Drake R E, Dhother S, Teague R A, Gabel J C
Department of Anesthesiology, University of Texas Medical School, Houston 77030, USA.
Am J Physiol. 1997 May;272(5 Pt 2):R1595-8. doi: 10.1152/ajpregu.1997.272.5.R1595.
Increases in systemic venous pressure (Pv) associated with heart failure cause an increase in microvascular fluid filtration into the tissue spaces. By removing this excess filtrate from the tissues, lymphatic vessels help to prevent edema. However, the lymphatics drain into systemic veins and an increase in Pv may interfere with lymphatic flow. To test this, we cannulated caudal mediastinal node efferent lymphatics in sheep. We used rapid cardiac ventricular pacing (240-275 beats/min) to cause heart failure for 4-7 days. Each day we determined the lymph flow rate two ways. First, we adjusted the lymph cannula height so that the pressure at the outflow end of the lymphatic was zero. After we determined the lymph flow with zero outflow pressure, we raised the cannula so that outflow pressure was equal to the actual venous pressure. We quantitated the effect of venous pressure on lymph flow rate by comparing the flow rate with outflow pressure = Pv to the flow rate with zero out low pressure. At baseline, Pv = 5.0 +/- 2.5 (SD) cmH2O and we found no difference in the two lymph flow rates. Pacing caused Pv and both lymph flow rates to increase significantly. However for Pv < 15 cmH2O, we found little difference in the two lymph flow rates. Thus increases in Pv to 15 cmH2O at the outflow to the lymphatics had little effect on lymph flow. By comparison, Pv > 15 cmH2O slowed lymph flow by 55 +/- 29% relative to the lymph flow rate with zero outflow pressure. Thus Pv values > 15 cmH2O interfere with lymph flow from the sheep caudal mediastinal lymph node.
与心力衰竭相关的体循环静脉压（Pv）升高会导致微血管内的液体滤过增加，进入组织间隙。淋巴管通过清除组织中多余的滤出液，有助于预防水肿。然而，淋巴管引流至体循环静脉，Pv升高可能会干扰淋巴液流动。为了验证这一点，我们对绵羊的纵隔后淋巴结传出淋巴管进行插管。我们采用快速心室起搏（240 - 275次/分钟）使绵羊发生心力衰竭4 - 7天。每天我们通过两种方法测定淋巴液流速。首先，我们调整淋巴插管的高度，使淋巴管流出端的压力为零。在确定零流出压力下的淋巴液流速后，我们升高插管，使流出压力等于实际静脉压。我们通过比较流出压力 = Pv时的流速与零流出压力时的流速，来定量静脉压对淋巴液流速的影响。在基线时，Pv = 5.0 ± 2.5（标准差）cmH₂O，我们发现两种淋巴液流速没有差异。起搏导致Pv和两种淋巴液流速均显著增加。然而，当Pv < 15 cmH₂O时，我们发现两种淋巴液流速差异不大。因此，淋巴管流出端的Pv升高至15 cmH₂O对淋巴液流动影响不大。相比之下，相对于零流出压力时的淋巴液流速，Pv > 15 cmH₂O使淋巴液流速减慢了55 ± 29%。因此，Pv值> 15 cmH₂O会干扰绵羊纵隔后淋巴结的淋巴液流动。
