Does enteral feeding potentially alter the PCO2 gap and pHi?
© Current Science Ltd 1999
Published: 16 March 2000
Measurement of pHi or the mucosal-arterial PCO2 gap is advocated to detect splanchnic ischaemia and covert shock. Nasogastric feeding may significantly affect these measurements. We used a previously described animal model  to evaluate the effect of enteral feeds on the luminal PCO2 response to intermittent splanchnic ischaemia.
Adult male Wistar rats (285-425 g) were anaesthetised with sodium pentobarbitone 60 mg/kg i.p. and ventilated with 100% oxygen and isoflurane via tracheostomy to a PaCO2 of 30-40 torr. Distal aortic pressure was monitored continuously. A sensor (Paratrend 7, Diametrix Medical Inc., Bucks, UK) was inserted into the ileal lumen to record PCO2 measurements every 2 s, Four rats received no feeds (controls) whilst in another four rats an ileal cannula was inserted and feed (Nutrison, Nutricia, Zoetermeer, Holland) infused at 3 ml/h. In each rat, five two-minute episodes of aortic hypotension were induced to a mean pressure of 30 mmHg by intermittent elevation of a silk sling placed around the proximal aorta.
See Table. Feeds significantly elevated the mean baseline luminal PCO2 and delayed and blunted the PCO2 increases (∆PCO2) in response to transient ischaemia.
55 ± 4
47 ± 15
180 ± 12
28 ± 8
67 ± 9*
51 ± 18
196 ± 16*
23 ± 4*
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