Use of Thromboelastography in Assessment of Snake Bite Coagulopathy

Abstract

Background: Monitoring for envenomation coagulopathy following snake bites has traditionally involved using serial coagulation studies.

Purpose: Thromboelastography (TEG), with its real-time assessment, could offer an alternative to standard of care. This study aims to evaluate the use of TEG with traditional coagulation labs in the assessment of snake bite coagulopathy.

Research Design: A retrospective review of patients who presented to a level 1 trauma center between 2014 and 2020 with snake bite envenomation was conducted, comparing traditional coagulation studies to TEG plus coagulation studies.

Results: The 12 patients who had studies within the stipulations of our review were tracked and subsequently progressed well clinically with no adverse effects and ultimately discharged home with an average hospital stay of 2.2 days.

Conclusions: Our data suggests that patients can be observed clinically without needing repeat coagulation studies if initial TEG and TCS are within normal limits.

Envenomation from North American crotalid snakes, such as cottonmouths, rattlesnakes, and copperheads, can cause a wide variety of envenomation syndromes and often lead to coagulopathy. During the acute period following envenomation, following the appropriate recommendations for antivenom therapy is critical to reducing post-exposure coagulopathy and thrombocytopenia. Following recurring coagulation panels every 6-12 h is also recommended. ¹ These labs typically consist of international normalized ratio, activated partial thromboplastin time, platelet count, fibrinogen, and mixing studies, which require a lab and can take minutes to hours to obtain the results. Thromboelastography (TEG) uses real-time assessment of the coagulation processes at the patient’s bedside. Though TEG has many benefits, such as point-of-care testing and the ability to detect dynamic changes in coagulation, ² it has yet to be widely utilized in acute envenomation treatment. This study aims to compare the use of TEG with traditional coagulation labs in the assessment of snake bite coagulopathy.

A retrospective review of patients who presented to our tier 1 trauma center with snake bite envenomation between 2014 and 2020 was conducted. There were 60 total patients who presented during this time. The following data was obtained: age of the patient, type of snake, snake bite location, clinical severity, initial coagulation studies, subsequent coagulation studies, and use of TEG vs no TEG. Patients who had initial TEG assessments and coagulation studies were compared to those patients who only had traditional coagulation monitoring.

Of the 60 patients who presented with snake bites from 2014 to 2020, 12 had their coagulation assessed with TEG. The average age of the TEG patients was 54.2 years old. 5 (42%) of the 12 TEG patients had normal coagulation studies and TEG reports during their initial assessment and required no additional assessments. These patients had an average hospital stay of 1.6 days. 7 (58%) of TEG patients had at least one abnormal TEG result during their initial assessments, requiring at least one additional TEG collection. These patients had an average hospital stay of 2.8 days, with one outlier (which was not included) of a hospital stay of 24 days following diffuse infection. The patients with repeat TEGs also had an average of 1.1 days in the intensive care units (ICUs). There were 48 patients who were only assessed using coagulation studies with no TEG assessment. The average age of non-TEG patients was 37.5 years old, with the oldest and youngest being 81 years and 1 year, respectively. 17 (35%) of 48 non-TEG patients had at least one abnormal coagulation study result. The average length of hospital stay for non-TEG patients was 1.58 days and an average ICU stay of .17 days. All patients who were reviewed for this retrospective study were eventually discharged alive from the hospital services. The most common type of snake identified was the copperhead snake (36.7%), rattlesnake (26.7%), water moccasin (11.7%), and unknown typing (25%). Snakebite locations consisted of distal extremities (98.3%) and scalp (1.7%).

The current standard practice methods include tracking coagulopathy secondary to snake bite envenomation by following coagulation studies every few hours. Our retrospective study has provided evidence that when pairing TEG with initial coagulation studies, patients have similar outcomes and length of hospital stay when compared to patients who received the standard of treatment for snake bites if the patients are doing well clinically. As seen above, patients with a single TEG and single coagulation study had an average length of hospital stay of 1.6 days. Patients who received multiple TEG studies had an average length of hospital stay of 2.8 days. This is compared to the standard of care for snake bite patients, who had an average of 1.58 days. It is important to note that the TEG patients must also be evaluated clinically before discharge from the hospital. A few of the patients in the TEG group and the standard of care group had their stays elongated secondary to their clinical pictures. It is proposed that it could be an option in the evaluation of acute snake bites to obtain an initial TEG and coagulation study, and if the results are normal and the patient is clinically stable, observe the patients until they are ready for discharge.

One limitation of this retrospective study is the overall sample size of the patients assessed with TEG. While conducting research, it was difficult to find studies with populations greater than 15 patients or with North American snake envenomations. Others have looked into TEG’s use in managing acute snake bites, but they have been in the form of case studies. Through these case studies, TEG has been shown to be an effective tool in the evaluation of clotting deficiencies that were not discovered by typical coagulation studies. ³ Another case study demonstrated TEG’s ability to detect improvements in clotting function before standard coagulation studies reported the functioning improvements. ⁴ It is essential to expand the use of TEG in evaluating and managing snake bite patient care with continued research into the topic. More widespread retrospective studies are warranted to develop larger patient pools who have used TEG in these situations. Advocating to trauma centers and trauma physicians around the country to begin initial assessment of these patients using TEG is also essential to continue to build support for the data recovered from this retrospective study.