Serum amylin correlates with delayed gastric emptying in critically ill children

Introduction

Delayed gastric emptying is common in critically ill patients. Amylin is a novel 37 amino acid polypeptide, which is co-localised and co-secreted with insulin by pancreatic beta cells [1]. In conjunction with its role in glucose homeostasis it is a potent inhibitor of gastric motility [2]. Thus we hypothesised that high circulating levels of amylin may be associated with delayed gastric emptying in critically ill children.

Method

Nineteen children were enrolled within 48 hours of ICU admission. Exclusion criteria included: liver disease, gastrointestinal abnormalities and use of prokinetic agents. All patients were N.P.O., and maintained on a ivi glucose (5-8 mg/kg/min). Gastric emptying (GE) was assessed clinically by feed intolerance and using a paracetamol absorption technique (PTA). Feed intolerance was defined as a residual gastric volume > 0.25 ml/kg after 4 hours of a bolus 2 ml/kg test milk feed. At this point (T0), a single 15 mg/kg dose of paracetamol was administered nasogastrically, and serial blood samples taken for paracetamol assay at 0, 15, 30, 60, 120, 240 and 360 min.

GE was calculated using the gastric emptying ratio (GER) which is the time to reach peak paracetamol level divided by its peak concentration, with high values reflecting delayed gastric emptying [3]. Blood amylin and insulin sample were taken at T0 and T360 with the mean of these two values used to reflect the average level over the study period. Amylin was measured by radioimmunoassay. Data were assumed non-parametric, thus Spearman's correlation coefficient and Mann-Whitney tests were used. Data are shown as median (interquartile range).

Results

Nineteen patients were enrolled with a median age 6 years (1.7-8.5), and weight 20 kg (11.5-31.5). Diagnoses included sepsis (n = 8), respiratory (n = 5), head injury (n = 2), neurology (n = 2) and other (n = 2). Four patients did not tolerate enteral feeds (median residual volume 4.4 ml/kg). Factors associated with impaired gastric emptying were not different between the two groups, in particular opiate infusions (4/4 vs 14/15 P = 0.6) and dopamine use (0/4 vs 2/15 P = 0.4). Amylin levels (pmol/l) were higher in patients (n = 4) with feed intolerance 44.1 (37.0-50.8) vs 22.7 (13.6-26.7), P = 0.009. This coincided with higher GER values 4.29 (2.75-5.25) vs 1.54 (0.69-2.25), P = 0.08. Overall, amylin levels correlated with GER r = 0.49 (95% CI 0.03-0.78), P = 0.03, and with insulin r = 0.51, (95% CI 0.08-0.78), P = 0.02, which is consistent with co-secretion.

Conclusion

Failure to establish enteral feeds in critically ill children may be due to raised amylin levels.