Changes of coagulation parameters during high altitude expedition

Data on changes of haemostatic parameters at altitudes above 5000 m are very limited. So far it is unknown, whether altered coagulation could contribute to the development of acute mountain sickness.

Thirty four healthy mountaineers were randomised to two acclimatisation protocols and undertook an expedition on Muztagh Ata (7549 m) in China. Tests were performed at five altitudes up to 6865 m. Haemostatic parameters, such as PT, aPTT, D-Dimer, APC-Resistance (APCR), von Willebrand Factor activity (RCo), ADAMTS-13 & C-Natriuretic Peptide (CNP) were assessed together with Lake Louise AMS score.

D-Dimer significantly increased with increasing altitude (median 0.62 to 0.81 mcg/L, p <0.0001). During ascent, PT increased (83% to >100%) and APCR decreased significantly from 0.95 to 0.8 (p <0.01). Furthermore, a significant increase of aPTT (38 to 43 sec) was paralleled by significant changes of RCo (102% to 62%) (both p <0.001). There were no significant changes in ADAMTS-13 and CNP. No significant relationship between investigated parameters and AMS scores could be detected. When comparing the participants of the two acclimatisation protocols, there was an overall higher RCo in patients with a faster ascent protocol (p = 0.04). This was accompanied by lower ADAMTS-13 of the coagulation system in these patients (p = 0.04).

Coagulation parameters change significantly during hypobaric hypoxia. Whereas we could detect no association between AMS scores and coagulation parameters, our results do show some parameters to be associated with an acclimatisation protocol and a successful ascent to the summit.