Bilateral Vagotomy Inhibits Apnea and Attenuates Other Physiological Responses After Blunt Chest Trauma

The anesthesiologist's guide to swine trauma physiology research: a report of two decades of experience from the experimental traumatology laboratory

PURPOSE

Swine are one of the major animal species used in translational research, with unique advantages given the similar anatomic and physiologic characteristics as man, but the investigator needs to be familiar with important differences. This article targets clinical anesthesiologists who are proficient in human monitoring. We summarize our experience during the last two decades, with the aim to facilitate for clinical and non-clinical researchers to improve in porcine research.

METHODS

This was a retrospective review of 337 swine with a mean (SD) weight 60 (4.2) kg at the Experimental Traumatology laboratory at Södersjukhuset (Stockholm south general hospital) between 2003 and 2023, including laboratory parameters and six CT-angiography examinations.

RESULTS

Swine may be ventilated through the snout using a size 2 neonatal mask. Intubate using a 35 cm miller laryngoscope and an intubating introducer. Swine are prone to alveolar atelectasis and often require alveolar recruitment. Insert PA-catheters through a cut-down technique in the internal jugular vein, and catheters in arteries and veins using combined cut-down and Seldinger techniques. Cardiopulmonary resuscitation is possible and lateral chest compressions are most effective. Swine are prone to lethal ventricular arrhythmias, which may be reversed by defibrillation. Most vital parameters are similar to man, with the exception of a higher core temperature, higher buffer bases and increased coagulation. Anesthesia methods are similar to man, but swine require five times the dose of ketamine.

CONCLUSION

Swine share anatomical and physiological features with man, which allows for seamless utilization of clinical monitoring equipment, medication, and physiological considerations.

Evaluating the Limits in the Biomechanics of Blunt Lung Injury

Thoracic blunt trauma is evident in up to one fifth of all hospital admissions, and is second only to head trauma in motor vehicle crashes. One of the most problematic injury mechanisms associated with blunt thoracic trauma is pulmonary contusion, occurring in up to 75% of blunt thoracic trauma cases. The source and effects of pulmonary contusion caused by blunt lung injury are not well defined, especially within the field of continuum biomechanics. This, paired with unreliable diagnostics for pulmonary contusion, leads to uncertainty in both the clinical entity and mechanics of how to predict presence of injury. There is a distinct need to combine the clinical aspects with mechanical insights through the identification and mitigation of blunt lung trauma and material testing and modeling. This is achieved through using the mechanical insights of lung tissue behavior in order to better understand the injurious mechanisms and courses of treatment of blunt-caused pulmonary contusion. This paper hopes to act as a step forward in connecting two perspectives of blunt lung injury, the clinical entity and mechanical testing and modeling, by reviewing the known literature and identifying the unknowns within the two related fields. Through a review of related literature, clinical evidence is correlated to mechanical data to gain a better understanding of what is being missed in identification and response to blunt lung injury as a whole.

The Complexity of Biomechanics Causing Primary Blast-Induced Traumatic Brain Injury: A Review of Potential Mechanisms

Primary blast-induced traumatic brain injury (bTBI) is a prevalent battlefield injury in recent conflicts, yet biomechanical mechanisms of bTBI remain unclear. Elucidating specific biomechanical mechanisms is essential to developing animal models for testing candidate therapies and for improving protective equipment. Three hypothetical mechanisms of primary bTBI have received the most attention. Because translational and rotational head accelerations are primary contributors to TBI from non-penetrating blunt force head trauma, the acceleration hypothesis suggests that blast-induced head accelerations may cause bTBI. The hypothesis of direct cranial transmission suggests that a pressure transient traverses the skull into the brain and directly injures brain tissue. The thoracic hypothesis of bTBI suggests that some combination of a pressure transient reaching the brain via the thorax and a vagally mediated reflex result in bTBI. These three mechanisms may not be mutually exclusive, and quantifying exposure thresholds (for blasts of a given duration) is essential for determining which mechanisms may be contributing for a level of blast exposure. Progress has been hindered by experimental designs, which do not effectively expose animal models to a single mechanism and by over-reliance on poorly validated computational models. The path forward should be predictive validation of computational models by quantitative confirmation with blast experiments in animal models, human cadavers, and biofidelic human surrogates over a range of relevant blast magnitudes and durations coupled with experimental designs, which isolate a single injury mechanism.

Non-impact, blast-induced mild TBI and PTSD: concepts and caveats

PRIMARY OBJECTIVE

A volumetric blood surge (rapid physical movement/displacement of blood) is hypothesized to cause the non-impact, mild TBI and battlefield PTSD induced by a blast over-pressure wave.

RESEARCH DESIGN

Systematic review of the literature.

METHODS AND PROCEDURES

Articles relating to the fields of blast injury, brain injury and relevant disorders were searched between the years 1968-2010 for keywords such as 'brain injury', 'post-traumatic stress disorder' and 'blast pressure wave'. Articles found through journal and Internet databases were cross-referenced.

MAIN OUTCOMES AND RESULTS

The blood surge, which is driven by elevated overall pressure in the ventral body cavity after exposure of the torso to blast wave, may move through blood vessels to the low-pressure cranial cavity from the high-pressure ventral body cavity. It dramatically increases cerebral perfusion pressure and causes damage to both tiny cerebral blood vessels and the BBB.

CONCLUSIONS

Three factors may be critical to the induction of blast-induced brain injuries: (1) the difference in pressure between the ventral body cavity and cranial cavity; (2) blood that acts as a transmission medium to propagate a pressure wave to the brain; and (3) the vulnerability of cerebral blood vessels and the BBB to a sudden fluctuation in perfusion pressure.

Anaesthetic and critical care management of thoracic injuries

Thoracic wounding has been a relatively common presentation of military wounds throughout modern conflict. When civilian casualties are included the incidence has remained constant at around 10%, although the frequency and severity of wounds to combatants has been altered by modern body armour. Whilst thoracic injury has a high initial mortality on the battlefield, those surviving to reach hospital frequently have injuries that only require simple management. In addition to penetrating ballistic injury, blunt chest trauma frequently occurs on operations as a result of road traffic collisions or tertiary blast injury. The physiological impact of thoracic wounds, however, is often great and survivors often require intensive care management and, where available, complex strategies to ensure oxygenation and carbon dioxide removal. This review examines the incidence and patterns of thoracic trauma and looks at therapeutic options for managing these complex cases.

A thoracic mechanism of mild traumatic brain injury due to blast pressure waves

The mechanisms by which blast pressure waves cause mild-to-moderate traumatic brain injury (mTBI) are an open question. Possibilities include acceleration of the head, direct passage of the blast wave via the cranium, and propagation of the blast wave to the brain via a thoracic mechanism. The hypothesis that the blast pressure wave reaches the brain via a thoracic mechanism is considered in light of ballistic and blast pressure wave research. Ballistic pressure waves, caused by penetrating ballistic projectiles or ballistic impacts to body armor, can only reach the brain via an internal mechanism and have been shown to cause cerebral effects. Similar effects have been documented when a blast pressure wave has been applied to the whole body or focused on the thorax in animal models. While vagotomy reduces apnea and bradycardia due to ballistic or blast pressure waves, it does not eliminate neural damage in the brain, suggesting that the pressure wave directly affects the brain cells via a thoracic mechanism. An experiment is proposed which isolates the thoracic mechanism from cranial mechanisms of mTBI due to blast wave exposure. Results have implications for evaluating risk of mTBI due to blast exposure and for developing effective protection.