• C Chin, J Lerman, and J Endo.
• Department of Anaesthesia and the Research Institute, The Hospital for Sick Children and University of Toronto, Ontario.
• Can J Anaesth. 1999 Mar 1; 46 (3): 282286282-6.

PurposeThe aim of this study was to compare the severity of the acute lung injury after tracheal instillation of acidified soya-based or Enfalac infant formula, or human breast milk (HBM) in anesthetized rabbits.MethodsAlveolar-arterial oxygen tension gradient (A-aDO2) and dynamic compliance were measured before (baseline) and hourly for four hours after tracheal instillation of 0.8 ml x kg(-1) soya-based or Enfalac infant formula or HBM (all acidified to pH 1.8 with hydrochloric acid) or no fluid (control) in 24 anesthetized and tracheotomized adult rabbits. The A-aDO2, the difference between alveolar and arterial oxygen tensions, was corrected for barometric pressure and carbon dioxide tension. Dynamic compliance was the ratio of the expired tidal volume to the peak inspiratory airway pressure, normalized to body weight.ResultsBaseline A-aDO2 and dynamic compliance were similar among the four groups. In the control rabbits, A-aDO2 remained unchanged throughout the four hours, whereas mean A-aDO2 increased 180 mm Hg in the soya-based group (P < 0.0025) and 350 and 275 mm Hg in the Enfalac and HBM groups respectively (P < 0.0002). The order of the A-aDO2 post-instillation was Enfalac approximately/= HBM > soya > control (P < 0.0002). Dynamic compliance decreased 10-12% in the control rabbits during the four post-instillation measurements compared with baseline (P < 0.033), decreased 20% in the soya-based group (P < 0.0002) and 40-50% in the Enfalac and HBM groups (P < 0.0002).ConclusionThe severity of the acute lung injury after intratracheal instillation of infant feeds in a volume of 0.8 ml x kg(-1) and at pH 1.8 in rabbits depends in part, on the type of feed: Enfalac approximately/= HBM > soya > control.

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