Page 515 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

CHAPTER 25 ■ Principles of Hemostasis and Thrombosis: Vasculature and Platelets 499

ADP ADP PGI
2
A3P5PS Clopidogrel

MRS2179 Ticlopidine
Cangrelor

P2 Y P2 Y IP IP IP
P2
P2Y
P2Y
Y
P2
Y
1 1 1 12
2
2
122
12
2
GTP
G GTPP g g G GTP GTP g
TP
GTP
G G
GG a b b a a b
q q
G
G G GG
PLCb
PL
PLCb i2 i2 s s
L
b
b
C
C
PI3K
PI3K
IP 3 DAG PIP 2
GTP
Rap1
Ca 2+ Ca 2+ ON AC
Ca 2+ PKC Akt

PLA ATP cAMP
2

PC Arachidonic PH Pleckstrin PH

Acid

FIGURE 25.9 Pl telet ctiv tion by ADP. wo receptors th t c n be ctiv te by ADP h ve been i entif e in pl telets. P2Y1 n P2Y12,

which re couple to i erent G proteins n there ore e i te i erent responses. Gq couples P2Y1 receptors to the ctiv tion o PLCβ.

T e Gi ily e ber, Gi2, couples P2Y12 to the inhibition o cAMP or tion (vi Gi2 α) n to e ector p thw ys th t inclu e PI3K

n R p1B (vi G βγ). (Fro M r er VJ, Air WC, Bennett JS, et l. Hemostasis and T rombosis, 6th e , Phil elphi , PA: Lippincott

Willi s & Wilkins, 2012.)

gents— or ex ple, eptif b ti e, nonpepti e nt gonist. Bleeding Tim e With and Without Aspirin

Abcixi b inhibits the f n l co on p thw y o pl telet T e blee ing ti e test is now n in requently per or e in

ggreg tion where f brinogen bin s to GP IIb/III receptor. vivo e sure ent o pl telet hesion n ggreg tion on

Neutr lizing ntibo ies to bcixi b c n or , there ore, loc lly injure v scul r suben otheliu . T is test provi es

the rug c n only be use once. GP IIb/III nt gonists c n n esti te o the integrity o the pl telet plug n thereby

c use severe blee ing, n it c n t ke over 12 hours or pl te-

let unction to be restore er stopping n in usion.

Other Agents BOX 25.2

Another ntipl telet rug is tic grelor. It is license or use with

spirin in preventing therothro botic events. T e newer P2Y12

nt gonists pr sugrel n tic grelor h ve ore pre ict ble ph r- Laboratory Assessment of Platelet Function

cokinetics n ph r co yn ics th n clopi ogrel.
Peripher l bloo s e r

Pl telet count
Laboratory Assessment of Platelets
Petechio eter

A pl telet count is un ent l co ponent in the ev lu - Pl telet ggreg tion

tion o p tient. Ex in tion o the peripher l bloo s e r A enosine iphosph te (ADP)

or pl telet nu ber n orphology is critic l bec use ny Epinephrine

clinic l clues y be obt ine ro n ev lu tion o pl te- Coll gen

let qu ntity n orphology. A nu l pl telet count n Ristocetin

peripher l s e r ev lu tion is b sic ssess ent. Except or Ar chi on te

extre ely low pl telet counts, tot l pl telet counts re per- T ro bin

or e on uto te equip ent. Pl telet lu i ggreg tion (rele se)

Pl telet ntibo ies (IgM n IgG)
Qualitative Assessm ent of Platelets Pl telet e br ne glycoproteins ( ow cyto etry)

I pl telet count is nor l but p tient h s suggestive Pl telet ctor IV

blee ing history, n ssess ent o pl telet unction shoul be (Bet )-thro boglobulin

con ucte . Metho s o ev lu tion (Box 25.2) inclu e ggre- T ro box nes

g ting gents, n lu i ggreg tion.