Remote ischemic preconditioning does not prevent acute mountain sickness after rapid ascent to 3450 m

Remote ischemic preconditioning (RIPC) has been shown to protect remote organs, such as the brain and the lung, from damage induced by subsequent hypoxia or ischemia. Acute mountain sickness (AMS) is a syndrome of non-specific neurologic symptoms and in high altitude pulmonary edema excessive hypoxic pulmonary vasoconstriction (HPV) plays a pivotal role. We hypothesized that RIPC protects the brain from AMS and attenuates the magnitude of HPV after rapid ascent to 3450 m. Forty non-acclimatized volunteers were randomized into 2 groups. At low altitude (750 m) the RIPC group (n=20) underwent 4x5 minutes of lower limb ischemia (induced by inflation of bilateral thigh cuffs to 200 mmHg), followed by 5 minutes of reperfusion. The control group (n=20) underwent a sham protocol (4x5 minutes of bilateral thigh cuff inflation to 20 mmHg). Thereafter, participants ascended to 3450 m by train over 2 hours and stayed there for 48 hours. AMS was evaluated by the Lake Louise score (LLS) and the AMS-C score. Systolic pulmonary artery pressure (SPAP) was assessed by transthoracic Doppler echocardiography. RIPC had no effect on the overall incidence (RIPC: 35%, control: 35%, P=1.0) and severity (RIPC versus control: P=0.496 for LLS; P=0.320 for AMS-C score) of AMS. RIPC also had no significant effect on SPAP (maximum after 10 hours at high altitude; RIPC: 33 (SD 8) mmHg; controls: 37 (SD 7) mmHg; P=0.19). This study indicates that RIPC, performed immediately before passive ascent to 3450 m, does not attenuate AMS and the magnitude of high altitude pulmonary hypertension.

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