Gastric versus duodenal feeding and gastric tonometric measurements.

OBJECTIVE

To compare the influence of gastric and postpyloric enteral feeding on the gastric tonometric PCO2 gap (tonometric PCO2 - PaCO2).

DESIGN

A prospective, clinical trial.

SETTING

Two intensive care units in a university hospital.

PATIENTS

Twenty patients undergoing mechanical ventilation and enteral feeding without catecholamines, sepsis, or sign of hypoxia.

INTERVENTIONS

Patients were randomized to receive feeding through the tonometer (gastric group), or through a postpyloric tube (postpyloric group).

MEASUREMENTS AND MAIN RESULTS

The patients received tube feeding at a rate of 50 mL/hr during 4 hrs. Baseline measurements included: mean arterial pressure, heart rate, tonometric parameters, arterial gases, and arterial lactate concentration. Except for lactate concentration, these measurements were repeated after 1 and 4 hrs of enteral feeding and 2 hrs after stopping enteral feeding. During the study, arterial pH and PaCO2 did not change. During enteral feeding, the PCO2 gap increased in the gastric group from a mean of 7+/-5 to 17+/-14 (SD) torr (0.9 0.7 to 2.3+/-1.9 kPa) (p< .O01) and did not change in the postpyloric group (5+/-5 to 3+/-1 torr [0.7+/-0.7 to 0.4+/-0.1 kPa]). Two hours after stopping enteral feeding, the PCO2 gap was still increased in the gastric group (15+/-9 vs. 7+/-5 torr [2.0+/-1.2 vs. 0.9+/-0.7 kPa]) (p < .01).

CONCLUSION

The results indicate that gastric enteral feeding increased the PCO2 gap. However, postpyloric enteral feeding does not interact with gastric tonometric measurements and should be used when using gastric tonometry in enterally fed patients.