Laboratory Monitoring of Unfractionated Heparin - Pathology

!aboratory )onitoring of
.nfractionated Heparin
4avid 6illiams, ).4., Ph.4.
Roger ?. Riley, ).4., Ph.4.
Ann Tidwell, ).T. CA?DPE ?H

He#arin Moni+oring
"nfra'tionat+, -+.arin i/ t-+ 0o/t
1i,+23 4/+, anti'oag42ant for t-+ra.+4ti'
.4r.o/+/ in -o/.ita2i6+, .ati+nt/7 8+.arin i/ a
-+t+rog+no4/ 0i9t4r+ of n+gati:+23 '-arg+,;
-ig-23t i/ not a=/or=+, fro0 t-+ ga/troint+/<
tina2 tra't an, 04/t =+ gi:+n =3 in?+'tion7 @
/ing2+ intra:+no4/ ,o/+ -a/ a -a2fnfractionated heparin is gradually being
!"#$%&$%'%()*++,-".+/0"1/23%*+4*+0+/(2("1/%15%
2%41*("1/%15%()+%)+42*"/%6)2"/$
replaced by low molecular weight heparin,
which has a longer half-life and more predictable
bioavailability.
"nfra'tionat+, -+.arin i/ a 'o0.2+9
0i9t4r+ of g23'o/a0inog23'an/ in t-+ 0o2+'4<
2ar 1+ig-t rang+ of 3;BBB to 3B;BBB Ea 1-i'- i/
.4rifi+, fro0 =o:in+ 24ng or .or'in+ int+/ti<
na2 04'o/a7 F-+ a'ti:+ 'o0.on+nt/ of t-i/
0i9t4r+ 'ontain a ,i/a''-ari,+ r+.+at of +i<
t-+r an i,4roni' GHBIJ or g24'4roni' a'i, an,
a g24'o/a0in+ t-at i/ oft+n ,i/42fat+,7 Kn23
a=o4t a t-ir, of t-+ g23'oa0inog23'an/ in t-+
0i9t4r+ in-i=it 'oag42ation at '2ini'a223
a'-i+:a=2+ 'on'+ntration/7
@ f4n'tiona223 a'ti:+ -+.arin 0o2+'42+
'ontain/ a 0ini040 of LH /a''-ari,+/; in<
'24,ing a /.+'ifi' .+nta/a''-ari,+ /+C4+n'+
t-at =in,/ antit-ro0=in7 Min,ing of anti<
t-ro0=in =3 t-+ .+nta/a''-ari,+ 'a4/+/ a
'onfor0ationa2 '-ang+ t-at a4g0+nt/ in-i=i<
tion of t-ro0=in an, fa'tor Na; an, to a 2+//+r
+9t+nt fa'tor/ >Na; N>a; an, N>>a7 @ 0ini040
2+ngt- of LH /a''-ari,+/ a22o1/ -+.arin to
/.an =+t1++n antit-ro0=in an, a =in,ing /it+
on t-+ in-i=it+, fa'tor7
F-+ a4g0+nt+, in-i=ition of t-ro0=in
i/ ,+.+n,+nt on t-+ a=i2it3 of -+.arin to =in,
=ot- 0o2+'42+/; 1-+r+a/ in-i=ition of fa'tor
Na 'an =+ a4g0+nt+, /o2+23 =3 t-+ 'onfor0a<
tiona2 '-ang+ a//o'iat+, 1it- =in,ing to anti<
t-ro0=in7 F-+ 2att+r o=/+r:ation for0/ t-+
=a/i/ for t-+ ,+:+2o.0+nt of 2o1 0o2+'42ar
1+ig-t -+.arin/7
8+.arin i/ not a=/or=+, /ignifi'ant23
t-ro4g- t-+ ga/troint+/tina2 tra't an, 04/t =+
a,0ini/t+r+, +it-+r =3 intra:+no4/ inf4/ion
or /4='4tan+o4/ in?+'tion7 F-+ =ioa:ai2a=i2it3
an, '2+aran'+ of -+.arin ,+.+n,/ on a n40<
=+r of fa'tor/ t-at 0aO+ t-+ra.+4ti' ,o/ing
'o0.2i'at+,7
8+.arin =in,/ to a n40=+r of .2a/0a
.rot+in/ an, '+22/ t-at 'o0.2i'at+ t-+ '2+ar<
an'+ an, anti

Heparin Monitoring
!ig$ &$ 'eparin bo/n0 to thro3bin an0 anti4
thro3bin. The complex between thrombin and
antithrombin is shown as a surface model with
thrombin colored green and antithrombin colored
blue. A heparin mimetic is shown in
spheres with the atoms colored by type.
heparin from the circulation (at a dose of 24
5/7g, the half life is :30 minutes), but as these
mechanisms become saturated the half-life
extends (at a dose of A00 5/7g, the half life is
:140 minutes). At the higher dosages, clearance
is predominantly through a slower renal
process. Therefore, a therapeutic dosage is
determined by monitoring the anti-coagulant
effect by measuring either the activated partial
thromboplastin time (aPTT) or an antifactor
Ja assay (See separate documents).
Traditionally, the aPTT has been used to
monitor the therapeutic effect of heparin.
This test remains the most readily available
and practical method to follow anticoagulation
by heparin. Lowever the relationship
between the aPTT and the concentration
of heparin varies between labs reflective of
differences in reagents, methodologies, sample
siMe, and other factors. The current recommendations
are for each lab to standardiMe
the aPTT therapeutic range to an anti-factor
Ja assay of 0.3 to 0.N 5/mO or a direct heparin
measurement by protamine titration of 0.2 to
0.A 5/mO. The current standardiMed recommended
therapeutic ranges of aPTT are reported
with each test result and are regularly
updated for each new reagent lot, or other
changes in laboratory reagents or instrumentation.
The PQrill-RdwardsS protocol is the most
widely used techniTue to measure the
heparin-responsiveness of aPTT assay in a
clinical laboratory. In the Qrill-Rdwards protocol,
40-100 plasma samples from different
individuals receiving unfractionated heparin
are obtained. The heparin concentration of
each sample is determined by the chromogenic
anti-Factor Ja techniTue, and the
corresponding aPTT of each sample is measured
with the laboratories reagents and in-
!ig$ 5$ 6 typi8a9 heparin re:pon:e 8/r;e$ The
solid line represents the regression line of
aPTT values platted against heparin levels determined
in fresh plasma specimens from at
least 60 patients on heparin therapy by the
anti-factor Ja assay. In this case, the therapeutic
aPTT range corresponding to heparin levels
of 0.3 to 0.N 5/mO is approximately N4-124 seconds.
!e#arin Monitorin, - T/era#e0ti1 Ran,e3 4

Heparin Monitoring
!tr$%&ntation+ - .&/arin r&!/on!& 0$r1& i!
0on!tr$0t&2 34 /5otting t.& a788 1a5$&!
again!t t.& 0orr&!/on2ing .&/arin 0on0&ntra9
tion! :;ig+ &gr&!!ion ana54!i! i! $!&2 to
2&t&r%in& t.& rang& of a788 1a5$&! 0orr&9
!/on2ing to @;A 5&1&5! of B+C9B+D E@F%G
:H.&/arin t.&ra/&$ti0 rang&I=+ 8.&or&ti0a554J
.&/arin 2o!ing to %aintain a788 1a5$&!
Kit.in t.& t.&ra/&$ti0 rang& Ki55 /r&1&nt
o1&r9 or $n2&r2o!ing+
- H3a!&5in&I a788 !.o$52 3& o3tain&2
/rior to t.& a2%ini!tration of .&/arin+ >&g$9
5ar %onitoring !.o$52 3&gin Kit. t.& a2%ini9
!tration of .&/arin an2 0ontin$& r&g$5ar54
t.&r&aft&r+ L$& to t.& 0o%/5i0at&2 /.ar%a0o9
24na%i0! of .&/arinJ an2 t.& /ot&ntia5 for
0.ang&! in 05&aran0&J t.& a788 !.o$52 3&
%onitor&2 2ai54J &1&n aft&r a t.&ra/&$ti0 2o!&
i! fo$n2+ Monitoring 3&0o%&! a %or& 2iffi0$5t
/ro35&% in /ati&nt! Kit. an a3nor%a5 a788
at 3a!&5in&J t.o!& K.o r&N$ir& .ig.&r t.an a19
&rag& 2o!&! of .&/arinJ an2 t.o!& K.o ar& $n9
2&rgoing tran!ition to ora5 anti0oag$5ation+
7ro5ongation of t.& 3a!&5in& a788 i!
/r&!&nt in r&0&i1ing 0on0o%itant ora5 anti0o9
ag$5ation an2 in t.o!& Kit. 5$/$! anti0oag$9
5ant!J 2&fi0i&n0i&! of t.& 0o%%on an2 intrin9
!i0 0oag$5ation /at.Ka4!J or !/&0ifi0 0oag$5a9
tion in.i3itor!+ 8.& 5a3orator4 targ&t a788
0annot 3& $!&2 for %onitoring in t.&!& /a9
ti&nt!+ -5t&rnati1&! in05$2& t.& $!& of 5oK %o9
5&0$5ar K&ig.t .&/arinJ or %onitoring 34
%&a!$r&%&nt of .&/arin /5a!%a 5&1&5! $!ing
t.& antifa0tor9Oa a!!a4+
7ati&nt! K.o r&N$ir& .ig.&r t.an a1&r9
ag& 2o!&! of .&/arin :$!$a554 PCQJBBB @F

!eparin )onitoring
!"trog'n "tat'"+ ora, -ontra-'.ti0'"1
.r'gnan-2
3a-tor 45551 in-r'a"'6 ,'0'," 789:;'.arin t?'ra.21 .r'0io@"
>2.'r'o"ino.?i,i- "2n6roA'
5nf'-ti0' 'n6o-ar6iti"
5ntraaorti- Ca,oon -o@nt'r.@,"ation
M'6i-ation"+ E.rotinin1 nitrog,2-'rin'1
.ro.?2,'n' g,2-o,
M'6i-ation"1 .r'0io@" tr'atA'nt+ >'.aF
rin1 "tr'.toGina"'
H'onata, r'".irator2 6i"tr'"" "2n6roA'
I,a"Aa.?'r'"i"
I,at','t ,'0',"1 in-r'a"'6
I,at','tFri-? .,a"Aa ?ar0'"ting
Io"t"@rgi-a, "tat'"
J?o-G1 C@rn"1 f'0'r1 t?roACo.?,'Citi"
Jtr'.toGina"'1 .r'0io@" tr'atA'nt
K?roACo"i"1 ongoing -,otting an6 @ti,iF
Lation of ?'.arin
>'.arin Aonitoring C2 A'a"@r'A'nt of
?'.arin .,a"Aa ,'0'," @"ing t?' antifa-torFMa
a""a2 i" r'-oAA'n6'6 in an2 .ati'nt Nit? a
GnoNn .r''Oi"ting -on6ition t?at Aa2 a,t'r
t?' ?'.arin -on-'ntrationFaIKK r',ation"?i.
or .ro6@-' ?'.arin r'"i"tan-'P Kr'atA'nt o.F
tion" for .ati'nt" r'"i"tant to ?'.arin in-,@6'
in-r'a"ing t?' 6o"' of ?'.arin1 @"ing QMW>1
a 6ir'-t t?roACin in?iCitor1 fon6a.arin@O1
fr'"? froL'n .,a"Aa 733I=1 an6Sor EK -on-'nF
trat'P
E" on' No@,6 'O.'-t1 antiF-oag@,ation
Nit? ?'.arin ,'a6" to a ri"G of C,''6ingP K?'
ri"G i" gr'at'"t for t?o"' .ati'nt" r'-'i0ing a
?ig?'r 6o"' an6 i" in-r'a"'6 in .ati'nt" Nit?
a ?i"tor2 of ?'a02 a,-o?o, -on"@A.tion1 N?o
ar' taGing a".irin1 an6 t?o"' Nit? r'na, in"@fF
fi-i'n-2P J'0'r' ?'Aorr?ag' i" r',ati0',2 inF
fr'T@'nt1 t?o@g?1 Nit? an in-i6'n-' C'tN''n U
to :5K=P E Ai,6 forA of >5K1 t2.' 51
o--@r" in Aan2 .ati'nt" on ?'.arin an6 ,'a6"
to a Ai,6 6'-r'a"' in .,at','t -o@nt" aft'r a6F
Aini"tration of ?'.arin C@t "ta2" aCo0'
9;;1;;;S!Q an6 ,'"" t?an a :;< 6'-r'a"' in
Ca"',in' -o@nt"P K?i" t?roACo-2to.'nia i"
g'n'ra,,2 "',fF,iAit'61 not iAA@n' A'6iat'61
an6 6o'" not ,'a6 to a "ignifi-ant ri"G of
C,''6ing or t?roACo"i"P K2.' 55 >5K on t?'
ot?'r ?an6 ,'a6" to a 6raAati- 6ro. in .,at'F
,'t -o@nt" 78:;< 6'-r'a"' or a 6'-r'a"' C',oN
9;;1;;;S!Q= t?at @"@a,,2 6'0',o." C'tN''n U
to 9: 6a2" aft'r initiating t?'ra.2 C@t Aa2
taG' a Aont? or Aor' to 6'0',o. '0'n aft'r
?'.arin ?a" C''n 6i"-ontin@'6 or Aa2 ari"'
Nit?in a 6a2 in a .ati'nt t?at ?a" C''n 'OF
.o"'6 to ?'.arin .r'0io@",2P K?' 6ro. r'f,'-t"
a .,at','t 6'"tr@-ti0' .ro-'"" 6ri0'n C2 t?'
.r'"'n-' of antiCo6i'" again"t ?'.arin Co@n6
to t?' .,at','t "@rfa-' .rot'in I3VP K?'"' antiF
?'.arinSI3V antiCo6i'" -an C' fo@n6 in Aan2
.ati'nt" on ?'.arin1 C@t on,2 a "@C"'t of .aF
ti'nt" Ni,, 6'0',o. >5KP K?'r'for'1 t?' 6iagnoF
"i" of >5K "?o@,6 C' Aa6' if t?'r' i" a 6ro. in
.,at','t" t'A.ora,,2 r',at'6 to t?' initiation of
?'.arin an6 -onfirA'6 C2 t?' .r'"'n-' of
antiF?'.arinSI3V antiCo6i'"P E "'rotonin r'F
,'a"' a""a2 i" Aor' ".'-ifi- for >5K C@t 6'F
.'n6" on t?' @"' of ra6ioi"oto.' ,aC','6 "'roF
tonin an6 i" not a0ai,aC,' in Ao"t ,aCoratoF
ri'"P Wn-' t2.' 55 >5K ?a" C''n r'-ogniL'61 a,,
forA" of ?'.arin "?o@,6 C' 6i"-ontin@'6 inF
-,@6ing ,oN Ao,'-@,ar N'ig?t ?'.arin an6
?'.arin f,@"?'" of inF6N',,ing -at?'t'r"P 5f t?'
.ati'nt n''6" -ontin@'6 antiF-oag@,ation1 t?'
6ir'-t t?roACin in?iCitor" -an C' @"'6 a" a,F
t'rnati0' t?'ra.2P >'.arin A@"t C' "to..'6 in
or6'r to a0oi6 t?' "'rio@" 2't .ara6oOi-a, 6'F
0 ' , o . A ' n t o f t ? r o A C o " ' " P K ? '
antig'n+antiCo62 -oA.,'O'" on t?' "@rfa-' of
.,at','t" -an "tiA@,at' aggr'gation an6 t?'
forAation of art'ria, an6 0'no@" t?roACo"'"
t?at -an C' T@it' 6iffi-@,t to Aanag' an6 ,if'F
t?r'at'ningP
!eparin Si*e +ffect/ 0

Heparin Monitoring
!"#an& () *ro- ./0arin2 to fa5tor 6a in.i#i7
tor2 an8 #/9on8) :;r) BCDE7EF& EFFG)
!n8/r2on&