PE12.5-6 | Vitamin K — Summary & Reflection

KEY TAKEAWAYS

Vitamin K (K1 = phylloquinone, K2 = menaquinones) is essential for the hepatic gamma-carboxylation of coagulation factors II, VII, IX, X, and proteins C and S. Without carboxylation, these factors are biologically inert (PIVKAs). Vitamin K deficiency prolongs both PT and aPTT while platelet count and bleeding time remain normal. RDA: 10–20 mcg/day for infants; dietary sources are green leafy vegetables and gut bacteria. Breast milk contains very little Vitamin K (1–3 mcg/L).

VKDB (Vitamin K Deficiency Bleeding) = early (<24h, maternal drugs), classic (day 2–7, breastfed + no prophylaxis), late (2 weeks–6 months, breastfed/malabsorption — ICH in 30–50%, 20% mortality). Treatment: IV Vitamin K 1 mg + FFP for active bleeding. Prophylaxis: 1 mg IM at birth (≥2.5 kg) or 0.5 mg IM (<2.5 kg) — prevents all three forms. The Vitamin K cycle is interrupted by warfarin (inhibits VKOR).

REFLECT

Consider the challenge of implementing universal Vitamin K prophylaxis in a country with high rates of home delivery and limited birth-attendant training. What barriers might prevent a newborn from receiving the injection, and what system-level changes could address these? Reflect on the mother's perspective: she is breastfeeding with the intention of providing her baby with optimal nutrition, yet breast milk is specifically deficient in Vitamin K. How would you explain this apparent paradox to her in a way that reassures her about breastfeeding while emphasising the importance of prophylaxis? Finally, consider how the Vitamin K cycle and warfarin pharmacology are direct applications of this basic nutritional biochemistry to clinical medicine.