Traumatic brain injury (TBI) is a major cause of death and disability, but invasive intracranial pressure (ICP) monitoring is risky, and current non-invasive methods lack the resolution and reliability needed for continuous clinical use. We present a multidimensional, non-invasive single-electrode capacitance (SEC) sensing system for continuous TBI monitoring. Carbon-nanotube paper composite (CPC) electrodes detect regional ICP changes through permittivity variations driven by cerebrovascular pulsations, cerebrospinal fluid (CSF) thickness changes, and brain tissue microvibrations. Surrogate tissue model testing confirms sensitivity to CSF layer thickness, water layer height, vessel wall thickness, and vessel diameter. In vivo pig testing, we analyze the correlation between multisite SEC signals and ICP to identify potential novel sensing metrics. In TBI experiments, these metrics are further evaluated by examining dynamic, cross-hemispheric relationships using four SEC sensors to capture spatially resolved pathophysiology before and after injury. Statistical and machine-learning (ML) approaches are applied to derive novel digital markers and to estimate conventional indices of cerebral autoregulation and intracranial compliance from non-invasive features. Together, this wearable system enables portable, spatially resolved neurocritical monitoring across diverse clinical environments.

Background: New strategies are needed to mitigate further tissue injury during traumatic limb ischemia in cases requiring damage control resuscitation (DCR). Little is known about the pathophysiology and injury course in acute limb ischemia (ALI) with DCR in polytraumatized casualties. We therefore investigated the effects of therapeutic limb hypothermia in a swine model of ALI and DCR. Methods: Fifteen swine underwent a published 6-h DCR protocol of hemorrhage and then resuscitation. After hemorrhage, animals were randomized to 5 degrees C or 15 degrees C cooling of one hindlimb; the contralateral limb serving as an uncooled control. Physiologic variables, limb temperature, and limb tissue metabolites (glucose, lactate, and pyruvate) were measured throughout the DCR protocol. Muscle and nerve biopsies were obtained after the 6-h protocol. Results: Lactate and pyruvate levels were significantly lower in the cooled limbs than in the uncooled control limbs but did not differ between the 5 degrees C and 15 degrees C groups. Tissue glucose levels did not differ between the 5 degrees C group, the 15 degrees C group, and controls. Mean histologic muscle score was significantly higher in the 5 degrees C group than in controls (P = 0.03). Mean nerve histology scores did not differ between the 5 degrees C and paired control limbs, or between the mean muscle and nerve histology scores of the 15 degrees C and paired control limbs. Conclusion: Cooling to 15 degrees C significantly reduced local tissue metabolites compared to paired controls, while producing no significant increase in histologic damage, whereas cooling to 5 degrees C increased histologic muscle damage. These results suggest an approach to prevention of ischemic injury through local hypothermia but warrant further functional testing.

Sleep deficiency (SD) is a growing concern for brain health, yet objective tools to assess chronic SD are limited. Intracranial pressure (ICP), which fluctuates with circadian cycles, sleep stages, and sleep events like obstructive sleep apnea, offers a promising biomarker for assessing SD. However, noninvasive ICP monitoring remains a major challenge, limiting the ability to validate this relationship. This study introduces a wearable sleep mask embedded with nanostructured capacitive sensors made from carbon nanotube-paper composites (CPC) to measure regional ICP (r-ICP) in a noninvasive manner. A single-electrode capacitance (SEC) sensing model is validated in pigs, showing correlations with ventricular ICP based on mean, respiratory (RS), and heartbeat (HB) band signals. In humans, r-ICP responses during postural changes and Valsalva maneuvers (VM) are confirmed to have physiological relevance. We further investigate r-ICP patterns in a nap study to explore potential markers of sleep quality. Machine learning (ML) analysis of nap studies reveals correlations between r-ICP patterns and chronic SD. These results demonstrate the potential of this non-invasive platform for monitoring sleep physiology and broader neurological health.

Background: Severe injury induces systemic microvascular impairment that reduces microvascular blood flow (MBF), even after resuscitation to normal blood pressure. These changes are associated with organ dysfunction and death, but the underlying causes and potential therapeutic approaches to address them remain unclear. Two possible contributors are hyperadhesive von Willebrand factor (VWF) secretion from an activated endothelium and oxidative modification of hemostatic proteins. N-acetylcysteine has been shown to address both of these processes and increase MBF in other disease states with similar features. Methods: Anesthetized, male Sprague-Dawley rats were subjected to a standardized polytrauma and pressure-targeted catheter hemorrhage. They then received either no treatment (control) or a single bolus of N-acetylcysteince (NAC), followed by autologous whole blood transfusion. Renal MBF was measured using contrast-enhanced ultrasound at prespecified time points. VWF multimer gels and other laboratory studies were performed. Histologic analysis of vascular thrombi was also performed on uninjured tissue from rats undergoing either this trauma protocol or a sham procedure. Results: NAC increased MBF at 3 h after resuscitation. This was accompanied by a decrease in VWF multimer size that was not seen in the control group. Histologic data showed an overall increase in systemic thrombus burden associated with trauma. Conclusions: NAC improves renal MBF, possibly by reducing VWF multimer size and reducing microthrombus burden. This is significant both mechanistically and therapeutically. It sheds light on the possible pathways involved in causing microvascular obstruction after trauma and identifies possible treatment approaches that could be developed further. Ultimately, targeting these pathways could move us closer to resuscitation strategies that optimize vital organ MBF.

Background: After severe injury, optical measures of microvascular blood flow (MBF) decrease and do not normalize with resuscitation to normal blood pressure. These changes are associated with organ dysfunction, coagulopathy, and death. However, the pathophysiology is not well understood. Several possible pathways could also contribute to the development of trauma-induced coagulopathy (TIC). A small-animal model of trauma-related MBF derangement that persists after resuscitation and includes TIC would facilitate further study. Parametric contrast-enhanced ultrasound (CEUS) is particularly advantageous in this setting, because it noninvasively assesses MBF in large, deep vascular beds. We sought to develop such a model, measuring MBF with CEUS. Methods: Sixteen male Sprague-Dawley rats were anesthetized, ventilated, and cannulated. Rats were subjected to either no injury (sham group) or a standardized polytrauma and pressure-targeted arterial catheter hemorrhage with subsequent whole blood resuscitation (trauma group). At prespecified time points, CEUS measurements of uninjured quadriceps muscle, viscoelastic blood clot strength, and complete blood counts were taken. Results: After resuscitation, blood pressure normalized, but MBF decreased and remained low for the rest of the protocol. This was primarily driven by a decrease in blood volume with a relative sparing of blood velocity. Viscoelastic blood clot strength and platelet count also decreased and remained low throughout the protocol. Conclusion: We present a rat model of MBF derangement in uninjured skeletal muscle and coagulopathy after polytrauma that persists after resuscitation with whole blood to normal macrohemodynamics. Parametric CEUS analysis shows that this change is primarily due to microvascular obstruction. This platform can be used to develop a deeper understanding of this important process.

Acute limb ischaemia (ALI) is an emergent clinical condition that strains pre-hospital resources and impacts healthcare costs and patient quality of life. Hypothermia has long been used in clinical and research settings to mitigate ischaemic damage in tissues, but prompt reperfusion is needed to prevent loss of limb or function from ALI. To address the unmet need for pre-hospital intervention of threatened limbs awaiting definitive specialty care, we have focused on controlled application of hypothermia. Over years of animal experiments, phantom limb creation, and materials selection, we conceptualised and created a portable limb-cooling device that can be used alone or combined with a traditional tourniquet or resuscitative endovascular balloon occlusion of the aorta. Here, we describe our process of building and testing the device, from computer simulation through animal-limb metabolic studies, to prototype testing.

Globally, traumatic injury is a leading cause of suffering and death. The ability to curtail damage and ensure survival after major injury requires a time-sensitive response balancing organ perfusion, blood loss, and portability, underscoring the need for novel therapies for the prehospital environment. Currently, there are few options available for damage control resuscitation (DCR) of trauma victims. We hypothesize that synthetic polymers, which are tunable, portable, and stable under austere conditions, can be developed as effective injectable therapies for trauma medicine. In this work, we design injectable polymers for use as low volume resuscitants (LVRs). Using RAFT polymerization, we evaluate the effect of polymer size, architecture, and chemical composition upon both blood coagulation and resuscitation in a rat hemorrhagic shock model. Our therapy is evaluated against a clinically used colloid resuscitant, Hextend. We demonstrate that a radiant star poly(glycerol monomethacrylate) polymer did not interfere with coagulation while successfully correcting metabolic deficit and resuscitating animals from hemorrhagic shock to the desired mean arterial pressure range for DCR – correcting a 60 % total blood volume (TBV) loss when given at only 10 % TBV. This highly portable and non-coagulopathic resuscitant has profound potential for application in trauma medicine.

Monitoring deep tissue biometrics is crucial in various clinical settings, including internal hemorrhage. Although optical and impedance tomography techniques offer real-time monitoring with minimal medical infrastructure, they still face challenges in accurately assessing deeper tissues in wearable formats. This study introduces a novel single-electrode capacitive sensor designed to measure deep tissue capacitance changes caused by variations in dielectric constant and pressure. The sensor features a carbon nanotube-paper composite (CPC) electrode integrated with a multi-walled carbon nanotube (MWCNT)-embedded foam. The CPC electrode, with its large surface area and high-aspect-ratio fibers, generates a high electric field for deeper tissue penetration, improving deep tissue monitoring performance. Penetration depth is characterized using surrogate tissue, heart, and lung models. Additionally, the integration of pressure-sensitive MWCNT foam significantly enhances the sensitivity, enabling precise detection of regional blood volume and tissue displacement. The novel sensing mechanism is applied to detect internal hemorrhage in a porcine model. By employing a machine learning algorithm, the sensor accurately estimates the severity of internal hemorrhage, offering a noninvasive alternative to catheter-based systems. This advancement lays the foundation for a real-time wearable system that monitors deep tissue health metrics, such as blood volume, blood pressure, as well as heart and lung functions.

Introduction We use a novel 4-dimensional (4D) volumetric M-mode (VMM) ultrasound (US) technique to assess intravascular volume by monitoring the inferior vena cava (IVC). The VMM method expands the spatial coverage of standard M-mode scanning (depth vs time) by including lateral image direction and adds transducer tilt to cover the region surrounding the IVC. Current ultrasound methods for volume assessment suffer from intra- and inter-operator variability. The VMM technique aims to address these limitations, aiding in early detection of hypovolemia/hemorrhage and guiding resuscitation. Methods/Technical Approach The 4D VMM technique was used on animals that underwent a swine hemorrhagic shock protocol with fluid resuscitation. 2D ultrasound images obtained were formatted in a 3D volume to capture changes over time in vessel size with respiration and volume status. Planes were then extracted from the 3D volume at multiple lateral locations to find and track the IVC. The vessel walls were manually traced on vertical planes (depth vs. time) to determine mean IVC diameter and IVC collapsibility at each measurement time point in the shock/resuscitation protocol. Planes at constant depth (lateral vs. time) were selected to extract respiratory and cardiac cycle data. Results Mean IVC diameter in the baseline phase was significantly greater than in the hemorrhage phase (p = 0.020). There was no significant different in mean IVC diameter between baseline and resuscitation (p = 0.064) or hemorrhage and resuscitation phases (p = 0.531). There was no statistically significant difference in mean collapsibility or ΔIVC diameter between protocol phases. The 4D VMM technique effectively measured heart and respiratory rates, consistent with monitored vitals. Conclusion 4D VMM identified IVC changes corresponding to blood loss and resuscitation during hemorrhagic shock as well as heart/respiratory rates. This innovative approach holds promise in reducing operator variability and providing actionable information during treatment of shock.

INTRODUCTION:Hemorrhage is responsible for 91% of preventable prehospital deaths in combat. Bleeding from anatomic junctions such as the groin, neck, and axillae make up 19% of these deaths, and reports estimate that effective control of junctional hemorrhage could have prevented 5% of fatalities in Afghanistan. Hemostatic dressings are effective but are time-consuming to apply and are limited when proper packing and manual pressure are not feasible, such as during care under fire. CounterFlow-Gauze is a hemostatic dressing that is effective without compression and delivers thrombin and tranexamic acid into wounds. Here, an advanced prototype of CounterFlow-Gauze, containing a range of low thrombin doses, was tested in a lethal swine model of junctional hemorrhage. Outcomes were compared with those of Combat Gauze, the current dressing recommended by Tactical Combat Casualty Care.MATERIALS AND METHODS:CounterFlow-Gauze containing thrombin doses of 0, 20, 200, and 500 IU was prepared. Swine received femoral arteriotomies, and CounterFlow-Gauze was packed into wounds without additional manual compression. In a separate study using a similar model of junctional hemorrhage without additional compression, CounterFlow-Gauze containing 500 IU thrombin was tested and compared with Combat Gauze. In both studies, the primary outcomes were survival to 3 h and volume of blood loss.RESULTS:CounterFlow-Gauze with 200 and 500 IU had the highest 3-h survival, achieving 70 and 75% survival, respectively. CounterFlow-Gauze resulted in mean peak plasma tranexamic acid concentrations of 9.6 ± 1.0 µg/mL (mean ± SEM) within 3 h. In a separate study with smaller injury, CounterFlow-Gauze with 500 IU achieved 100% survival to 3 h compared with 92% in Combat Gauze animals.CONCLUSIONS:An advanced preclinical prototype of CounterFlow-Gauze formulated with a minimized thrombin dose is highly effective at managing junctional hemorrhage without compression. These results demonstrate that CounterFlow-Gauze could be developed into a feasible alternative to Combat Gauze for hemorrhage control on the battlefield.

BACKGROUND:Our objective was to optimize a novel damage control resuscitation (DCR) cocktail composed of hydroxyethyl starch, vasopressin, and fibrinogen concentrate for the polytraumatized casualty. We hypothesized that slow intravenous infusion of the DCR cocktail in a pig polytrauma model would decrease internal hemorrhage and improve survival compared with bolus administration. METHODS:We induced polytrauma, including traumatic brain injury (TBI), femoral fracture, hemorrhagic shock, and free bleeding from aortic tear injury, in 18 farm pigs. The DCR cocktail consisted of 6% hydroxyethyl starch in Ringer's lactate solution (14mL/kg), vasopressin (0.8U/kg), and fibrinogen concentrate (100mg/kg) in a total fluid volume of 20mL/kg that was either divided in half and given as two boluses separated by 30 minutes as control or given as a continuous slow infusion over 60 minutes. Nine animals were studied per group and monitored for up to 3 hours. Outcomes included internal blood loss, survival, hemodynamics, lactate concentration, and organ blood flow obtained by colored microsphere injection. RESULTS:Mean internal blood loss was significantly decreased by 11.1mL/kg with infusion compared with the bolus group (p = .038). Survival to 3 hours was 80% with infusion and 40% with bolus, which was not statistically different (Kaplan Meier log-rank test, p = .17). Overall blood pressure was increased (p < .001), and blood lactate concentration was decreased (p < .001) with infusion compared with bolus. There were no differences in organ blood flow (p > .09). CONCLUSION:Controlled infusion of a novel DCR cocktail decreased hemorrhage and improved resuscitation in this polytrauma model compared with bolus. The rate of infusion of intravenous fluids should be considered as an important aspect of DCR.

Immune cell inflammation is implicated in the pathophysiology of acute trauma-induced coagulopathy (TIC). We hypothesized that leukocyte inflammation contributes to TIC through the oxidation and proteolysis of fibrinogen. To test this hypothesis, antioxidants and a novel anti-inflammatory melanocortin fusion protein (AQB-565) were used to study the effects of interleukin-6 (IL-6)-stimulated human leukocytes on fibrinogen using single-cell imaging flow cytometry and multiplex fluorescent western blotting. We also studied the effects of AQB-565 on fibrinogen using an in vivo rat trauma model of native TIC. IL-6 induced cellular inflammation and mitochondrial superoxide production in human monocytes, causing fibrinogen oxidation and degradation in vitro. Antioxidants suppressing mitochondrial superoxide reduced oxidative stress and inflammation and protected fibrinogen. AQB-565 decreased inflammation, inhibited mitochondrial superoxide, and protected fibrinogen in vitro. Trauma with hemorrhagic shock increased IL-6 and other proinflammatory cytokines and chemokines, selectively oxidized and degraded fibrinogen, and induced TIC in rats in vivo. AQB-565, given at the onset of hemorrhage, blocked inflammation, protected fibrinogen from oxidation and degradation, and prevented TIC. Leukocyte activation contributes to TIC through the oxidation and degradation of fibrinogen, which involves mitochondrial superoxide and cellular inflammation. Suppression of inflammation by activation of melanocortin pathways may be a novel approach for the prevention and treatment of TIC.

Critical illness leads to rapid fibrinogen consumption, hyperfibrinolysis, and coagulopathy that exacerbates bleeding and increases mortality. Immune cell activation and inflammation are associated with coagulopathy after injury but play an undetermined role. We performed high dimensional immunophenotyping and single-cell imaging flow cytometry to investigate for a pathophysiological mechanism governing the effects of leukocyte-associated inflammation on fibrinogen function. Fibrinogen was oxidized early, followed by its degradation after 3 hours of lipopolysaccharides (LPS)-induced sterile inflammation in a rat model in vivo. Fibrinogen incubated with human leukocytes activated by TNFα was similarly oxidized, and later proteolyzed after 3 hours in vitro. TNFα induced mitochondrial superoxide generation from neutrophils and monocytes, myeloperoxidase (MPO)-derived reactive oxygen species (ROS) from neutrophils, and nitric oxide from lymphocytes and monocytes. Inhibition of mitochondrial superoxide prevented oxidative modification and proteolysis of fibrinogen, whereas inhibition of MPO attenuated only fibrinogen proteolysis. Quenching of both mitochondrial superoxide and MPO-derived ROS prevented coagulopathy better than tranexamic acid. Collectively, these findings indicate that neutrophil and monocyte mitochondrial superoxide generation can rapidly oxidize fibrinogen as a priming step for fibrinogen proteolysis and coagulopathy during inflammation.

The resuscitation of polytrauma with hemorrhagic shock and traumatic brain injury (TBI) is a balance between permissive hypotension and maintaining vital organ perfusion. There is no current optimal solution. This study tested whether a multifunctional resuscitation cocktail supporting hemostasis and perfusion could mitigate blood loss while improving vital organ blood flow during prolonged limited resuscitation. Anesthetized Yorkshire swine were subjected to fluid percussion TBI, femur fracture, catheter hemorrhage, and aortic tear. Fluid resuscitation was started when lactate concentration reached 3–4 mmol/L. Animals were randomized to one of five groups. All groups received hydroxyethyl starch solution and vasopressin. Low- and high-dose fibrinogen (FBG) groups additionally received 100 and 200 mg/kg FBG, respectively. A third group received TXA and low-dose FBG. Two control groups received albumin, with one also including TXA. Animals were monitored for up to 6 h. Blood loss was decreased and vital organ blood flow was improved with low- and high-dose fibrinogen compared to albumin controls, but survival was not improved. There was no additional benefit of high- vs. low-dose FBG on blood loss or survival. TXA alone decreased blood loss but had no effect on survival, and combining TXA with FBG provided no additional benefit. Pooled analysis of all groups containing fibrinogen vs. albumin controls found improved survival, decreased blood loss, and improved vital organ blood flow with fibrinogen delivery. In conclusion, a low-volume resuscitation cocktail consisting of hydroxyethyl starch, vasopressin, and fibrinogen concentrate improved outcomes compare to controls during limited resuscitation of polytrauma.

The adhesion of blood clots to wounds is necessary to seal injured vasculature and achieve hemostasis. However, it has not been specifically tested if adhesive failure of clots is a major contributor to rebleeding and what mechanisms prevent clot delamination. Here, we quantified the contribution of adhesive and cohesive failure to rebleeding in a rat model of femoral artery injury, and identified mechanisms that contribute to the adhesive strength of bulk clots in a lap-shear test in vitro. In the rat bleeding model, the frequency of clot failures correlated positively with blood loss (R = 0.81, p = 0.014) and negatively with survival time (R = − 0.89, p = 0.0030), with adhesive failures accounting for 51 ± 14% of rebleeds. In vitro, adhesion depended on fibrinogen and coagulation factor XIII (FXIII), and supraphysiological FXIII improved adhesive strength. Furthermore, when exogenous FXIII was topically applied into the wound pocket of rats, eleven adhesive failures occurred between eight rats, compared to seventeen adhesive failures between eight untreated rats, whereas the number of cohesive failures remained the same at sixteen in both groups. In conclusion, rebleeding from both adhesive and cohesive failure of clots decreases survival from hemorrhage in vivo. Both endogenous and exogenous FXIII improves the adhesive strength of clots.

Disorders of sleep and wakefulness occur in the majority of individuals who have experienced traumatic brain injury (TBI), with increased sleep need and excessive daytime sleepiness often reported. Behavioral and pharmacological therapies have limited efficacy, in part, because the etiology of post-TBI sleep disturbances is not well understood. Severity of injuries resulting from head trauma in humans is highly variable, and as a consequence so are their sequelae. Here, we use a controlled laboratory model to investigate the effects of TBI on sleep-wake behavior and on candidate neurotransmitter systems as potential mediators. We focus on hypocretin and melanin-concentrating hormone (MCH), hypothalamic neuropeptides important for regulating sleep and wakefulness, and two potential downstream effectors of hypocretin actions, histamine and acetylcholine. Adult male C57BL/6 mice (n=6–10/group) were implanted with EEG recording electrodes and baseline recordings were obtained. After baseline recordings, controlled cortical impact was used to induce mild or moderate TBI. EEG recordings were obtained from the same animals at 7 and 15 days post-surgery. Separate groups of animals (n=6–8/group) were used to determine effects of TBI on the numbers of hypocretin and MCH-producing neurons in the hypothalamus, histaminergic neurons in the tuberomammillary nucleus, and cholinergic neurons in the basal forebrain. At 15 days post-TBI, wakefulness was decreased and NREM sleep was increased during the dark period in moderately injured animals. There were no differences between groups in REM sleep time, nor were there differences between groups in sleep during the light period. TBI effects on hypocretin and cholinergic neurons were such that more severe injury resulted in fewer cells. Numbers of MCH neurons and histaminergic neurons were not altered under the conditions of this study. Thus, we conclude that moderate TBI in mice reduces wakefulness and increases NREM sleep during the dark period, effects that may be mediated by hypocretin-producing neurons and/or downstream cholinergic effectors in the basal forebrain.

The factors by which aging predisposes to critical illness are varied, complex, and not well understood. Sepsis is considered a quintessential disease of old age because the incidence and mortality of severe sepsis increases in old and the oldest old individuals. Aging is associated with dramatic changes in sleep quality and quantity and sleep increasingly becomes fragmented with age. In healthy adults, sleep disruption induces inflammation. Multiple aspects of aging and of sleep dysregulation interact via neuroimmune mechanisms. Tumor necrosis factor-alpha (TNF), a cytokine involved in sleep regulation and neuroimmune processes, exerts some of its effects on the CNS by crossing the blood-brain barrier (BBB). In this study we examined the impact of sepsis, sleep fragmentation, and aging on BBB disruption and TNF transport into brain. We used the cecal ligation and puncture (CLP) model of sepsis in young and aged mice that were either undisturbed or had their sleep disrupted. There was a dichotomous effect of sepsis and sleep disruption with age: sepsis disrupted the BBB and increased TNF transport in young mice but not in aged mice, whereas sleep fragmentation disrupted the BBB and increased TNF transport in aged mice, but not in young mice. Combining sleep fragmentation and CLP did not produce a greater effect on either of these BBB parameters than did either of these manipulations alone. These results suggest that the mechanisms by which sleep fragmentation and sepsis alter BBB functions are fundamentally different from one another and that a major change in the organism's responses to those insults occurs with aging. Published by Elsevier Inc.