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Continuous measurement of gut luminal pCO2 in an animal model — a sensitive index of reduced perfusion

The sensitivity of gastric tonometry to fluctuations in mucosal perfusion is limited by long equilibration periods (minimum 30 min with saline). Delayed detection of splanchnic ischaemia may negate any benefit from subsequent improvements in splanchnic oxygen delivery. Continuous luminal pCO2 measurement for prompt detection and quantification of mucosal ischaemia could make gastric tonometry a more valid therapeutic end point. We tested the sensitivity of one continuous system to graded brief reductions in gut perfusion.

Five Sprague-Dawley rats (430–r510 g) were anaesthetised with intraperitoneal sodium pentobarbitone and ventilated with 100% oxygen via tracheostomy to a paCO2 of 30–r50 mmHg. Distal aortic pressure was monitored invasively, and a Paratrend 7™ sensor inserted into the ileal lumen. Normal saline was infused at 3 ml/h, and isoflurane titrated to a mean aortic pressure of 80–r100 mmHg. Distal aortic pressure was reduced to predefined levels for 2 min intervals by digital elevation of an aortic silk sling above the coeliac artery, with intervening recovery periods to allow restabilisation of luminal PCO2. Measurements were downloaded every 2 s to a data acquisition system. Data are mean (SEM).


Continuous luminal pCO2 measurement by the Paratrend 7 was highly sensitive and rapidly responsive to brief reductions in aortic pressure. The peak pCO2 elevation above baseline and area of the CO2 elevation curve above baseline both correlated significantly with insult severity. Combined with continuos arterial blood gas analysis, the technique could be used to monitor pHi or the luminal-arterial pCO2 gradient real-time and provide a better therapeutic end point in the individual patient.


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Morgan, J., Venkatesh, B. & Endre, Z. Continuous measurement of gut luminal pCO2 in an animal model — a sensitive index of reduced perfusion. Crit Care 1 (Suppl 1), P087 (1997).

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