Pepsin, a reliable marker of gastric aspiration, is frequently detected in tracheal aspirates from premature ventilated neonates: Relationship with feeding and methylxanthine therapy

Objectives: To determine the frequency of pepsin detection in tracheal aspirate (TA) samples of mechanically ventilated premature neonates and its association with feedings and methylxanthine therapy. Patients and Methods: Serial TA samples (days 1, 3, 5, 7, 14, 21, 28 and > 28 days) were collected from premature neonates receiving ventilatory support. An enzymatic assay with a fluorescent substrate was used to detect pepsin. Pepsin was also measured in 10 serum samples collected in conjunction with the TA samples from 8 neonates. Results: A total of 239 TA samples was collected from 45 premature neonates (mean birth weight, 762 +/- 166 g; mean gestational age, 25.5 +/- 1.5 wk). Pepsin was detectable in 222 of 239 TA samples (92.8%) and in none of the serum samples. Pepsin was significantly lower on day 1 (mean, 170 +/- 216 ng/mL) when compared with all other time points (P < 0.05). Mean concentration of pepsin was significantly lower when infants were unfed (265 +/- 209 ng/mL) compared with levels during feeding (390 +/- 260 ng/mL, P = 0.02). The mean level of pepsin was significantly higher in infants during xanthine therapy (419 +/- 370 ng/mL) compared with no xanthine therapy (295 +/- 231 ng/mL, P = 0.037). Conclusion: Pepsin, a marker of gastric contents, was detected in more than 92% of TA samples from premature infants on mechanical ventilation. The level of pepsin was higher in fed infants when compared with unfed infants. Xanthine therapy was also associated with increased pepsin in TA samples. Chronic aspiration of gastric contents may worsen lung disease in premature infants.