Remote ischemic preconditioning delays the onset of acute mountain sickness in normobaric hypoxia

Abstract

Acute mountain sickness (AMS) is a neurological disorder occurring when ascending too fast, too high. Remote ischemic preconditioning (RIPC) is a noninvasive intervention protecting remote organs from subsequent hypoxic damage. We hypothesized that RIPC protects against AMS and that this effect is related to reduced oxidative stress. Fourteen subjects were exposed to 18 hours of normoxia (21% oxygen) and 18 h of normobaric hypoxia (12% oxygen, equivalent to 4500 m) on different days in a blinded, randomized order. RIPC consisted of four cycles of lower limb ischemia (5 min) and 5 min of reperfusion, and was performed immediately before the study room was entered. A control group was exposed to hypoxia (12% oxygen, n = 14) without RIPC. AMS was evaluated by the Lake Louise score (LLS) and the AMS-C score of the Environmental Symptom Questionnaire. Plasma concentrations of ascorbate radicals, oxidized sulfhydryl (SH) groups, and electron paramagnetic resonance (EPR) signal intensity were measured as biomarkers of oxidative stress. RIPC reduced AMS scores (LLS: 1.9 ± 0.4 vs. 3.2 ± 0.5; AMS-C score: 0.4 ± 0.1 vs. 0.8 ± 0.2), ascorbate radicals (27 ± 7 vs. 65 ± 18 nmol/L), oxidized SH groups (3.9 ± 1.4 vs. 14.3 ± 4.6 μmol/L), and EPR signal intensity (0.6 ± 0.2 vs. 1.5 ± 0.4 × 106) after 5 h in hypoxia (all P < 0.05). After 18 hours in hypoxia there was no difference in AMS and oxidative stress between RIPC and control. AMS and plasma markers of oxidative stress did not correlate. This study demonstrates that RIPC transiently reduces symptoms of AMS and that this effect is not associated with reduced plasma levels of reactive oxygen species.

One session of remote ischemic preconditioning does not improve vascular function in acute normobaric and chronic hypobaric hypoxia

“…Together, these findings suggest that preconditioning might offer a degree of protection against the onset of high-altitude pulmonary oedema. In addition, RIPC has also been linked to reduced oxidative stress and lower symptoms of acute mountain sickness after acute exposure to normobaric hypoxia (Berger et al 2015a); however, these findings were observed only transiently (0-12 h). After a brief period of no observable protection, a second delayed window of protection appears after ß18-20 h and lasts for 1-2 days (Pérez-Pinzón, 2004;Koch et al 2014).…”

“…After a brief period of no observable protection, a second delayed window of protection appears after ß18-20 h and lasts for 1-2 days (Pérez-Pinzón, 2004;Koch et al 2014). Although clinical outcomes as a result of RIPC seem promising (Thielmann et al 2013), only a very limited number of studies have investigated RIPC and potential further protection against hypoxia (Foster et al 2011(Foster et al , 2014Berger et al 2015a).…”

Remote Ischemic Preconditioning

“…25 Although the latter effects are systemic and may affect virtually any organ, 17,18,26 other benefits of RIPC may extend to processes such as fracture healing, fibrotic prevention, acute mountain sickness, exercise performance, or pancreatitis. 18,[27][28][29][30] On the contrary, the variety of potential action mechanisms may pose limits to the clinical application of RIPC. Commonly used anesthetics/analgesics (eg.…”

Remote ischemic preconditioning versus intermittent hypoxia training: a comparative analysis for cardioprotection

“…Recent study [76] demonstrates that RIPC (four cycles of lower limb ischemia (5 min) and 5 min of reperfusion) transiently reduces symptoms of acute mountain sickness. However, Lalonde [77] investigating the effect of the same RIPC regimen on anaerobic performance in healthy participants, concluded that remote ischemic preconditioning does not offer any significant benefits for anaerobic performance.…”