What Are the Steps of Hemostasis?
The steps of hemostasis are bodily processes that work together to stem blood flow and keep bacteria out after an injury. Hemostasis is the result of a series of natural reactions that try to prevent the body from bleeding out.
The four steps of hemostasis are: (1) vascular spasm, (2) platelet clotting, (3) coagulation cascade, and (4) fibrin remodeling. These processes reduce blood flow to the injury site, seal the wound to prevent infections, and ideally stop the flow of blood. In the case of a serious injury, the body’s response won’t be sufficient, and immediate action is needed to prevent life-threatening blood loss.
The Four Steps of Hemostasis
Hemostasis combines the Ancient Greek roots “hemo” (meaning “blood”) and “stasis” (meaning “halt”). It’s the term for the process in which your body stops bleeding. Rather than being just a single process, hemostasis involves four steps that happen in quick succession when you are injured.
1. Vascular Spasm
When a blood vessel suffers damage, the body’s first response is to constrict the damaged vessel. Damaged endothelial cells release peptides called endothelins that cause the smooth muscle around them to contract.
This constriction reduces blood flow to the site of the injury to limit the amount of blood loss. The degree of constriction depends on the severity of the damage. Smaller blood vessels constrict more effectively than large blood vessels.
2. Primary Hemostasis (Formation of a Platelet Plug)
Primary hemostasis occurs when the body creates a temporary plug to seal a wound. This happens when platelets adhere to the damaged tissue and activate. By activating, more platelets join to make a platelet plug. This is what stops blood loss from the wound. The clot formed during this process keeps blood in and germs out.
3. Secondary Hemostasis (Coagulation Cascade)
Though a blood clot forms during primary hemostasis, it won't be stable enough to stay in place without secondary hemostasis. The stabilization of the plug requires molecules called coagulation factors which increase the clotting as the sequence goes on.
This process is referred to as a cascade because the activation of one factor leads to the activation of the next. For example, the activation of Factor X (its conversion into Xa) causes prothrombin (Factor II) to convert into thrombin (Factor IIa), and so on (see our article on the Clotting Cascade for a more detailed coverage of this process).
The tissue factor is the primary initiator of blood coagulation. When it binds to Factor VIIa, the tissue factor activates the coagulation cascade through proteolysis (the process in which proteins break down partially or completely), resulting in the production of fibrin which stabilizes the platelet plug.
If bleeding isn't controlled naturally or through pressure or ligature (a tourniquet), hemostatic agents can be used to accelerate the clotting cascade and stop the bleeding. Hemostatic dressings contained in trauma kits can help to accelerate hemostasis after a trauma when bleeding doesn't stop using other methods.
4. Fibrin Clot Remodeling
The final stage in hemostasis involves remodeling the clot into a fibrin clot. This is needed because the formation of the platelet plug and coagulation aren't a permanent solution. During the process of fibrinolysis, your body transforms the clot into the same tissue that existed before the injury occurred.
The process of hemostasis should result in the formation of a blood clot. However, coagulation disorders can disrupt the normal formation of blood clots. This can mean that blood clots don’t form when they should or—the opposite problem—form when they shouldn’t.
Coagulation disorders can happen due to deficiencies in clotting factors or—in the case of DVT—sitting for too long without moving. These are some of the best-known clotting disorders:
Perhaps the best-known coagulation disorder, hemophilia inhibits proper blood coagulation because the body lacks the necessary proteins to clot the blood. A minor injury can be serious for a person suffering from hemophilia as they will bleed much more than the average person.
Deep Vein Thrombosis
DVT occurs when a blood clot forms in deep veins. This happens because the veins are injured or normal blood flow is impeded. A blood clot inside a blood vessel can partially or totally block blood flow through the vein. Part of the clot can also break off and travel into the lungs causing a pulmonary embolism, which is potentially life-threatening.
Von Willebrand Disease
The body needs the von Willebrand Factor protein to clot blood. If someone has lower-than-normal levels of this protein, or the protein doesn’t work as it should, their body will struggle to properly clot blood. This genetic disorder is known as von Willebrand disease (VWD).
How to Promote Clotting in a Bleeding Emergency
If someone suffers a serious injury and is bleeding (more than a slow trickle), it’s critical to act immediately:
5. Apply Direct Pressure
Apply direct pressure to the wound with a sterile dressing or folded pieces of clothing if a sterile dressing isn’t available. Continue applying pressure while calling the emergency services.
6. Elevate the Extremities
If the patient is losing blood from an arm or leg, lay them flat and elevate the bleeding limb above the heart. Keep it elevated until emergency assistance arrives.
7. Cover the Bleeding Wound
If there is more than one person available, one person should press the dressing firmly against the wound while another secures the dressing with a roller gauze. A standard gauze, contained in regular bleeding control kits, is appropriate for mild bleeding. Hemostatic gauze, found in premium bleeding control kits, accelerates the clotting process and is useful for moderate to severe bleeding.
8. Monitor the Bleeding
Never lift the gauze to see if the bleeding has stopped. If blood seeps through the dressing, add another gauze on top of the first one. If the bleeding slows down, wrap the gauze with a sterile bandage.
9. Apply a Tourniquet
If the bleeding continues after a minute or two of direct pressure and emergency assistance has not arrived, you may need to apply a tourniquet. Please note that tourniquets can only be applied to limbs (arms or legs).
- Place the tourniquet two or more inches above the wound (on the heart side of the wound) and turn the windlass until the bleeding stops.
- Secure the windlass and write down the time that the tourniquet was applied.
Important note about removal: A tourniquet shouldn't be left on for more than two hours. However, it should only be removed by a medical professional once the patient is safely in hospital. Never remove a tourniquet yourself.
10. Apply Hemostatic Gauze
For serious wounds, a dressing with hemostatic agents—hemostatic gauze—can establish hemostasis more quickly than a regular dressing. The hemostatic agents contained in gauzes like the QuikClot® Combat Gauze or NuStat Hemostatic Dressing can help stop bleeding by:
- Concentrating coagulation factors
- Adhering to the damaged tissue
- Delivering pro-coagulation factors to the site of the hemorrhage.
In a 2019 study by Johnson and Johnson, the QuikClot Combat Gauze was reported to achieve initial hemostasis in 100% of subjects. NuStat® has also been shown to promote blood coagulation, leading to improved control of hemorrhages.
Bleeding Control Kits Help With Hemostasis
The body is an incredible and complex system that has mechanisms in place for self-protection, including the four steps of hemostasis. However, when bleeding is too heavy for the body to control effectively, a helping hand is needed.
To be prepared for bleeding emergencies at home, work, school, and on the road, it’s essential to have a well-stocked bleeding control kit that includes sterile dressings, a commercial tourniquet, and preferably hemostatic gauze. These pieces of equipment can help to establish hemostasis faster and potentially save someone’s life.