Gastric-arterial pCO₂ gradient, but not lactate levels, is related to multiple organ dysfunction assessed by SOFA score in septic patients

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Introduction

The gut hypoperfusion could contribute to development of multiple organ dysfunction in septic patients. However, there is no definitive study correlating the time course of gastric mucosal PCO₂ and organ dysfunction.

Methods

We have studied prospectively 27 adult severe septic patients consecutively admitted in two large mixed ICUs. Each patient had a nasogastric tonometer and a pulmonary artery catheter. Every 8 h, systemic hemodynamic and oxygen variables, plasma lactate levels and gastric mucosal pCO₂ (PgCO₂) were measured. All these variables were measured on inclusion day (Day 0) and on the 1st, 2nd and 3rd days. pCO₂-gap was calculated as the difference between PgCO₂ and PaCO₂. Daily, we measured the SOFA score to characterize organ dysfunction evolution. We used the median pCO₂-gap and lactate values of each day and time course of these variables to correlate to organ dysfunction and outcome (mortality on day 28). Changes over time were analyzed using a Kruskal-Wallis test and the relative risk (RR) was calculated.

Results

The median age was 55 years and median APACHE II score was 18.5. The overall mortality rate was 52%. Table 1 shows the RR and CI 95% of each variables on day 0, 1, 2 and 3. The best cutoff values of pCO₂-gap,lactate values and SOFA score were 15 mmHg, 2 mEq/l and 11, respectively. On the 0, 1st, 2nd and 3rd days, the patients that had pCO₂-gap values of more than 14 mmHg, either the SOFA score remained high or the patients died on the 10th day (P<0.05). In contrast, on the same days, lactate levels did not discriminate either organ dysfunction development or death on the 10th day.

Table 1 RR and CI 95% of each variable to estimate outcome on 28th day

Conclusions

There was a good correlation between pCO₂-gap and multiple organ dysfunction assessed by SOFA score. Lactate levels were not able to predict outcome.