SHEEP LUNG LYMPH SHUNTING

RE Drake, SJ Allen, J Katz, JC Gabel, GA Laine

Abstract


The caudal mediastinal lymph node
(CMN) has several efferent lymph vessels in
most sheep. When investigators cannulate one
of the CMN efferent vessels in order to collect
lung lymph, it is possible that lymph may be
shunted between the cannulated vessel and other
vessels which drain from the CMN into the
systemic veins. If shunting does occur then an
increase in venous pressure could cause lymph
to be shunted to the cannulated lymph vessel.
This would increase the flow of lymph from the
cannula and could falsely indicate that lung
lymph flow had increased. To test this possibility
we cannulated CMN efferent vessels in 7 sheep
and then used a balloon to raise the pressure
in the superior vena cava. Because uncannulated
CMN efferent vessels ultimately drain into the
superior vena cava, an increase in pressure may
cause lymph to be shunted through the lymph
cannula. We found, however, that lymph flow
increased in only one of seven sheep and
conclude that lymph shunting is uncommon
when operative preparation includes meticulous
ligation of collateral common efferent lymph
vessels.


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