Hemostasis is an essential physiological process that keeps blood within your blood vessels, preventing or halting blood flow when a blood vessel is injured. It constitutes the initial wound healing process and significantly contributes to maintaining good health. 

Primary hemostasis is the initial step of blood clotting that occurs just after injury to blood vessels. 

Primary hemostasis is the first step in preventing immediate bleeding following injury by providing a temporary seal of the vessel until secondary hemostasis, the coagulation cascade, further stabilizes the clot. 

Stages of hemostasis 

• Vascular spasm: Vasoconstriction, where the smooth muscle of the blood vessel contracts, reduces blood flow, and thus blood loss when damaged. 
• Platelet plug formation: Platelets bind at the site of damage, release chemicals that attract more platelets, and form a temporary platelet plug. 
• Coagulation (Secondary Hemostasis): Blood coagulation factors interplay in a complex cascade to form fibrin strands that support the platelet plug, creating a stable blood clot. 
• Clot Retraction and Repair: The clot then contracts, thereby pulling the edges of the wound together. Eventually, the clot is liquefied due to the healing process of the blood vessel through fibrinolysis. 

Vascular Spasm (Vasoconstriction): 

A blood vessel wall, once damaged, provokes a reflexive contraction of the smooth muscle to reduce blood flow and minimize blood loss. 

Platelet Plug Formation-Primary Hemostasis: 

Because of exposure to collagen and other products from vessel wall injury, platelets are activated. 

They become sticky and hence attach themselves to the site of injury; thus, plugging the site/area together for bleeding to stop. 

Coagulation-Secondary Hemostasis: 

The activation of the coagulation factors leads to a cascade of enzymatic reactions that eventually produce fibrin. 

The formed fibrin creates a mesh around the platelet plug, encapsulating and thereby stabilizing it to form a more stable clot. 

Clot retraction and Repair: 

Upon clot formation, the platelets contract to reduce the size of the clot and pack it down. 

As the vessel wall heals, fibrinolysis starts breaking down the clot, and eventually, the vessel’s patency is restored when the vessel wall is adequately healed. 

Trauma: Physical injury resulting in blood vessel damage. 

Coagulation Disorders: Diseases caused by clotting factors or platelet malfunction, such as hemophilia or von Willebrand disease. 

Medicines: Certain medications may interfere with platelet function or clotting cascade. 

Autoimmune Disorders: Examples include diseases wherein the body attacks its clotting factors. 

Genetic Disorders: Inherited disorders affecting clotting factors or platelets. 

Abnormalities of Vessels: Weakened blood vessel walls increase their propensity to bleed. 

Infections: Some infections may be associated with abnormal clotting or bleeding. 

Coagulation factor assays 

Prothrombin time and activated partial prothrombin time  

Platelet count  

Coagulopathies 

Liver Disease 

Platelet Disorders 

Medication 

Trauma or Surgery 

Vascular Disorders 

• Acute Bleeding: This would refer to sudden, severe bleeding, including that resulting from trauma or surgery, and conditions like hemophilia and von Willebrand’s disease. 
• Chronic Bleeding: This often occurs with disorders like liver disease or some factor deficiencies, where bleeding may be less sudden but recurrent or prolonged. 
• Thrombosis: It is abnormal clotting that could result in deep vein thrombosis, pulmonary embolism, or stroke. Acuity ranges from sudden onset on the part of PE to more insidious development like DVT. 
• Thrombocytopenia: Low platelet count causing bleeding of variable intensity depending upon the degree of thrombocytopenia and other factors. 

• Vascular Spasm: A constriction of the blood vessels to limit blood flow. 
• Platelet plug formation: Platelets closing in on a site of an injury bind to the area and secrete chemicals that attract more platelets, eventually forming a temporary plug. 
• Coagulation: A complicated cascade of clotting factors forms fibrin, a protein that reinforces the platelet plug to form a stable blood clot. 
• Clot retraction: The clot’s contraction reduces the damaged area’s size. 
• Fibrinolysis: Breakdown of the clot after tissue repair is complete. 

Hematology

• Pressure: Direct pressure to the wound compresses blood vessels, reducing their diameter and flow. The reduced blood flow contributes to the formation of the blood clot. 
• Cleanliness: A clean wound is less likely to become infected. 
• Temperature: Normal body temperature: Enzymatic reactions involved in clotting occur optimally at average body temperatures. 
• Moisture: Moist environment but not too wet: Aids the migration of cells involved in wound healing and clot formation. 

Hematology

• Antifibrinolytics: The medications prevent fibrinolysis or the breaking down of blood clots. This includes: 
• Tranexamic acid: This is given to avoid excessive bleeding in an operation or can be used in patients with bleeding disorders such as hemophilia. 
• Aminocaproic acid: Like tranexamic acid, this also prevents clot breakdown. 

Hematology

Clotting factor and platelet stimulants: These are medications that enhance the ability to form and maintain blood clots: 

Desmopressin: This medication stimulates the release of von Willebrand factor and factor VIII. 

Hematology

• Hemostatic Agents: These are substances used directly on wounds to promote clotting: 
• Topical thrombin: Applied to surgical sites to enhance clotting. 
• Fibrin sealants: Contain fibrinogen and thrombin, which create a clot at the site of application. 

Hematology

• Compression: Direct pressure to a bleeding spot holds back bleeding. 
• Suturing: Sealing a wound by stitching its edges to keep it from bleeding. 
• Cauterization: There is sealing of the bleeding vessels through heating using an electrical current or chemicals. Applying clotting agents like gauze impregnated with such substances will form clots. These are known as hemostatic agents. 
• Embolization: Closure of the blood vessels that are feeding the bleeding process by usually small particles or coils. 
• Ligation: It is a surgical tying of the blood vessels, mainly to prevent bleeding. 

Hematology

• Primary Hemostasis: This is the first event in response to the blood vessels by causing vascular constriction and reducing blood flow. Platelets then attach to the vessel wall at the injury site and form a temporary plug. 
• Secondary Hemostasis: Also known as the coagulation phase, secondary hemostasis is the process by which the coagulation cascade becomes activated, ultimately forming fibrin strands that stabilize the platelet plug and form a more permanent clot. 
• Fibrinolysis: After an injury has healed, fibrinolysis ensues to break down the fibrin clot once the repair work of tissue is completed. 
• Anticoagulation and control: These anticoagulant drugs are sometimes used in clinical practice to prevent or dissolve clots.