LMWHs, consist of only short chains of polysaccharide. LMWHs are defined as heparin salts having an average molecular weight of less than 8000 Da and for which at least 60% of all chains have a molecular weight less than 8000 Da. These are obtained by various methods of fractionation or depolymerisation of polymeric heparin.
Heparin derived from natural sources, mainly porcine intestine or bovine lung, can be administered therapeutically to prevent thrombosis. However, the effects of natural, or unfractionated heparin are more unpredictable than LMWH.
Evidence suggests low molecular weight heparin reduces cerebral edema and improves neurological recovery following stroke and traumatic brain injury (TBI), through blunting of cerebral leukocyte (LEU) recruitment. It remains unknown if unfractionated heparin (UFH) similarly affects brain inflammation and neurological recovery post TBI.
Prophylaxis was associated with decreased risk of pulmonary embolism and deep vein thrombosis, but no increase in risk of late neurosurgical intervention or death. Early prophylaxis may be safe and should be the goal for each patient in the context of appropriate risk stratification 1).
Unfractionated heparin (UFH) after TBI reduces LEU recruitment, microvascular permeability and brain edema to injured brain. Lower UFH doses concurrently improve neurological recovery while higher UFH may worsen functional recovery. Further study is needed to determine if this is due to increased bleeding from injured brain with higher UFH doses 2).
Low-dose heparin pretreatment may decrease the development of post-SAH early brain injury (EBI) 3).