Small intestinal motor patterns in critically ill patients after major abdominal surgery

OBJECTIVES: In patients who have had major surgery or trauma. early enteral feeding is safer and more effective than parenteral or nasogastric feeding but is frequently associated with diarrhea. Limited recordings have shown that the patterning of duodenal interdigestive motor activity is frequently abnormal after surgery or in patients who are critically ill. The aims of this study were to evaluate the effects of major abdominal surgery on small intestinal motility, and to elucidate the motor patterns that occur postoperatively in critically ill patients in response to enteral feeding. METHODS: The effects of elective aortic aneurysm repair on small intestinal motility were studied in I I patients aged 63-77 yr. A 3.5-mm diameter multilumen extrusion was used to monitor pressures at 12 points, distributed between the antrum and 100 cm distal to the pylorus. An additional lumen allowed enteral feeding into the duodenum. Recordings commenced immediately postoperatively and continued for up to 4 days. Data are given as means and SEMs. RESULTS: Bursts (frequency > 10/min) of small intestinal pressure waves that resembled phase Ill interdigestive motor activity occurred in all patients immediately after surgery. During mechanical ventilation, the timing of bursts along the segment evaluated was frequently abnormal for true interdigestive phase Ill activity, with simultaneous onset in multiple channels (46%), multiple or distal origins (8%), or retrograde migration (20%). When patients were not being ventilated, the migration pattern of the bursts was more typical of interdigestive phase Ill activity. The interval between bursts was unusually short for interdigestive motor activity, although it increased from 30 +/- 12 min on day I to 41 +/- 18 min on day 3 (P < 0.05). A phase Il pattern of pressure waves was virtually absent in all patients on all study days. In six patients who received postoperative enteral nutrition. the bursts of pressure waves were not abolished by feeding, contrary to normal phase Ill activity. CONCLUSIONS: Small intestinal pressure wave bursts are seen immediately after elective aortic aneurysm repair, but the migration of these bursts is frequently abnormal for phase Ill interdigestive activity. Duodenal nutrient delivery did not interrupt the occurrence of these bursts. Persistence of pressure wave bursts in this setting may be important in the delivery of enteral nutrition.