What a curious study. I read it with a strange fascination, but was
bothered by some points as they relate (or don't relate) to the thread
of our discussion on "silent aspiration":

> 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].

I believe our discussion was focusing on when premies were coordinated
enough to take in a feeding by sucking, in which case the milk has not
yet mixed with gastric acid. The pH of breast milk is 7.29, cow's milk
6.57, and various formulas 6.4-6.97 (Barrie et al. 1975. Lancet i, 1330.
Milk for babies.) Thus I doubt breastmilk aspirated during a feeding
would be damaging to lung tissue; it would simply be absorbed from that
site as a physiological solution.

The rabbit study was done by anesthesiologists who were understandably
concerned about *reflux* which by definition has entered the stomach and
is returning from "whence it came." The possibility of reflux during
induction of anesthesia, before the patient can be intubated and the
trachea protected, is quite real and a major problem in anesthesia. I
rather prefer the following study since it at least uses humans (I
recall a recent posting that described breastmilk as considered a
"clear' liquid" - yes? - in which case, one can extrapolate easily from
apple juice to breastmilk):

Title: Effects of 2-, 4- and 12-hour fasting intervals on preoperative
gastric fluid pH and volume, and plasma glucose and lipid homeostasis in
children. Acta Anaesthesiol Scand. 1993 Nov. 8 (37) 783-7.
Authors: Maekawa N; Mikawa K; Yaku H; Nishina K; Obara H;

(Quoting from the abstract:)There were no significant differences
between the three groups in either gastric fluid volume or pH. In
addition, there were no significant differences between the groups with
respect to the proportion with a pH < 2.5 and volume > 0.4 ml/kg b.w.
Neither plasma concentrations of glucose, triglycerides, nor cortisol at
the time of anaesthetic induction differed between the three groups.
Both 4 and 12 h nil per os (NPO) caused an increase in lipolysis, which
was presumably a compensatory mechanism to maintain normoglycaemia. The
 plasma NEFA and total ketone bodies concentrations were therefore
ignificantly higher in these two fasting intervals than in 2 h NPO.
These data suggest that a 2-h NPO, after a large volume of ingested
apple juice, may offer additional benefits by preventing an increase in
lipolysis during the fasting interval without either increasing the
volume of gastric fluid or decreasing the gastric pH.