TBIs and their sequelae have long been associated with wars.
Brain Neurotrauma: Molecular, Neuropsychological, and Rehabilitation Aspects: Chapter 2: Combat TBI History, Epidemiology, and Injury Modes* by Ralph G DePalma offers a brief and fascinating historic overview, starting with Iliad accounts of TBIs, PTSD, and post-war mental illness from the legendary Trojan War. This chapter contains a wealth of links to pieces on "shell shock" blast injuries of WWI and WWII.
Between 2000-2012, 255,852 US military service members sustained TBIs. 83% of these were mild, and 80% were estimated to have occurred in non-deployed settings, for example during training, sports, or vehicle accidents. A New York Times investigation examined TBI rates amongst US artillery companies who conducted heavy shelling campaigns against ISIS during the 2016-2017 anti-ISIS offensive. Some soldiers fired over 10,000 artillery shells in the space of just a few months. A military-ordered study of Fox battery, 2nd Battalion, 10th Marines, found that half of the unit had sustained TBIs during artillery firing operations. Study of microscopic damage caused by repeated lower-level blast exposures, or "Chronic Traumatic Encephalopathy" (CTE) is a young science. Under pressure from Veteran's groups, between 2018-2022 Congress passed bills ordering the Pentagon to start a large "Warfighter Brain Health Initiative". This initiative will endeavor to measure blast exposure and create protocols to protect troops. A growing pool of data suggests that safe blast exposure levels may be much lower than was previously assumed. The issue of CTE recently featured in the headlines; the brain of Robert Card, a former military grenade instructor who had a sudden onset of psychosis at age 40 and committed a mass shooting in Maine, will be examined for signs of blast-related CTE.
Massive use of heavy artillery in the current Ukraine War (firing up to 7,000 shells/day by the Ukraine side, and up to 60,000/day by the Russians), along with increased blast survivability made possible by modern medicine and armor, has created potential for long-term TBI impacts on a scale not seen since WWII. Heavy use of thermobaric weapons increases the risk of blast-wave injury.
Manpower shortages mean a lack of post-injury recovery time away from the front. Casualties with mild TBIs are often re-subjected to repeated blasts as soon as a day or two post-injury. As these challenges are likely to be seen in other potential future near-peer conflicts, it can be hoped that Ukraine will systematically work to gather data and implement measures to improve TBI outcomes, and share lessons learned with overseas medical practitioners.
In his book, Ralph G. DePalma writes: "Closed blast TBI has been postulated to relate to vascular surge from the thorax through the neck vessels, air embolism, and piezoelectric currents generated between the skull and the shock wave (Johnson, 2010). Viscoelastic dynamic rippling of the skull secondary to the blast has been postulated based on modeling (Moss et al., 2009). Interactions between the advancing shock wave and blast overpressure, the configuration of the skull, and the brain, including its meninges and cerebrospinal fluid, are complex and cause heterogeneous injury patterns including brain swelling, cerebral vasospasm (Armonda et al., 2006), and diffuse axonal injury (DAI) with disruption across attentional networks (Vakhtin et al., 2013)... Kucherov et al. (2012b) postulated a novel mechanism of primary nonimpact blast injury. Calculations show a dramatic shortening the linear scale of the blast shock wave as it passes through brain tissue. The example of a shock wave interacting with water was used, with the assumption that brain tissue’s physical properties, on the whole, are quantitatively similar to the properties of water. CSF is even closer to water in its physical characteristics. The proposed mechanism, based upon the dynamic behavior of phonons in water, predicts the length scale of damage to be ~30–200 nm. This phonon-based model recently has been shown to accurately describe failure waves in brittle solids (Kucherov, 2012a). A shock wave traveling through the brain is characterized by a shock front, which is a thermodynamic boundary between shocked and nonshocked states of water. The shock front thickness depends on several parameters and decreases in dimensions relative to the intensity of the shock or blast. For intense shocks, the shock wave front equals the interatomic spacing in the specific medium of propagation. The difference between the two states, the blast wave front and the blast wave pressure, is that some of the energy gets deposited behind the shock front, causing a change in thermodynamic parameters of pressure, volume (density), and temperature. For intense shocks, the change in these parameters becomes pronounced, predicting nanoscale damage occurring within microseconds, in contrast to acceleration injuries having durations measured in milliseconds."
A TBI can present as loss or alteration of consciousness at the time of the injury, a confused or disorientated state and/or memory loss during the first 24 hours, and/or abnormal brain imaging. GCS of 13-15 characterizes a mild TBI, 9-12 characterizes a moderate TBI, and 3-8 characterize a severe TBI.
A growing body of evidence shows that prehospital care greatly affects outcomes in TBI patients. While the initial trauma sustained by the patient results in a certain level of irreversible brain cell death, additional secondary injury due to hypotension and hypoxia may be preventable during pre-hospital care.
The EPIC project is a collaboration between the University of Arizona, Arizona Department of Public Health, and over 130 Arizona Fire Departments, and ground and air EMS transport services. The goal of the EPIC Project is to "dramatically increase the number of severe TBI victims who survive with good neurologic outcome by thoroughly implementing the national EMS TBI guidelines." EPIC trained 11,000 EMTs and Paramedics, with emphasis on avoiding hypotension and hypoxia, and maintaining eucapnia. 21,852 patients were included in the effort between 2009-2015. After implementation of the EPIC guidelines, patient survival-to-discharge doubled. Survival tripled amongst TBI patients who required intubation.
A 2017 study published in the Annals of Emergency Medicine found that odds of death increased by 2.5x with a single episode of hypoxia <90%, by 3x with an episode of hypotension <90, and by 6.1x in patient with at least one episode of both hypoxia and hypotension. EPIC guidelines call for pre-oxygenation, with the aim of maintaining an O2 level of 100%. This should be done by applying immediate and continuous high-flow O2 via NRB, starting prior to extrication if applicable. In TBI patients, the risks from short-term hyperoxia are dwarfed by the risks from potential hypoxia.
The target capnography reading is 35-45. It is crucial to avoid hyperventilation, which reduces blood flow and oxygenation of brain tissues. A possible exception is during active brain herniation. Current TCCC guidelines still recommend hyperventilation at 20/minute for patients with signs of brain herniation. However, EPIC guidelines recommend against hyperventilation in any situation, having found that it did not enhance survival to discharge in herniating patients, and caused active harm to non-herniating patients who presented with herniation-like signs.
Opiate pain medications and benzodiazepines may cause blood pressure to drop suddenly in patients with compensated shock, and should be used with extreme caution.
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