Regulation of plasma volume in male lowlanders during 4 days of exposure to hypobaric hypoxia equivalent to 3500 m altitude.

Acclimatization to hypoxia leads to a reduction in plasma volume (PV) that restores arterial O <sub>2</sub> content. Findings from studies investigating the mechanisms underlying this PV contraction have been controversial, possibly as experimental conditions were inadequately controlled. We examined the mechanisms underlying the PV contraction evoked by 4 days of exposure to hypobaric hypoxia (HH) in 11 healthy lowlanders, while strictly controlling water intake, diet, temperature and physical activity. Exposure to HH-induced an ∼10% PV contraction that was accompanied by a reduction in total circulating protein mass, whereas diuretic fluid loss and total body water remained unchanged. Our data support an oncotically driven fluid redistribution from the intra- to the extravascular space, rather than fluid loss, as the mechanism underlying HH-induced PV contraction. Extended hypoxic exposure reduces plasma volume (PV). The mechanisms underlying this effect are controversial, possibly as previous studies have been confounded by inconsistent experimental conditions. Here, we investigated the effect of hypobaric hypoxia (HH) on PV in a cross-over study that strictly controlled for diet, water intake, physical activity and temperature. Eleven males completed two 4-day sojourns in a hypobaric chamber, one in normoxia (NX) and one in HH equivalent to 3500 m altitude. PV, urine output, volume-regulating hormones and plasma protein concentration were determined daily. Total body water (TBW) was determined at the end of both sojourns by deuterium dilution. Although PV was 8.1 ± 5.8% lower in HH than in NX after 24 h and remained ∼10% lower thereafter (all P < 0.002), no differences were detected in TBW (P = 0.17) or in 24 h urine volumes (all P > 0.23). Plasma renin activity and circulating aldosterone were suppressed in HH during the first half of the sojourn (all P < 0.05) but thereafter similar to NX, whereas no differences were detected for copeptin between sojourns (all P > 0.05). Markers for atrial natriuretic peptide were higher in HH than NX after 30 min (P = 0.001) but lower during the last 2 days (P < 0.001). While plasma protein concentration was similar between sojourns, total circulating protein mass (TCP) was reduced in HH at the same time points as PV (all P < 0.03). Despite transient hormonal changes favouring increased diuresis, HH did not enhance urine output. Instead, the maintained TBW and reduced TCP support an oncotically driven fluid redistribution into the extravascular compartment as the mechanism underlying PV contraction

Data and methods to calculate cut-off values for serum potassium and core temperature at hospital admission for extracorporeal rewarming of avalanche victims in cardiac arrest.

The data and estimation methods presented in this article are associated with the research article, "Cut-off values of serum potassium and core temperature at hospital admission for extracorporeal rewarming of avalanche victims in cardiac arrest: a retrospective multi-centre study" [1]. In this article we estimate recommended cut-off values for in-hospital triage with respect to extracorporeal rewarming. With only 6 survivors of 103 patients collected over a period of 20 years the ability to estimate reliable threshold values is limited. In addition, because the number of avalanche victims is also limited, a significantly larger dataset is unlikely to be obtained. We have therefore adapted two non-parametric estimation methods (bootstrapping and exact binomial distribution) to our specific needs and performed a simulations to confirm validity and reliability

Excavation of a neolithic house at Yarnbury, near Grassington, North Yorkshire

YesLandscape geophysical survey around the small upland ‘henge’ at Yarnbury, Grassington, North Yorkshire revealed few anthropogenic features around the enclosure but did identify a small rectangular structure in the same field. Sample trenching of this feature, radiocarbon and archaeomagnetic dating proved it to be an earlier Neolithic post and wattle structure of a type that is being increasingly recognised in Ireland and the west of Britain. It is the first to be recognised in the Yorkshire Dales and it is argued that the Dales may have been pivotal in the Neolithic for east–west trade as well as pastoral upland agriculture

Acute mountain sickness in a subject with metabolic syndrome at high altitude.

Visitors at high altitude are increasing in age and comorbidities, which can lead to a failure in acclimatization. We describe the development of acute mountain sickness (AMS) in a 44-year-old man with metabolic syndrome and the time- and altitude-dependent correlation between the development of AMS and blood pressure and heart rate changes. Our observations support a dominant role of endothelial dysfunction in the pathogenesis of AMS and suggest new behavioral indications