Abdominal lymph flow response to intraperitoneal fluid in awake sheep

Area of Science:

• Physiology
• Lymphatic System
• Abdominal Cavity

Background:

• Lymphatic vessels are crucial for draining excess fluid from the abdominal space, preventing ascites.
• In sheep, diaphragmatic lymph vessels connect the abdominal space to the caudal mediastinal lymph node, with efferent vessels draining into neck veins.

Purpose of the Study:

• To estimate the lymph flow response to excess intraperitoneal fluid in sheep.
• To investigate the relationship between lymph flow, lymphatic outflow pressure, and abdominal pressure.

Main Methods:

• Cannulation of a caudal mediastinal node efferent lymphatic in 5 sheep.
• Measurement of lymph flow (QL) and lymph protein concentration (CL).
• Infusion of Ringers solution into the abdominal space to induce excess fluid.

Main Results:

• Baseline lymph flow (QL) was 154 ± 161 μl/min with a lymph protein concentration (CL) of 3.7 ± 9 g/dl.
• Lymph flow decreased linearly with increasing lymphatic outflow pressure above 6 cmH2O.
• Infusion of Ringers solution increased QL significantly (7.0 ± 4.1 times baseline) and decreased CL significantly (0.7 ± 0.6 g/dl).
• Despite increased abdominal pressure (from 10.6 ± 2.8 to 15.8 ± 2.1 cmH2O), lymphatic driving pressure did not increase.

Conclusions:

• Sheep lymphatic system effectively increases lymph flow in response to excess intraperitoneal fluid.
• The lymphatic driving pressure remained unchanged despite increased abdominal pressure, indicating a complex regulatory mechanism.
• This study provides insights into the physiological response of lymphatic vessels to fluid overload in the abdominal space.