Association of Mechanism of Injury with Risk for Venous Thromboembolism After Trauma. Karcutskie CA, Meizoso JP, Ray JJ, Horkan D, Ruiz XD, Schulman CI, Namias N, Proctor KG. JAMA Surg. 2017 Jan 1;152(1):35-40.
Venous thromboembolism (VTE) is a serious complication of injury. Risk factors, diagnosis and management of VTE in trauma have been extensively investigated. Scoring tools were also developed to identify patients with higher risk to develop VTE. Various protocols exist in trauma centers to screen the injured patients for the presence of VTE. In this well-written article, the authors highlight a deficiency in these protocols and screening tools – they are not stratified by the mechanism of injury, i.e. blunt or penetrating. The authors point out previous work that demonstrated relationship between mechanism of injury and outcomes.
This study was a retrospective cohort study of trauma patients at a single level I trauma center (University of Miami) between August 2011 and January 2015. Exclusion criteria included: patients younger than 18 years, incarcerated, pregnant patients, or those who died less than 72 hours after admission. Greenfield Risk Assessment Profile (RAP, first developed in 1997) was calculated for all patients. A score more than 10 deemed the patient high risk of VTE and initiated a weekly screening process using ultrasound (30% of the cohort). If patients were not high risk, they were screened only if they became symptomatic. VTE was diagnosed if ultrasound study was positive as read by an attending radiologist. Computed tomography was used for diagnosis of pulmonary embolism. Both high risk and low risk patients were included in the analysis. The study was not meant to explore the difference in the risk of VTE between blunt and penetrating trauma patients (the risk was similar: 9% vs. 9.6%, respectively, and despite early prophylaxis initiation.) Instead, the authors explored the association of different risk factors with the development of VTE in blunt and penetrating trauma separately. The individual components of the RAP score were included in univariate analyses.Those that were significant were then entered into a multivariable logistic regression model. In the multivariable regression models there were differences in risk factors that significantly increased the odds of developing VTE between blunt and penetration trauma. In blunt trauma, 4 or more transfusions (OR 3.47; 95%CI 2.04 – 5.91), GCS<8 (OR 2.75; 95%CI 1.23 – 4.94) and pelvic fractures (OR 2.09; 95%CI 1.23 – 3.55) were significant. In penetrating trauma, factors that significantly increased the odds of developing VTE included: repair and/or ligation of a vascular injury (OR 3.32; 95%CI 1.37 – 8.03), AIS score of the abdomen > 2 (OR 2.77 (1.19 – 6.45), and age between 40 – 59 (OR 2.69; 95%CI 1.19 – 6.08). These factors are similar to those identified in the EAST Practice Management Guidelines on risk factors of VTE. Interestingly, the age group that was associated with the highest risk of VTE is the youngest of the age categories in the RAP score, but is generally older than the typical penetrating trauma age distribution. However, there is no comparison between this age group and those who are younger than 40 years in penetrating trauma. When these identified factors were used in a reduced model of RAP, the diagnostic ability of RAP did not noticeably change – in blunt trauma the area under the curve (AUC) was 0.745 (fair) for the full model and 0.730 (fair) for the reduced model; and in penetrating trauma the AUC was 0.803 (good) for the full model and 0.760 (fair) for the reduced model.
The authors clearly state the limitations of and biases in the retrospective nature of the study. However, they successfully reveal “an inherent difference in the risk of VTE that is dependent on the mechanism of injury”. Such finding should be implemented clinically in identifying patients with individual risk factors for VTE, and therefore guide the development of personalized screening protocols.
Temporary Arterial Shunts in Damage Control: Experience and Outcomes. Mathew S, Smith BP, Cannon JW, Reilly PM, Schwab CW, Seamon MJ. J Trauma Acute Care Surg. 2017 Mar;82(3):512-517.
This article is a retrospective review of injured patients at a busy level I trauma center (University of Pennsylvania) over 8 years to identify those who had a vascular shunt placed on initial operation. The authors investigated the risk factors of shunt complications, specifically the shunt dwell time. The use of temporary shunts has been an acceptable and recommended intervention in damage control vascular injuries, both in military and civilian trauma. They are most commonly used in damage control surgeries due to physiologic instability or due to combined vascular and orthopedic injuries. This is similar to what the authors found in this review, as damage control surgery was the indication in 64.3% and the combined vascular/orthopedic injuries in 23.8%. EAST Practice Management Guidelines recommend the use of temporary shunts to restore arterial flow in combined vascular/orthopedic injuries to facilitate limb perfusion during orthopedic stabilization (level 3). However, the authors point out the absence of a recommended shunt dwell time and the paucity of studies that explored the relationship between the dwell time and shunt complications.
Shunt complications were defined as shunt dislodgement, thrombosis, or distal ischemia during the shunt dwell time. Dwell time was evaluated in two categories with 6 hours being the chosen cutoff because of its clinical utility as a threshold for warm ischemia time after vascular injury. Forty-two patients were identified to have had a temporary shunt during the study period. Seven of these patients were later excluded from the final analysis due to death prior to definitive vascular repair and shunt removal. The patients were analyzed based on both dwell time (less and more than 6 hours) and the development of VTE or lack of. The majority of the patients were young, men, and sustained penetrating trauma with severe vascular injuries (AIS 4, IQR 3 – 4). Most patients were hypotensive and required vasopressors support. Five patients (14.3% of entire cohort and 31.2% of those with dwell time>6 hours) had shunt complications (3 distal ischemia and 2 shunt thrombosis). All these patients had dwell time more than 6 hours. There was no statistical difference between patients groups (based on dwell time) in age, gender, hemodynamics, AIS, ISS, or outcomes. There was no statistical difference between patients groups (based on development of shunt complications) in age, injury mechanism, hemodynamics, associated injuries, AIS, ISS or the use of systemic anticoagulation. The authors did not report a subgroup analysis of a direct comparison between patients with shunt complications and those without complications within the group of a dwell time more than 6 hours. Interestingly, 3 of the 5 patients with shunt complications had proximal injuries (chest of pelvis). This is consistent with the study by Subramanian et al. (referenced by the authors in the discussion) that showed increased risk of thrombosis in truncal shunts compared to extremity shunts. The distribution of time to complication was bimodal with 2/5 of the patients developing a complication at 7 and 8 hours time point and 3/5 of the patients developing a complication after 24 hours of dwell time.
The authors recommended limiting the dwell time of temporary vascular shunts to less than 6 hours “when clinically feasible”. They acknowledged that clinical decisions would vary on a case-by-case basis. They also clearly defined the limitations of this study, such as the specific patient population, surgeon discretion in operative decisions, and documentation limitations due to the retrospective nature of the study. Additionally, the small sample size and the small number of events limited the ability to perform a stratified analysis or a regression analysis to explore the strength of the relationship between shunt dwell time and complications while controlling for other covariates. Nevertheless, this was an important study that identified the potential increased risk of temporary vascular shunts’ complications with prolonged dwell time.
Combat MEDEVAC: A comparison of care by provider type for en route trauma care in theater and 30-day patient outcomes. Maddry JK, Mora AG, Savell S, Reeves LK, Perez CA, Bebarta VS. J Trauma Acute Care Surg. 2016 Nov;81(5 Suppl 2 Proceedings of the 2015 Military Health System Research Symposium):S104-S110.
This is a retrospective review of MEDEVAC patient care records for US military personnel injured in Operation Enduring Freedom theater of operations between January 2011 through March 2014 obtained from Joint Trauma System. The goal of this study was to compare outcomes and procedures performed by provider type and evaluate 30-day outcomes including mortality particularly following the 2012 initiation of paramedic-level training for medics and increased utilization of paramedics. Data from point of injury to the first military treatment facility collected included demographics, injury description, provider type (medic, paramedic, and advanced level provider (ADV)), procedures, medications administered, clinical events, analgesics administered, and survival.
The investigators reviewed 1237 records revealing 76% of providers were medics, 21% paramedics, and 3% ADVs). The records were 99% male, average age of 24, 69% blast-related injury type, and average ISS of 14. There were no differences in demographics, injury types, and severity when comparing the three provider groups. ADVs were more likely to intubate, perform needle decompression, and provide hypothermia prevention. Paramedics were most likely to administer blood. There were no differences between the groups in rate of chest tubes, chest seals, tourniquets, CPR, cricothyrotomies, IVF, oxygen support, spine stabilization, vascular access, and pressure packing. Medics were least likely to administer medications while paramedics were more likely to give medications en route. Provider type was not associated with difference in ventilator days, ICU days, hospital days, or survival (in theater and final). Similar findings were found in a subset analysis of patients with ISS>16. Availability of analgesics, narcotics, and blood products may influence the pattern of administration. Medics are most likely to transport casualties to a Role 2 facility whereas paramedics are generally co-located with Role 3 facilities and most likely to transport casualties directly to a Role 3 which may influence outcomes. The lack of difference in outcome would suggest not needing advanced providers. However, this study is limited to injured US military personnel likely protected by body armor and suffering fewer thoracic-abdominal injuries, and with an average evacuation time of less than 50 minutes. In future conflicts, prolonged transport times and prolonged field care may result in utilization of forward deployed mobile surgical units and advanced resuscitation in the aircraft.
Evaluation of role 2 (R2) medical resources in the Afghanistan combat theater: Initial review of the joint trauma system R2 registry. Mann-Salinas EA, Le TD, Shackelford SA, Bailey JA, Stockinger ZT, Spott MA, Wirt MD, Rickard R, Lane IB, Hodgetts T, Cardin S, Remick KN, Gross KR. J Trauma Acute Care Surg. 2016 Nov;81(5 Suppl 2 Proceedings of the 2015 Military Health System Research Symposium):S121-S127.
This is a retrospective review of the Joint Trauma System Role 2 Registry (JTS R2R) conducted to describe the initial review of available R2R data. The authors explain that this is a first step toward understanding R2 use to support future deployment of forward surgical capabilities. Investigators reviewed 12,849 patient records which met inclusion criteria (>18yoa, injured in Afghanistan during Operation Enduring Freedom, battle and non-battle injury (trauma), injured between February 2008 and September 2014). Variables collected for analysis included age, gender, regional location, prehospital/en route care, time to R2 (pre/post 15 June 2009 “Golden Hour” directive and > or < 60 minutes), arrival status (dead/alive), diagnosis, and discharge status (dead/alive).
The authors found that 36.4% of the patients were US Forces and 35.4% were Afghan Forces, 96.7% male, median age of 25, 76.2% battle injury, and mechanisms of injuries included 41% explosions, 24% gunshot wounds with overall 52.3% penetrating while 31.3% were blunt. The majority of the casualties were injured in the East region (67%) followed by the South region (16%). Overall arrival time was 75 minutes, with times consistently reduced after “Golder Hour” initiative. Review also determined that 33.2% of patients underwent prehospital interventions, 13.4% tourniquets, 15.6% prehospital medications, and 52.1% had procedures performed at R2. Dead upon arrival to R2 was 1.3% and death on R2 discharge was 2.7%. Limitations of this study include the lack of JTS R2R data before implementation in 2008, the voluntary participation of personnel at R2 to enter data, and lack of ISS/ multiply injured definitions of severity. This study was able to describe patient profiles and common interventions performed at sample of US R2 facilities. This initial analysis was meant to be the first step to a more complete review of R2 care that may provide evidence-based guidance to military planners and medical leaders on how to best allocate R2 resources in future operations and prepare teams for deployment.