Page 565 - TNFlipTest

Toronto Notes 2019 Hemostasis Folate Deficiency
• uncommonindevelopedcountriesduetoextensivedietarysupplementation(enrichedinflour) • folatestoresaredepletedin3-6mo
• folatecommonlyfoundingreen,leafyvegetablesandfortifiedcereals
Hematology H25
Etiology
Table 17. Etiology of Folate Deficiency
Diet/Deficiency
Alcoholism Substance abuse Elderly/infants Poor intake
Clinical Features
Malabsorption
Celiac sprue
IBD
Infiltrative bowel disease Short bowel syndrome
Drugs
Anti-folates (methotrexate) Anticonvulsants (phenytoin) Alcohol
Oral contraceptive
Increased Demand
Pregnancy
Hemolysis
Prematurity
Exfoliative dermatitis/psoriasis Hemodialysis
• anemia,mildjaundice,glossitis,diarrhea,confusion,pallor
• unlike B12 deficiency, folate deficiency has no neurologic manifestations
• considersocialhistory,alcohol/drugabuse,verypoordiet(e.g.elderly,depressed)
Investigations
• similar to B12 deficiency (CBC, reticulocytes, blood film, RBC folate, and serum B12) • if decreased RBC folate, rule out B12 deficiency as cause
Management
• folicacid1-5mgPOODx1-4mo;then1mgPOODmaintenanceifcauseisnotreversible
Hemostasis
Stages of Hemostasis
1 . Primary Hemostasis
• cellulardefense–involvestheplateletandvWFpredominantly
• goalisrapidcessationofbleeding;maineffectisonmucocutaneousbleeding
• vesselinjuryresultsincollagen/subendothelialmatrixexposureandreleaseofvasoconstrictors
• bloodflowisimpededandplateletscomeintocontactwithdamagedvesselwall(Figure12a,H26)
■ adhesion: platelets adhere to subendothelium via von Willebrand factor (vWF)
■ activation: platelets are activated resulting in change of shape and release of adenosine diphosphate
(ADP) and thromboxane A2
■ aggregation: these factors further recruit and aggregate more platelets resulting in formation of
localized hemostatic plug
2 . Secondary Hemostasis
• plateletplugisreinforcedbyproductionoffibrinclot(Figure12b,H26)
• extrinsic(initiation)pathway:initiationofcoagulationinvivo
• intrinsic(amplification)pathway:amplificationoncecoagulationhasstartedviapositivefeedback
• bothintrinsicandextrinsicpathwaysconvergeontothecommonpathwaywhichresultsinthrombin
generation and fibrin formation
3 . Fibrin Stabilization
• conversionfromsolubletoinsolubleandstableclot
4 . Fibrinolysis
• oncehealinginitiated,clotdissolutionviaactionofthefibrinolyticsystem
Never give folate alone to an individual with megaloblastic anemia because it will mask B12 deficiency and neurological degeneration will continue
Normal hemostasis occurs as a result of the balance between procoagulant and anticoagulant factors
Phases of Hemostasis
• Primary hemostasis
Vascular response and platelet plug formation via vWF
• Secondary hemostasis Fibrin clot formation
• Fibrin stabilization
Fibrinolysis