Lipid-laden macrophages in the tracheal aspirate of ventilated neonates receiving Intralipid (R): A pilot study

Lipid-laden macrophages (LLM) in tracheal aspirates are reported to be path ognomonic findings in exo- and endogenous lipoid pneumonia in adults. A pil ot study was carried out to evaluate the effect of lipid infusion on the LL M index of the tracheal aspirates from ventilated neonates. All intubated i nfants were eligible for the study. Infants receiving parenteral nutrition had intravenous (IV) lipid introduced by 4-7 days of age; most samples afte r 7 days were from infants receiving IV lipid. Four infants received minima l gastric feeding; none had evidence of aspiration pneumonia. Tracheal aspi rates from 28 infants were analyzed for the LLM index. Alveolar macrophages were graded 0-4 in direct relation to the amount of lipid per cell. One hu ndred macrophages were graded; the maximum possible LLM index was 400. Two hundred forty-five of 387 tracheal aspirate samples were acceptable for ana lysis. LLM indices increased during the first week after birth; the mean LLM index then continued in the same range, but with a wide distribution of individu al values. The mean LLM index from infants receiving an IV lipid infusion d uring days 4-7 was 87.9 (SD = 44.8), and was significantly higher compared to 58.7 (SD = 40.8) in infants receiving no IV lipid (P < 0.003). Tracheal aspirates from infants with and without IV lipid infusion yielded many LLM index values >100. These observations invalidate the use of the LLM index > 100 as proof of aspiration pneumonia in this group of infants. Pediatr Pulm onol, 1999; 28:101-108, (C) 1999 Wiley-Liss, Inc.