RELATIONSHIP BETWEEN THE MEASURED AND CALCULATED COLLOID OSMOTIC PRESSURE OF PLASMA AND LUNG LYMPH IN THE SHEEP

RH Demling, M Manohar, JA Will

Abstract


The colloid osmotic pressure of plasma, 1rp, and lung
lymph 1ri, in the adult sheep was measured with a
membrane osmometer and calculated from the protein
content using the Landis and Pappenheimer
equation. Measured (M) plasma oncotic pre sure was
6 mm Hg lower than calculated (C), for normal
sheep plasma. The difference between (M) and (C)
decreaed as protein content decreased. The (M)
lymph value, considered to be equal to interstitial
fluid, was only I mm Hg lower than (C) for normal
lymph. This re ulted in a difference between the
calculated and measured oncotic gradient (1Tp"1Ti) of
nearly 5 mm Hg. This difference decreased as protein
content decreased in plasma and lymph. The
difference between measured and calculated values
may in part be explained by the difference in A/G
ratio between human and sheep plasma and between
sheep plasma and lymph. Measured oncotic pressure
in plasma and lymph after severe hemorrhagic and
cndotoxic shock did not differ significantly from
that in the normal animal.


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