Descriptive Analysis of Intratheater Critical Care Air Transport Team Patient Movements During Troop Drawdown: Afghanistan (2017-2019).

BACKGROUND: The majority of critical care air transport (CCAT) flights are regulated, meaning that a theater-validating flight surgeon has confirmed that the patient is medically cleared for flight and that evacuation is appropriate. If the conditions on the ground do not allow for this process, the flight is unregulated. Published data are limited regarding CCAT unregulated missions to include the period of troop drawdown at the end of the Afghanistan conflict. The objective of our study was to characterize the unregulated missions within Afghanistan during troop drawdown and compare them to regulated missions during the same timeframe. STUDY DESIGN: We performed a retrospective review of all CCAT medical records of patients transported via CCAT within Afghanistan between January 2017 and December 2019. We abstracted data from the records, including mission characteristics, patient demographics, injury descriptors, preflight military treatment facility procedures, CCAT procedures, in-flight CCAT treatments, in-flight events, and equipment issues. Following descriptive and comparative analysis, a Cochran-Armitage test was performed to evaluate the statistical significance of the trend in categorical data over time. Multivariable regression was used to assess the association between vasopressors and preflight massive transfusions, preflight surgical procedures, injury patterns, and age. RESULTS: We reviewed 147 records of patients transported via CCAT: 68 patients were transported in a regulated fashion and 79 on an unregulated flight. The number of patients evacuated increased year-over-year (n = 22 in 2017, n = 57 in 2018, and n = 68 in 2019, P < .001), and the percentage of missions that were unregulated grew geometrically (14%, n = 3 in 2017; 37%, n = 21 in 2018; and 81%, n = 55 in 2019, P < .001). During the time studied, CCAT teams were being used more to decompress forward surgical teams (FST) and, therefore, they were transporting patients just hours following initial damage control surgery in an unregulated fashion. In 2 instances, CCAT decompressed an FST following a mass casualty, during which aeromedical evacuation (AE) crews assisted with patient care. For the regulated missions, the treatments that were statistically more common were intravenous fluids, propofol, norepinephrine, any vasopressors, and bicarbonate. During unregulated missions, the statistically more common treatments were ketamine, fentanyl, and 3% saline. Additional analysis of the mechanically ventilated patient subgroup revealed that vasopressors were used twice as often on regulated (38%) vs. unregulated (13%) flights. Multivariable regression analysis demonstrated that traumatic brain injury (TBI) was the only significant predictor of in-flight vasopressor use (odds ratio = 3.53, confidence interval [1.22, 10.22], P = .02). CONCLUSION: During the troop drawdown in Afghanistan, the number of unregulated missions increased geometrically because the medical footprint was decreasing. During unregulated missions, CCAT providers used ketamine more frequently, consistent with Tactical Combat Casualty Care guidelines. In addition, TBI was the only predictor of vasopressor use and may reflect an attempt to adhere to unmonitored TBI clinical guidelines. Interoperability between CCAT and AE teams is critical to meet mass casualty needs in unregulated mission environments and highlights a need for joint training. It remains imperative to evaluate changes in mission requirements to inform en route combat casualty care training.

Prehospital end-tidal carbon dioxide is predictive of death and massive transfusion in injured patients: An Eastern Association for Surgery of Trauma multicenter trial.

BACKGROUND: Prehospital identification of the injured patient likely to require emergent care remains a challenge. End-tidal carbon dioxide (ETCO2) has been used in the prehospital setting to monitor respiratory physiology and confirmation of endotracheal tube placement. Low levels of ETCO2 have been demonstrated to correlate with injury severity and mortality in a number of in-hospital studies. We hypothesized that prehospital ETCO2 values would be predictive of mortality and need for massive transfusion (MT) in intubated patients. METHODS: This was a retrospective multicenter trial with 24 participating centers. Prehospital, emergency department, and hospital values were collected. Receiver operating characteristic curves were created and compared. Massive transfusion defined as >10 U of blood in 6 hours or death in 6 hours with at least 1 U of blood transfused. RESULTS: A total of 1,324 patients were enrolled. ETCO2 (area under the receiver operating characteristic curve [AUROC], 0.67; confidence interval [CI], 0.63-0.71) was better in predicting mortality than shock index (SI) (AUROC, 0.55; CI, 0.50-0.60) and systolic blood pressure (SBP) (AUROC, 0.58; CI, 0.53-0.62) (p < 0.0005). Prehospital lowest ETCO2 (AUROC, 0.69; CI, 0.64-0.75), SBP (AUROC, 0.75; CI, 0.70-0.81), and SI (AUROC, 0.74; CI, 0.68-0.79) were all predictive of MT. Analysis of patients with normotension demonstrated lowest prehospital ETCO2 (AUROC, 0.66; CI, 0.61-0.71), which was more predictive of mortality than SBP (AUROC, 0.52; CI, 0.47-0.58) or SI (AUROC, 0.56; CI, 0.50-0.62) (p < 0.001). Lowest prehospital ETCO2 (AUROC, 0.75; CI, 0.65-0.84), SBP (AUROC, 0.63; CI, 0.54-0.74), and SI (AUROC, 0.64; CI, 0.54-0.75) were predictive of MT in normotensive patients. ETCO2 cutoff for MT was 26 mm Hg. The positive predictive value was 16.1%, and negative predictive value was high at 98.1%. CONCLUSION: Prehospital ETCO2 is predictive of mortality and MT. ETCO2 outperformed traditional measures such as SBP and SI in the prediction of mortality. ETCO2 may outperform traditional measures in predicting need for transfusion in occult shock. LEVEL OF EVIDENCE: Diagnostic test, level III.

Impact of antithrombin III and enoxaparin dosage adjustment on prophylactic anti-Xa concentrations in trauma patients at high risk for venous thromboembolism: a randomized pilot trial.

The impact of antithrombin III activity (AT-III) on prophylactic enoxaparin anti-factor Xa concentration (anti-Xa) is unknown in high-risk trauma patients. So too is the optimal anti-Xa-adjusted enoxaparin dosage. This prospective, randomized, pilot study sought to explore the association between AT-III and anti-Xa goal attainment and to preliminarily evaluate two enoxaparin dosage adjustment strategies in patients with subprophylactic anti-Xa. Adult trauma patients with Risk Assessment Profile (RAP) ≥ 5 prescribed enoxaparin 30 mg subcutaneously every 12 h were eligible. AT-III and anti-Xa were drawn 8 h after the third enoxaparin dose and compared between patients with anti-Xa ≥ 0.1 IU/mL (goal; control group) or anti-Xa < 0.1 IU/mL (subprophylactic; intervention group). The primary outcome was difference in baseline AT-III. Subsequently, intervention group patients underwent 1:1 randomization to either enoxaparin 40 mg every 12 h (up to 50 mg every 12 h if repeat anti-Xa < 0.1 IU/mL) (enox12) or enoxaparin 30 mg every 8 h (enox8) with repeat anti-Xa assessments. The proportion of patients achieving goal anti-Xa after dosage adjustment were compared. A total of 103 patients were included. Anti-Xa was subprophylactic in 50.5%. Baseline AT-III (median [IQR]) was 87% [80-98%] in control patients versus 82% [71-96%] in intervention patients (p = 0.092). Goal trough anti-Xa was achieved on first assessment in 38.1% enox12 versus 50% enox8 patients (p = 0.67), 84.6% versus 53.3% on second assessment (p = 0.11), and 100% vs. 54.5% on third trough assessment (p = 0.045). AT-III activity did not differ between high-risk trauma patients with goal and subprophylactic enoxaparin anti-Xa concentrations, although future investigation is warranted. Enoxaparin dose adjustment rather than frequency adjustment may be associated with a higher proportion of patients achieving goal anti-Xa over time.

Effects of Early Altitude Exposure on the Open Abdomen After Laparotomy in Trauma.

INTRODUCTION: While damage control surgery and resuscitation techniques have revolutionized the care of injured service members who sustain severe traumatic hemorrhage, the physiologic and inflammatory consequences of hemostatic resuscitation and staged abdominal surgery in the face of early aeromedical evacuation (AE) have not been investigated. We hypothesized that post-injury AE with an open abdomen would have significant physiologic and inflammatory consequences compared to AE with a closed abdomen. MATERIALS AND METHODS: Evaluation of resuscitation and staged abdominal closure was performed using a murine model of hemorrhagic shock with laparotomy. Mice underwent controlled hemorrhage to a systolic blood pressure of 25 mmHg and received either no resuscitation, blood product resuscitation, or Hextend resuscitation to a systolic blood pressure of either 50 mmHg (partial resuscitation) or 80 mmHg (complete resuscitation). Laparotomies were either closed prior to AE (closed abdomens) or left open during AE (open abdomens) and subsequently closed. AE was simulated with a 1-hour exposure to a hypobaric hypoxic environment at 8,000 feet altitude. Mice were euthanized at 0, 4, or 24 hours following AE. Serum was collected and analyzed for physiologic variables and inflammatory cytokine levels. Samples of lung and small intestine were collected for tissue cytokine and myeloperoxidase analysis as indicators of intestinal inflammation. Survival curves were also performed. RESULTS: Unresuscitated mice sustained an 85% mortality rate from hemorrhage and laparotomy, limiting the assessment of the effect of simulated AE in these subgroups. Overall survival was similar among all resuscitated groups regardless of the presence of hypobaric hypoxia, type of resuscitation, or abdominal closure status. Simulated AE had no observed effects on acid/base imbalance or the inflammatory response as compared to ground level controls. All mice experienced both metabolic acidosis and an acute inflammatory response after hemorrhage and injury, represented by an initial increase in serum interleukin (IL)-6 levels. Furthermore, mice with open abdomens had an elevated inflammatory response with increased levels of serum IL-10, serum tumor necrosis factor alpha, intestinal IL-6, intestinal IL-10, and pulmonary myeloperoxidase. CONCLUSION: These results demonstrate the complex interaction of AE and temporary or definitive abdominal closure after post-injury laparotomy. Contrary to our hypothesis, we found that AE in those animals with open abdomens is relatively safe with no difference in mortality compared to those with closed abdomens. However, given the physiologic and inflammatory changes observed in animals with open abdomens, further evaluation is necessary prior to definitive recommendations regarding the safety or downstream effects of exposure to AE prior to definitive abdominal closure.

Do Autopsies Still Matter? The Influence of Autopsy Data on Final Injury Severity Score Calculations.

BACKGROUND: Despite a proven record of identifying injuries missed during clinical evaluation, the effect of autopsy on injury severity score (ISS) calculation is unknown. We hypothesized that autopsy data would alter final ISS and improve the accuracy of outcome data analyses. MATERIALS AND METHODS: All trauma deaths from January 2010 through June 2014 were reviewed. Trauma registrars calculated Abbreviated Injury Scale and ISS from clinical documentation alone. The most detailed available autopsy report then was reviewed, and AIS/ISS recalculated. Predictors of ISS change were identified using multivariate logistic regression. RESULTS: Seven hundred thirty-nine deaths occurred, of which 682 (92.3%) underwent autopsy (31% view-only, 3% with preliminary report, and 66% with full report). Patients undergoing full autopsy had a lower median age (39 versus 74 years, P < 0.01), a higher rate of penetrating injury (41.7% versus 0%, P < 0.01), and a higher emergency department mortality rate (30.8% versus 0%, P < 0.01) than those receiving view-only autopsy. Incorporating autopsy findings increased mean ISS (21.3 to 29.6, P < 0.001) and the percentage of patients with ISS ≥ 25 (49.9% to 69.2%, P < 0.001). Multivariate analysis identified length of stay, death in the emergency department, full rather than view-only autopsy, and presenting heart rate as variables associated with ISS increase. CONCLUSIONS: Autopsy data significantly increased ISS values for trauma deaths. This effect was greatest in patients who died early in their course. Targeting this group, rather than all trauma patients, for full autopsy may improve risk-adjustment accuracy while minimizing costs.

Variable saline resuscitation in a murine model of combined traumatic brain injury and haemorrhage.

BACKGROUND: Resuscitation strategies for combined traumatic brain injury (TBI) with haemorrhage in austere environments are not fully established. Our aim was to establish the effects of various saline concentrations in a murine model of combined TBI and haemorrhage, and identify an effective resuscitative strategy for the far-forward environment. METHODS: Male C57BL/6 mice underwent closed head injury and subjected to controlled haemorrhage to a systolic blood pressure of 25 mmHg via femoral artery cannulation for 60 min. Mice were resuscitated with a fixed volume bolus or variable volumes of fluid to achieve a systolic blood pressure goal of 80 mmHg with 0.9% saline, 3% saline, 0.1-mL bolus of 23.4% saline, or a 0.1-mL bolus of 23.4% saline followed by 0.9% saline (23.4+). RESULTS: 23.4% saline and 23.4+ resulted in higher mortality at 6 h compared to 0.9% saline. Use of 3% saline required less volume to achieve targeted resuscitation, did not affect survival, and did not exacerbate post-traumatic inflammation. While 23.4+ resuscitation utilized lower volume, it resulted in hypernatremia, azotemia, and elevated systemic pro-inflammatory cytokines. All groups except 3% saline demonstrated progression of neuron damage, with cerebral oedema highest with 0.9% saline. CONCLUSIONS: 3% saline demonstrated favourable balance of survival, blood pressure restoration, minimization of inflammation, and prevention of ongoing neurologic injury without contributing to significant physiologic derangements. 23.4% saline administration may not be appropriate in the setting of concomitant hypotension.

Trauma patients are safe to fly 72 hours after tube thoracostomy removal.

BACKGROUND: Current recommendations for safe air travel following traumatic pneumothorax are 2 to 3 weeks after radiographic resolution. These recommendations are based on several small observational studies and expert consensus, which cite a theoretical risk of recurrence and hypoxia because of decreased oxygen tension at altitude. We sought to systematically study the timing of chest drain removal after traumatic pneumothorax and risk of recurrence in relation to air travel. METHODS: A retrospective cohort study of consecutively admitted patients who sustained a traumatic chest injury treated with tube thoracostomy over a 5-year period was undertaken. Adult patients with a postremoval expiratory chest x-ray demonstrating absence of pneumothorax and at least a 24-hour observation period before flight were eligible for study. All patients were transferred to a participating medical center for continued care. In-flight medical monitoring was available for all patients. Baseline patient characteristics, interval period from drain removal to flight, in-flight medical records, and incidence of radiographic or clinical recurrence of pneumothorax at the destination facility were recorded. RESULTS: Seventy-three patients who met the inclusion criteria were studied. All were male with a median age of 24 years (interquartile range [IQR], 22-26 years), injury severity score of 30 (IQR, 24-38), and chest abbreviated injury scale value of 3 (IQR, 2-4). The majority of patients sustained a penetrating injury (74%). The median duration of tube thoracostomy was 4 days (IQR, 3-6 days). The median period between thoracostomy tube removal and flight was 2.5 days (IQR, 1.5-4 days). Twenty-nine patients (40%) remained mechanically ventilated during transport. There were no reported in-flight medical emergencies for the entire cohort. There were no reported postflight radiographic or clinical recurrences during the subsequent 30 days. CONCLUSIONS: After a 72-hour period of observation, air travel after tube thoracostomy removal appears safe for both mechanically ventilated and nonventilated patients. LEVEL OF EVIDENCE: Therapeutic, level IV.

Proximal penetrating extremity injuries-An opportunity to decrease overtriage?

BACKGROUND: Penetrating injuries to the extremity proximal to the elbow or knee are anatomic criteria for full trauma team activation (FFTA) by the American College of Surgeon's Committee on Trauma standards. This criterion lacks objective evidence-based support. Overtriage of trauma team activation may result in excessive costs and resource burden at trauma centers. We hypothesized that FFTA for penetrating injuries to the proximal extremities by anatomic criteria alone may lead to significant overtriage. METHODS: A 3-year retrospective review (2013-2015) was completed of all patients evaluated at an urban Level I trauma center with isolated penetrating extremity injuries. Data included the number of full and limited trauma team activations as well as criterion met, Injury Severity Score (ISS), injury, limb characteristics, and disposition. Overtriage was defined as FFTA for an ISS of 15 or less, with a goal rate less than 50%. RESULTS: We identified 6,335 total trauma team activations with 795 isolated penetrating extremity injuries. Of these injuries, 413 (51.9%) were injuries proximal to the joint. Within this subgroup, 71.2% of patients were discharged from the emergency department with a median ISS of 1 and no additional intervention. Only 5.3% of patients that did not meet additional FFTA criteria underwent immediate operative intervention. By comparison, 21% of FFTAs and 5.8% of limited trauma team activations underwent immediate operative intervention during the 3-year period. Of the 413 isolated penetrating proximal-extremity injuries, only one had an ISS of 15 or greater, resulting in a 99.7% overtriage rate. CONCLUSION: Penetrating injuries to the extremities are common in urban trauma centers. Full trauma team activation based on anatomic, rather than physiologic, criteria may lead to a significant overtriage rate. Further distinction in the level of trauma team activation may be made based on hard signs of neurovascular injury. LEVEL OF EVIDENCE: Epidemiological study, level III; Care Management, level IV.

Characteristics of Combat-Associated Small Bowel Injuries.

INTRODUCTION: Although there are multiple studies regarding the management and outcomes of colonic injuries incurred in combat, the literature is limited with regard to small bowel injuries. This study seeks to provide the largest reported review of the characteristics of combat-associated small bowel injuries. MATERIALS AND METHODS: The Department of Defense Trauma Registry was queried for U.S. Armed Forces members who sustained hollow viscus injuries in the years 2007-2012 during Operations Enduring Freedom, Iraqi Freedom, and New Dawn. Concomitant injuries, procedures, and complications were delineated. Fisher's exact test was used to analyze the relationship of bowel injury pattern to rates of repeat laparotomy, fecal diversion, and complications. RESULTS: One hundred seventy-one service members had small bowel injuries. The mean age was 25.8 ± 6.6 yr with a mean injury severity score of 27.9 ± 12.4. The majority of injuries were penetrating (94.2%, n = 161) as a result of explosive devices (61.4%, n = 105). The median blood transfusion requirement in the first 24 h was 6.0 units (interquartile range 1.0-17.3 units). The most frequent concomitant injuries were large bowel (64.3%, n = 110), pelvic fracture (35.7%, n = 61), and perineal (26.3%, n = 45). Fifty patients (29.2%) had a colostomy, and nine patients (5.3%) had an ileostomy; 62.6% (n = 107) of soldiers underwent more than one laparotomy. The mortality rate was 1.8% (n = 3). The most common complications were pneumonia (15.2%, n = 26), deep vein thrombosis (14.6%, n = 25), and wound infection (14.6%, n = 25). The need for repeat laparotomy and fecal diversion was found to be significantly associated with injury pattern (p = 0.00052 and p < 0.0001, respectively). CONCLUSION: We found that two-thirds of service members with small bowel injuries also had a large bowel injury. One-third of the patients required diversion and two-thirds had more than one laparotomy. The pattern of bowel injury significantly affected the need for repeat laparotomy and fecal diversion.

Early traumatic brain injury screen in 6594 inpatient combat casualties.

INTRODUCTION: The purpose of this study was to review the inpatient traumatic brain injury (TBI) screening program at a Role IV regional resource trauma center. TBI has been coined the "signature wound" during current U.S. combat operations. All patients injured in Iraq or Afghanistan who transit through Landstuhl Regional Medical Center (LRMC) undergo an initial TBI screen regardless of anatomic injury. The incidence and factors associated with positive screening for concussion (physical event+alteration of consciousness (AOC)) and TBI diagnoses were examined. METHODS: A retrospective review of consecutively admitted patients to LRMC who underwent a TBI screen from 5/06 to 7/11 was performed. Patient characteristics, self-reported symptoms, and TBI diagnoses were analyzed. FINDINGS: Among 43,852 patients screened during the 5-year period, 6594 were admitted, of whom, 6590 received a complete TBI screen. Predominantly male (97.1%), the mean age was 26.7±7.4 yrs. The average GCS and ISS at admission were 13.9±2.8 and 10.1±8.6, respectively. Positively screened patients averaged 1.8 deployments, 69.5% experienced one or more blasts, 16.1% experienced one or more vehicular crashes, with 18.0% reporting a prior head injury. Of the 2805 (42.6%) who screened positive for possible concussion, 2393 (85.3%) were diagnosed with a concussion/TBI during their inpatient stay; the remaining 412 (14.7%) were identified by screening only. Of the screened positive patients, 1953 (69.6%) reported 1 or more current concussion/TBI-related symptoms; of those with symptom(s), 532 (27.2%) reported 5 or more. CONCLUSIONS: Early screening based on self-report identified a large number of patients admitted directly from the combat zone with possible deployment-related concussion and TBI symptoms. Such screening provides valuable information to guide decisions about early management and return to duty. LEVEL OF EVIDENCE: Level III, Therapeutic.

Automated control of endotracheal tube cuff pressure during simulated flight.

BACKGROUND: Successful mechanical ventilation requires that the airway be controlled by an endotracheal tube (ETT) with an inflatable cuff to seal the airway. Aeromedical evacuation represents a unique challenge in which to manage ETT cuffs. We evaluated three methods of automatic ETT cuff pressure adjustment during changes in altitude in an altitude chamber. METHODS: Size 7.5 and 8.0 mm ETTs that are currently included in the Critical Care Air Transport Team allowance standard were used for the evaluation. Three automatic cuff pressure controllers-Intellicuff, Hamilton Medical; Pyton, ARM Medical; and Cuff Sentry, Outcome Solutions-were used to manage cuff pressures. The fourth group had cuff pressure set at sea level without further adjustment. Each ETT was inserted into a tracheal model and taken to 8,000 feet and then to 16,000 feet at 2,500 ft/min. Baseline cuff pressure at sea level was approximately 25 cm H2O. RESULTS: Mean cuff pressure at both altitudes with both size ETTs was as follows: Control arm, 141 ± 64 cm H2O; Pyton, 25 ± 0.8 cm H2O; Cuff Sentry, 22 ± 0.3 cm H2O; and Intellicuff, 29 ± 6.6 cm H2O. The mean time that cuff pressure was >30 cm H2O using Intellicuff at both altitudes was 2.8 ± 0.8 minutes. Pressure differences from baseline in the control arm and with Intellicuff were statistically significant. Cuff pressure with the Cuff Sentry tended to be lower than indicated on the device. CONCLUSIONS: Mean cuff pressures were within the recommended range with all three devices. Intellicuff had difficulty regulating the cuff pressure initially with increases in altitude but was able to reduce the pressure to a safe level during the stabilization period at each altitude. The Pyton and Cuff Sentry allowed the least variation in pressure throughout the evaluation, although the Cuff Sentry set pressure was less than the actual pressure. LEVEL OF EVIDENCE: Therapeutic study, level V.

Rhabdomyolysis among critically ill combat casualties: Associations with acute kidney injury and mortality.

BACKGROUND: Rhabdomyolysis has been associated with poor outcomes in patients with traumatic injury, especially in the setting of acute kidney injury (AKI). However, rhabdomyolysis has not been systematically examined in a large cohort of combat casualties injured in the wars in Iraq and Afghanistan. METHODS: We conducted a retrospective study of casualties injured during combat operations in Iraq and Afghanistan who were initially admitted to the intensive care unit from February 1, 2002, to February 1, 2011. Information on age, sex, Abbreviated Injury Scale (AIS) score, Injury Severity Score (ISS), mechanism of injury, shock index, creatine kinase, and serum creatinine were collected. These variables were examined via multivariate logistic and Cox regression analyses to determine factors independently associated with rhabdomyolysis, AKI, and death. RESULTS: Of 6,011 admissions identified, a total of 2,109 patients met inclusion criteria and were included for analysis. Rhabdomyolysis, defined as creatine kinase greater than 5,000 U/L, was present in 656 subjects (31.1%). Risk factors for rhabdomyolysis identified on multivariable analysis included injuries to the abdomen and extremities, increased ISS, male sex, explosive mechanism of injury, and shock index greater than 0.9. After adjustment, patients with rhabdomyolysis had a greater than twofold increase in the odds of AKI. In the analysis for mortality, rhabdomyolysis was significantly associated with death until AKI was added, at which point it lost statistical significance. CONCLUSION: We found that rhabdomyolysis is associated with the development of AKI in combat casualties. While rhabdomyolysis was strongly associated with mortality on the univariate model and in conjunction with both ISS and age, it was not associated with mortality after the inclusion of AKI. This suggests that the effect of rhabdomyolysis on mortality may be mediated by AKI. LEVEL OF EVIDENCE: Prognostic and epidemiologic study, level III.

Hypoxemia during aeromedical evacuation of the walking wounded.

BACKGROUND: Hypobaric hypoxemia is a well-known risk of aeromedical evacuation (AE). Validating patients as safe to fly includes assessment of oxygenation status as well as oxygen-carrying capability (hemoglobin). The incidence and severity of hypoxemia during AE of noncritically injured casualties have not been studied. METHODS: Subjects deemed safe to fly by the validating flight surgeon were monitored with pulse oximetry from the flight line until arrival at definitive care. All subjects were US military personnel or contractors following traumatic injuries. Noninvasive oxygen saturation (SpO2), pulse rate, and noninvasive hemoglobin were measured every 5 seconds and recorded to electronic memory. Patient demographics and physiologic data were collected by chart abstraction from the Air Force Form 3899, patient movement record. The incidence and duration of hypoxemic events (SpO2 < 90%) and critical hypoxemic events were determined (SpO2 < 85%). RESULTS: Sixty-one casualties were evaluated during AE from Bagram Air Base to Landstuhl Regional Medical Center. The mean (SD) age was 26.2 (6) years, Injury Severity Score (ISS) was 8 (11), and mean SpO2 before AE was 96% (2%). The mean (SD) transport time was 9.3 (1.3) hours. Patients were monitored before AE for a brief period, yielding a total recording time of 10.28 hours. The mean (SD) hemoglobin at the time of enrollment was 13.2 (3.5) g/dL (9.4-18.0 g/dL). Hypoxemia (SpO2 < 90%) was seen in 55 (90%) of 61 subjects. The mean duration of SpO2 less than 90% was 44 minutes. The mean (SD) change in SpO2 from baseline to mean in-flight SpO2 was 4% (1.2%). Thirty-four patients (56%) exhibited an SpO2 less than 85% for 11.7 (15) minutes. CONCLUSION: Hypoxemia is a common event during AE of casualties. In patients with infection and concussion or mild traumatic brain injury, this could have long-term consequences. LEVEL OF EVIDENCE: Epidemiologic/prognostic study, level V.

Rhabdomyolysis and acute kidney injury in the injured war fighter.

BACKGROUND: Rhabdomyolysis is a recognized complication of traumatic injury. The correlation of an elevated creatine kinase (CK) level and the development of acute kidney injury (AKI) has been studied in the civilian population. We sought to review the prevalence of rhabdomyolysis in injured war fighters and determine if peak CK levels correlate with AKI. METHODS: This is a retrospective cohort study of patients admitted at a US military treatment facility from January to November 2010. Inclusion criteria were active duty patients transported after explosive, penetrating, or blunt injury. Patients with burns or non-trauma-related admissions were excluded. Rhabdomyolysis was defined as a CK level greater than 5,000 U/L. AKI was defined using the Kidney Disease: Improving Global Outcomes classification. Mann-Whitney U-tests were used to determine the significance for continuous data. Correlations were determined using Spearman's ρ. Significance was set at p < 0.05. RESULTS: Of the 318 patients included in our analysis, 310 (98%) were male, and the median age was 24 years (21-28 years). Blast was the predominant mechanism of injury (71%), with a median Injury Severity Score (ISS) of 22 (16-29). Rhabdomyolysis developed in 79 patients (24.8%). The median peak CK for all patients was 4,178 U/L and ranged from 208 U/L to 120,000 U/L. Stage 1, 2, and 3 AKI developed in 56 (17.6%), 3 (0.9%), and 7 (2.2%) patients, respectively. There was a weak but statistically significant correlation between peak CK and AKI (r = 0.26, p < 0.05). CONCLUSION: Elevated peak CK levels in the injured war fighter are weakly associated with the development of AKI but are not predictive. The development of clinical practice guidelines would help standardize treatment for rhabdomyolysis in combat casualties and would allow for standardized comparisons in future work. LEVEL OF EVIDENCE: Epidemiologic/prognostic study, level III.

Early implementation of continuous renal replacement therapy optimizes casualty evacuation for combat-related acute kidney injury.

BACKGROUND: The purpose of this report was to review the initial use and feasibility of continuous renal replacement therapy (CRRT) among combat casualties in a war zone. Although rapid evacuation to more advanced levels of care has emerged as the standard approach, life-threatening sequelae of acute kidney injury (AKI) can preclude safe patient evacuation. For the first time in US combat casualty care, a sustained, intensivist-led CRRT program was initiated during 2010 at an Air Force theater hospital. METHODS: A prospective study of consecutive US service members (USSMs) who developed combat-related renal failure and underwent CRRT at the Craig Joint Theater Hospital was undertaken. Baseline patient characteristics, indications for CRRT, laboratory values, and outcomes were evaluated. RESULTS: Nine USSMs were treated during 14-months. All were male, with a mean (SD) age of 28 (7) years and mean (SD) Injury Severity Score (ISS) of 34 (12). The dominant mechanism was blast injury (8 of 9), followed by gunshot wound (1 of 9). Most patients were Acute Kidney Injury Network (AKIN) 3 and all developed critical hyperkalemia (mean [SD], peak K⁺ 6.4 [0.4]). The peak plasma creatinine ranged from 1.4 mg/dL to 4.2 mg/dL (mean [SD], 3.3 [0.9] mg/dL). Patients had a mean (SD) of 17.6 [8.1] hours of CRRT before evacuation to higher echelons of care. All USSMs survived to achieve safe evacuation from the combat zone to the regional trauma center in Landstuhl, Germany (Landstuhl Regional Medical Center). Three patients died of multiorgan failure at Landstuhl Regional Medical Center. Six patients survived to undergo additional treatment in the United States. CONCLUSION: Intensivist-led CRRT is an effective therapeutic adjunct in the treatment of combat-related AKI. Provision of this extracorporeal therapy provides physiologic stabilization of casualties who might otherwise succumb to the sequelae of combat-related renal failure. These findings suggest that a self-sustaining CRRT program can be successfully implemented in combat support hospitals.

Transfusion of red blood cells in patients with a prehospital Glasgow Coma Scale score of 8 or less and no evidence of shock is associated with worse outcomes.

BACKGROUND: Red blood cell transfusion practices vary, and the optimal hemoglobin for patients with traumatic brain injury has not been established. METHODS: A retrospective review of data collected prospectively as part of a randomized, controlled trial involving emergency medical service agencies within the Resuscitation Outcomes Consortium was conducted. In patients with a Glasgow Coma Scale (GCS) score of 8 or less without evidence of shock (defined by a systolic blood pressure [SBP] < 70 or SBP of 70 to 90 with a heart rate ≥108), the association of red blood cell transfusion with 28-day survival, adult respiratory distress syndrome-free survival, Multiple Organ Dysfunction Score (MODs), and 6-month Extended Glasgow Outcome Scale (GOSE) score was modeled using multivariable logistic regression with robust SEs adjusting for age, sex, injury severity (Injury Severity Score [ISS]), initial GCS score, initial SBP, highest field heart rate, penetrating injury, fluid use, study site, and hemoglobin (Hgb) level. RESULTS: A total of 1,158 patients had a mean age of 40, 76% were male, and 98% experienced blunt trauma. The initial mean GCS score was 5, and the initial mean SBP was 134. The mean head Abbreviated Injury Scale (AIS) score was 3.5. A categorical interaction of red blood cell transfusion stratified by initial Hgb showed that when the first Hgb was greater than 10 g/dL, volume of packed red blood cell was associated with a decreased 28-day survival (odds ratio, 0.83; 95% confidence interval [CI], 0.74-0.93; p < 0.01) and decreased adult respiratory distress syndrome-free survival (odds ratio, 0.82; 95% CI, 0.74-0.92; p < 0.01). When the initial Hgb was greater than 10, each unit of blood transfused increased the MODs by 0.45 (coefficient 95% CI, 0.19-0.70; p < 0.01). CONCLUSION: In patients with a suspected traumatic brain injury and no evidence of shock, transfusion of red blood cells was associated with worse outcomes when the initial Hgb was greater than 10. LEVEL OF EVIDENCE: Therapeutic study, level III.

Cellular and molecular regulation of skeletal muscle side population cells.

Muscle progenitor cells (satellite cells) function in the maintenance and repair of adult skeletal muscle. Side population (SP) cells are enriched in repopulating activity and also reside in adult skeletal muscle. In this study, we observed that Abcg2 is a determinant of the SP cell phenotype. Using reverse transcription polymerase chain reaction and immunohistochemical techniques, we localized Abcg2-expressing cells in the interstitium and in close approximation to the vasculature of adult skeletal muscle. Muscle SP cells are able to differentiate into myotubes and increase in number after cardiotoxin-induced muscle injury. Similar to myogenic progenitor cells, muscle SP cells express Foxk1 and are decreased in number in Foxk1 mutant skeletal muscle. Using emerging technologies, we examine the molecular signature of muscle SP cells from normal, injured, and Foxk1 mutant skeletal muscle to define common and distinct molecular programs. We propose that muscle SP cells are progenitor cells that participate in repair and regeneration of adult skeletal muscle.