Reduced Lymphatic Activity During Positive Pressure Ventilation and General Anesthesia-A Cause of Postoperative Edema?

BACKGROUND: Edema is a common problem after long surgery or intensive care stays. The use of mechanical ventilation could be a contributing factor. The lymphatic system is responsible for draining the interstitial fluid throughout the body and is probably dependent on the outflow pressure at the lymphovenous junctions. It is known that positive pressure ventilation (PPV) raises central venous pressure, and some studies also suggest an inhibition of central lymphatic drainage. However, the systemic lymphatic response to mechanical ventilation remains unknown.

METHODS: Peripheral lymphatic activity of individuals undergoing corrective jaw surgery was investigated during spontaneous respiration, mechanical ventilation with normal and elevated (aim +10 cmH2O) positive end-expiratory pressure and a short ventilation pause, and in the post-operative ward shortly after waking. Lymphatic activity was examined using near-infrared fluorescence imaging of the left lower limb.

RESULTS: In total, 21 patients were included. Peripheral lymphatic contraction frequency declined from a baseline median of 1.5 (IQR 0.8-2.1) to 0.5 (IQR 0.3-0.8) min-1 at standard pressure ventilation (p-value < 0.001, 95% CI: 0.49-1.08). There was no significant change in contraction frequency between standard pressure ventilation, elevated pressure ventilation (median 0.5, IQR 0.2-0.8 min-1), ventilation pause (median 0.7, IQR 0.0-1.0 min-1), and post-operative (median 0.7, IQR 0.5-1.2 min-1) measurements. Peripheral lymphatic propulsion velocity did not change significantly between any of the investigations. A greater number of vessels were completely inactive during PPV compared to spontaneous breathing.

CONCLUSION: Peripheral lymphatic activity is reduced during PPV with general anesthesia compared to awake, spontaneously breathing individuals. The effect was present even at standard ventilatory settings, indicating that impaired lymphatic drainage should be an area of further investigation with regard to post-operative and intensive care unit-related edema.