Department of Anesthesia, St. Michael's Hospital, 30 Bond Street, Toronto, ON, M5B 1W8, Canada.
Department of Physiology, University of Toronto, Toronto, ON, Canada.
Can J Anaesth. 2021 Feb;68(2):214-225. doi: 10.1007/s12630-020-01848-5. Epub 2020 Nov 10.
The kidney plays a central physiologic role as an oxygen sensor. Nevertheless, the direct mechanism by which this occurs is incompletely understood. We measured renal microvascular partial pressure of oxygen (PO) to determine the impact of clinically relevant conditions that acutely change PO including hyperoxia and hemodilution.
We utilized two-wavelength excitation (red and blue spectrum) of the intravascular phosphorescent oxygen sensitive probe Oxyphor PdG4 to measure renal tissue PO in anesthetized rats (2% isoflurane, n = 6) under two conditions of altered arterial blood oxygen content (CO): 1) hyperoxia (fractional inspired oxygen 21%, 30%, and 50%) and 2) acute hemodilutional anemia (baseline, 25% and 50% acute hemodilution). The mean arterial blood pressure (MAP), rectal temperature, arterial blood gases (ABGs), and chemistry (radiometer) were measured under each condition. Blue and red light enabled measurement of PO in the superficial renal cortex and deeper cortical and medullary tissue, respectively.
PO was higher in the superficial renal cortex (~ 60 mmHg, blue light) relative to the deeper renal cortex and outer medulla (~ 45 mmHg, red light). Hyperoxia resulted in a proportional increase in PO values while hemodilution decreased microvascular PO in a linear manner in both superficial and deeper regions of the kidney. In both cases (blue and red light), PO correlated with CO but not with MAP.
The observed linear relationship between CO and PO shows the biological function of the kidney as a quantitative sensor of anemic hypoxia and hyperoxia. A better understanding of the impact of changes in PO may inform clinical practices to improve renal oxygen delivery and prevent acute kidney injury.
肾脏作为一种氧气感受器，在生理上起着核心作用。然而，其发生的直接机制尚不完全清楚。我们测量了肾脏微血管的局部氧分压（PO），以确定包括高氧血症和血液稀释在内的几种临床上会引起 PO 急性变化的情况对其的影响。
我们利用血管内磷光氧敏感探针 Oxyphor PdG4 的双波长激发（红光和蓝光光谱），在两种动脉血氧含量改变的情况下（CO）测量麻醉大鼠（2%异氟烷，n=6）的肾脏组织 PO：1）高氧血症（吸入氧分数 21%、30%和 50%）和 2）急性血液稀释性贫血（基线、25%和 50%急性血液稀释）。在每种情况下，均测量平均动脉压（MAP）、直肠温度、动脉血气（ABG）和化学（Radiometer）。蓝光和红光分别用于测量浅层肾皮质和深层皮质和髓质组织中的 PO。
浅层肾皮质的 PO 较高（60mmHg，蓝光），而深层肾皮质和外髓质的 PO 较低（45mmHg，红光）。高氧血症导致 PO 值成比例增加，而血液稀释以线性方式降低了浅层和深层肾脏区域的微血管 PO。在两种情况下（蓝光和红光），PO 与 CO 相关，但与 MAP 无关。
观察到的 CO 与 PO 之间的线性关系表明肾脏作为一种定量贫血缺氧和高氧传感器的生物学功能。更好地了解 PO 变化的影响可能会为改善肾脏氧输送和预防急性肾损伤的临床实践提供信息。
