Military-to-civilian translation of battlefield innovations in operative trauma care.

BACKGROUND: Historic improvements in operative trauma care have been driven by war. It is unknown whether recent battlefield innovations stemming from conflicts in Iraq/Afghanistan will follow a similar trend. The objective of this study was to survey trauma medical directors (TMDs) at level 1-3 trauma centers across the United States and gauge the extent to which battlefield innovations have shaped civilian practice in 4 key domains of trauma care. METHODS: Domains were determined by the use of a modified Delphi method based on multiple consultations with an expert physician/surgeon panel: (1) damage control resuscitation (DCR), (2) tourniquet use, (3) use of hemostatic agents, and (4) prehospital interventions, including intraosseous catheter access and needle thoracostomy. A corresponding 47-item electronic anonymous survey was developed/pilot tested before dissemination to all identifiable TMD at level 1-3 trauma centers across the US. RESULTS: A total of 245 TMDs, representing nearly 40% of trauma centers in the United States, completed and returned the survey. More than half (n = 127; 51.8%) were verified by the American College of Surgeons. TMDs reported high civilian use of DCR: 95.1% of trauma centers had implemented massive transfusion protocols and the majority (67.7%) tended toward 1:1:1 packed red blood cell/fresh-frozen plasma/platelets ratios. For the other 3, mixed adoption corresponded to expressed concerns regarding the extent of concomitant civilian research to support military research and experience. In centers in which policies reflecting battlefield innovations were in use, previous military experience frequently was acknowledged. CONCLUSION: This national survey of TMDs suggests that military data supporting DCR has altered civilian practice. Perceived relevance in other domains was less clear. Civilian academic efforts are needed to further research and enhance understandings that foster improved trauma surgeon awareness of military-to-civilian translation.

Vented versus unvented chest seals for treatment of pneumothorax and prevention of tension pneumothorax in a swine model.

BACKGROUND: Unvented chest seals (CSs) are currently recommended for the management of penetrating thoracic injuries in the battlefield. Since no supporting data exist, we compared the efficacy of a preferred unvented with that of a vented CS in a novel swine model of pneumothorax (PTx). METHODS: An open chest wound was created in the left thorax of spontaneously air-breathing anesthetized pigs (n = 8). A CS was applied over the injury, then tension PTx was induced by incremental air injections (0.2 L) into the pleural cavity via a cannula that was also used to measure intrapleural pressure (IP). Both CS were tested on each pig in series. Tidal volume (V(T)), respiratory rate, IP, heart rate, mean arterial pressure, cardiac output, central venous pressure, pulmonary arterial pressure, venous and peripheral oxygen saturations (SvO2, SpO2) were recorded. Tension PTx was defined as a mean IP equal to or greater than +1 mm Hg plus significant (20-30%) deviation in baseline levels of the previously mentioned parameters and confirmed by chest x-ray study. PaO2 and PaCo2 were also measured. RESULTS: PTx produced immediate breathing difficulty and significant rises in IP and pulmonary arterial pressure and falls in V(T), SpO2, and SvO2. Both CSs returned these parameters to near baseline within 5 minutes of application. After vented CS was applied, serial air injections up to 2 L resulted in no significant change in the previously mentioned parameters. After unvented CS application, progressive deterioration of all respiratory parameters and onset of tension PTx were observed in all subjects after approximately 1.4-L air injection. CONCLUSION: Both vented and unvented CSs provided immediate improvements in breathing and blood oxygenation in our model of penetrating thoracic trauma. However, in the presence of ongoing intrapleural air accumulation, the unvented CS led to tension PTx, hypoxemia, and possible respiratory arrest, while the vented CS prevented these outcomes.

Analysis of remote trauma transfers in South Central Texas with comparison with current US combat operations: results of the RemTORN-I study.

BACKGROUND: This study aimed to analyze demographic, epidemiologic, temporal, and outcome data from an integrated trauma registry of patients undergoing initial stabilization and transfer within a mature domestic trauma network; compare data with a companion subset from the Department of Defense Trauma Registry. Texas Trauma Service Area-P is composed of 25 counties, 15 rural Level IV trauma centers (no acute care surgery), and two Level I trauma centers. METHODS: This study has a retrospective cohort design. We hypothesize that Injury Severity Scores (ISSs), time intervals, and other clinical indicators would be complimentary to contemporary combat casualties. Inclusion criteria include age 18 years to 80 years, transferred from Level IV to Level I trauma center, or expired en route. RESULTS: A total of 543 subjects (84%) met the criteria and were analyzed. Averages and confidence intervals were as follows: age of 40 years (38-41 years), males at 81%, ISS of 10 (10-11), intensive care unit stay of 2 days (1-3 days), and hospital stay of 5 days (4-6 days). Mechanisms of injury were as follows: penetrating (15%), blunt weapon (19%), stabs (9%), burns (5%), and gunshots (5%). Eight percent received blood within the first 24 hours. Survival was at 98%. Time intervals (95% confidence interval) were as follows: prehospital at 1:43 (1:29-1:58), Level IV dwell time at 3:17 (3:06-3:28), interfacility transfer at 1:43 (1:36-1:49), and total at 6:39 (6:20-6:58). RemTORN cases were older, spent longer time en route to Level I, and had ISS similar to combat casualties. Rates of blood transfusion in the first 24 hours and survival were similar in order of magnitude. CONCLUSION: The RemTORN platform is operational. Demographic, epidemiologic, and temporal characteristics as observed will support clinical investigations of traumatic coagulopathy, shock, and potential interventions before Level I arrival. Results of such investigations will likely be applicable to the contemporary and future battlefield.

Promoting early diagnosis of hemodynamic instability during simulated hemorrhage with the use of a real-time decision-assist algorithm.

BACKGROUND: This study aimed to test the hypothesis that the addition of a real-time decision-assist machine learning algorithm by emergency medical system personnel could shorten the time needed to identify an unstable patient during a hemorrhage profile as compared with vital sign information alone. METHODS: Fifty emergency medical team-paramedics from a large, urban fire department participated as subjects. Subjects viewed a monitor screen on two occasions as follows: (1) display of standard vital signs alone and (2) with the addition of an index (Compensatory Reserve Index) associated with estimated central blood volume status. The subjects were asked to push a computer key at any point in the sequence they believed the patient had become unstable based on information provided by the monitor screen. The average difference in time to identify hemodynamic instability between experimental and control groups was assessed by paired, two-tailed t test and reported with 95% confidence intervals (95% CI). RESULTS: The mean (SD) amount of time required to identify an unstable patient was 18.3 (4.1) minutes (95% CI, 17.2-19.4 minutes) without the algorithm and 10.7 (4.2) minutes (95% CI, 9.5-11.9 minutes) with the algorithm (p < 0.001). CONCLUSION: In a simulated patient encounter involving uncontrolled hemorrhage, the use of a monitor that estimates central blood volume loss was associated with early identification of impending hemodynamic instability. Physiologic monitors capable of early identification and estimation of the physiologic capacity to compensate for blood loss during hemorrhage may enable optimal guidance for hypotensive resuscitation. They may also help identify casualties benefitting from forward administration of plasma, antifibrinolytics and procoagulants in a remote damage-control resuscitation model.

"Fluidless" resuscitation with permissive hypotension via impedance threshold device therapy compared with normal saline resuscitation in a porcine model of severe hemorrhage.

BACKGROUND: One approach to improve outcomes after trauma and hemorrhage is to follow the principles of permissive hypotension by avoiding intravascular overpressure and thereby preventing dislodgement of platelet plugs early in the clotting process. We hypothesized that augmentation of negative intrathoracic pressure (nITP) by treatment with an impedance threshold device would improve hemodynamics without compromising permissive hypotension or causing hemodilution, whereas aggressive fluid resuscitation with normal saline (NS) would result in hemodilution and SBPs that are too high for permissive hypotension and capable of clot dislodgement. METHODS: Thirty-four spontaneously breathing anesthetized female pigs (30.6 ± 0.5 kg) were subjected to a fixed 55% hemorrhage over 30 minutes; block randomized to nITP, no treatment, or intravenous bolus of 1-L NS; and evaluated over 30 minutes. Results are reported as mean ± SEM. RESULTS: Average systolic blood pressures (SBPs) (mm Hg) 30 minutes after the study interventions were as follows: nITP, 82.1 ± 2.9; no treatment, 69.4 ± 4.0; NS 89.3 ± 5.2. Maximum SBPs during the initial 15 minutes of treatment were as follows: nITP, 88.0 ± 4.3; no treatment, 70.8 ± 4.3; and NS, 131 ± 7.6. After 30 minutes, mean pulse pressure (mm Hg) was significantly higher in the nITP group (nITP, 32.3 ± 2.2) versus the no-treatment group (21.5 ± 1.5 controls) (p < 0.05), and the mean hematocrit was 25.2 ± 0.8 in the nITP group versus 19 ± 0.6 in the NS group (p < 0.001). CONCLUSION: In this porcine model of hemorrhagic shock, nITP therapy significantly improved SBP and pulse pressure for 30 minutes without overcompensation compared with controls with no treatment. By contrast, aggressive fluid resuscitation with NS but not nITP resulted in a significant rise in SBP to more than 100 mm Hg within minutes of initiating therapy that could cause a further reduction in hematocrit and clot dislodgment.

Impact of critical care-trained flight paramedics on casualty survival during helicopter evacuation in the current war in Afghanistan.

BACKGROUND: The US Army pioneered medical evacuation (MEDEVAC) by helicopter, yet its system remains essentially unchanged since the Vietnam era. Care is provided by a single combat medic credentialed at the Emergency Medical Technician - Basic level. Treatment protocols, documentation, medical direction, and quality improvement processes are not standardized and vary significantly across US Army helicopter evacuation units. This is in contrast to helicopter emergency medical services that operate within the United States. Current civilian helicopter evacuation platforms are routinely staffed by critical care-trained flight paramedics (CCFP) or comparably trained flight nurses who operate under trained EMS physician medical direction using formalized protocols, standardized patient care documentation, and rigorous quality improvement processes. This study compares mortality of patients with injury from trauma between the US Army's standard helicopter evacuation system staffed with medics at the Emergency Medical Technician - Basic level (standard MEDEVAC) and one staffed with experienced CCFP using adopted civilian helicopter emergency medical services practices. METHODS: This is a retrospective study of a natural experiment. Using data from the Joint Theater Trauma Registry, 48-hour mortality for severely injured patients (injury severity score ≥ 16) was compared between patients transported by standard MEDEVAC units and CCFP air ambulance units. RESULTS: The 48-hour mortality for the CCFP-treated patients was 8% compared to 15% for the standard MEDEVAC patients. After adjustment for covariates, the CCFP system was associated with a 66% lower estimated risk of 48-hour mortality compared to the standard MEDEVAC system. CONCLUSIONS: These findings demonstrate that using an air ambulance system based on modern civilian helicopter EMS practice was associated with a lower estimated risk of 48-hour mortality among severely injured patients in a combat setting.

Use of respiratory impedance in prehospital care of hypotensive patients associated with hemorrhage and trauma: a case series.

BACKGROUND: The respiratory pump can be optimized to enhance circulation in patients with hypotension by having patients spontaneously breathe through a low level of inspiratory resistance. This can be achieved with an impedance threshold device (ITD) designed to provide 7 cm H2O resistance during spontaneous inspiration with minimal resistance during expiration. Little is known about the effects of harnessing this physiological concept to increase blood pressure (BP) in the prehospital setting of care for patients with hypotension caused by blood loss or trauma. In this case series, we report on the feasibility, effectiveness, and safety of rapidly deploying the ITD by first responders to treat hypotension secondary to blood loss and trauma in the urban setting by emergency medical services personnel. METHODS: Hemodynamic data from hypotensive patients (pretreatment systolic BP [SBP] <100 mm Hg) from 3 U.S. cities where the ITD is deployed were evaluated. The primary end point was maximum change in SBP and diastolic BP (DBP) from before to during ITD use in patients with hypotension secondary to documented blood loss or trauma. Secondary end points were device tolerance, whether the patient felt "better," change in heart rate, O2 saturation, and adverse events. RESULTS: Of the 255 hypotensive patients treated, there were 26 categorized with blood loss and 13 with trauma. In this 39-patient subgroup, the SBP and DBP (mean ± SD) increased from 79 ± 14 mm Hg and 48 ± 12 mm Hg before ITD placement to 110 ± 17 mm Hg and 66 ± 14 mm Hg after ITD placement (p < 0.001). Breathing through the ITD resulted in no reported adverse events, was well tolerated, and resulted in feeling "better" in more than 85% of the patients. CONCLUSION: Use of an ITD by emergency medical services personnel on hypotensive spontaneously breathing patients secondary to blood loss and trauma increased SBP and DBP and was feasible, well tolerated, and not associated with adverse effects (e.g., increased bleeding).

Prehospital and emergency care research at the US Army Institute of Surgical Research: enabling the next great leap in combat casualty survival.

Minimizing preventable death continues to be a primary focus of the combat casualty care research community, and of the Army Medical Department as a whole. Toward that end, tremendous successes have been realized in resuscitative surgery, critical care, rehabilitation, preventive medicine, and in our collective ability to project effective medical care into the most austere locations throughout the globe. Innovation in the care rendered outside of theater hospitals or strategic air evacuation conveyances, however, has not kept the same pace. The US military experience in World War II, Korea, and Vietnam served as a prime source for the development of the tactics, techniques, and procedures which spawned modern civilian sector trauma care and emergency medical services. But this ascendance was driven by the dedicated medics, corpsmen, physicians, nurses, and allied health practitioners from those conflicts who left the military for the civilian sector, leaving their replacements, in many cases, to repeat the same mistakes, and to relearn hard lessons that otherwise might have been assimilated had they been effectively captured and integrated into doctrine and training. A prime example of this phenomenon is the recent acknowledgement of the "en route care gap" existing in tactical medical evacuation. The US Army Institute of Surgical Research (USAISR) and the Army emergency medicine community have made a significant commitment toward elucidating the requirements, capability gaps, and a way-forward in search of the development of an integrated prehospital combat casualty care system, nested within the Joint Theater Trauma System. This paper examines specific research programs, concept development, and collaborations with other Army, joint, and civilian center organizations which comprise the USAISR Prehospital and Emergency Care Research Program, including the Remote Damage Control Resuscitation initiative, Emergency Telemedical Direction of Role-I providers, Combat Medical Voice Documentation System, and establishment of the Remote Trauma Outcomes Research Network.

A Pilot Study of the Performance Characteristics of the D-dimer in Presumed Sepsis.

OBJECTIVES: To determine if a sensitive D-dimer assay can exclude progression to organ dysfunction, death, and intensive care unit (ICU) admission in patients presenting to the emergency department (ED) with suspected infection, and if increasing levels of D-dimer are predictive of those end points. METHODS: The study took place at two academic EDs, both located in tertiary care hospitals. This was a prospective convenience sample of adult patients presenting with an infective process and at least two of four criteria for the Systemic Inflammatory Response Syndrome. We measured D-dimer levels in the participants and abstracted their records for the end points. Sensitivity and specificity were calculated and receiver operating characteristic analysis was performed to determine if a higher cutoff would have a greater specificity for our end points. RESULTS: We enrolled 134 patients. Twelve were excluded from analysis (10 for lack of a D-dimer, one for recent surgery, and one for complete loss to follow up). Using the cutoff of 0.4 established by our laboratories as positive, the D-dimer had a sensitivity of 94% (CI95; 76-99) for organ dysfunction in the ED, 93% (72-99) for organ dysfunction at 48 hours, 93% (81-98) for ICU admission, and 100% (63-100) for 30-day mortality. However, at this cutoff, specificity was not statistically significant. Significantly raising the cutoff for a positive resulted in a decrease in sensitivity but improved specificity. CONCLUSION: This study was limited by its nonconsecutive patient recruitment and sample size. A normal D-dimer may exclude progression to organ dysfunction, ICU admission, and death and, at higher cutoff levels, could help risk stratify patients presenting to the ED with signs of sepsis.

Takayasu arteritis presenting as a recurrent respiratory tract infection: a diagnosis facilitated by bedside echocardiography and increased erythrocyte sedimentation rate.

Takayasu arteritis is a rare autoimmune disease affecting large and moderate sized arteries, often involving the aorta or coronary vasculature. We report a case of an adolescent male with a history of recurrent respiratory tract infections who presented with fever, cough, and shortness of breath and who was diagnosed with acute aortic valve failure and coronary ischemia. Ultimately, the patient's condition was attributed to Takayasa arteritis. This typical presentation of an atypical disease provides valuable teaching points, including the use of bedside echocardiography for the diagnosis of acute aortic insufficiency and the differential diagnosis of increased erythrocyte sedimentation rate. It also serves to remind clinicians to maintain a high index of suspicion for unusual disease processes in patients who fail to respond to empiric therapy for recurrent subacute illnesses.