Vitamin K

Question 1

How can vitamin K be administered?

Answer 1

• 1mg IM vitamin K

- 2mg oral vitamin K - given at birth, at newborn screening (Day 3-5) and at four weeks

Question 2

Compare oral and IM administration.

Answer 2

• IM administration is a one-off dose; oral takes 3 doses spaced over 4 weeks
• Orally relies on parental willingness and ability to give the final oral dose at week 4
• Oral and IM are equally effective for Classical VKDB
• IM is significantly more effective at preventing late VKDB (with IM <0.3/100,000 births, with oral 2.5/100,000 births)

Question 3

Why do we use vitamin K?

Answer 3

• To prevent vitamin K deficient bleeding (VKDB)

Question 4

What are the types of vitamin K dependent bleeding? What is their prevalence, presentation and risk factors?

Answer 4

Early

• Day 1
• Mother has been taking medications that affect vitamin K metabolism (coumarins, rifampicin, anti epileptics: phenytoin, barbiturates, carbamazepine)
• Prevalence = isolated to mothers with above issues - if the mother does not take prophylaxis prior to birth prevalence 6-12%

Classical

• Day 2-7
• All neonates have relative vitamin K deficiency (minimal crosses placenta, and newborn liver does not yet have stores, it accumulates over first months of life)
• Thus low levels of circulating vitamin K dependent clotting factors (II, VII, IX, X)
• Afterwards vitamin K levels become dietary dependent
• Inadequate feeding, illness, cholestatic liver disease, and exclusive breast feeding increase the risk of VKDB
• Presentation: bleeding from umbilicus, GIT, skin punctures and rarely intracranial
• Prevalence: 0.25-1.5% untreated newborn

Late

• After day 7 to 6 months
• Most severe form, but rare
• Causes as for classical
• Presentation: 30-50% intracranial bleed, 30% mortality, bruising, bleeding from umbilicus/GIT/skin puncture sites etc. May have signs of cholestatic liver disease: jaundice, pale stools, dark urine.
• Prevalence: 5-20/100,000 untreated newborns

Question 5

Which women should be counselled to start taking vitamin K replacement 2 weeks prior to expected birth date?

What dose?

Answer 5

Women taking medications which affect vitamin K metabolism:

• rifampicin
• coumarins
• anti epileptics: phenytoin, barbiturates, carbamezapine

They should commence 20mg vitamin K orally OD from 2 weeks prior to birth.

Question 6

Why are newborn susceptible to VKDB?

Answer 6

• All neonates have relative vitamin K deficiency (minimal crosses placenta, and newborn liver does not yet have stores, it accumulates over first months of life)
• Thus low levels of circulating vitamin K dependent clotting factors (II, VII, IX, X)
• Afterward birth vitamin K levels become dietary dependent - therefore delayed feeding due to illness can exacerbate
• Breast milk also has very low levels of vitamin K, whereas formula is supplemented with vitamin K, thus exclusively breast-fed babies are at higher risk
• Cholestatic liver disease affects vitamin K absorption by the gut; reduced productionand flow of bile means reduced intraluminal biliary salt reducing the emulsification of fats and absorption of fat soluble vitamins (A,D,E,K)

Question 7

What is the evidence for vitamin K prophylaxis?

Answer 7

Oral or IM vitamin K virtually eliminates classical VKDB.

IM vitamin K reduces late VKDB from 5-20 to <0.3/ 100,000 births.
Oral vitamin K is significantly less effective (2.5/100,000 births).