Platelet count, platelet aggregation and fibrinogen levels following acute induction to high altitude (3200 and 3771 metres).

Two groups of 20 subjects each were separately exposed to altitudes of 3200 m and 3771 m for 10 days by rapid induction requiring 14 and 16 hours respectively to reach high altitude camps. A statistically significant fall in platelet counts was observed from day 2 at 3200 m and day 3 at 3771 m and counts remained decreased. Platelet aggregation was also decreased initially at both altitudes. Blood fibrinogen decreased only on day 2 at 3771 m with a significant increase over control values by day 10 at both altitudes.