MONITORING OF HEMOSTASIS IN LIVER TRANSPLANTATION AND IN PATIENT ON ANTIPLATELET AGENTS

Abstract

Theanesthetistarefacingdaily variablemedical caseswhichaffectingthe hemostasisthisvital physiological process.So, understandingnormal physiology ofhemostasisandtwoofthe common pathologicalchange affectingit " patientonantiplatelet drugand during liver transplantation" and its monitoringisvery helpfulduringmanagementofsuch cases.

Hemostasis is the process that maintainsthe integrity ofaclosed,highpressurecirculatorysystem aftervasculardamage(Furie andFurie, 2008). Enables an organismto close off damaged vessels, keep the blood inafluid state,andremove bloodclotsafter restorationof vascular integrity(Versteeget al.,2013).

Hemostasiswasclassically descriptedby plasma basedmodel of coagulationinwhich,Primary haemostasisisinitiatedwithinsecondsofabreachin thevasculature,with plateletsforminga plugat thesite ofinjury. Secondaryhaemostasisinvolvesacomplex interaction between plasma coagulationfactors "coagulationcascade"depictedasintrinsic, extrinsic pathwaysandfinalcommonpathway,resultinginthe

formation anecessary quantities of fibrin strands to strengthenthe plateletplug. (Curry andPierce, 2007)

This in vitro model disregards theinteraction betweenprimaryandsecondary haemostasisanddoes notcorrelate wellwith the in vivo process.Itremainsa useful descriptivetoolfororganizingdiscussionof plasma-mediatedhemostasis.

In the last few years, the currently accepted model ofcoagulationhasbeenupdated;moreclosely reflecting in vivoactivity" thecell-based model"this process isdescribedinstepsInitiation,amplification, propagation, stabilization,andinhibitionoffurther coagulation.(Curry andPierce, 2007)

Propagation of haemostasis throughoutthe vasculature is prevented and controlled by many systemswithafivemajor anticoagulant inhibitory systemssuchas,tissue-factorpathway inhibitor,protein C andantithrombin(Curry andPierce, 2007).

Thecoronary artery diseaseandstrokerepresent thetoptwocausesofmortalityworldwide,asreported bytheWorldHealthOrganizationinareportupdatedin 2013.The keyroleinthese pathologicaleventsisplayed bythe platelets.

Antiplatelet agents are considered the first-line therapyinpreventingtheseevents,usedas monotherapy orincombination.Accordingly,patientsonthem are presentingmorefrequently foranaesthesia. theuseof suchantiplateletregimensraisesanumber ofquestions for preoperative preparation, surgery, anaesthesia,and postoperativecare.So,theperioperativeteam must designanoptimalstrategy tomanageantiplateletagents according to risk of developing a cardiovascular thrombotic eventandrisk ofsurgical bleeding.(Oprea andPopescu,2013)

Awidearray ofantiplateletagentsisavailable, each withdifferent pharmacologicalproperties. Perioperative management of antiplateletagents is complex. Severalfactorsneedto beconsideredbeforea decision about antiplatelet drugs, Such as the initial indicationfor therapy,Individual drugsand durationof DAPT in case of stents, The point-of-care testing devices may help in this strategies. (Benzon etal., 2011)

For anotherpintof view,theliver istheprimary site of synthesis of most of the clotting factorsand the proteinsofthefibrinolyticsystem, alsointhelive, Removal and clearance of activated clotting and

fibrinolyticfactors. (Cesarman-Maus and Hajjar,

2005)