Increased lymphatic pressure without increased neck vein pressure during intravenous infusions

Postnodal intestinal lymphatic pressure increases during rapid intravenous infusions with Ringer solution in sheep. Part of the lymphatic pressure increase is due to increased venous pressure at the lymphatic outflow (the neck veins). We tested the hypothesis that other factors besides increased neck vein pressure may cause increased lymphatic pressure during intravenous infusions. We placed cannulas into postnodal lymphatic vessels in eight sheep. After the sheep recovered from the surgery, we infused Ringer solution [46 +/- 21 (SD) ml/kg body wt in 30 min] intravenously into the sheep and inflated a balloon in the inferior vena cava. We adjusted the balloon inflation to prevent any increase in neck vein pressure during the infusions. At baseline, the intestinal lymphatic pressure was 15.5 +/- 2.5 cmH2O. During the infusions, lymphatic pressure increased significantly, and for the last 10 min of the infusion period, intestinal lymphatic pressure was 24.0 +/- 6.1 cmH2O. These results are consistent with the hypothesis that factors in addition to increased neck vein pressure may cause increased intestinal lymphatic pressure during rapid intravenous infusions.