Background: Prolongation of prothrombin time (PT) without clinical impairment of haemostasis was previously shown for some synthetic derivatives of vancomycin and was reagent or method specific.1 We report for the first time two cases with prolonged PT during vancomycin therapy, resulting in therapeutic problem in the ICU, which we assume to be of similar mechanism as mentioned above.

Case report: Case 1. Patient M.M. 75. yrs was given vancomycin therapy due to the parapharyngeal abscess complicated by sepsis and bilateral pneumonia. He was mechanically ventilated for 3 days. Coagulation tests performed after 5 days of vancomycin therapy have shown extremely prolonged PT (0.14, 3.97 INR) with normal fibrinogen and aPTT. PT was measured using Innovin reagent (Siemens). ROTEM control was normal in INTEM and FIBTEM, with prolonged only clotting time (CT) in EXTEM. Central venous catheter was placed uneventfully. After 8 days vancomycin was stopped. Before patient was discharged his PT was 0.57 (1.35 INR).

Case 2. Patient T.V., 33 yrs was submitted in the ICU after surgical treatment of malignant brain tumour. Preoperative coagulation tests were normal. He was given vancomycin therapy for 10 days. Percutaneous tracheostomy was considered, but coagulation tests have shown prolongation of PT (0.45, 1.5 INR), high fibrinogen (7.5) and normal aPTT. ROTEM had confirmed hypercoagulability in EXTEM, INTEM and FIBTEM analyses. Tracheostomy was uneventfully performed. After vancomycin therapy was stopped, PT returned to normal.

Discussion: ROTEM may be useful additional tool for clarifying diagnostic problems related to the coagulation disorders in the ICU patients, and may help to identify falsely elevated values of PT.

Learning points: PT testing with different reagents and at different time points during and after vancomycin administration should be considered. Interference of PT measurement should be further investigated by in vitro testing on pooled normal human plasma.

References: 1Belley, A., Antimicrob Agents Chemother. 2017;61(2).

11 / Prolonged prothrombin time during the vancomycin therapy in the ICU – therapeutic problem resolved using rotational thromboelastometry (ROTEM)