Haemostasis Flashcards
What is Hemostasis?
the process that maintains the integrity of a closed, high-pressure circulatory system following vascular damage
What are the 5 steps to primary hemostasis?
- platelets adhere to exposed subendothelial collagen either directly or via collagen-bound Von Willebrand’s Factor
- Adherence triggers series of cytosolic rxns resulting in a shape change & activation of the platelet
- Activation involves the release of agonists from granules & via arachidonic acid metabolism
- Agonists recruit
- Activate more platelets & alter the avidity & affinity of fibrinogen-binding receptors leading to aggregation & formation of a platelet plug
Secondary Hemostasis is mediated by what factors?
Intrinsic factor VIII & XII
Extrinsic tissue factor
Tissue-Factor is the main mediator of a
secondary clot
Tertiary Hemostasis is also known as
Fibrinolysis
Hyperfibrinolytic syndrome is seen in … What occurs? What can be given to assist?
Sighthounds, greyhounds, etc
Bleeding 24-48 hrs after initial trauma
Fibrinolytics orally or IV
What occurs during tertiary hemostasis/fibrinolysis?
Activated concurrently w/ coagulation & restricts clot formation to area of vascular injury
Preserves vascular patency by dismantling clot as healing occurs
Stops fibrin clot from getting out of hand & blocking the vessel diameter/blood flow
What are the various types of hemorrhage?
Time -> primary, reactive, secondary
Source -> arterial, venous, capillary
Location -> external, internal
What are some consequences of intra-operative hemorrhage?
Obscures surgeon’s vision
cardiovascular/hemorrhagic shock
massive hemorrhage
death
What are some consequences of post-operative hemorrhage?
increased incidence of surgical site infection
increased dead space
impaired wound healing
Run through the sequence of hemorrhagic shock.
decreased blood volume -> decreased CO -> decreased bp (pale mm) -> decreased oxygen delivery to tissues (shock) (increase HR to pump more) -> tissue hypoxia -> cell death & release of inflammatory mediators -> systemic vasoconstriction to preserve blood flow to the brain -> end organ damage -> death
Pre-operative patient assessment includes…
complete Hx & physical exam
PCV/TP
CBC, biochem, U/a
Specific assessment of hemostasis depending on signalment, Hx, previous findings, Sx risk
Primary hemostatic testing includes
Checking for bleeding from mucosal sites, bruises & cavity bleeds (uncommon)
Platelet number
Platelet fxn
Von willebrand factor
What might bleeding from mucosal sites look like?
Petechia
Ecchymoses
Epistaxis
Hyphemia
Hematuria
hematochezia
melaena
retinal hemorrhage
What is normal for testing the blood mucosal bleeding time?
Normal = 2-5 mins for clotting after nicking the mucosal surface
Von Willebrand Factor is involved in … & is assessed by
platelet plug formation
Blood assay
When is secondary hemostatic testing warranted?
severe bleeding from any site
bruising
bleeding into body cavities
What tests can be performed to test clotting times & coagulation factors?
PT/PTT
APTT
PIVKA
Activated clotting time
What percent of sighthounds, greyhounds, whippets, lurchers have fibrinolysis?
about 20%
fibrinolysis can lead to severe systemic illness such as…
DIC
What bloods should you check when concerned about fibrinolysis?
D-dimer
Increased FDPs
Decreased fibrinogen concentration
What are Halstead’s Principles
Aseptic Technique
Meticulous Hemostasis
Gentle Tissue Handling
Tension-Free Closure
Closure of Dead Space
Careful Approximation of Tissues
Minimize Foreign Material
What are the main ways to prevent hemostasis?
Gentle & accurate dissection
Anatomic Knowledge
Careful surgical approach
Vessel identification & ligation/cauterization prior to transection
Avoid ‘cut now, stop later’
What are the 4 main ways to reduce blood flow?
Tamponade/pressure
Topical vasoconstriction
Hypotension/hypothermia
Distant control of blood flow
What are the 3 main types of topical hemostatic agents?
Mechanical
Actives
Sealants
What is the main antifibrinolytic used?
Tranexamic Acid
