🍼 At birth, babies have only a small store of vitamin K, which is quickly depleted in the first few days of life.
⚠️ This may lead to vitamin K deficiency bleeding (VKDB) – haemorrhage from umbilical stump, nose, mouth, or internally (including intracranial bleeds).
💉 Giving newborns vitamin K (IM or oral) effectively prevents VKDB.
ℹ️ About
- 🌿 Vitamin K1 (phytonadione): from plants, main dietary source.
- 🦠 Vitamin K2 (menaquinone): synthesised by gut bacteria.
- 💊 Both forms are fat-soluble and stored in the liver.
🧬 Aetiology & Physiology
- Vitamin K is a fat-soluble vitamin essential for clotting factor synthesis.
- Absorbed in the small intestine, stored in the liver.
- Cofactor in γ-carboxylation of glutamic acid residues on clotting factors II, VII, IX, and X, plus proteins C & S.
- 🔑 Without vitamin K → inactive clotting factors → impaired coagulation.
⚠️ Causes of Deficiency
- 🥗 Poor dietary intake (rare in adults except severe malnutrition)
- 🚫 Intestinal malabsorption (biliary obstruction, coeliac, cystic fibrosis)
- 🩸 Liver disease (impaired storage & reduced clotting factor synthesis)
- 👶 Newborns (physiological deficiency due to sterile gut, low placental transfer, low breast milk content)
🩺 Clinical Features
- Easy bruising, mucosal bleeding
- Melena or GI bleeding
- Retroperitoneal or intramuscular haemorrhage
- ⚠️ Intracranial haemorrhage → seizures, neurological deficit, death
🔎 Investigations
- 🧪 Prolonged PT (earliest change, factor VII affected first)
- 🧪 aPTT prolonged later in severe deficiency
- 🧪 Normal fibrinogen & platelets (distinguishes from DIC)
- Factor VIII activity unaffected (not vitamin K–dependent)
💊 Management
- 💊 Vitamin K supplementation: Oral or IV 1–5 mg; effect within 6 hours.
- 🚨 Emergency bleeding: Prothrombin complex concentrate (e.g. Beriplex/Octaplex) ± FFP if PCC not available.
- 🍼 Newborn prophylaxis: IM vitamin K at birth (gold standard) or oral regimen (requires compliance with multiple doses).
📌 Exam Pearl:
– PT prolonged first (factor VII has the shortest half-life).
– Always give prophylactic vitamin K to newborns – prevents catastrophic intracranial haemorrhage.
– Warfarin overdose mimics vitamin K deficiency (same pathway blocked).
📚 References
