Dalinghaus M, Gratama J W, Zijlstra W G, Kuipers J R
Beatrix Children's Hospital, Division of Pediatric Cardiology, University of Groningen, The Netherlands.
Am J Physiol. 1995 Mar;268(3 Pt 2):H974-9. doi: 10.1152/ajpheart.1995.268.3.H974.
Cardiovascular responses to acute hypoxemia are in part mediated through adrenergic and chemoreceptor stimulation. In chronic hypoxemia the response to these stimuli may be blunted. Therefore, we determined whether the cardiovascular responses to acute hypoxemia superimposed on 3-4 wk of chronic hypoxemia were blunted in lambs with an experimental cardiac right-to-left shunt (combination of atrial septal defect and variable pulmonary stenosis). Cardiovascular variables and regional blood flows were determined during chronic hypoxemia and after acutely reducing the arterial oxygen saturation by increasing the cardiac right-to-left shunt. Arterial oxygen saturation decreased (65 +/- 7 to 40 +/- 7%, P < 0.001) and systemic blood flow increased (164 +/- 63 to 233 +/- 100 ml.min-1.kg-1, P < 0.01), maintaining systemic oxygen supply and oxygen uptake. Blood flow to the myocardium (P < 0.01), the adrenals (P < 0.05), and the brain (0.05 < P < 0.10) increased, and oxygen supply to these organs was maintained. Conversely, blood flow to the kidneys and the gastrointestinal tract was unaltered, so that oxygen supply to these organs was decreased. The responses to acute hypoxemia in chronically hypoxemic lambs were similar to those previously reported in normoxemic lambs. We conclude that the cardiovascular responses to acute hypoxemia in chronically hypoxemic lambs are not blunted.
心血管系统对急性低氧血症的反应部分是通过肾上腺素能和化学感受器刺激介导的。在慢性低氧血症中，对这些刺激的反应可能会减弱。因此，我们确定了在患有实验性心脏右向左分流（房间隔缺损和可变肺动脉狭窄的组合）的羔羊中，叠加在3-4周慢性低氧血症上的急性低氧血症的心血管反应是否会减弱。在慢性低氧血症期间以及通过增加心脏右向左分流急性降低动脉血氧饱和度后，测定心血管变量和局部血流。动脉血氧饱和度降低（65±7%至40±7%，P<0.001），全身血流增加（164±63至233±100 ml·min⁻¹·kg⁻¹，P<0.01），维持全身氧气供应和氧气摄取。流向心肌（P<0.01）、肾上腺（P<0.05）和大脑（0.05<P<0.10）的血流增加，这些器官的氧气供应得以维持。相反，流向肾脏和胃肠道的血流未改变，因此这些器官的氧气供应减少。慢性低氧血症羔羊对急性低氧血症的反应与之前在正常氧合羔羊中报道的反应相似。我们得出结论，慢性低氧血症羔羊对急性低氧血症的心血管反应不会减弱。
