Thromboelastography on-the-go: Evaluation of the TEG 6s device during ground and high-altitude Aeromedical Evacuation with extracorporeal life support. Roberts TR, Jones JA, Choi JH, Sieck KN, Harea GT, Wendorff DS, Beely BM, Karaliou V, Cap AP, Davis MR, Cancio LC, Sams VG, Batchinsky AI. J Trauma Acute Care Surg. 2019 Jul;87(1S Suppl 1):S119-S127.
Extracorporeal life support (ECLS) technology, such as extracorporeal membrane oxygenation and continuous renal replacement therapy, are adjuncts used during ground and aeromedical evacuation of critically ill patients. Therapeutic anticoagulation mitigates this increased risk of clotting from platelet and factor activation but must be monitored frequently during ECLS. Currently, most on-the-go monitoring is limited to activated clotting time (ACT), which provides limited information on the impact of drugs, hemodilution and other factors. Thromboelastography (TEG) allows for measurement of whole blood clotting activity beyond isolated clot formation. This study evaluated the mobile use of the TEG 6s device in simulated aeromedical evacuation.
Yorkshire swine (n=8) were placed on venovenous ECLS then underwent transport from an ICU via ground transport to a hypobaric chamber for a 4-hour simulated aeromedical evacuation (5,000 to 8,000 feet with a rapid decompression to 30,000 feet) then ground transport back to an ICU. Each pig underwent the protocol twice: first in an uninjured state (actively heparinized), then after bilateral pulmonary contusions (anticoagulation held). The TEG 6s machine was transported and operated bedside with the swine at all locations. Duplicate samples were evaluated concurrently on the mobile TEG6s and a stationary, ground level TEG 5000 and ACT analyzer before, during and after flights.
There were no cartridge failures or abnormal tracings during the transport use of the TEG 6s machine. The mean difference in measurements was similar with the TEG 6s at altitude, in transport or in the ICU. On regression analysis, the TEG 6s and TEG 5000 had better measurement agreement across more parameters at sea level than at altitude. Similarly better agreement was observed with a stationary TEG 6s rather than mobile. The TEG 6s consistently had higher ACTs with heparinized blood when compared to a standard ACT analyzer.
This study demonstrated the possibility of mobile TEG 6s use during ground and aeromedical transport to provide detailed coagulation monitoring. Limitations of this study include no direct comparison to a stationary TEG 6s and failure to capture all stresses (e.g. vibrational) of aeromedical transport in this model. Further studies will need to investigate the reliability of this technology under a variety of environmental stress conditions.
Trends in Prehospital Analgesia Administration by US Forces From 2007 Through 2016. Schauer SG, Naylor JF, Maddry JK, Hinojosa-Laborde C, April MD. Prehosp Emerg Care. 2019 Mar-Apr;23(2):271-276.
Previous studies have shown pain related to combat injuries may be undertreated in the pre-hospital setting and can lead to long term complications including post-traumatic stress disorder. Historically, morphine (both intravenous (IV) and intramuscular (IM) via auto-injectors) has been the first line drug for traumatic pain. Updates to the Tactical Combat Casualty Care (TCCC) guidelines recommend only the IV route for morphine and added oral transmucosal fentanyl citrate (OTFC) and ketamine (IV, IM, IO or intranasal) to the medic’s toolbox. This study reviewed trends in prehospital analgesia over a 10-year period in Iraq and Afghanistan.
This was a retrospective review of the Department of Defense Trauma Registry evaluating care rendered pre-hospital, defined as before presentation to a forward surgical team or combat support hospital. Trends were evaluated over time as defined by change in TCCC guidelines (~2012) to include ketamine and OTFC. Of 28,222 subjects in the database, 31.8% received pre-hospital analgesia, most frequently IV morphine (13.3%) and IV fentanyl (8.9%). Across the decade, IM morphine had a stable low rate of use while IV morphine was significantly variable. There were increases in both ketamine (3.9 to 19.8%) and OTFC (0.7 to 7.9%) use, with the largest change immediately after the TCCC change.
In summary, this study observed an increase in fentanyl and ketamine use, with a decrease in IV morphine usage. As a retrospective registry review, limitations include a lack of data on location of administration, dosage or efficacy of analgesia. Future direction of inquiry could examine the selection and dosing of pre-hospital agents as well as patient outcomes in the combat setting.
A Prospective Evaluation of Thromboelastometry (ROTEM) to Identify Acute Traumatic Coagulopathy and Predict Massive Transfusion in Military Trauma Patients in Afghanistan. Cohen J, Scorer T, Wright Z, Stewart IJ, Sosnov J, Pidcoke H, Fedyk C, Kwan H, Chung K, Heegard K, White C, Cap A. Transfusion. 2019 Apr;59(S2):1601-1607.
Major hemorrhage is frequently associated with an Acute Traumatic Coagulopathy (ATC) that is present in up to 38% of transfused combat casualties. Conventionally ATC has been defined as an INR > 1.2 or 1.5. Using the INR > 1.5 as a definer of coagulopathy, casualties with coagulopathy have a 5-fold increase in mortality compared to those with an INR < 1.5. Conventional coagulation tests (PT, INR, PTT & fibrinogen) are of limited utility in guiding resuscitation in acute hemorrhage as they have been demonstrated to be poor predictors of massive transfusion (MT) and "crude" instruments to guide specific blood component therapy. Limitations of conventional coagulation tests include: Slow turnaround time, they do not determine specific coagulopathic phenotypes, quantify clotting only during the initiation phase and failure to describe functional activity of platelets and fibrin cross-linking. Viscoelastic tests (VETs) include: Thromboelastography (TEG) and rotational thromboeslastometry (ROTEM). VETs have been used to help identify and managed ATC. VETs use whole blood samples (not platelet-poor plasma as conventional assays do) and allow rapid identification of changes in the coagulation cascade and permit evaluation of relative contributions of fibrinogen and platelets to clot strength and also permit lysis determination. Reports have supported the benefits of VETs with regards to: Adherence to damage control resuscitation (DCR) guidelines, identifying clinically relevant coagulopathy, and identification of increased risk of MT and hemorrhage-related mortality.
The goals of the study reported in the paper were to: 1) Determine the relative capacities to identify ATC and predict MT between the lower INR cutoff of 1.2 and ROTEM EXTEM A5 (≤ 35mm) and/or EXTEM LI30 (<97%), and 2.) Identify practices that failed to correct ATC by 24hours.
The study was a prospective observational study done at Bagram in Afghanistan from 2012-2013. Ultimately 40 patients had ROTEM done and clinical data available for analysis. Blood was obtained at admission, 6hr and 24hr later. Fourteen of the 40 patients did not have 24hr data because of death or transfer. Notably, results of ROTEM were not available to the treatment team. MT was defined as 10 or more pRBC units within 24hr and units of cryoprecipitate and apheresis platelets were converted to whole blood derivatives for analysis (1:10 and 1:6, respectfully). An integrated ROTEM model was used to define ATC: INR > 1.2, EXTEM A5 ≤35mm and/or EXTEM LI < 97% at admission; presence of 1 or more of these criteria were included in the ATC cohort.
For the 40 patients analyzed: Median age = 26, median ISS 21.5, and 70% of all patients met the criteria for severe trauma with ISS >15. Median ISS was higher, 27 vs 17) for those who required MT, and all patient who required MT had ISS >15 and all that required MT were dismounted IED casualties. Twenty-eight patients (70%) met ATC criteria at admission by the integrated model (ROTEM/INR) whereas 22 (55%) met ATC criteria by INR alone. There was no significant correlations between admission ISS, base deficit, platelet count, hemoglobin or creatinine and degree of coagulopathy for any individual ROTEM parameter or INR. In those 12 patients who did not have ATC at admission, 4 exhibited drops in EXTEM A5 to meet integrated model ATC subsequently with no deaths. The development of hyperfibrinolysis was not observed in the first 24hr for any patient with normal EXTEM LI30 at admission. The integrated model was found to have increased sensitivity (86% vs. 64%), positive likelihood ratio (1.4 vs. 1.3) and negative likelihood ratio (0.4 vs. 0.7) than INR >1.2 in identifying ATC. The study population was young and pre-injury healthy. The integrated model identified an additional 15% of patients presenting with ATC who would have been unidentified by INR alone and these accounted for 20% of all MTs.
This was a relatively small prospective observational study that was male and pre-injury healthy, and subjected to high injury trauma that may or may not be translatable to civilian trauma. Both of the models investigated had poor specificity, implying that that not all coagulopathic patients experience significant hemorrhage and this underscores the importance of using these tests only in a larger clinical context. The additional benefit of VET assays is demonstrated as compared to traditional coagulation testing. The study also demonstrates that DCR successfully mitigates ATC development after admission and underscores the value of balanced blood product resuscitation (1:1:1:1).
Analysis of Limb Outcomes by Management of Concomitant Vein Injury in Military Politeal Artery Trauma. Guice JL, Gifford SM, hata K, Shi X, Propper BW, Kauvar DS. Annals of Vascular Surgery. 2020 Jan;62:51-56.
The lower extremity is the most common site of arterial injury in military and civilian trauma. Popliteal artery injuries are common in both civilian and combat injuries and are associated with high amputation rates, especially in combat injuries. Concomitant popliteal vein injuries are present with up to 1/3 of popliteal artery injuries and consensus does not exist on whether it is beneficial or even necessary to reconstruct the popliteal vein in such cases; indeed whether the vein is reconstructed or ligated appears to be a coin toss (~50:50). Despite the potential effects of venous hypertension, limb congestion and potential compartment syndrome, major lower extremity venous ligation has not consistently been associated with adverse consequences, and its effect on amputation rates is unclear. Popliteal venous repair adds time and complexity to an already challenging injury and in forward deployed military settings vascular reconstructions are often left to non-vascular surgeons. Additionally, in the military environment the decision to allocate time and resources to such a repair may complicate the care of other casualties.
Given the limited and discordant outcomes data, the authors' sought to determine if the surgical management (reconstruction vs. ligation) of popliteal vein injuries in the setting of arterial injury was associated with limb salvage.
This was a retrospective cohort study with data obtained from the Global War on Terror Vascular Initiative (GWOT-VI) database. All cases of concomitant ipsilateral popliteal artery and vein injuries diagnosed in the combat theater, not managed with primary amputation, and that survived to be admitted to a main theater hospital (Role 3) were reviewed. If both of a casualty's limbs sustained such an injury, then each limb was included individually. Analyses were performed on a per-limb basis. Limbs were then divided into 2 groups based on initial management of the venous injury: Repair (primary or graft) or ligation. Primary outcome was secondary amputation (BKA or AKA) in a subsequent operation. Secondary outcomes included reconstruction related complications.
Fifty-four casualties were included, 2 casualties had bilateral injuries and therefore a total of 56 limbs were included in analysis. Twenty-nine (52%) limbs underwent popliteal vein repair (repair group), and the remainder underwent vein ligation (ligation group). ISS were similar between groups. Overall, 27 (48%) of the index vascular injuries were above the knee and 29 (52%) of limbs had a prehospital tourniquet. Limb injury characteristics were similar between the groups, with most of the limbs having fractures and about half having nerve injuries. Bypass graft was the most common type of popliteal arterial repair with autologous vein being most commonly used (n=49, 88%), and the distribution of repairs was also similar between the groups. Of the 29 vein repairs, 13 (45%) were primary repairs and 16 (55%) were venous bypass grafts. There was no difference in fasciotomy rate between repair vs. ligation groups. Arterial shunts were placed at the index operation for transport in roughly 1/3 of the limbs and only 7 venous shunts were used. There were 24 (43%) secondary amputations total. Amputation rates were 38% in repair vs. 41% in the ligation group (p=0.76) and additionally no difference was observed whether injury was above or below knee, nor were rates different based on type of venous repair. Reasons for amputation were similar between groups, however failure of arterial repair was more commonly associated with amputation in the ligation group, but not statistically so (p=0.08). Notably, complications of the arterial grafts were similar between the groups with the exception of a higher infection rate in the repair group (14% vs. 0%) that was nearly, but not statistically significant (p=0.07). Timing of amputations did not differ between groups, with most occurring in the first 30 days after injury.
In this small retrospective study that, uniquely, included review of cases that spanned spectrums of medical care and geographic movement, the ligation of popliteal veins as definitive management was not associated with failure of limb salvage in casualties with high energy popliteal artery and vein injuries. The rate of venous repair patency was high, 86%, indicating that these repairs are not at all doomed to failure; however the authors do point out that observational bias may have under identified vein reconstruction thrombosis. The amputation rate was higher than reported for civilian injuries, as were other complication rates. This likely reflects the high-energy nature of the injuries, but does require some perhaps some consideration when applying this data to a civilian practice. Overall, for the military surgeon this study provides guidance in that to repair or not to repair at the initial operation does not avoid or mandate amputation/limb salvage.