Massive Transfusion Protocol - Understanding the clotting cascade

The Clotting Cascade: A Vital Process in Bleeding Management

When faced with a bleeding patient, understanding the intricacies of the clotting cascade, and the pivotal role these processes have in managing bleeding provides the foundation for integration of therapeutic guidelines into clinical practice. This cascade involves a sequence of events that kick into action whenever there's damage to the blood vessels. Whether it's a surgical procedure or trauma, the body's response involves  processes designed to restore haemostasis and prevent excessive bleeding.

Activation of the Clotting Cascade

Image source: McLaughlin C. (2023)The physiology of coagulation and blood product transfusions JEMS  

The clotting cascade is an efficient process between various factors and components. When the endothelium, the lining of blood vessels, experiences damage, both the intrinsic and extrinsic pathways of the clotting cascade are activated. This marks the beginning of a sequence that ultimately leads to the formation of a stable clot.

Platelets and Factor X: Building Blocks of Clot Formation

As the cascade begins, platelets are released to the site of injury. These tiny blood cells play a pivotal role in forming the initial foundation of the clot. Factor X, a crucial player in the cascade, is activated and prompts the production of prothrombin. Prothrombin is then converted into thrombin, which acts as the catalyst for fibrinogen to transform into fibrin. This mesh of fibrin covers the platelet foundation, fortifying the clot and effectively controlling the bleeding.

However, it's important to note that this process isn't without consequences. The consumption of platelets and clotting factors is an inevitable part of this intricate sequence. As the clotting cascade progresses, these resources are utilised to ensure effective haemostasis.

Restoration of Haemostasis and Fibrinolysis

The clotting cascade's involvement doesn't end with the successful formation of a clot. The second part of the cascade is dedicated to restoring haemostasis and preventing an excessive or unnecessary buildup of clots. This is where fibrinolysis comes into play.

Activated plasminogen, a precursor, transforms into plasmin. The role of plasmin is to initiate the breakdown of the clot by dissolving the fibrin mesh, thereby ensuring that blood flow isn't obstructed once the damage is repaired and the clot is no longer needed.

The Finely Tuned Mechanism: Clot Formation and Dissolution

In essence, the clotting cascade is a finely tuned mechanism that combines both clot formation and dissolution to ensure efficient healing and prevent further complications. Understanding the balance between clot formation and fibrinolysis is crucial in managing bleeding disorders, postoperative care, and trauma cases.

Learn More - Clinical Application 

Activation of the massive transfusion protocol is based on several clinical criteria.  Most commonly the MTP or a Code Crimson is needed in trauma, obstetric and intra or postoperative emergencies. These protocols include specific strategies to manage the patient's clinical status, and maximise rational use of blood products. 

Learn more in our:

• Code Crimson Critical Bytes 
• Reversible Causes of Cardiac Arrest Lunch & Learn