Routine blood gas analysis does not provide information on regional metabolism of the stomach obtained by gastric tonometry in patients with left ventricular failure

Full text

Purpose of the study

To define the association between variables reflecting regional perfusion and metabolism of the stomach obtained by gastric air tonometry with routine blood gas analysis and global hemodynamics in patients with cardiac failure.

Methods

In 50 mechanically-ventilated patients with severe left ventricular failure gastric intramucosal PCO₂(PgCO₂) was assessed utilising the Tonocap. Simultaneously hemodynamics were measured and routine blood gas analysis was carried out. Independent variables were correlated and the discriminative power to predict a low pHi <7.32 was calculated using Receiver Operating Characteristics (ROC).

Results

564 paired measurements of cardiorespiratory and gastric tonometry variables were collected. Neither global hemodynamics nor arterial lactate values correlated with one of the tonometric parameters or patients' outcome at any timepoint. Correlation of arterial PCO₂, arterial pH, arterial bicarbonate, and base excess with PgCO₂ was only weak. According to the areas under ROC prediction of pHi <7.32 was excellent for PgCO₂ and CO₂ Gap (difference of PgCO₂ and arterial PCO₂) (areas under ROC curve 0.90 ± 0.01 and 0.92 ± 0.01, cutoff values 51 mmHg and 13 mmHg, respectively).

Conclusion

Both PgCO₂ and CO₂ Gap are reliable predictors of low pHi, thought to reflect gastric mucosal hypoperfusion. None of the cardiorespiratory parameters were capable of predicting a pHi <7.32. Thus, in patients with severe left ventricular failure assessment of regional perfusion indices using gastric tonometry cannot be replaced by one of the tested routinely applied monitoring modalities.