Ayus J C, Armstrong D, Arieff A I
Department of Medicine, University of Texas Health Sciences Center, San Antonio, 78229, USA.
Kidney Int. 2006 Apr;69(8):1319-25. doi: 10.1038/sj.ki.5000187.
Hypoxia appears to be a prominent component of brain damage among patients with hyponatremic encephalopathy. Effects of hypoxia on brain in the presence of hyponatremia are not known. In order to evaluate the contributions of hypoxia to brain damage, three separate experiments were conducted in three groups of rodents. Experiment I evaluated the effects of hypoxia and acute (< 4 h) hyponatremia (plasma Na < 120 mmol/l) on brain adaptation in rabbits. Experiment II evaluated the effects of hypoxia and chronic (4 days) hyponatremia on cerebral perfusion in rats. Experiment III evaluated the effects of hypoxia and chronic hyponatremia on brain histology in rats. In experiment I, rabbits with acute hyponatremia demonstrated brain adaptation with significant falls in brain Na content (by 14.2%, P < 0.01) and osmolality (by 8.3%, P < 0.01), and a rise in brain water (by 10.6%, P < 0.05). Rabbits with combined hypoxia and hyponatremia failed to demonstrate brain adaptation. In experiment II, rats with chronic hyponatremia plus hypoxia had a decrease in cerebral perfusion index by more than 50% (P < 0.01). In experiment III, 23% of hypoxic rats had brain lesions, which were in the cerebellum, thalamus, reticular formation, and basal ganglia. Hyponatremia without hypoxia resulted in no brain lesions. Hypoxia in normonatremic animals results in cerebral edema and histopathologic lesions similar to those found in rats whose plasma Na was overcorrected. Hypoxia in hyponatremic animals aggravates cerebral edema, impairs brain adaptation, and decreases cerebral perfusion.
低氧血症似乎是低钠血症性脑病患者脑损伤的一个突出组成部分。低钠血症状态下低氧血症对脑的影响尚不清楚。为了评估低氧血症对脑损伤的作用，在三组啮齿动物中进行了三项独立实验。实验I评估了低氧血症和急性（<4小时）低钠血症（血浆钠<120 mmol/L）对家兔脑适应性的影响。实验II评估了低氧血症和慢性（4天）低钠血症对大鼠脑灌注的影响。实验III评估了低氧血症和慢性低钠血症对大鼠脑组织学的影响。在实验I中，急性低钠血症家兔表现出脑适应性，脑钠含量显著下降（下降14.2%，P<0.01），渗透压下降（下降8.3%，P<0.01），脑含水量增加（增加10.6%，P<0.05）。合并低氧血症和低钠血症的家兔未表现出脑适应性。在实验II中，慢性低钠血症加低氧血症的大鼠脑灌注指数下降超过50%（P<0.01）。在实验III中，23%的低氧血症大鼠出现脑损伤，损伤部位在小脑、丘脑、网状结构和基底神经节。无低氧血症的低钠血症未导致脑损伤。正常钠血症动物的低氧血症导致脑水肿和组织病理学损伤，类似于血浆钠过度纠正的大鼠。低钠血症动物的低氧血症会加重脑水肿，损害脑适应性，并降低脑灌注。
