Coagulation and Transfusion

Chapter 78 Coagulation and Transfusion



Rohit A. Patel, MD, Kevin M. Bradley, MD




Cases Considered



1. 22-year-old male for preoperative assessment of bleeding risk

2. 55-year-old female with ongoing bleeding from superficial abrasions after a fall

3. 76-year-old female with a GI bleed and atrial fibrillation

4. 47-year-old male with epistaxis and easy bruising

5. 57-year-old male with bleeding in the setting of severe pneumonia



Speaking Intelligently


Identifying a source of bleeding can be challenging. I try to exclude a surgically correctable cause and always consider the hemodynamic consequences of the bleeding process. The etiology of most disorders of coagulation can be identified by obtaining a pertinent hx, including family hx, review of admission medications, a complete physical examination, and appropriate laboratory investigations.



Clinical Thinking


Achievement of the following specific objectives will help guide your clinical thinking process for coagulation and transfusion issues in the ICU.


1. Describe the normal hemostatic processes.

2. Identify the common tests used in evaluating coagulation.

3. Develop an approach to commonly encountered coagulopathies.

4. Recognize etiologies of thrombocytopenia and describe their management.

5. Be alert to heparin-induced thrombocytopenic thrombosis (HITT).

6. List the blood products available for transfusion and be mindful of the potential complications of each.



Coagulation



Medical Knowledge


The normal hemostatic balance is a physiologic process whereby clotting is promoted at the site of an injured vessel, but prevented in an intact vessel. The normal hemostatic process can be arbitrarily divided into two stages, primary and secondary.



Primary Hemostasis



image Vasoconstriction.

image Activated platelet adhesion to the damaged vessel wall.

image Platelet aggregation—adhesion of activated platelets to each other.

image Platelet adhesion and platelet aggregation together form a platelet plug that seals the damaged vessel and stops hemorrhage.


Secondary Hemostasis



image The platelet plug is stabilized by the deposition of fibrin formed through the activation of the coagulation cascade (can occur via the intrinsic, extrinsic, or common coagulation pathways).


Components of the Hemostatic Process











Extrinsic System Intrinsic System
Damaged tissue releases factor III, which (with Ca++) activates factor VII, initiating the extrinsic mechanism. Factor XII from active platelets activates factor XI, initiating the intrinsic mechanism.

Both active factor VII and active factor XI promote cascade reactions, which activate factor X. The common pathway is the process initiated by activated factor X (Xa), leading to the production of fibrin. Xa activates prothrombin activator. Prothrombin activator converts prothrombin to thrombin, and thrombin converts fibrinogen to fibrin.


Fibrin initially forms a loose mesh, which ultimately forms a more dense mesh under the influence of factor XIII. Platelets and red blood cells become trapped by this mesh and the result is a blood clot.


The intrinsic pathway is tested by measuring the activated partial thromboplastin time (aPTT). The extrinsic pathway is tested by measuring the prothrombin time (PT).


image Inhibitors of coagulation: Limit clotting to the vicinity of tissue injury
image Antithrombin III

image Heparin cofactor II

image Alpha2-macroglobulin

image Protein C and protein S

image Fibrinolytic system: The function of the fibrinolytic system is to digest excess deposits of fibrin to prevent thrombosis of the vascular tree. Fibrin degradation products (FDP, also known as fibrin split products [FSP] or degradation dimers (D-dimers) can be measured as an index of fibrinolytic activity. See Sabiston 6, 24; Becker 8, 9.



Case 1


A 22-year-old male presents to your office for elective repair of an inguinal hernia.



Working Dx


Routine preoperative evaluation.




Medical Knowledge


In order to evaluate this patient’s risk for perioperative bleeding, ascertain pertinent features of the hx and physical examination. Historical features suggesting a bleeding potential include:


image Features of coagulopathy
image Bleeding into viscera, muscle or joints, gingival bleeding after brushing teeth

image Bleeding following surgery or trauma

image Hx that local pressure is ineffective in stopping minor bleeding

image Features of platelet disorders
image Purpura, petechiae, epistaxis, bleeding from the GI tract or superficial skin defects

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  4. Nutrition Support in the ICU

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Mar 20, 2017 | Posted by in GENERAL SURGERY | Comments Off on Coagulation and Transfusion

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