Page 545 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

CHAPTER 27 ■ Principles of Hemostasis and Thrombosis: Blood Coagulation Factors and Natural Coagulant Systems 529

in the hu an bo y, an on y s a a ounts are nee e

or b oo coagu ation. A ca ciu e ciency wou not be

ex resse as a coagu ation ys unction, exce t in cases o

assive trans usion.

Factor V (Proaccelerin)

Factor V is an extre e y abi e g obu in rotein. It ete-

riorates ra i y, having a ha - i e o 16 hours. Factor V is

consu e in the c otting rocess an is essentia to the ater

stages o thro bo astin or ation.

Factor VII (Proconvertin)

Factor VII, a beta-g obu in, is not an essentia co onent

o the intrinsic thro bo astin-generating echanis . It is FIGURE 27.1 Pro es o thro bin an actor Xa generation.

not estroye or consu e in c otting an is oun in both (Fro Greer JP, et a . e s. Wintrobe’s Clinical Hematology, 13th e ,

as a an seru , even in seru e at roo te erature Phi a e hia, PA: Li incott Wi ia s & Wi kins, 2014.)

or u to 3 ays. T e action o actor VII is the activation

o tissue thro bo astin an the acce eration o the ro uc- T e ain ro e o activate actor IX in b oo coagu ation

tion o thro bin ro rothro bin. T is actor is re uce is to or the intrinsic tenase co ex, which e cient y acti-

by vita in K antagonists. vates actor X to activate actor X ( actor Xa). T e intrinsic

tenase co ex generates the secon burst o actor Xa that
Factor VIII (Antihem ophilic Factor) resu ts in the ro agation hase o the activation o ro-

T is actor, an acute- hase reactant, is consu e uring the thro bin to thro bin. T is is i ortant in he orrhagic

c otting rocess an is not oun in seru . Factor VIII is isease inherite he o hi ia A an B (Fig. 27.1). In he o-

extre e y abi e, with a 50% oss within 12 hours at 4°C in hi iac atients, thro bin generation can escribe the b ee -

vitro an a si i ar 50% oss in vivo within 8 to 12 hours a er ing ten ency an the risk o b ee ing better than tra itiona

trans usion. In a ition, actor VIII can be a se y ecrease tests.

in the resence o u us anticoagu ant (LA).

Factor VIII can be sub ivi e into various unctiona Factor X (Stuart Factor)

co onents. T e tota o ecu e, consisting o both a high– T is a ha-g obu in is a re ative y stab e actor that is not

o ecu ar weight raction an a ow– o ecu ar weight rac- consu e uring c otting. ogether with actor V, actor

tion, is escribe by the no enc ature VIII/vWF. Factor X in the resence o ca ciu ions or s the nal common

VIII/vWF consists o two ajor oieties. T e high– o ec- pathway through which the ro ucts o both the extrinsic

u ar weight oiety consists o the vWF, VIIIR:RCo, an an intrinsic thro bo astin-generating syste s erge to

VIIIR:Ag co onents. T e ow– o ecu ar weight oiety or the u ti ate thro bo astin that converts rothro -

consists o the VIII:C an VIIIC:Ag co onents. bin to thro bin. T e activity o actor X a ears to be re ate

Factor VIII:C has procoagulant activity as easure by to actor VII.

c otting assay techniques. Factor VIII/vWF u ti ers or

ionic bon s with actor VIII:C an trans ort VIII:C in the Factor XI (Plasm a Throm boplastin Antecedent)

circu ation. Factor XI, a beta-g obu in, can be oun in seru because it

Factor VIIIC:Ag is a rocoagu ant antigen as easure is on y artia y consu e uring the c otting rocess. T is

by i uno ogica techniques using antibo ies or actor actor is essentia to the intrinsic thro bo astin-generating

VIII:C. Factor VIIIR:Ag is a re ate actor VIII antigen that echanis .

has been i enti e using i uno ogica techniques e oy-

ing hetero ogous antibo ies to VIII/vWF. Factor XII (Hagem an Factor)

Factor VIIIR:RCo e onstrates ristocetin co actor activ- Factor XII is a stab e actor that is not consu e uring

ity, which is require or the aggregation o hu an ate ets the coagu ation rocess. A sor tion o actor XII an

in uce by the antibiotic ristocetin. kininogen (with boun reka ikrein an actor XI) to

Factor VIII/vWF is actor VIII-vWF. En othe ia ce s are negative y charge sur aces such as g ass or suben othe-

known to synthesize an secrete VIII/vWF u ti ers. iu (co agen) ex ose by b oo vesse injury initiates the

intrinsic coagu ation athway. Sur ace absor tion a ters
Factor IX (Plasm a Throm boplastin Com ponent) an artia y activates actor XII to actor XIIa by ex os-

Factor IX is a stab e rotein actor that is neither consu e ing an active enzy e ( rotease) site. Because o a ee back

uring c otting nor estroye by aging at 4°C or 2 weeks. It echanis , ka ikrein (activate F etcher actor) c eaves

is an essentia co onent o the intrinsic thro bo astin- artia y activate actor XIIa o ecu es a sorbe onto the

generating syste , where it inf uences the a ount rather suben othe iu to ro uce a ore kinetica y e ective

than the rate o thro bo astin or ation. or o XIIa.