INTESTINAL LYMPHATIC PRESSURE INCREASES DURING INTRAVENOUS INFUSIONS IN AWAKE SHEEP

Intravenous fluid infusions cause increased venous pressure and increa sed lymph flow throughout the body. Together the increased lymph flow and increased venous pressure (the outflow pressure to the lymphatic s ystem) should increase the pressure within the postnodal intestinal ly mphatics. To test this, we measured the pressure in postnodal intestin al lymphatics and the neck vein pressure in five awake sheep. At basel ine, the neck vein pressure was 1.2 +/- 1.5 (SD) cmH2O and the lymphat ic pressure was 12.5 +/- 1.7 cmH2O. When we infused Ringer solution in travenously (10% body weight in approximately 50 min), the neck vein p ressure increased to 17.3 +/- 0.9 cmH2O and the lymphatic pressure inc reased to 24.6 +/- 3.8 cmH2O (both P < 0.05). In two additional sheep, the thoracic duct lymph flow rate increased from 0.8 +/-0.4 ml/min at baseline to 5.5 +/- 2.0 ml/min during the infusions. Our results show that postnodal intestinal lymphatic pressure may increase substantial ly during intravenous fluid infusions. This is important because incre ases in postnodal lymphatic pressure may slow lymph flow from the inte stine.