Introduction to Hemostasis: Specimen Collection Flashcards
List the four major systems involved in maintaining hemostasis
- Vascular system (1st)
- Platelets (2nd)
- Plasma coagulation factors (3rd)
- Fibrinolytic system (4th)
Process by which the body (upon vessel injury) spontaneously stops bleeding and maintains blood in the fluid state w/in the vascular system
Hemostasis
Prevents blood loss from injuries by the formation of a thrombus, and reestablish blood flow during the healing process
Hemostasis (formal definition)
Process of clot formation
Coagulation
A blood clot w/in the vascular system; “platelet plug”
Thrombus
Refers to formation of blood clot or thrombus, but usually considered to be an abnormal finding
Thrombosis
Which system is responsible for primary hemostasis?
Platelets (2nd system)
Which system is responsible for secondary hemostasis?
Plasma coagulation factors (3rd system)
Define fibrinolysis
Breakdown of fibrin
Reduces blood flow to area of injury to minimize blood loss and also draws platelets close to the injured vessel wall
Vasoconstriction
Damaged endothelial cells secrete ____
von Willebrand factor (vWF)
What is activated by exposure of tissue thromboplastin/tissue factor (TF)?
Plasma coagulation system
Platelet adhesion,aggregation, and secretion is necessary to form ____
Platelet plug
What three consequences leads to the formation of fibrin?
Coagulation, inflammation, and tissue repair
Two stages of hemostasis
Primary and secondary hemostasis
Primary hemostasis
- Function
Platelets interact w/ injured vessels (and other platelets) to seal the wound and form a primary platelet plug
Primary hemostasis
- Short vs. long-term effect
Short-term → temporarily arrests bleeding
Primary hemostasis
- Associated systems
- Vascular intima
- Platelets
Primary hemostasis
- “Type” of tests used to differentiate
Platelet tests
- Platelet count
- Bleeding time
- Platelet fxn analyzer (PFA)
- Platelet aggregation
Secondary hemostasis
- Function
Thrombin generated via coagulation cascade, in turn, generate fibrin and froms secondary hemostatic plug
Secondary hemostasis
- Short vs. long-term effect
Long-term → strengthens the platelet plug
Secondary hemostasis
- Associated systems
Coagulation and fibrinolysis
Secondary hemostasis
- “Type” of tests used to differentiate
Coagulation tests
- PT (prothrombin time)
- APPT (activated partial thromblastin time)
Briefly describe an overview of hemostasis… beginning with the initial damage to the blood vessel. and ending with fibrinolysis
- Vessel injury
- Collagen exposed/vWF secreted…platelet adhesion
- ADP secreted from granules → platelet aggregation = 1° hemostasis
- Platelet plug reinforced by fibrin = 2° hemostasis
- Thrombus dissolved by fibrinolytic system
List 7 types of bleeds associated w/ a platelet or vascular defect (problem w/ primary hemostasis)
- Petechiae
- Purpura
- Epistaxis
- Hematemesis
- Menorrhagia
- Telangiectasia
- Mucosal bleeding
Pinpoint hemorrhages from arterioles or venules
Petechiae
Purple discoloration of skin cuased by many petechiae (small bruises)
Purpura
Nosebleeds
Epistaxis
Vomiting blood
Hematemesis
Abnormal, prolonged menstruation
Menorrhagia
Spider-like dilations of small blood vessel
Telangiectasia
List 3 types of bleeds associated w/ disorders of coagulation (problem w/ secondary hemostasis)
- Ecchymoses
- Hemarthrosis
- Delayed bleeding and oozing from wounds
Very severe bleed(s) into deep tissues/muscles (large bruises)
Ecchymoses
Joint bleed(s) characteristic of hemophilia
Hemarthrosis
Hemostasis is a combination of ____ and ____
Cellular; biochemical events
List 2 types of mechanisms in enzyme systems
Coagulation and fibrinolysis mechanisms
This includes vascular intima, platelets, erythrocytes, neutrophils, and monocytes
Cellular component of hemostasis
What occurs when hemostatic systems are out of balance?
Thrombosis or hemorrhage or both may occur
What is the preferred venipuncture method?
Evacuated Tube System (ETS)
List three venipuncture methods
- Evacuated tube system
- Butterfly/syringe
- Indwelling catheter
What is the correct specimen collection and handling requirement for evacuated tube system?
- MUST HAVE GOOD VEINS
- Assures correct blood: anticoagulant ratio
What is the correct specimen collection and handling requirements for butterfly/syringe?
- Used w/ small, fragile veins
- Pose additional needle stick risk when transferring blood into tube
This method is discouraged as heparin contaminates sample and prolongs clotting times if not properly flushed
Indwelling catheter
What is the correct specimen collection and handling requirement for Indwelling catheter?
- Flush line w/ saline
- Withdraw 5-10 mL blood and discard
- Collect specimen
Most common anticoagulant used
3.2% sodium citrate (PT/APPT)
Blood: anticoagulant ratio
9:1 need a full tube draw
Chelates (binds) free plasma calcium to prevent clotting
3.2% sodium citrate
Specimen collection and handling requirement for 3.2% sodium citrate tube
Must be plastic or siliconized glass and mix tube well by gentle inversion–DO NOT shake
What is order of blood draw?
- ALWAYS use a non-additive discard tube with a winged needle (butterfly) collection…“dead space”
- Always draw blue top after a non-additive tube
Why do we always draw a blue top after a non-additive tube?
To prevent contamination w/ the previous tube’s anticoagulant
Why don’t we use EDTA tube to collect blood for coag?
EDTA chelates calcium to prevent blood from clotting and it also binds reagent calcium in clot testing, so CANNOT USE!
How does increased hematocrit (>55%) affect routine coagulation (PT/APTT)?
- Increased hct in plasma vol relative to whole blood decreases plasma: anticoagulant ratio
- Excess anticoagulant may then bind to the CaCl (added during the testing procedure) prolonging the clotting time
List five unacceptable specimens
- Clotted
- Hemolyzed
- Lipemia
- Short draw sodium citrate tubes
- Increased hematocrit (before reporting results)
Explain how the clotted specimen will affect routine coagulation testing?
- Many factors, platelets, and RBCs are consumed in clotting.
- Be sure to gently invert tube after venipuncture (4-6X) to prevent clots
Would clotted specimens be falsely prolonged or falsely shortened clotting times?
Falsely prolonged clotting times
Would hemolyzed specimen have falsely prolonged or falsely shortened clotting times?
Falsely shortened clotting times
In hemolyzed specimens procoagulant substances released from cells and tissues to ______
Activate clotting pathways
Hemolyzed specimens can be in vitro or in vivo. What causes in vitro hemolysis?
- Prolonged tourniquet application
- Excessive needle manipulation
- Mixing blood too vigorously
- Forcing blood through a small bore needle
- Pulling too hard on a syringe
What results are given when specimens are lipemic?
Additional light scatter from lipid droplets gives erroneous results
Would lipemic specimen be falsely prolonged or falsely shortened?
Falsely prolonged clotting times
Why are short drawn specimens not acceptable?
- If tube is under filled, excess anticoagulant remains in the plasma layer after spinning
- This excess anticoagulant may then bind to the CaCl
- 9:1 ratio must be maintained
Would short drawn specimens be falsely prolonged or falsely shortened?
Falsely prolonged clotting times
What are transportation and storage requirements for specimens?
- Keep tube stoppered and in upright position to maintain proper pH
- Samples should not be chilled (chilled WB may activate platelets, Factors VII/VIIa, and contact system)
- Transport to the lab at RT
Never refrigerate blood/plasma for ____; and test w/in ____ hours
PT; 24 hours
May refrigerate blood/plasma for ____; but need to test w/in ____ hours plus must spin and/or remove plasma w/in ____ if patient is on heparin
APTT; 4 hours; 1 hour
Platelet rich plasma (PRP) is slow spun and used for _____
Platelet aggregation studies
Platelet poor plasma (PPP) is spun faster and used for ____
Used for all routine coagulation assays such as PT and APTT
Do PT and APTT measure platelets?
NO
Platelet free plasma (PFP) is spun faster, plasma is removed, and re-spun and is used for ____
Heparin or heparin-induced Ab
What does APTT stand for?
Activated partial thromboplastin time
What does PT stand for?
Prothrombin time