When to Switch From Parenteral to Enteral Feeding With Intestinal Grafts? Can Serum Citrulline Provide the Answer?

Abstract

Introduction: Serum citrulline was used as a biochemical marker to direct nutritional therapy in two phases of the post-operative course after intestinal transplantation. Methods: On a predetermined day of the week, serum citrulline levels were monitored on a weekly basis after small bowel transplantation. A level of 13 μmol/l with a normal GFR was used as a cut off to guide patient's feeding regimes. Citrulline levels above 13μmol/l were a trigger to start weaning TPN. Levels >18μmol/l were a trigger to stop TPN and achieve full enteral feeds. Patients were studied in two separate time periods: just after implantation and during acute graft dysfunction following a stable period of function. Results:From October 2007 to date, 24 patients underwent intestinal transplantation. Four patients had stomach included in the graft and 20 had isolated intestines. Mean citrulline levels in the first, second and third week after transplantation were 15.9±3.8μmol/L 13.4±5.6μmol/L and 21.9±9.1μmol/L respectively. Mean stoma output in the first, second and third week was 20mls/kg/24 hours, 25mls/kg/24 hours and 20mls/kg/24 hours respectively. Seven patients presented with acute onset intestinal dysfunction after a stable graft in the first year. Four were treated for acute rejection. Mean citrulline levels for the seven patients presenting with intestinal dysfunction were 15.2±1.9μmol/l and at 48 hours after presentation 10.7±11.9μmol/l. Mean time to achieve TPN independence after transplantation was 18 days (range 15- 30 days). Mean time to achieve TPN independence after acute graft dysfunction was 22 days (range 13- 35 days). Conclusion: Serum citrulline levels correlate well with stoma output and therefore the absorptive mass of the intestinal grafts. Serum citrulline levels initially show a drop in the second week after transplantation before a subsequent rise in the third week. Whatever the cause of acute graft dysfunction, initial TPN may be required and subsequent introduction of enteral nutritional therapy can be directed by serum citrulline.