of a single pressor drug (two required no pressors during the study). In addition, patients only received enteral feedings for two hours, and all feedings were designed to be hypocaloric (40 mL bolus, followed by 40 mL per hour x 2 hours – total kcal = 120).
Take home message:
This study has a limited clinical applicabilitybecause of the short duration and limited amount of the feedings, and because of the “stable” nature of the patients. The results would not necessarily apply to a much more unstable patient, or a patient with significant prior cardiovascular disease with severe hypotension. However, this study is valuable to let us know that it is NOT necessarily correct to make sweeping statements “that patients on pressors should not receive enteral feedings.” It is important to remember how infrequent intestinal Ischemia is, compared to the large number of critically ill patients who receive enteral feedings each day in this country. A more complete discussion of many of these issues can be found in the August 2003 Nutrition in Clinical Practice articles and editorials by Kudsk, McClave, Zaloga, and Tappenden.
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