Coagulation Activation by Hyperosmolar Agents in Intracranial Hypertension

Osmotherapy is commonly used in the treatment of intracranial hypertension (ICH) due to a variety of causes, including head trauma, intracranial neoplasia, infection or hemorrhage, and status epilepticus. The principle goal of osmotherapy is to shift fluid from the intracellular into the extracellular compartment using intravenous hyperosmolar agents, thereby reducing brain edema and improving cerebral perfusion pressure. Although 10-20% mannitol is considered the gold standard hyperosmolar agent in the treatment of ICH, mannitol-induced osmotic diuresis may cause hypovolemia and reduction in cerebral perfusion pressure. In recent years, 3.0-7.5% hypertonic saline (HTS) has gained popularity in the treatment of ICH as it has less pronounced diuretic effects and therefore does not cause hypovolemia. Indeed, in the face of hypovolemic shock and traumatic brain injury, HTS provides the advantage of volume expansion, restoring adequate cerebral perfusion pressures, and reducing brain edema, which makes it superior to mannitol in trauma patients with shock. Both mannitol and HTS have been shown to interfere with whole blood coagulation and platelet function. This is in part due to dilutional coagulopathy. Furthermore, 7.2% HTS may directly disturb both fibrin formation and platelet function, and mannitol may interfere with coagulation by reducing clot strength. In addition, hyperosmolarity is supposed to lead to impairment of both whole blood coagulation and platelet function . In consequence, the safety of using these agents in patients with ICH and intracranial hemorrhage remains unclear. Previous in vitro studies in humans have demonstrated anticoagulant effects of both mannitol and HTS, although one clinical study failed to demonstrate any negative effect on hemostasis using either solution in patients undergoing elective intracranial surgery. However, in vivo studies in a clinical setting are lacking.