HEMOSTASIS IN SURGERY

What these lessons are about and what the user will learn/ Enroll in the hemostasis activity under all courses

Hemostasis is the process of stopping bleeding from a damaged blood vessel while maintaining intravascular fluidity. Knowledge of hemostasis is useful for managing surgical patients to prevent excessive blood loss and complications. It is also crucial in order to be able to avoid the complications of thrombosis, such as pulmonary embolism and disseminated intravascular coagulopathy. In the study of hemostasis the students should pay attention to the following concepts:

• Understand the hemostatic mechanisms.
• Understand the hemostatic methods.
• Understand factors affecting the hemostatic mechanisms.
• Understand how to manipulate (enhance or inhibit) the hemostatic mechanisms.
• Understand the application and how to select the hemostatic methods
• Understand the types of hemorrhage and how to manage the different types
• Understand how to assess the risk of bleeding and coagulopathy in surgical patients
• Understand how to manage the risk of bleeding and coagulopathy in surgical patients

The lesson notes will be presented in modules which will be uploaded at intervals. There will be interactive activities for each of the modules. The interactive activities will include simple recall quizzes, simple and complex clinical application quizzes, discussion and decision-making activities.

The interactive activities are specially designed to help users quickly recall the concepts, to help users assess their understanding of the concepts, to help users refocus their studies and prepare for exams, and to help reshape the users thinking in readiness to apply the knowledge for clinical practice. Users may need to enroll for the lesson to access the interactive activities.

How these lesson notes are prepared: The lessons are prepared using multiple sources of information from the internet, standard surgery textbooks and clinical experience. The lesson and modules notes are specifically designed to boost understanding of the concepts, to aid easy recollection and save the users plenty of time during revision and preparation for examinations. The interactive modules are designed to help users transform raw information into applicable knowledge

HEMOSTASIS IN SURGERY MODULE 1: Introduction of hemostatic Mechanism and Methods

LEARNING OBJECTIVES

Understanding hemostasis in Surgical Patients

Define hemostasis and hemostatic methods

Identify the mechanisms and role of hemostasis

Compare and contrast hemostasis mechanisms and hemostatic methods

Definition: Hemostasis is the process of preventing bleeding and ensuring intravascular fluidity of blood. Hemostasis refers to the body’s physiological or natural processes that prevent and control bleeding while maintaining blood fluidity.

Hemostasis is a dynamic and finely balanced process encompassing two opposing yet complementary mechanisms:

1. Clot formation (coagulation cascade): This complex series of enzymatic reactions triggered by injury leads to the formation of fibrin, a protein mesh that traps blood cells and seals off injured vessels.
2. Clot breakdown (fibrinolytic system) and anthrombotic Mechanisms : This system constantly breaks down existing clots to prevent them from obstructing healthy blood flow. This process is crucial for maintaining vascular patency. The antithrombotic mechanisms prevent excess clot formation.

Role of hemostatic Mechanisms in Surgery

1. Minimize blood loss and maintain hemodynamic stability: Adequate blood volume is crucial for organ perfusion and preventing complications like hypotension, organ failure, and shock.
2. Optimize surgical field visibility: Effective Hemostasis improves visualization of the surgical site, allowing for precise dissection and minimizing tissue injury.
3. Promote wound healing and tissue repair: Controlled bleeding prevents hematoma formation, which can impair wound healing and increase infection risk.
4. Reduce transfusion requirements: Effective Hemostasis can significantly decrease the need for blood transfusions, minimizing potential transfusion-related complications and conserving scarce blood resources.

HEMOSTATIC MECHANISM AND HEMOSTATIC METHODS

Hemostasis is the body’s natural (endogenous) process of preventing and controlling bleeding and maintaining blood flow within the vascular system. The process of preventing excessive bleeding is a complex interplay between three main components:

1. Vascular constriction (vasoconstriction): Injured blood vessels constrict rapidly, minimizing blood loss.
2. Platelet plug formation (primary Hemostasis): Platelets adhere to the injured vessel wall and aggregate, forming a temporary plug to stop initial bleeding.
3. Coagulation cascade (secondary Hemostasis): A series of enzymatic reactions leads to fibrin clot formation, strengthening and stabilizing the platelet plug.

Hemostatic Methods:

These are external (exogenous) techniques or devices to assist or supplement the body’s natural hemostatic mechanisms, stopping or controlling bleeding and preserving intravascular fluidity.

Common hemostatic Methods

1. Positioning:

• Elevation: Raising the bleeding part above the heart level promotes venous return and reduces pressure in the bleeding area. Particularly good for venous bleeds and low pressure arterial bleeds

2. Mechanical methods:

• Pressure: Applying direct pressure with sterile gauze is often the first line of defense, this is particularly good for a short period while other mechanisms are instituted.
• Sutures, clips, and ligatures: These physically close and seal bleeding vessels, used for vessel that might not give consequences when tied off used for veins and arteries not effective for wide area of capillary bleed or oozing
• Staples: Used mainly for skin closure and minor bleeding from smaller vessels

3. Thermal/energy-based methods:

• Cautery: Heat from diathermy, laser, or ultrasound seals bleeding vessels.
• Electrocoagulation: Electric current disrupts tissue and seals blood vessels.

4. Hemostatic pastes, gels and powders:

• Hemostatic powders and adhesives: Promote clotting and seal small wounds and capillary bleeding. The hemostatic pastes are different natural materals and proteins that have the ability to absorb blood and swell creatign pressure  mechanical barrier and form platform the activates plaletet and clot aslo providng platform forplatelet and clotting factors to accumulate. Examples are Cellulose, Fibrin glue, Gelatin, Chitosan , Cyanoacrylate.

• Fibrin glue: This is a biological product made from human plasma. It is composed on fibrin and thrombin which are mixed together at the site of application. Some examples of fibrin glue products are Tisseel, Evicel, and Quixil.
• Cellulose: This is a natural polymer derived from plants. It can absorb blood and swell to create a mechanical barrier. It can also activate platelets and clotting factors. Some examples of cellulose products are Tabotamp, Surgicel, and Oxycel.
• Gelatin: This is a natural protein derived from animal collagen. It can absorb blood and swell to create a mechanical barrier. It can also activate platelets and clotting factors. Some examples of gelatin products are Gelitacel, Surgifoam, and Gelfoam.
• Chitosan: This is a natural polysaccharide derived from the shells of crustaceans. It has antimicrobial and biodegradable properties. It can form a gel-like matrix when in contact with blood and activate platelets and clotting factors. Some examples of chitosan products are AllaQuix, ChitoSAM, and HemCon.
• Cyanoacrylate: This is a synthetic adhesive that can bond to the skin or tissues and seal a wound. It can also stop bleeding by creating a mechanical barrier and compressing the blood vessels. Some examples of cyanoacrylate products are Dermabond, Histoacryl, and Indermil

5. Systemic methods and chemicals:

• Drugs: Antiplatelets, antifibrinolytics, and procoagulants can influence bleeding control throughout the body.
• Blood products: Transfusion of red blood cells, platelets, or plasma can replenish lost blood components and support clotting.

Key differences between mechanisms and methods:

• Endogenous vs. Exogenous: Hemostatic mechanisms are the body’s natural processes, while methods are external interventions.
• Specificity vs. Broadness: Mechanisms are specific to each stage of Hemostasis, while methods can target different stages or have broader effects.
• Stage-based and sequential vs. Diverse: The three mechanisms occur in a specific sequence, while methods can be used in various combinations and contexts

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