Global REACH 2018: renal oxygen delivery is maintained during early acclimatization to 4,330 m.

Early acclimatization to high altitude is characterized by various respiratory, hematological, and cardiovascular adaptations that serve to restore oxygen delivery to tissue. However, less is understood about renal function and the role of renal oxygen delivery (RDO) during high altitude acclimatization. We hypothesized that ) RDO would be reduced after 12 h of high altitude exposure (high altitude ) but restored to sea level values after 1 wk (high altitude ) and ) RDO would be associated with renal reactivity, an index of acid-base compensation at high altitude. Twenty-four healthy lowlander participants were tested at sea level (344 m, Kelowna, BC, Canada) and on and at high altitude (4,330 m, Cerro de Pasco, Peru). Cardiac output, renal blood flow, and arterial and venous blood sampling for renin-angiotensin-aldosterone system hormones and NH-terminal pro-B-type natriuretic peptides were collected at each time point. Renal reactivity was calculated as follows: (Δarterial bicarbonate)/(Δarterial Pco) between sea level and high altitude and sea level and high altitude . The main findings were that ) RDO was initially decreased at high altitude compared with sea level (ΔRDO: -22 ± 17%, < 0.001) but was restored to sea level values on high altitude (ΔRDO: -6 ± 14%, = 0.36). The observed improvements in RDO resulted from both changes in renal blood flow (Δ from high altitude : +12 ± 11%, = 0.008) and arterial oxygen content (Δ from high altitude : +44.8 ± 17.7%, = 0.006) and ) renal reactivity was positively correlated with RDO on high altitude ( = 0.70, < 0.001) but not high altitude (= 0.26, = 0.29). These findings characterize the temporal responses of renal function during early high altitude acclimatization and the influence of RDO in the regulation of acid-base balance.