Years ago I posted on Lactnet about some studies in rabbits on the  
aspiration of human milk.  Why they used human milk and not rabbit milk, I  don't know. 
;-)   
 
I just found two in the Lactnet archives from 1997:
 
1)
  "  In an experiment using human milk with rabbits the  researchers 
"instilled 0.4
ml per kg of breast milk  at its native pH level (6.6 - 7.4) into  rabbits'
lungs [and] found NO EVIDENCE of lung  injury."  Emphasis mine.

That study was the Can J Anaesth 1994  41:A57 article by Shorten et al: The
effects of pulmonary aspiration of human  breast milk and normal saline in
the intubated rabbit.

Now if this  isn't even milk species specific and doesn't cause damage then it
would seem  to be no problem for humans."



A second study 'doctored' the milk with hydrochloric acid, I suppose to  
simulate milk taht had been in the stomach for a while:
 
2) 
 
"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 mimic 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 after 
this
so they  don't know 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 intratracheal  injection of
mild, feeding mixtures, 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


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