New insights on vitamin K.
ABSTRACT Vitamin K catalyzes the post-translational carboxylation of coagulation proteins C, S, and factors II, VII, XI, and X. Detection of the noncarboxylated forms allows an indirect and specific measure of the vitamin K deficiency found in early, classic, and late hemorrhagic disease of the newborn (HDN), malabsorption syndromes, and drug related (warfarin, anticonvulsants, and antibiotics) states. Idiopathic late HDN (CNS bleeding) occurs in exclusively breast-fed infants and is prevented by appropriate parenteral and oral vitamin K prophylaxis given at birth. All newborn infants and older infants with malabsorption syndromes should receive prophylactic vitamin K.
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ABSTRACT: Oral or parenteral administration of vitamin K is the accepted practice for prevention of early vitamin K deficiency bleeding (VKDB) in the newborn. However, vitamin K prophylaxis in the newborn continues to be a worldwide health concern, particularly in breastfed infants. This paper reviews the current status of the use of vitamin K for the prevention of early and late VKDB.Acta paediatrica (Oslo, Norway: 1992). Supplement 11/2005; 94(449):125-8.
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ABSTRACT: To determine the incidence of perioperative protein C deficiency in patients undergoing free flap reconstruction of cancer-related defects in the head and neck. Prospective case series. Ten patients underwent microvascular reconstruction after surgical therapy of carcinomas of the oral cavity or oropharynx. Coagulation studies were determined in all patients 72 hours after surgery. Academic tertiary care medical center Protein C deficiency was detected in 70% of patients. One free flap failure was attributed to protein C deficiency. Vitamin K-dependent clotting factors are frequently deficient during the postoperative period after major head and neck surgery, which may result in a state of hypercoagulability. Protein C deficiency should be considered as a possible cause of free flap thrombosis in patients who undergo microvascular head and neck reconstruction.The Laryngoscope 03/1999; 109(2 Pt 1):259-65. · 1.98 Impact Factor
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ABSTRACT: To compare the pharmacokinetics and efficacy of oral versus intravenous mixed micellar vitamin K prophylaxis in infants with cholestatic liver disease, a known risk factor for vitamin K deficiency bleeding. Prospective randomised controlled study. Paediatric Liver Unit. Forty four infants less than 6 months of age with conjugated hyperbilirubinaemia. Serum concentrations of vitamin K(1) and undercarboxylated prothrombin (PIVKA-II; a sensitive functional indicator of vitamin K status) before and for up to four days after a single dose of mixed micellar K(1) 1 mg intravenously or 2 mg orally. Comparison of K(1) levels 24 hours after oral K(1) with those from 14 healthy newborns given the same dose. At admission, 18 infants (41%) had elevated levels of serum PIVKA-II and eight (18%) had low K(1) concentrations, indicative of subclinical vitamin K deficiency. Median serum K(1) concentrations were similar in the oral and intravenous groups at baseline (0.92 v 1.15 ng/ml), rising to 139 ng/ml six hours after intravenous K(1) but to only 1.4 ng/ml after oral administration. In the latter group, the low median value (0.95 ng/ml) and wide range (< 0.15-111 ng/ml) of serum K(1) compared unfavourably with the much higher levels (median 77, range 11-263 ng/ml) observed in healthy infants given the same oral dose, and suggested impaired and erratic intestinal absorption in cholestatic infants. The severity of malabsorption was such that only 4/24 (17%) achieved an incremental rise in serum K(1) > 10 ng/ml. The intestinal absorption of mixed micellar K(1) is unreliable in infants with conjugated hyperbilirubinaemia. Given the strong association between cholestasis and late vitamin K deficiency bleeding, these data provide an explanation for the failure of some oral vitamin K(1) prophylaxis regimens in infants with latent cholestasis.Archives of Disease in Childhood - Fetal and Neonatal Edition 04/2003; 88(2):F113-8. · 3.45 Impact Factor