Shock after blast wave injury is caused by a vagally mediated reflex

Measurement of blast wave by a miniature fiber optic pressure transducer in the rat brain

Exposure to blast wave that is generated during an explosion may result in brain damage and related neurological impairments. The aim of this study was to investigate pressure changes induced by exposure to blast inside the rat brain. For intracranial pressure measurement we used a miniature optic fiber sensor (o.d. 550 microm) with a computer recording system. The sensor was placed in the third cerebral ventricle of anesthetized rats exposed to 40 kPa blast wave in a pneumatic-pressure driven shock tube. Short pressure waves lasting several ms were detected inside the brain with the magnitude that might result in nervous tissue damage.

Blast injuries from Madrid terrorist bombing attacks on March 11, 2004

Blast injuries after terrorist attacks are seen with increasing frequency worldwide. Thousands of victims were attended in the hospitals of Madrid, Spain, on March 11, 2004 after the bombing attacks against the commuter trains. Thirty-six patients were attended in our institution. Seventeen of them suffered from severe or life-threatening injuries, and 19 had mild injuries. The most common lesions were thoracic trauma and blast lung injury, acoustic trauma, and orbital and paranasal sinus fractures. Other findings were hepatic and splenic lacerations, and vertebral and limb fractures. Emergency radiology had an important role in the correct management of the victims. Prompt radiological diagnoses of these complex lesions are crucial to efficient treatment. Therefore, radiologists have to become familiar with the injury patterns and specific lesions caused by blast wave.

Lung Injury and Recovery After Exposure to Blast Overpressure

BACKGROUND

A critical immediate determinant of survival after exposure to blast overpressure (BOP) is pulmonary damage, but mechanisms of injury and the course of recovery are not well understood. The objective of this study was to characterize the progression of oxidative and inflammatory responses in lungs as well as the activation of consequent protective mechanisms after exposure to medium intensity BOP.

METHODS

Rats were exposed to a moderate (approximately 120 kPa) level of BOP in a pneumatically driven shock tube. At different times (2-192 hours) after exposure, lungs were examined for pathologic signs of injury, markers of inflammatory responses, and indicators of oxidative and nitrative damage.

RESULTS

The results showed a postblast activation of inflammatory response (increase of myeloperoxidase activity, CINC-1, ICAM-1, and iNOS), increase in protein oxidation and nitration, and development of gross diffused hemorrhage in lungs. The initial phase of lung damage that peaked at 24 to 48 hours after exposure to BOP was followed by gradual dissolution of inflammation and oxidation that were complete by 192 hours. Resolution of morphologic damage and inflammation in lungs concurred with activation of expression of antioxidant enzymes heme oxygenase-1 (HO-1) and manganese superoxide dismutase (MnSOD). Plasma level of gelsolin, a marker of acute lung damage was decreased at 24 hours postblast and later returned to the control level.

CONCLUSIONS

The study shows the role of adaptive anti-oxidant and anti- inflammatory mechanisms in lung recovery after injury caused by exposure to BOP.

Terrorist Homicide Bombings: A Primer for Preparation

Contemporary planning for disaster response to terrorist events usually assumes the use of chemical, radiological, or biological weapons. Historically, most victims of terrorist attacks are injured by the use of conventional explosives rather than weapons of mass destruction. Such attacks will likely produce victims who have suffered burn injuries along with conventional trauma. Alternately, the large number of patients sustaining conventional soft-tissue or crush injuries will benefit from burn center expertise. This study summarizes the current state of knowledge related to the management of terrorism mass casualty incidents caused by the use of conventional explosives. A review of pertinent medical, technical, and popular literature relating to terrorism and explosives, along with instruction received at Hadassah Hospital, Jerusalem, Israel on the management of mass casualty terrorism events was undertaken, and the pertinent medical and scientific literature relating to bomb delivery methods, blast mechanics, blast pathophysiology, and medical response to a terrorist bombing is presented here. Although terrorist use of chemical, radiological, or biological weapons is possible, historical analysis consistently demonstrates that the most likely terrorist weapon causing a mass casualty event is a standard explosive device detonated in a crowded area. The medical basis for management of such casualties is herein described.

Conventional terrorism and critical care

Incidents of conventional weapons terror are increasingly part of the reality of the modern world, and in Israel, 19,948 incidents have been reported from September 2000 to December 2003. Most victims are injured in explosions resulting from suicide bombings. Exposure to the blast (primary mechanism of injury) may produce unique injuries affecting gas-containing organs, including perforation of the eardrums (most common injury); pulmonary blast injury, characterized by alveolar capillary disruption and bronchopleural fistulas; and bowel perforation, which is uncommon and may be delayed from 1 to 14 days after the injury. However, most injuries are the result of penetrating trauma (secondary mechanism) resulting from bomb fragments and nails, bolts, and steel pellets embedded in the bomb striking the victim, and blunt trauma (tertiary mechanism) sustained when the victim is propelled against an object by the blast wind. The severity of the injuries is increased when the blast occurs in a confined space. Victims of terror-inflicted injuries have a high Injury Severity Score (30% >16), a high requirement for intensive care unit admission (22.8% in Israel), and have a more prolonged hospital course and higher mortality than victims of any other form of trauma.

Neuroprotective Role of Aminoguanidine in Behavioral Changes after Blast Injury

BACKGROUND

The present study investigated the neuroprotective role of aminoguanidine, a known inducible nitric oxide synthase inhibitor, in both behavioral and morphologic changes in rats subjected to nonpenetrative blast injury.

METHODS

Male Sprague-Dawley rats were randomly divided into groups to receive either normal saline or aminoguanidine (AG) before or after exposure to two blast dosages of either 2.8 or 20 kPa. The neurobehavioral alterations were determined by subjecting the animals to rotametric, grip-strength, passive avoidance, total and ambulatory locomotor activities, and acoustic startle response tests.

RESULTS

Exposure to blast at 20 kPa resulted in a significant performance decrement on rotametric and grip-strength tests in rats treated with normal saline. In contrast, animals receiving AG either prophylactically before or after the blast seemed unaffected by the same blast. This finding also correlates well with histologic examination that showed a reduction in degenerating cortical neurons in AG-treated rats compared with those receiving saline injection.

CONCLUSION

It is thus suggested that AG could play a neuroprotective role in rats subjected to blast exposure.

Explosions and blast injuries

Powerful explosions have the potential to inflict many different types of injuries on victims, some of which may be initially occult. Flying debris and high winds commonly cause conventional blunt and penetrating trauma. Injuries caused by blast pressures alone result from complex interactions on living tissues. Interfaces between tissues of different densities or those between tissues and trapped air result in unique patterns of organ damage. These challenge out-of-hospital personnel, emergency physicians, and trauma surgeons to specifically seek evidence of these internal injuries in individuals with multiple trauma, adjust management considerations to avoid exacerbation of life-threatening problems caused by the blast wave itself, and ensure appropriate disposition of these patients in possible mass-casualty situations. Knowledge of the potential mechanisms of injury, early signs and symptoms, and natural courses of these problems will greatly aid the management of blast-injured patients.