Investigation into the effects of enteral feeding on gastric tonometry monitoring using the saline technique and the Tonocap

Aims of study

A prospective study of gastric PrCO₂ in ventilated neurosurgical patients when given enteral feed comparing two techniques: time corrected saline (TCS) tonometry and air tonometry (Tonocap).

Methods

After Ethical committee approval and patient assent, two tonometric catheters were inserted into patients who after an overnight fast, were given 30 ml per hour of water for 4 h and following a 1 h rest, 30 ml per hour of enteral feed for 4 h. All patients received iv ranitidine. The PrCO₂ was measured hourly using both techniques.

Results

Eight neurosurgical intensive care patients were studied (mean age 52 years, SD 15.3 years). All patients were stable and had no significant changes in cardiovascular or blood gas parameters during the study.

There was a significant difference between the TCS and Tonocap PrCO₂: 4.84 (± 2.78) kPa compared to 6.74 (± 4.46) (r ² = 0.36). Bland–Altman analysis showed the mean bias between TCS and Tonocap PrCO₂ and -1.85 kPa with a precision of ± 3.49 kPa.

There was no significant difference between the effects of feeding with the two techniques.

Figure

Effect of Feed

Conclusion

Enteral feeding has no effect on PrCO₂ in neurosurgical patients. Saline tonometry under reads compared to the Tonocap similar to that of general intensive care patients.