The development of hypoprothrombinaemia following antibiotic therapy in malnourished patients with low serum vitamin K1 levels

Abstract

Summary. A group of nine well‐nourished patients, with normal serum vitamin K₁ levels (mean 546, range 310–1350 pg/ml), maintained normal prothrombin times (PTs) and factor VII clotting activities throughout a 7 d course of i.v. cefotetan disodium, an N‐methyl‐thiotetrazole (NMTT) containing cephalosporin antibiotic. However, 11 of 20 patients, with acute intra‐abdominal sepsis and initially normal PTs who underwent emergency surgery, developed prolonged PTs (INR 1.4–3.1) associated with reduction in factor VII activities (0.74–0.38 u/ml) after 3–7 d of antibiotic therapy. Nine of these 11 patients had clinical evidence of malnutrition and nine had subnormal serum vitamin K₁ levels (mean 119, range 43–354 pg/ml) on admission. Seven received cefotetan but four were treated with a non‐NMTT‐containing cephalosporin or antibiotics belonging to other groups. The nine patients who maintained normal PTs all had normal nutritional status and normal serum vitamin K₁ levels (mean 279, range 103–915 pg/ml) at presentation. The PT is a relatively insensitive indicator of vitamin K stores, and malnourished patients with low serum vitamin K₁ levels are at risk of developing hypoprothrombinaemia following intravenous antibiotic therapy.