Blood viscosity in patients with bone fractures and long term bedrest.

Eighteen patients with bone fractures and without systemic disease were studied for blood rheology. Blood and plasma viscosities, haematocrit, red cell aggregation and filterability as well as plasma colloid oncotic pressure were measured. Results show that patients exhibit a substantial haemorheological deficit on admission. During bedrest this returns to normal, owing to marked 'autohaemodilution'. It is concluded that trauma causes increased viscosity of blood in these patients. This change could predispose to deep vein thrombosis. However, such a risk is reduced by 'autohaemodilution' which is most probably an effect of immobilization.