College of Science, Health, Engineering and Education, Murdoch University, Perth, Western Australia, Australia.
Faculty of Engineering and Mathematical Sciences, The University of Western Australia, Perth, Western Australia, Australia.
Am J Physiol Renal Physiol. 2019 Dec 1;317(6):F1483-F1502. doi: 10.1152/ajprenal.00315.2019. Epub 2019 Sep 4.
We have previously developed a three-dimensional computational model of oxygen transport in the renal medulla. In the present study, we used this model to quantify the sensitivity of renal medullary oxygenation to four of its major known determinants: medullary blood flow (MBF), medullary oxygen consumption rate (V̇o), hemoglobin (Hb) concentration in the blood, and renal perfusion pressure. We also examined medullary oxygenation under special conditions of hydropenia, extracellular fluid volume expansion by infusion of isotonic saline, and hemodilution during cardiopulmonary bypass. Under baseline (normal) conditions, the average medullary tissue Po predicted for the whole renal medulla was ~30 mmHg. The periphery of the interbundle region in the outer medulla was identified as the most hypoxic region in the renal medulla, which demonstrates that the model prediction is qualitatively accurate. Medullary oxygenation was most sensitive to changes in renal perfusion pressure followed by Hb, MBF, and V̇o, in that order. The medullary oxygenation also became sensitized by prohypoxic changes in other parameters, leading to a greater fall in medullary tissue Po when multiple parameters changed simultaneously. Hydropenia did not induce a significant change in medullary oxygenation compared with the baseline state, while volume expansion resulted in a large increase in inner medulla tissue Po (by ~15 mmHg). Under conditions of cardiopulmonary bypass, the renal medulla became severely hypoxic, due to hemodilution, with one-third of the outer stripe of outer medulla tissue having a Po of <5 mmHg.
我们之前已经开发了一种肾脏髓质氧气传输的三维计算模型。在本研究中，我们使用该模型来量化肾脏髓质氧合对其四个主要已知决定因素的敏感性：髓质血流量 (MBF)、髓质耗氧量 (V̇o)、血液中的血红蛋白 (Hb) 浓度以及肾脏灌注压。我们还检查了在脱水、等渗盐水输注引起的细胞外液体积扩张以及心肺旁路期间血液稀释等特殊情况下的髓质氧合。在基础条件下，预测整个肾脏髓质的平均髓质组织 Po 约为 30 mmHg。外髓层束间区域的外围被确定为肾脏髓质中最缺氧的区域，这表明模型预测是定性准确的。髓质氧合对肾脏灌注压的变化最敏感，其次是 Hb、MBF 和 V̇o，按此顺序。髓质氧合也因其他参数的促缺氧变化而变得敏感，导致多个参数同时变化时髓质组织 Po 下降更大。与基础状态相比，脱水不会引起髓质氧合的显著变化，而体积扩张会导致内髓质组织 Po 大幅增加（约 15 mmHg）。在心肺旁路条件下，由于血液稀释，肾脏髓质会变得严重缺氧，三分之一的外髓外层组织的 Po <5 mmHg。
