GASTRIC TONOMETRY DURING MAJOR ABDOMINAL- SURGERY

Objective: To investigate whether changes in gastric intramucosal pH ( pH(im)) occur during major abdominal surgery, and if so, to determine the relationship between classic global indices of tissue perfusion su ch as mean arterial blood pressure (MAP), heart rate (HR), central ven ous pressure (CVP), urine flow (UF) and arterial pH (pHa). Study desig n: Prospective descriptive study. Patients: Seven ASA2 patients underg oing major abdominal surgery. Methods: After induction of anaesthesia and endotracheal intubation, a tonometer nasogastric tube was position ed in the stomach, Measurements of ionometric PCO2 (PCO(2)ss), end-tid al PCO2 (PETCO(2)), PaCO2, bicarbonates [bicarb .], pHa, MAP, HR, CVP and UF were collected at baseline (H0), and one, two, three, and 24 ho urs (H1, H2, H3, and H24) after the beginning of surgery. Results: Hae modynamics did not significantly change during anaesthesia. During rec overy HR increased and CVP decreased significantly. The pH(im) decreas ed significantly from 7.42 +/- 0.03 at H0 to 7.30 +/- 0.02 at H3. This was associated with a significant decrease in pHa (from 7.43 +/- 0.02 at H0 to 7.33 +/- 0.02 at H3) and in [bicarb .] from 22 +/- 1 mmol at H0 to 20 +/- 1 mmol at H3). The PaCO2 increased significantly from 33 .5 +/- 1.5 mmHg at H0 to 39.5 +/- 2.8 at H3. On the other hand, pH(imc orr) (7.40 - (pHa-pH(im)) and Delta CO2 (PCO(2)ss-PETCO(2)) did not va ry during anaesthesia. Postoperative organ failure did not occur in th ese patients. Conclusions: The pH(im) may decrease during anaesthesia without evidence of abnormal tissue perfusion. In order to avoid confo unding factors such as PaCO2 and [bicarb .] we propose to monitor Delt a CO2 or pH(imcorr) instead of pH(im).