PSYCH 1XX3 Lecture Notes - Lecture 11: Vitamin K Deficiency, Hemostasis, Antihemorrhagic
19 May 2018
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1.27 - DEVELOPMENTAL HAEMOSTASIS IN THE NEONATE
1. Differences in fetal coagulation factor and platelet quantity and quality account for coagulation
disorders seen in the newborn
• coagulation factors do not cross the placenta; synthesis starts in utero from about 10weeks and
levels increase as term progresses
o hence PT, APTT and TT all decrease as term progresses
• haeostasis is ‘ipaired i the ewor eause of:
o decreased synthesis & accelerated clearance of coagulation factors
o synthesis of proteins with decreased functional capacity
o fetal/newborn megakaryocytes are small and less mature
o platelet responses to certain stimuli may be impaired in the fetus/newborn
2. Factor 8 & fibrinogen reach adult values at term, otherwise newborns are largely vitamin K-
dependent factor deficient
Factor
% of adult value reached at term
F7
53%
F9
32%
F10
40%
Prothrombin
44%
F8
94%
Fibrinogen
=>100%
3. Acquired coagulation/platelet disorders
Acquired haemostatic disorders in the newborn:
• haemorrhagic disease of the newborn (HDN)
• DIC
• liver disease
• Neonatal thrombocytopenia
HDN is due to vitamin K deficiency
• poor placental transfer of vitamin K
• low fetal vitamin K stores
• low vit K content of breast milk
• absent bacterial vit K synthesis in neonatal gut
• immaturity of fetal liver
HDN usually presents within a week
• Haemorrhages in the brain, GIT, post circumcision and excessive bruising/purpura
• Diagnose with prolonged PT
• Manage with prophylactic and/or episodic Vitamin K or FFP if bleeding is severe
HDN classification
Time of presentation
causes
early
within 1 day
maternal drugs
classic
within 1 week
physiological [see above]
late
2-12weeks
liver disease, breast feeding
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Document Summary
=>100% liver disease immaturity of fetal liver: acquired coagulation/platelet disorders. Acquired haemostatic disorders in the newborn: haemorrhagic disease of the newborn (hdn, dic, neonatal thrombocytopenia. Hdn is due to vitamin k deficiency: poor placental transfer of vitamin k, absent bacterial vit k synthesis in neonatal gut. Time of presentation within 1 day within 1 week. 2-12weeks causes maternal drugs physiological [see above] liver disease, breast feeding. Neonatal thrombocytopenia is the commonest abnormality in newborn babies: reduced platelet production transient - maternal htn/ dm and fetal iu growth restriction rare bm failure, fanconi anaemia. Increased platelet clearance immune mediated - maternal itp, neonatal alloimmune thrombocytopenia: non-immune mediated dic, infections (cmv, rubella) Inherited haemostatic disorders in the newborn: haemophilia a/b, t3 vwd, rare coagulation factor deficiencies. Haemophilia is the commonest inherited coagulation disorder and is frequently diagnosed post circumcision: affected boys may present with excessive bleeding after circumcision, cephalohaemoatomas,
