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Rotational thromboelastometry (ROTEM) guided treatment of an Afghanistan viper envenomation at a NATO military hospital

Although frequently used in surgical settings [1], the utility of rotational thromboelastometry (ROTEMR ; TEM International, Munich, Germany) in the management of venom-induced consumptive coagulopathy (VICC) has been inadequately studied. We report a case of a 30-year-old male who presented to the Kandahar Airfield NATO Role 3 Multinational Medical Unit two hours after being bitten on his right foot by a self-identified saw scaled viper (Echis carinatus). There was no evidence of petechial or mucosal bleeding. Fresh blood was collected in sodium citrate and the prothrombin time (PT), international normalized ratio (INR) and activated partial thromboplastin time (aPTT) were measured with the Hemochron Jr SignatureR (ITC, Edison, NJ). Initial results, shown in Table 1, were consistent with VICC. In addition, ROTEM was used to guide treatment with Razi polyvalent antivenin (Razi Vaccine & Serum Research Institute, Iran). Initial assays showed no clot formation (Figure 1(A)). A comparison of EXTEM and FIBTEM assays showed afibrinogenemia for the first 24 h. He was administered 5-vials of Razi antivenin at 3-, 7-, and 9-h post-envenomation. Per military antivenin guidelines, laboratory tests were repeated one-hour after antivenin dose completion. Serial ROTEM analysis was performed concurrently (Figure 1(B–F)). The clotting time (CT), the time until clot 2mm in amplitude is detected, was improving by 6-h post-envenomation. The clot formation time (CFT), the time until detection of a clot 20mm in amplitude, was detectable 10-h post-envenomation. The alpha angle, which describes the clot kinetics, with a steeper angle representing more robust clot formation, showed improvement over 48h, as did the clot firmness, represented by the amplitude of the light grey or dark grey shaded areas. No blood products were administered and the patient was discharged in good condition and normal INR after 48 h. In our case, the ROTEM showed improvement in clotting mechanics prior to recovery of the PT/INR, as evidenced by the improvement of the clotting time and alpha-angle at 6and 8-h post-envenomation when the INR was >10 and 10, respectively. Stable clot formation – represented by the clot formation time – was detectable 10-h post-envenomation when the INR was still 4.8. Without evidence of hemorrhage and reassuring ROTEM results, no further doses of antivenin were administered. We were unable to measure venom concentrations, so it is unclear if the improvements detected on ROTEM were due to the natural recovery of clotting factors after the first dose of antivenin or if additional doses were necessary. Prior studies have demonstrated that for Echis spp. envenomation, multiple doses of antivenin reduces the time to normalization of coagulation tests [2,3], which is in contrast to the treatment of VICC by elapids [4]. Coupled with poison control’s recommendations, we, therefore, erred on the side of providing additional antivenin until improvement in the ROTEM or INR. Although costs will likely limit the adoption of thromboelastography in resource poor settings where most toxic envenomations occur [5], we found ROTEM useful in the treatment of our patient. We encourage further study into its utility for the management of VICC.