To the Editor:—

The clinical spectrum of lung and systemic injury resulting from pulmonary aspiration of particulate material is broad. For instance, witnessed aspiration can have essentially no adverse clinical effects 1or can lead to acute lung injury/acute respiratory distress with multiple distant organ failures and even death. 2 

In addition to differing animal models (i.e. , species-specific effects) or patient characteristics, several aspects of the aspirate per se  may affect the severity of injury. As pointed out by O’Hare et al.  in a recent article in ANESTHESIOLOGY, 3these include the degree of acidity (pH), volume of the aspirate, the particle size, and concentration of the particles. However, another factor O’Hare et al.  do not emphasize concerns the characteristics of the particulate aspirated. Thus, in some instances, it seems that with some particulate aspirates (e.g. , human breast milk), there is no relation with pH and the severity of lung injury and systemic response. 3However, with other particulates, such as sucralfate, 4there can be a synergistic interaction between acidity and particulate-induced lung injury. 4,5 

Warner MA, Warner ME, Weber JG: Clinical significance of pulmonary aspiration during the perioperative period. A NESTHESIOLOGY 1993; 78:56–62
Lewis RT, Burgess JH, Hampson LG: Cardiorespiratory studies in critical illness: Changes in aspiration pneumonitis. Arch Surg 1971; 103:335–40
O’Hare B, Chin C, Lerman J, Endo J: Acute lung injury after instillation of human breast milk into rabbits’ lungs: Effects of pH and gastric juice. A NESTHESIOLOGY 1999; 90:1112–8
Shepherd KE, Faulkner CS, Leiter JC: Acute effects of sucralfate aspiration: Clinical and laboratory observations. J Clin Anesth 1994; 6:119–23
Knight PR, Rutter T, Tait AR, Coleman E, Johnson K: Pathogenesis of particulate lung injury: A comparison and interaction with acidic pneumonitis. Anesth Analg 1993; 77:754–60