[A suspicious case of coagulation disorder caused by vitamin K deficiency associated with fasting and antibiotics].

Coagulation disorders due to some antibiotics containing N-methyl-thiotetrazole group and vitamin K (VK) deficiency by microbial substitution in the intestinal flora can occur. We report a case of coagulation disorder under fasting with conventional antibiotics which are not containing N-methyl-thiotetrazole. A 91-year-old man was hospitalized for diagnosis of acute exacerbation of chronic heart failure because of bronchitis. He received treatment of fasting, fluid replacement, antibiotics, and a diuretic. On the 3rd day, left frontal lobe bleeding occurred. We performed conservative treatment with central venous nutrition not containing VK. Administration of antibiotics was completed after 14 days. On the 28th day, catheter-related bloodstream infection developed. Vancomycin and cefazolin were administered. The prothrombin time-international standard ratio (PT-INR) on the 1st day of administration was 1.2; however, it gradually increased to 7.4 on the 7th day of administration. Menatetrenone and fresh frozen plasma were administered as symptomatic treatment. Vancomycin was discontinued because a blood culture was positive for methicillin- susceptible coagulase negative Staphylococcus (CNS). After the 8th day of administration, the PT-INR improved to 1.1, but it increased to 1.9 on the 14th day. VK deficiency due to the antimicrobial drug was predicted. Therefore, VK and fresh frozen plasma were re-administered to improve the PT-INR. The PT-INR returned to normal after administration of cefazolin was terminated. Antimicrobial administration in the long term under the fasting condition can suppress endogenous production of VK by changing intestinal bacteria. And it has been reported that cefazolin which containing Methyl-thiadiazole thiol inhibits VK metabolic cycle and causes coagulation disorder. These reasons seems to a coagulation disorder. Therefore, physicians should monitor the coagulation system in this situation.