Correlation of gastric-mucosal tonometry and procalcitonin (PCT) values in intensive care patients

Background and goal of study

Measurement of the gastric-mucosal tonometry difference is an indicator of splanchnic hypoxia, which often is a predictor of severe clinical complications like inflammation and/or sepsis. Beyond these aspects other biochemical indicators like procalcitonin (PCT), lipopolysaccharide binding protein (LBP), or IL-6 are suitable diagnostic markers. Therefore the hypothesis occurs whether there is a correlation between gastric tonometry and biochemical indicators of inflammation.

Materials and methods

Twenty-six intensive care patients (five women and 21 men) were selected after surgery. All of them showed n increasing gastric-arterial PCO₂ (CO₂ gap) difference within at least 6 hours. An increasing CO₂ gap was taken as an indicator of decreasing splanchnic perfusion. Furthermore, each patient was matched with one postsurgery intensive care patient without an increase of CO₂ gap.

Tonometric variables via a nasogastric tube (Tonocap Datex, Helsinki Finland), hemodynoamic variables, temperature and arterial lactate were measured every hour.

The differences of the PCT (pct-diff), IL-6 (il_diff) and LBP (lbp_diff) values of day 1 after surgery and day 0 were also assessed.

By means of the SAPS and APACHE score systems, the general condition of each patient was evaluated and afterwards enrolled into two groups (group 1, SAPS ≤ 5; group 2, SAPS > 5). Statistical analysis was done using covariance analysis (the time patients were breathed in the operating room was defined as covariate).

Results and discussion

The mean pct-diff was significantly higher (adjusted mean = 2.22, P = 0.01) for the group with increasing CO₂ gap than for the decreasing group (adj. mean = 0.59).

Their was no significant difference in LBP values for both groups but a significant one due to the general condition of the patients (adj. mean SAPS group 1 = 20.22; adj. mean SAPS group 2 = 14.03; P = 0.13).

In IL-6 values there were also no significant differences, but the mean for each group suggests that the il_diff values are even higher in the group with decreasing or stable CO₂ gap 1 day after surgery (adj. mean stable-group = 41.34, adj. mean increasing-group = -134.6; P = 0.056).

There were no other significant differences in lactate, cardiac index, blood pressure or mean arterial pressure between the two groups.

Furthermore there was a tendential significant difference in ICU time. Patients with increasing CO₂ gap have been longer on the ICU than other patients (mean group with increasing CO₂ gap = 4642 min vs 2934 min for the other one; P = 0.094).

Conclusion

The differences in the PCT values suggest that an increase in CO₂ gap measured by air tonometry is accompanied by a later increase in PCT values. Tonometry is the earlier method to detect aspects of inflammation.

These findings fit with the longer time on the ICU for patients with an increasing CO₂ gap.