CAN MOUNTAIN SICKNESS SYMPTOMS BE PREDICTED ON THE BASIS OF BLOOD COAGULATION PARAMETERS?: 9A.04

Abstract

Objective: The present study was performed to investigate the possible occurrence of global changes of blood coagulation (thromboelastometry) during exposure to high altitude hypoxia, and their relation with the occurrence of mountain sickness symptoms (quantified by the Lake Louise Score, LLS), in the frame of the HIGH altitude Cardiovascular Research(HIGHCARE) project at Everest base camp (BC,5400 m). Design and Method: All participants (n = 47;40 ± 9 yrs)to HIGHCARE expedition underwent baseline clinical and instrumental evaluation at sea level(baseline), the day after reaching 3400 m by helicopter (Namche), after acute (BC1) and prolonged (2 weeks,BC2) exposure at 5400 m. Thromboelastometry (ROTEM Pentapharm, Munich, Germany), was performed on simple recalcified citrated plasma (spontaneous contact activation,NATEM) and upon addition of ellagic acid (intrinsic pathway,INTEM). All clinical and instrumental parameters were then entered in stepwise multivariate regression analysis to select independent predictors of LLS, which was determined in each study conditions. Results: At Namche 23 out of 47 subjects had no symptoms of high altitude sickness (LLS = 0) with LLS>3 in 2 subjects. At BC1 40 subjects had symptoms, 14 reporting a LLS >3 (0 in only 7 subjects). After chronic adaptation(BC2), only 17 had symptoms (LLS >3 in 1 subject). Oxygen saturation (beta = -0.859;p < 0.0001), haematocrit (beta-0.228;p < 0.004), expedition day (-0.263;p < 0.006) and maximum velocity of clot formation at INTEM assay (beta = 0.176;p < 0.013) were identified as independent predictor of LLS at stepwise regression analysis. A score index, calculated on the basis of the four predictors corrected for regression coefficients, was then retrospectively used to stratify subjects in three classes of mountain sickness risk, according to data measured at Namche (acute hypoxia exposure).One out of 12 subjects in the first tertile versus 12 out of the remaining 35 subjects had LLS>3 at BC1(p < 0.001). Conclusions: INTEM assay revealed a reduced activity of coagulation intrinsic pathway at altitude. However the maximum velocity of clot formation at INTEM assay was selected as a positive independent predictor of LLS, indicating a link between rheological changes and adaptation to altitude.