Effect of the combination of mannitol and ringer acetate or hydroxyethyl starch on whole blood coagulation in vitro.

Mannitol is administered to decrease the intracranial pressure and to improve surgical conditions during craniotomy. Simultaneously a crystalloid infusion is always given and sometimes hydroxyethyl starch (HES) is indicated for intravascular volume replacement. As normal coagulation profile is required during craniotomy, we aimed at determining the effect of mannitol with or without HES or Ringer acetate on blood coagulation in this randomized cross-over in vitro study. Blood samples were withdrawn from 10 volunteers. From whole blood we prepared 10 vol.% and 20 vol.% dilutions of mannitol (15% Mannitol) alone, mannitol and Ringer acetate, and mannitol and HES 130/0.4 (Voluven) at a ratio of 1:1. Blood samples were analyzed by modified thromboelastometry. Coagulation parameters: clotting time, clot formation time, and maximum clot firmness (MCF), were registered. Clot formation time was prolonged in all dilutions compared with control (P<0.05). MCF decreased in all dilutions compared with control (P<0.05). MCF in 20 vol.% dilution of mannitol with HES was lower than MCF in the corresponding dilution with Ringer acetate (P<0.05). Fibrinogen-dependent MCF in 10 vol.% dilution of mannitol with HES was lower than MCF in the corresponding dilution with Ringer acetate (P<0.05). We conclude that mannitol in combination with HES 130/0.4 impairs clot propagation and clot strength in vitro. Fibrin clot strength impairment is more pronounced when mannitol is combined with HES than Ringer acetate. Our findings indicate that HES in combination with mannitol should be avoided whenever a disturbance in hemostasis is suspected during craniotomy.