Hemostasis
In biology, hemostasis or haemostasis is a process to prevent and stop bleeding, meaning to keep blood within a damaged blood vessel (the opposite of hemostasis is hemorrhage). It is the first stage of wound healing. Hemostasis involves three major steps:
- vasoconstriction
- temporary blockage of a hole in a damaged blood vessel by a platelet plug
- blood coagulation (formation of fibrin clots)
Coagulation, the changing of blood from a liquid to a gel which forms the fibrin clots, is essential to hemostasis. Intact blood vessels moderate blood's tendency to form clots. The endothelial cells of intact vessels prevent blood clotting with a heparin-like molecule and thrombomodulin, and prevent platelet aggregation with nitric oxide and prostacyclin. When endothelium of a blood vessel is damaged, the endothelial cells stop secretion of coagulation and aggregation inhibitors and instead secrete von Willebrand factor, which initiates the maintenance of hemostasis after injury. These processes seal the injury or hole until tissues are healed.
Etymology and pronunciation
The word hemostasis (
Steps of mechanism
Hemostasis occurs when blood is present outside of the body or blood vessels. It is the innate response for the body to stop bleeding and loss of blood. During hemostasis three steps occur in a rapid sequence. Vascular spasm is the first response as the blood vessels constrict to allow less blood to be lost. In the second step, platelet plug formation,
- pain receptors, which helps promote vasoconstriction. The damaged vessels will constrict (vasoconstrict) which reduces the amount of blood flow through the area and limits the amount of blood loss. Collagen is exposed at the site of injury, the collagen promotes platelets to adhere to the injury site. Platelets release cytoplasmic granules which contain serotonin, ADP and thromboxane A2, all of which increase the effect of vasoconstriction. The spasm response becomes more effective as the amount of damage is increased. Vascular spasm is much more effective in smaller blood vessels.[5][6]
- Platelet plug formation: Platelets adhere to damaged endothelium to form a platelet plug (primary hemostasis) and then degranulate. This process is regulated through thromboregulation. Plug formation is activated by a glycoprotein called von Willebrand factor (vWF), which is found in plasma. Platelets play one of major roles in the hemostatic process. When platelets come across the injured endothelium cells, they change shape, release granules and ultimately become ‘sticky’. Platelets express certain receptors, some of which are used for the adhesion of platelets to collagen. When platelets are activated, they express glycoprotein receptors that interact with other platelets, producing aggregation and adhesion. Platelets release cytoplasmic granules such as adenosine diphosphate (ADP), serotonin and thromboxane A2. Adenosine diphosphate (ADP) attracts more platelets to the affected area, serotonin is a vasoconstrictor and thromboxane A2 assists in platelet aggregation, vasoconstriction and degranulation. As more chemicals are released more platelets stick and release their chemicals; creating a platelet plug and continuing the process in a positive feedback loop. Platelets alone are responsible for stopping the bleeding of unnoticed wear and tear of our skin on a daily basis. This is referred to as primary hemostasis.[5][7]
- Clot formation: Once the platelet plug has been formed by the platelets, the heart attack, or pulmonary embolism respectively. However, without this process the healing of a wound would not be possible.[3]
Types
Hemostasis can be achieved in various other ways if the body cannot do it naturally (or needs help) during surgery or medical treatment. When the body is under shock and stress, hemostasis is harder to achieve. Though natural hemostasis is most desired, having other means of achieving this is vital for survival in many emergency settings. Without the ability to stimulate hemostasis the risk of
Developmental Haemostasis refers to the differences in the haemostatic system between children and adults.
In emergency medicine
Debates by physicians and medical practitioners still continue to arise on the subject of hemostasis and how to handle situations with large injuries. If an individual acquires a large injury resulting in extreme blood loss, then a
Some main types of hemostasis used in emergency medicine include:
- Chemical/topical – This is a topical agent often used in surgery settings to stop bleeding. Microfibrillar collagen is the most popular choice among surgeons [recent source?] because it attracts the patient's natural platelets and starts the blood clotting process when it comes in contact with the platelets. This topical agent requires the normal hemostatic pathway to be properly functional.[9]
- Direct pressure or pressure dressing – This type of hemostasis approach is most commonly used in situations where proper medical attention is not available. Putting pressure and/or dressing to a bleeding wound slows the process of blood loss, allowing for more time to get to an emergency medical setting. Soldiers use this skill during combat when someone has been injured because this process allows for blood loss to be decreased, giving the system time to start coagulation.[10]
- Sutures and ties – Sutures are often used to close an open wound, allowing for the injured area to stay free of pathogens and other unwanted debris to enter the site; however, it is also essential to the process of hemostasis. Sutures and ties allow for skin to be joined back together allowing for platelets to start the process of hemostasis at a quicker pace. Using sutures results in a quicker recovery period because the surface area of the wound has been decreased.[11]
- Physical agents (gelatin sponge) – Gelatin sponges have been indicated as great hemostatic devices. Once applied to a bleeding area, a gelatin sponge quickly stops or reduces the amount of bleeding present. These physical agents are mostly used in surgical settings as well as after surgery treatments. These sponges absorb blood, allow for coagulation to occur faster, and give off chemical responses that decrease the time it takes for the hemostasis pathway to start.[12]
Disorders
The body's hemostasis system requires careful regulation in order to work properly. If the blood does not clot sufficiently, it may be due to bleeding disorders such as
Hemostasis disorders can develop for many different reasons. They may be
History of artificial hemostasis
The process of preventing blood loss from a vessel or organ of the body is referred to as hemostasis. The term comes from the Ancient Greek roots "heme" meaning blood, and "stasis" meaning halting; Put together means the "halting of the blood".[3] The origin of hemostasis dates back as far as ancient Greece; first referenced to being used in the
Research
There is currently a great deal of research being conducted on hemostasis. The most current research is based on genetic factors of hemostasis and how it can be altered to reduce the cause of
Von Willebrand disease is associated with a defect in the ability of the body to create the platelet plug and the fibrin mesh that ultimately stops the bleeding. New research is concluding that the von Willebrand disease is much more common in adolescence. This disease negatively hinders the natural process of Hemostasis causing excessive bleeding to be a concern in patients with this disease. There are complex treatments that can be done including a combination of therapies, estrogen-progesterone preparations, desmopressin, and Von Willebrand factor concentrates. Current research is trying to find better ways to deal with this disease; however, much more research is needed in order to find out the effectiveness of the current treatments and if there are more operative ways to treat this disease.[15]
See also
- Blood tests:
- Prothrombin time
- Partial thromboplastin time
References
- ^ "hemostasis". Merriam-Webster.com Dictionary. Retrieved 2016-01-21.
- ^ "hemostasis". Lexico UK English Dictionary. Oxford University Press. Archived from the original on 2020-03-22.
- ^ a b c Marieb, Elaine Nicpon; Hoehn, Katja (2010). Human Anatomy & Physiology (8th ed.). San Francisco: Benjamin Cummings. pp. 649–650.
- ^ Boon, G. D. "An Overview of Hemostasis." Toxicologic Pathology 21.2 (1993): 170–179.
- ^ a b Alturi, Pavan (2005). The Surgical Review: An Integrated Basic and Clinical Science Study Guide. Philadelphia: Lippincott Williams & Wilkins. p. 300.
- ISBN 9781587160363.
- PMID 21071698.
- ^ a b Kulkarni Roshni (2004). "Alternative and Topical Approaches to Treating the Massicely Bleeding Patient" (PDF). Advances in Hematology. 2 (7): 428–431. Archived from the original (PDF) on 2009-01-06. Retrieved 2012-04-26.
- ^ Aldo Moraci, et al. "The Use Of Local Agents: Bone Wax, Gelatin, Collagen, Oxidized Cellulose." European Spine Journal 2004; 13.: S89–S96.
- PMID 10594624.
- ^ Kozak Orhan; et al. (2010). "A New Method For Hepatic Resection And Hemostasis: Absorbable Plaque And Suture". Eurasian Journal of Medicine. 41: 1–4.
- .
- PMC 2606227.
- PMID 16524747.
- PMID 20934894.
External links
- Hemostasis at the U.S. National Library of Medicine Medical Subject Headings (MeSH)