What is hemostasis?
Hemostasis describes the process by which the body stops bleeding. The word “hemostasis” comes from ancient Greek and is composed of the words “haima” (blood) and “stasis” (stasis).
Hemostasis can be roughly divided into two steps: Through primary hemostasis, a wound (vascular leak) is provisionally treated via a rather unstable clot (white thrombus). In contrast, secondary hemostasis (blood clotting) leads to stable wound closure via a red thrombus. Despite the division, primary and secondary hemostasis both occur almost simultaneously and interact with each other through many mechanisms.
Primary hemostasis
The platelets, which are stored together, release various substances that attract further platelets and the so-called fibrinogen (precursor of the blood fiber fibrin). They also change their shape and form spiny extensions that are cross-linked with the help of fibrinogen. The enzyme cyclooxygenase (COX) also stimulates the interconnection of platelets. This ultimately forms a dense structure – the white thrombus, which closes the wound.
Secondary hemostasis (blood clotting)
To learn how blood clotting occurs with the help of a red thrombus, see the article Blood Clotting.
When do you determine the levels of hemostasis?
If wounds bleed for an unusually long time in a patient, laboratory tests must be used to rule out a disorder of primary hemostasis or secondary hemostasis. Hemostasis is also checked before surgery to protect the patient.
Hemostasis values
The physician takes a small blood sample, usually from the vein. The patient does not necessarily have to be fasting for this, as food intake does not significantly change the hemostasis values. The number of platelets in healthy adults is between 150,000 and 400,000 per microliter.
The so-called bleeding time is also important. Here, depending on the method, the physician inflicts a more or less standardized small skin injury on the patient and then checks the time until the resulting bleeding stops. The standard values differ depending on the measurement method. A prolonged bleeding time indicates thrombocytopathy or thrombocytpenia.
Your doctor will explain the results to you after the evaluation and will explain any further examination or treatment steps.
When are hemostasis values too low?
A low platelet count can have many causes. These include:
- heavy bleeding
- infections, for example malaria
- various forms of blood cancer (leukemias)
- destruction of platelets by the body itself (autoimmunological destruction, for example thrombotic thrombocytopenic purpura)
- blood thinning therapy
- Allergies, toxins, medications and vitamin deficiencies
- tumors
- Pregnancy
- Cirrhosis of the liver
- increased degradation in the spleen (triggers can be liver cirrhosis and infections)
Sometimes a decreased platelet value is also due to an incorrect measurement.
A too short bleeding time is not medically relevant.
When are hemostasis values too high?
The increase of the bleeding time can be an indication of a platelet deficiency. However, it is mainly used to detect plateletopathies. Possible causes of such platelet dysfunction include the use of certain drugs such as ASA (acetylsalicylic acid) or chemotherapeutic agents. Hereditary diseases such as von Willebrand-Jürgens syndrome and Bernard-Soulier syndrome can also be the cause of thrombocytopathy.
If the blood contains too many platelets (thrombocytosis), the risk of blood clots increases. The reason for thrombocytosis can be bone marrow diseases or malignant tumors.
