While the discussion on silent aspirations was going on, I kept thinking I'd
read something about an experiment examine the effects of human milk on lung
tissue.  I found it today at the health science library.

Anesthesiology 1996:84:1386-91. Brendan O'Hare et al.  Acute Lung Injury
after Instillation of Human Breast Milk or Infant Formula into Rabbits'
Lungs.

This is a funny one.  The research was prompted by discussions of shortening
the preoperative guidelines for clear liquids.

Can we draw any conclusions from it??

Their intro. talks about "large residuals volume of breast milk in the
stomachs of infants who were fasted only two hours before elective surgery."


 Eighteen adult rabbits were anesthetized and three fluids were instilled
into the lungs.

Now, these are rabbits and mature ones, not babies.  They instilled  infant
formula or 0.9% saline or human milk, all acidified - titrated with
hydrochloric acid (not gastric fluids) to a pH level of 1.8 - one standard
deviation below that of the mean pH of residual fluid in stomachs of infants
2 hrs after breastfeeeding [to maimic mixture with gastric secretions].   Is
human milk physiologic for rabbits??!!!  I would think it better to use
rabbit milk as an instillation since it would a better physiologic match for
a rabbit.

These rabbits had tracheostomies done; ventilation was controlled with drugs
and a ventilator.  Could they cough?  They were paralyzed with drugs for the
procedure.

Histological exam of the then deceased rabbits revealed changes of alveolar
edema, vascular engorgement, septal & intraalveolar neutrophil margination
with focal areas of atelectasis & hemorrhage.  The neutrophil counts was the
similar for the formula and human milk, significantly greater than the saline
group.  [A bar graph show the formula group to have the highest neutrophil
count.]  The injury lasts at least 4 hours (the rabbits were killed afterthis
so they don'tknow what happens after that).  Physiologic evidence of injury
included significantly decreased dynamic compliance and increased alveolar-
to- arterial oxygen gradient

The the final paragraph the authors themselves point out the limitations of
the study as applied to human infants (it was not a clinical study) but do
point out that acute lung injury did occur.

The bibliography does list a few studies that I did not have time to acquire
today.  The same group of authors (+ or - a couple) Shorten GD: The effects
of pulmonary aspiration of human breast milk and normal saline in the
intubated rabbit.  Can J Anaesth 1994; 41:A57

Moran TJ: Milk-aspiration pneumonia produced by intratarcheal injection of
mild, feeding mixutres, and sugars. Am J Dis Child 1953. 86:45 -50  Is this
cow 's milk??

There were only 15 references, none others specifically mentioning human milk
in the title.

Mardrey Swenson