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Background and goal of study: In critically ill patients hypoperfusion of the gastrointestinal tract cause gut ischaemia and hypoxia leading to multiple organ failure (MOF). Calculation of gastric intramucosal PH (PHi) has been used to assess the degree of gastrointestinal perfusion. However, continuous gastric intramucosal CO2 tension or gastric-arterial PCO2 difference seems to be a better approach to measure the adequacy of gut perfusion [1, 2]. The goal of the study was to investigate the relationship between calculated PHi and all measured PCO2 differences.
Patients and methods: We studied 10 severely ill patients with multiple trauma or abdominal sepsis to investigate the correlation between arterial, mixed venous, end-tidal and gastric intramucosal PCO2 differences and PHi. All patients were on mechanical ventilation, monitored with a pulmonary artery catheter and with a gastric tonometer (TRIP, Tonometrics). Measurements of PaCO2, PvCO2, PtCO2, PrCO2 and pHi were performed at 1, 12, 24, 48 and 72 h after admission. PaCO2-PrCO2, PrCO2-PtCO2 and PaCO2-PvCO2 differences were calculated. Mean ± SD and linear regression analysis of pooled data.
Results and discussion: Eight male and 2 female, 62 ± 15 years old, APACHE II 19 ± 8, TISS 51 ± 12. All patients received vasoactive drugs. Five patients developed MOF and three died. Mean PrCO2-PaCO2 difference was 19 mmHg (range 2 to 52 mmHg) and mean PHi was 7.22 (range 7.03 to 7.39). No relationship was found between PrCO2 and PaCO2 (r = 0.25, P = 0.08), while the correlation coefficient between PvCO2 and PaCO2 was 0.71 (P < 0.01) and between PHi and PrCO2 was 0.56 (P<0.01). A significant linear relationship was found also between PrCO2-PaCO2 difference and PHi (r = 0.66, P < 0.01) and between PrCO2-PaCO2 and PrCO2-PtCO2 difference (r = 0.91, P < 0.01).
Conclusions: In this small group of critically ill patients PrCO2 was not related to PaCO2 meaning that PrCO2 was a good marker of gastrointestinal perfusion. In addition, the close relationship between PrCO2-PaCO2 and PrCO2-PtCO2 difference indicates that PrCO2-PtCO2 difference can be used as an 'on line' gastrointestinal perfusion marker.
