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heparin

Heparin

Heparin (from Ancient Greek ηπαρ (hepar), liver), also known as unfractionated heparin, a highly sulfated glycosaminoglycan, is widely used as an injectable anticoagulant, and has the highest negative charge density of any known biological molecule.

It can also be used to form an inner anticoagulant surface on various experimental and medical devices such as test tubes and renal dialysis machines.

Although it is used principally in medicine for anticoagulation, its true physiological role in the body remains unclear, because blood anticoagulation is achieved mostly by heparan sulfate proteoglycans derived from endothelial cells

Heparin is usually stored within the secretory granules of mast cells and released only into the vasculature at sites of tissue injury. It has been proposed that, rather than anticoagulation, the main purpose of heparin is defense at such sites against invading bacteria and other foreign materials.

In addition, it is observed across a number of widely different species, including some invertebrates that do not have a similar blood coagulation system.

It is on the World Health Organization's List of Essential Medicines, a list of the most important medication needed in a basic health system.

Types

Two types of heparins are commonly used as anticoagulants – unfractionated heparin (UFH) and low molecular weight heparins (LMWHs). UFH has been used for the prevention and treatment of thrombosis for several decades. UFH has variable anticoagulant effects and pharmacological properties and also has limited bioavailability and highly variable anticoagulant response. LMWHs are derived from UFH by depolymerization. Each LMWH product has a specific molecular weight distribution that determines its anticoagulant activity and duration of action. LMWHs are associated with a predictable dose–response and have fewer non-haemorrhagic side-effects. Because of these clinical advantages, LMWHs have gradually replaced UFH for most indications.

Indications

Venous thromboembolic prophylaxis

Venous thromboembolic prophylaxis (VTEp) is often delayed following traumatic brain injury (TBI), yet animal data suggest that it may reduce cerebral inflammation and improve cognitive recovery.

Medical charts of severe TBI patients admitted to a level 1 trauma center in 2009-2010 were queried for admission Glasgow Coma Scale (GCS), head Abbreviated Injury Scale, Injury Severity Score (ISS), osmotherapy use, emergency neurosurgery, and delay to VTEp initiation. Progression (+1 = better, 0 = no change, -1 = worse) of brain injury on head CTs and neurologic exam (by bedside MD, nurse) was collected from patient charts. Head CT scan Marshall scores were calculated from the initial head CT results. RESULTS: A total of 22, 34, and 19 patients received VTEp at early (<3 days), intermediate (3-5 days), and late (>5 days) time intervals, respectively. Clinical and radiologic brain injury characteristics on admission were similar among the three groups (P > 0.05), but ISS was greatest in the early group (P < 0.05). Initial head CT Marshall scores were similar in early and late groups. The slowest progression of brain injury on repeated head CT scans was in the early VTEp group up to 10 days after admission. CONCLUSION: Early initiation of prophylactic heparin in severe TBI is not associated with deterioration neurologic exam and may result in less progression of injury on brain imaging. Possible neuroprotective effects of heparin in humans need further investigation 1).

Complications

1)
Kim L, Schuster J, Holena DN, Sims CA, Levine J, Pascual JL. Early initiation of prophylactic heparin in severe traumatic brain injury is associated with accelerated improvement on brain imaging. J Emerg Trauma Shock. 2014 Jul;7(3):141-148. PubMed PMID: 25114421.
heparin.txt · Last modified: 2016/08/18 11:56 (external edit)