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Lymph flow in sheep with rapid cardiac ventricular pacing
R E Drake1, S Dhother, R A Teague
1Department of Anesthesiology, University of Texas Medical School, Houston 77030, USA.
The American Journal of Physiology
|May 1, 1997
Summary
Elevated systemic venous pressure (Pv) from heart failure can impede lymphatic fluid removal. Lymphatic flow is significantly reduced when venous pressure exceeds 15 cmH2O, potentially worsening edema.
Area of Science:
- Cardiovascular Physiology
- Lymphatic System Dynamics
- Edema Formation and Resolution
Background:
- Heart failure increases systemic venous pressure (Pv), leading to greater fluid filtration into tissues.
- Lymphatic vessels normally remove this excess fluid, preventing edema.
- However, lymphatic drainage into systemic veins means elevated Pv may obstruct lymphatic flow.
Purpose of the Study:
- To investigate the impact of increased systemic venous pressure (Pv) on lymphatic fluid flow.
- To determine the threshold of Pv at which lymphatic drainage is impaired.
Main Methods:
- Sheep underwent rapid cardiac pacing to induce heart failure for 4-7 days.
- Efferent lymphatics of the caudal mediastinal node were cannulated.
- Lymph flow rate was measured at zero outflow pressure and at actual venous pressure (Pv).
- The effect of Pv on lymph flow was quantified by comparing these two measurements.
Main Results:
- Pacing significantly increased Pv and lymph flow rates.
- Lymph flow was not significantly affected when Pv was below 15 cmH2O.
- Lymph flow was reduced by 55% when Pv exceeded 15 cmH2O compared to zero outflow pressure.
Conclusions:
- Systemic venous pressure (Pv) above 15 cmH2O significantly interferes with lymphatic fluid transport from the caudal mediastinal lymph node in sheep.
- Impaired lymphatic drainage due to elevated Pv may contribute to edema in heart failure.