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Gastric emptying assessment in critically ill patients with feed intolerance; comparison of 13C octanoic acid, paracetamol and 3-O-methylglucose absorption tests


Delayed gastric emptying (GE) occurs frequently in critically ill patients and may result in impaired small intestinal delivery of drugs and nutrients. Use of direct methods of GE assessment (scintigraphy) in the ICU for clinical monitoring or research is challeng-ing. Indirect methods that utilize substances which rely on effective GE and rapid absorption from the small intestine offer a feasible estimate of GE. Three substances with these characteristics are 13C-octanoic acid (13C), paracetamol (PA) and 3-O-methylglucose (OMG). We have previously shown significant correlation to scintigraphy for 13C (r = 0.63) and OMG absorption (r = -0.77 to -0.87). The current study examined the relationship between three indirect methods of GE assessment: 13C, PA, OMG.


GE was concurrently assessed in mechanically ventilated patients (n = 33) with enteral feeding intolerance (gastric residual volume >200 ml) on two occasions 24 hours apart. A test meal of 100 ml Ensure with 100 μl 13C, 1,000 mg PA, 3 g OMG was infused into the stomach over 5 minutes. Breath samples for 13C and plasma samples for PA, OMG determination were collected over the subsequent 4-hour period. Bivariate Pearson correlations were calculated between the following parameters; 13C (gastric emptying coefficient (GEC)), PA (concentration at 60 minutes (C60), AUC0-60 min), OMG ((C60), AUC0-60 min). See Table 1.

Table 1 Correlations between GE parameters


Observed GE rates for all parameters were across the spectrum from fast to delayed (for example, with r range = 0.534 to 0.758, P < 0.0001).


These three practical indirect methods of GE assessment may provide similar estimates of GE in critically ill patients.

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Correspondence to M Chapman.

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Chapman, M., Fraser, R., Nguyen, N. et al. Gastric emptying assessment in critically ill patients with feed intolerance; comparison of 13C octanoic acid, paracetamol and 3-O-methylglucose absorption tests. Crit Care 16, P162 (2012).

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  • Paracetamol
  • Gastric Emptying
  • Indirect Method
  • Enteral Feeding
  • Octanoic Acid