Enteral nutrition via a jejunostomy decreases both jejunal and gastric tube intra-mucosal pH following oesophagectomy

Background

Many animal and human studies have demonstrated that gastrointestinal intra-mucosal pH (pHi) which is usually measured using a gastric tonometer is partly dependent upon mucosal perfusion, and that its measurement can predict for poor outcome in the critically ill. There is increasing evidence that not only in this group of patients but also following upper gastrointestinal surgery that the early introduction of enteral nutrition may reduce morbidity and mortality and increase enteric mucosal tissue perfusion. Theoretically this effect may be especially desirable following oesophagectomy and oesophagogastric anastomosis as gastric blood flow is compromised following gastroplasty. However, the measurement of gastric pHi using the tonometric method is thought to be confounded during infusion of enteral feed by the release of carbon dioxide from the feed itself following enzymic digestion. This study assessed the effect of a standard enteral feed upon both gastric and jejunal pHi measured using gas tonometry when delivered via a feeding jejunostomy.

Method

Nineteen patients undergoing oesophageal resection for carcinoma and reconstitution of gastrointestinal continuity using a gastric tube were studied. During surgery tonometer balloons (Tonometric division, Instrumentarium Division, Helsinki, Finland) were placed 5 cm distal to the anastomosis within the stomach and 10 cm from the duodeno-jejunal flexure within the jejunum. The jejunal tonometer was placed alongside a standard 8 F Foley feeding jejunostomy tube. The tonometers were connected to separate `Tonocap' analysers (Datex, Helsinki, Finland). Five days following surgery all the patients had left the intensive care unit and had returned to the surgical ward and were being fed (Fresubin Standard, Fresenius Ltd, Runcorn, Cheshire, UK) via the jejunostomy tube (mean rate 108 ml/h). The feed was stopped for a minimum of 6 h and then both jejunal and gastric pHi was measured using a simultaneously taken arterial blood gas sample. The feed was then recommenced and after 2 h the measurements were repeated. The results were analysed using the Mann-Whitney test for non-parametric data.

Results

Prior to the commencement of feeding mean (SD) jejunal and gastric pHi were 7.44 (0.06) and 7.37 (0.08) respectively Following 2 h of enteral nutrition jejunal and gastric pHi had fallen to 7.26 (0.09) and gastric pHi to 7.29 (0.12). These falls were both significant (P < 0.005 and P < 0.05, respectively).

Conclusion

Standard enteral nutrition delivered via a feeding jejunostomy appears to cause a fall in tonometrically measured jejunal pHi. That this may at least in part reflect a fall in mucosal blood flow rather than have been caused by the release of carbon dioxide from the feed is supported by the finding that gastric pHi also falls despite the fact that no feed was introduced into the stomach. That an enteric reflex may be responsible for this finding seems likely although its significance with regard to its effect upon anastomotic perfusion remains unknown.