Early in-theater management of combat-related traumatic brain injury: A prospective, observational study to identify opportunities for performance improvement

Hyperventilation During Manual Ventilation Can Be Reduced Using a Novel Ventilator but Not With Education Interventions

INTRODUCTION

Traumatic brain injury (TBI) is the leading cause of combat casualties in modern war with an estimated 20% of casualties experiencing head injury. Since the release of the Brain Trauma Foundation's Guidelines for the Management of Severe Traumatic Brain Injury in 1995, recommendations for management of TBI have included the avoidance of routine hyperventilation. However, both published and anecdotal data suggest that many patients with TBI are inappropriately ventilated during transport, thereby increasing the risk of morbidity and mortality from secondary brain injury.

MATERIALS AND METHODS

Enlisted Air Force personnel with prior emergency medical technician training completing a 3-week trauma course were evaluated on their ability to provide manual ventilation. Participants provided manual ventilation using either an in-situ endotracheal tube (ETT) or standard face mask on a standardized simulated patient manikin with TBI on the first and last days of the course. Manual ventilation was provided via a standard manual ventilator and a novel manual ventilator designed to limit tidal volume (VT) and respiratory rate (RR). Participants were given didactic and hands-on training on the third day of the course. Half of the participants were given simulator feedback during the hands-on training. All students provided 2 minutes of manual ventilation with each respirator. Data were collected on the breath-to-breath RR, VT, and peak airway pressures generated by the participant for each trial and were averaged for each trial. A minute ventilation (MV) was then derived from the calculated RR and VT.

RESULTS

One hundred fifty-six personnel in the trauma course were evaluated in this study. Significant differences were found in the participant's performance with manual ventilation with the novel compared to the traditional ventilator. Before training, MV with the novel ventilator was less than with the traditional ventilator by 2.1 ± 0.4 L/min (P = .0003) and 1.6 ± 0.5 L/min (P = .0489) via ETT and face mask, respectively. This effect persisted after training with a difference between the devices of 1.8 ± 0.4 L/min (P = .0069) via ETT. Both traditional education interventions (didactics with hands-on training) and simulator-based feedback did not make a significant difference in participant's performance in delivering MV.

CONCLUSIONS

The use of a novel ventilator that limits RR and VT may be useful in preventing hyperventilation in TBI patients. Didactic education and simulator-based feedback training may not have significant impact on improving ventilation practices in prehospital providers.

[Current mortality from war injuries-A narrative review]

BACKGROUND

The war in Ukraine has led to a strategic reorientation of the German Armed Forces towards national and alliance defense. This has also raised the need for medical and surgical adaptation to scenarios of conventional warfare. In order to develop appropriate and effective concepts it is necessary to identify those war injuries that are associated with a relevant primary and secondary mortality and that can be influenced by medical measures (potentially survivable injuries).

OBJECTIVE

The aim of this selective literature review was to identify war injuries with high primary and secondary mortality.

METHODS

A selective literature review was performed in the PubMed® database with the search terms war OR combat AND injury AND mortality from 2001 to 2023. Studies including data of war injuries and associated mortality were included.

RESULTS

A total of 33 studies were included in the analysis. Severe traumatic brain injury and thoracoabdominal hemorrhage were the main contributors to primary mortality. Injuries to the trunk, neck, traumatic brain injury, and burns were associated with relevant secondary mortality. Among potentially survivable injuries, thoracoabdominal hemorrhage accounted for the largest proportion. Prehospital blood transfusions and short transport times significantly reduced war-associated mortality.

CONCLUSION

Control of thoracoabdominal hemorrhage has the highest potential to reduce mortality in modern warfare. Besides that, treatment of traumatic brain injury, burns and neck injuries has a high relevance in reducing mortality. Hospitals of the German Armed Forces need to focus on these requirements.

Recombinant Erythropoietin Induces Oligodendrocyte Progenitor Cell Proliferation After Traumatic Brain Injury and Delayed Hypoxemia

Traumatic brain injury (TBI) can result in axonal loss and demyelination, leading to persistent damage in the white matter. Demyelinated axons are vulnerable to pathologies related to an abnormal myelin structure that expose neurons to further damage. Oligodendrocyte progenitor cells (OPCs) mediate remyelination after recruitment to the injury site. Often this process is inefficient due to inadequate OPC proliferation. To date, no effective treatments are currently available to stimulate OPC proliferation in TBI. Recombinant human erythropoietin (rhEPO) is a pleiotropic neuroprotective cytokine, and its receptor is present in all stages of oligodendroglial lineage cell differentiation. Therefore, we hypothesized that rhEPO administration would enhance remyelination after TBI through the modulation of OPC response. Utilizing a murine model of controlled cortical impact and a primary OPC culture in vitro model, we characterized the impact of rhEPO on remyelination and proliferation of oligodendrocyte lineage cells. Myelin black gold II staining of the peri-contusional corpus callosum revealed an increase in myelinated area in association with an increase in BrdU-positive oligodendrocytes in injured mice treated with rhEPO. Furthermore, morphological analysis of OPCs showed a decrease in process length in rhEPO-treated animals. RhEPO treatment increased OPC proliferation after in vitro CSPG exposure. Erythropoietin receptor (EPOr) gene knockdown using siRNA prevented rhEPO-induced OPC proliferation, demonstrating that the rhEPO effect on OPC response is EPOr activation dependent. Together, our findings demonstrate that rhEPO administration may promote myelination by increasing oligodendrocyte lineage cell proliferation after TBI.

Outcomes Following Penetrating Brain Injuries in Military Settings: A Systematic Review and Meta-Analysis

OBJECTIVE

While neurosurgeons are experienced in treating penetrating brain injuries (PBIs) in civilian settings, much less is known about management and outcomes of PBIs in military settings.

METHODS

A systematic review was performed according to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Data extracted included surgical management, age, gender, location/type of injury, initial Glasgow Coma Scale (GCS) score, and outcomes. The primary outcomes were last reported Glasgow Outcome Score (GOS) and mortality. The secondary outcomes included central nervous system infections, seizures, and cerebrospinal fluid leak/fistula. Odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were used for outcome analysis.

RESULTS

Twelve studies with 1738 patients treated for PBIs in military settings were included. The weighted mean age was 27.8 years, 86.7% were male, and 64.3% underwent neurosurgical intervention. Most patients (64.3%) presented with a GCS score >8, while 31.0% presented in a coma (GCS score <8). Over a median last follow-up time of 9 months, 68.6% achieved a favorable (GOS = 4-5) outcome and 34.2% achieved a poor (GCS score = 1-3) outcome. The overall mortality was 18.0%. A meta-analysis was performed using 5 of 12 studies to evaluate the effect of the presenting GCS score on primary outcomes. Patients with an initial GCS score <8 had statistically significant lower odds of a favorable (GOS = 4-5) outcome (OR: 0.03; 95% CI: 0.00-0.19; P: 0.000) and higher odds of mortality (OR: 28.46; 95% CI: 8.62-94; P: 0.000) than patients with an initial GCS score >8. The pooled rates of central nervous system infection, seizures, and cerebrospinal fluid leak/fistula were 13.8%, 13.2%, and 5.4%, respectively.

CONCLUSIONS

In this first systematic review and meta-analysis of outcomes following combat-related PBIs, a GCS score >8 at presentation was found to be an important predictor of a favorable GOS and decreased mortality.

Patients With Traumatic Brain Injury Transported by Critical Care Air Transport Teams: The Influence of Altitude and Oxygenation during Transport

INTRODUCTION

Traumatic brain injuries (TBIs) are life-threatening, and air transport of patients with TBI requires additional considerations. To mitigate the risks of complications associated with altitude, some patients fly with a cabin altitude restriction (CAR) to limit the altitude at which an aircraft's cabin is maintained. The goal of this study was to examine the effects of CARs on patients with TBI transported out of theater via Critical Care Air Transport Teams.

MATERIALS AND METHODS

We conducted a retrospective chart review of patients with moderate-to-severe TBI evacuated out of combat theater to Landstuhl Regional Medical Center via Critical Care Air Transport Teams. We collected demographics, flight and injury information, procedures, oxygenation, and outcomes (discharge disposition and hospital/ICU/ventilator days). We categorized patients as having a CAR if they had a documented CAR or maximum cabin altitude of 5,000 feet or lower in their Critical Care Air Transport Teams record. We calculated descriptive statistics and constructed regression models to evaluate the association between CAR and clinical outcomes.

RESULTS

We reviewed the charts of 435 patients, 31% of which had a documented CAR. Nineteen percent of the sample had a PaO2 lower than 80 mm Hg, and 3% of patients experienced a SpO2 lower than 93% while in flight. When comparing preflight and in-flight events, we found that the percentage of patients who had a SpO2 of 93% or lower increased for the No CAR group, whereas the CAR group did not experience a significant change. However, flying without a CAR was not associated with discharge disposition, mortality, or hospital/ICU/ventilator days. Further, having a CAR was not associated with these outcomes after adjusting for additional flights, injury severity, injury type, or preflight head surgery.

CONCLUSIONS

Patients with TBI who flew with a CAR did not differ in clinical outcomes from those without a CAR.

The Prehospital Evaluation and Care of Moderate/Severe TBI in the Austere Environment

Increased resource constraints secondary to a smaller medical footprint, prolonged evacuation times, or overwhelming casualty volumes all increase the challenges of effective management of traumatic brain injury (TBI) in the austere environment. Prehospital providers are responsible for the battlefield recognition and initial management of TBI. As such, targeted education is critical to efficient injury recognition, promoting both provider readiness and improved patient outcomes. When austere conditions limit or prevent definitive treatment, a comprehensive understanding of TBI pathophysiology can help inform acute care and enhance prevention of secondary brain injury. Field deployable, noninvasive TBI assessment and monitoring devices are urgently needed and are currently undergoing clinical evaluation. Evidence shows that the assessment, monitoring, and treatment in the first few hours and days after injury should focus on the preservation of cerebral perfusion and oxygenation. For cases where medical management is inadequate (eg, evidence of an enlarging intracranial hematoma), guidelines have been developed for the performance of cranial surgery by nonneurosurgeons. TBI management in the austere environment will continue to be a challenge, but research focused on improving evidence-based monitoring and therapeutic interventions can help to mitigate some of these challenges and improve patient outcomes.

N-acetylcysteine reduces brain injury after delayed hypoxemia following traumatic brain injury

Preclinical investigations into neuroprotective agents for traumatic brain injury (TBI) have shown promise when administered before or very early after experimental TBI. However clinical trials of therapeutics demonstrating preclinical efficacy for TBI have failed to replicate these results in humans, a lost in translation phenomenon. N-acetylcysteine (NAC) is a potent anti-oxidant with demonstrated efficacy in pre-clinical TBI when administered early after primary injury. Utilizing our clinically relevant mouse model, we hypothesized that NAC administration in a clinically relevant timeframe could improve the brain's resilience to the secondary insult of hypoxemia. NAC or vehicle administered daily starting 2 h prior to hypoxemia (24 h after controlled cortical impact) for 3 doses in male mice reduced short-term axonal injury and hippocampal neuronal loss. Six month behavioral assessments including novel object recognition, socialization, Barnes maze, and fear conditioning did not reveal performance differences between sham controls and injured mice receiving NAC or saline vehicle. At 7 months after injury, NAC administered mice had reduced hippocampal neuronal loss but no reduction in lesion volume. In summary, our preclinical trial to test the neuroprotective efficacy of NAC against a secondary hypoxic insult after TBI demonstrated short and long-term neuropathological evidence of neuroprotection but a lack of detectable differences in long-term behavioral assessments between sham controls and injured mice limits conclusions on its impact on long-term neurobehavioral outcomes.

Management of Penetrating Traumatic Brain Injury: Operative versus Non-Operative Intervention

BACKGROUND

Penetrating traumatic brain injury (pTBI) is the most lethal form of TBI, with mortality rates as high as 90%. This high mortality rate leads many providers to feel that the treatment of pTBI is futile. Contrary to this point of view, several studies have shown that victims of pTBI who present with a Glasgow Coma Scale (GCS) ≥6 have a reasonable chance of a meaningful outcome. This study sought to investigate outcomes of pTBI patients based on GCS score who underwent neurosurgical intervention (craniotomy or craniectomy) and compare them with patients who did not undergo surgical intervention.

MATERIALS AND METHODS

The study represents a secondary analysis of the data that were collected from 2006 to 2016 from 17 institutions as part of a multi-center study, investigating clinical outcomes for adult patients sustaining pTBI and surviving >72 h. Patients were divided into those with GCS 3-5 and those with GCS ≥6. Within these groups, patients were stratified by whether they received surgical intervention, compared with standard non-surgical care. Patient level data (age and gender), clinical data (Injury Severity Score and Abbreviated Injury Score), GCS on admission, post-op infection rates, and outcomes data (mortality, length of stay [LOS], intensive care unit LOS) were collected. Both groups were compared using independent sample t-test or chi-squared test.

RESULTS

Seven hundred twenty patients with pTBI were identified over 11 y, out of which 336 (46.7%) underwent surgery. The mean Injury Severity Score and Abbreviated Injury Score on admission were higher in the surgical intervention group than their non-surgical counterpart in patients with a GCS ≥6 (P < 0.0001). Patients with GCS of 3-5 with surgical intervention demonstrated a higher survival rate than non-surgical patients (P < 0.0001). In the GCS ≥6 group, surgical intervention did not impact near-term mortality. Intensive care unit LOS was significantly longer in the surgical intervention group in patients with GCS ≥ 6 (P < 0.0001) and GCS of 3-5 (P < 0.0001), as was total hospital LOS (P < 0.0001). Patients with a GCS 3-5 and ≥6 who underwent surgical intervention were more likely to develop a central nervous system infection (P = 0.016; P = 0.017).

CONCLUSIONS

Surgical intervention in pTBI patients with GCS 3-5 results in improved mortality but comes at a cost of increased resource utilization in the form of longer LOS and higher infection rate. On the other hand, in patients with GCS ≥6, surgery does not provide significant benefits in patient survival. Future prospective studies providing insight as to the impact of surgery on the resource utilization and quality of survival would be beneficial in determining the need for surgical intervention in this population.

Tactical Neurocritical Care

Neurocritical care is usually practiced in the comfort of an intensive care unit within a tertiary care medical center. Physicians deployed to the frontline with the US military or allied military are required to use their critical care skills and their neurocritical skills in austere environments with limited resources. Due to these factors, tactical critical care and tactical neurocritical care differ significantly from traditional critical care. Operational constraints, the tactical environment, and resource availability dictate that tactical neurocritical care be practiced within a well-defined, mission-constrained framework. Although limited interventions can be performed in austere conditions, they can significantly impact patient outcome. This review focuses on the US Army approach to the patient requiring tactical neurocritical care specifically point of injury care and care during transportation to a higher level of care.

[Topical respiratory strategies in neurocritical care]

Management of the respiratory tract and maintenance of adequate gas exchange are the basic goals of critical care. Injury to the nervous system is often accompanied by development of respiratory disorders. On the other hand, changes in the gas composition of arterial blood can cause brain damage. In addition, approaches to the patient with respiratory failure, which are used in general critical care and neurocritical care, may differ. The presented literature review is devoted to modern respiratory strategies used in neurocritical care.

Delayed Hypoxemia after Traumatic Brain Injury Exacerbates Long-Term Behavioral Deficits

Hypoxemia during initial stabilization of patients with severe traumatic brain injury (TBI) has been associated with poorer outcomes. However, the effects of delayed hypoxemia occurring during intensive care post-TBI on outcome is unclear. Pre-clinical models of TBI have rarely shown cognitive or behavioral deficits beyond 6 weeks post-injury and commonly have not included modeling of secondary insults. We have previously developed a murine model of TBI followed by delayed hypoxemia to model the secondary insult of hypoxemia and brain hypoxia occurring in the intensive care setting. Understanding long-term effects of delayed hypoxemia post-TBI in our murine model is critical for future testing of candidate therapeutics targeting secondary brain hypoxia. For this study, forty 5-week-old male mice were randomized to controlled cortical impact (CCI; N = 24) or sham surgery (N = 16). One day later, awake animals were randomized to 60 min of hypoxemia or normoxemia. Six months after initial injury, animals underwent behavior testing (Morris water maze, social interaction, and tail suspension) before euthanasia for immunohistochemistry (IHC) assessments. At 6 months post-injury, mice experiencing CCI and hypoxemia (CCI+H) had longer swim distances to the hidden platform (51 cm) compared to CCI alone (26 cm) or sham animals (22 cm). During social interaction assessments, CCI + H mice spent less time interacting with novel stimulus mice (79 sec) than CCI alone (101 sec) or sham animals (139 sec). CCI + H had larger lesion volumes compared to CCI alone (14.0% vs. 9.9%; p < 0.003). Glial fibrillary acidic protein IHC at 6 months post-injury demonstrated increased astrogliosis in the ipsilateral white matter of CCI + H compared to CCI alone. To summarize, this clinically relevant model of delayed hypoxia post-TBI resulted in long-term behavioral deficits and evidence of exacerbated structural injury.

Delayed Hypoxemia Following Traumatic Brain Injury Exacerbates White Matter Injury

Hypoxemia immediately following traumatic brain injury (TBI) has been observed to exacerbate injury. However, it remains unclear whether delayed hypoxemia beyond the immediate postinjury period influences white matter injury. In a retrospective clinical cohort of children aged 4-16 years admitted with severe TBI, 28/74 (35%) patients were found to experience delayed normocarbic hypoxemia within 7 days of admission. Based on these clinical findings, we developed a clinically relevant mouse model of TBI with delayed hypoxemia by exposing 5-week old (adolescent) mice to hypoxic conditions for 30 minutes starting 24 hours after moderate controlled cortical impact (CCI). Injured mice with hypoxemia had increased axonal injury using both β-amyloid precursor protein and NF200 immunostaining in peri-contusional white matter compared with CCI alone. Furthermore, we detected increased peri-contusional white matter tissue hypoxia with pimonidazole and augmented astrogliosis with anti-glial fibrillary acidic protein staining in CCI + delayed hypoxemia compared with CCI alone or sham surgery + delayed hypoxemia. Microglial activation as evidenced by Iba1 staining was not significantly altered by delayed hypoxemia. These clinical and experimental data indicate the prevention or amelioration of delayed hypoxemia effects following TBI may provide a unique opportunity for the development of therapeutic interventions to reduce axonal injury and improve clinical outcomes.