Page 576 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

560 PART 7 ■ Principles and Disorders of Hemostasis and Thrombosis

Selected Characteristics 1. Initiation o the intrinsic c otting casca e resu ting in

TABLE 28.8 of Primary and Secondary thro bin or ation
Fibrinolysis 2. Partici ation as a co actor or the conversion o reka -
ikrein to ka ikrein

Laboratory Primary Secondary 3. Initiation o brino ysis

Test Fibrinolysis Fibrinolysis Regar ess o the initiating event, DIC is characterize

by excess thro bin or ation, conversion o brinogen to
Platelet count Normal Decreased
brin, an ate et consu tion an e osition. Secon ary
Protamine sulfate Negative Positive brino ysis occurs as a resu t o brin e osition an can
test ecrease as a coagu ation actors, ea ing to a he or-

Fibrin split products Increased Increased rhagic iathesis.

Fibrinogen Decreased Decreased T ro bin is centra to the echanis o consu tive
coagu o athy. T e action o thro bin on the coagu ation

syste s inc u es the o owing:

is a so known as consu tive coagu o athy or e brination 1. Proteo ytic c eavage o brinogen to brin ono er,

syn ro e. riggering events that ay re is ose atients to re easing brino e ti es A an B ( brin ono er ay

DIC inc u e a terations in the en othe iu , irect activation or so ub e co exes with brinogen or or brin

o brinogen, re ease o thro bo astin- ike substances, an thro bi that entra ate ets uring thro bus or ation).

erythrocyte or ate et estruction. Extravascu ar trau a, 2. Activation o actor XIII, which stabi izes ibrin by

abru tio acentae, a niotic f ui e bo is , ow ate et cross- inking.

(HELLP) syn ro e/ec a sia, a vance a ignancy, eu- 3. Sti u ation o ate ets, resu ting in ecrease circu ating

ke ia, an retaine eta syn ro e are exa es o c ini- ate ets. T ese sti u ate ate ets un ergo sha e change,

ca situations in which tissue thro bo astin can activate a hesion, aggregation, an secretion. T e contents o the

coagu ation. In ections, ost co on y Gra -negative ense a ha-granu es are re ease , ea ing to an acquire

icroorganis s, can trigger DIC by ro ucing en otoxins storage oo e ciency. I , uring erha s a 3-hour s an,

that ex ose co agen. Stasis, shock, or tissue necrosis can ate et counts an brinogen eve s ecrease signi cant y

have the sa e e ect. Snakebites ay intro uce substances in a critica y i atient, DIC shou be the ri e sus ect

that initiate coagu ation by irect activation o brinogen to as the cause o this change.

or brin. 4. Activation o actors V an VIII; however, thro bin acti-

Re b oo ce or ate et injury ay contribute to the vation resu ts in unstab e en ro ucts that have ecrease

consu tive coagu o athy by re easing hos ho i i s that actor V an VIII activity.

acce erate coagu ation. Re ce injury ay be a resu t o 5. Activation o rotein C, which egra es actors V an

intravascu ar he o ysis cause by a aria, inco atib e VIII.

trans usion ro ucts, an other c inica states. P ate et T e e osition o brin thro bi in the vascu ature, ri-

estruction a so re eases coagu ation actors V, VIII, XII, ari y in the icrovascu ature, initiates brino ysis. T is

an XIII. secon ary brino ysis is res onsib e or the he orrhagic

Other causes o DIC can inc u e iver isease, y ho - co ication o DIC.

ro i erative isor ers, an rena isease. In a ition, DIC can When the brino ytic syste is activate , as inogen is

a so be triggere by trau a inc u ing shock, hy other ia, converte to as in. A ha-2 anti as in is the brino ytic

an extensive tissue a age, such as in yocar ia in arc- inhibitor unique y esigne to co e with as in. T e ore

tion an ec a sia. It has been associate with u ti e as in generate , the ore a ha-2 anti as in the atient

surgica , obstetrica , an e ica isor ers. Co a an con- consu es. T is ro uces a vicious cyc e in which increase

vu sions can resu t.
activation ea s to ecrease inhibitors; this, in turn, a ows
ore increase activation to continue. T is is known as a

Pathophysiology ositive ee back oo an ea s to a situation inco atib e

T e overa DIC rocess invo ves coagu ation actors, ate- with i e.

ets, vascu ar en othe ia ce s, brino ysis, an as a Da age tissue, es ecia y rena ce s, re eases as ino-
inhibitors. T is ajor break own o the he ostatic ech- gen activators that convert as inogen to as in. P as in

anis occurs when the rocoagu ant actors outweigh the is a roteo ytic enzy e that estroys brin, brinogen, an
anticoagu ant echanis s. c otting actors V an VIII. Circu ating as in ay ea to

Initiation o DIC can be cause by a nu ber o actors. I syste ic brino ysis, causing increase he orrhagic events.
vascu ar en othe ia a age resu ts in the ex osure o co - In the icrocircu ation, as in’s action is ri ari y

agen an base ent e brane, co agen can activate actor irecte against brin. In the circu ation, the break own o
XII. Factor XII has u ti e ro es in the irect or in irect brin resu ts in FSPs, abe e X, Y, D, an E, which inhibit

activation o coagu ation inc u ing thro bin an nor a ate et unction.