The relationship between data of gastric tonometry by determination of polymorphonuclear leukocytes (PMNs, i.e., myeloperoxidase activity) and gut mucosal hypoperfusion in elective cardiac surgical patients

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Introduction

The expression of polymorphonuclear leukocytes (PMNs) as a result of local and systemic inflammation in patients undergoing cardiac surgery by using the CPB is considered to be an important cofactor in tissue hypoxia and the pathogenesis of multiple organ failure [1]. Therefore, an early detection of tissue hypoxia is very useful for the prevention of MOFS. It has been shown that gastric tonometry improves clinical applicability of gut mucosal oxygenation monitoring [2]. In a previous paper the correlation between gastric tonometry and PMNs was warranted [3]. This was done in the following study.

Methods

Following institutional approval, 66 adult male patients undergoing elective cardiac surgery using cardiopulmonary bypass were studied. They were monitored with the Tonocap^™ in addition to standard monitoring (ECG, CVP, arterial pressure) and the pulmonary artery catheter. The PiCO₂ was measured every 15 min after admission to the ICU. In addition, documentation of CO₂-gap, arterial and pulmonary arterial hemodynamics, arterial and mixed-venous blood gas analyses and lactate followed four times until extubation. The patients were shifted into three groups by using the terciles of preoperative expression of the PMNs (group I <1451 μg/l; group II ≤ 2487 μg/l; group III >2487 μg/l).

Results

The course of CO₂-gap was parallel to the PMNs. Both parameters increased after admission to the ICU. Using the Wilcoxon-Wilcox test the increase in CO₂-gap and PMNs was significant in all groups. These differences did not occur in the parameters obtained from blood gas analyses (BE, lactate, mixed venous saturation) and in hemodynamic parameters.

Conclusions

Gastric tonometry is superior to other techniques in detecting dysfunctions of gut oxygenation if PMNs are used as a biochemical indicator. Questions of therapeutic interventions in increasing CO₂-gaps and PMNs need further investigations.