Why the study?
To evaluate whether prolonged normobaric hypoxia induces acclimatization and recovery of LV function, and to investigate the role of hypoxic sympathetic activation using adrenergic blockade.
Key points are not available for this paper at this time.
Comparison
Normobaric hypoxia vs normal room air, with 0.9% NaCl infusion vs different adrenergic blockers
Design
Animal experimental study
Follow-up
72 h
Findings in rat hypoxia model warrant caution extrapolating to humans; leaves open whether acclimatization restores LV function after prolonged exposure.
In rats, acute normobaric hypoxia depressed left ventricular (LV) inotropic function. After 24 h of hypoxic exposure, a slight recovery of LV function occurred. We speculated that prolonged hypoxia (72 h) would induce acclimatization and, hence, recovery of LV function. Moreover, we investigated biomarkers of nitrosative stress and apoptosis as possible causes of hypoxic LV depression. To elucidate the role of hypoxic sympathetic activation, we studied whether adrenergic blockade would further deteriorate the general state of the animals and their cardiac function. Ninety-four rats were exposed over 72 h either to normal room air (N) or to normobaric hypoxia (H). The rodents received infusion (0.1 mL/h) with 0.9% NaCl or with different adrenergic blockers. Despite clear signs of acclimatization to hypoxia, the LV depression continued persistently after 72 h of hypoxia. Immunohistochemical analyses revealed significant increases in markers of nitrosative stress, adenosine triphosphate deficiency and apoptosis in the myocardium, which could provide a possible explanation for the absence of LV function recovery. Adrenergic blockade had a slightly deteriorative effect on the hypoxic LV function compared to the hypoxic group with maintained sympathetic efficacy. These findings show that hypoxic sympathetic activation compensates, at least partially, for the compromised function in hypoxic conditions, therefore emphasizing its importance for hypoxia adaptation.
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Neubert et al. (2023) studied this question.
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