Experimental Study Of Craniocerebral Firearm Wound Under Hot And Humid Field Environment

Source: The scientific research project comes from armed forces "nine-five"military medicine research project(98M067)and Guangdong province scientific research fund project(99M04606G)Objective: Craniocerebral trauma is an acute, severe, rapid change injury with high incidences, high death and disability rate in peace age and wartime. The craniocerebral firearm wound causes tissue disorganization, bleed, primary cellular defect, brain edema and neuroendocrine system change throughout the body due to high kinetic energy bullet producing invade effect and cavum effect. When people live in the hot and humid environment, especially in military fight and long-time high intensity work, the body has great heat production, eccrine sweat glands evaporation difficulty and accepts large apposition heat, which results in body heat disequilibrium, water-electrolyte metabolism disturbance and blood circulation collapse, and finally causes body temperature raise, metabolic rate increase, body fluid loss and internal environment chaos. When combined with craniocerebral firearm wound, brain tissue pathological lesion becomes more severe and aggravates internal environment turbulence and importance organs' loading and damage including bleeding, cell hurt, brain edema and nerve endocrine system change, which fastens the development of the illness. The study of craniocerebral firearm wound under hot and humidenvironment have important significance to the patient treatment in the South war zone in the future, in the Taiwan Strait crisis, South China Sea territory guard, as well as the working and living crowd in the district. The dogs, as experimental animals, with the craniocerebral firearm wound in a short distance and the hot and humid environment were successively studied to analyze the brain tissue damages, and the heart, lungs, liver, kidney lesion characteristics, further to study medicine centre hypothermia and to cut down cerebral metabolic rate route.Mothods: 81 cross-breed dogs were separated randomly into 11 groups:craniocerebral firearm wound in normal temperature group, hot and humid environment group, craniocerebral firearm wound under hot and humid environment group, low-dose Urapidil group and Etomidate group with craniocerebral firearm wound under hot and humid environment, high dose Urapidil group and Etomidate group with craniocerebral firearm wound under hot and humid environment, Urapidil union Etomidate group with craniocerebral firearm wound under hot and humid environment, solarization group under hot and humid environment and the matched control group. The craniocerebral firearm wound modeling was established with "54" military gun and 7.62 mm bullet in a distance of 30 cm in coronal direction leaning 10 degree behind 1 cm lateral canthus and 1.5 cm high. The breath parameter and the brain tissue pathological changes were observed and recorded; The tympanic temperature, hemorheology, electrolyte, blood gas analysis and blood coagulation function were determined; the heart rate, respiratory frequency and live time were compared; and the brain, heart, lungs, liver and kidneys tissues specimens were frozen, sliced and stained pathologically for observation under electron microscope. The ballistics was analyzed after craniocerebral firearm wound through the craniocerebral common radial line, CT photographs. The treatment groups with Etomidate to lower cerebral metabolic rate, or 5-HT1A receptor agonist Urapidil todecrease the central temperature, or drug combination, were observed in the brain tissue and systemic effects after craniocerebral firearm wound under hot and humid environment. The experiment environmental conditions: common surrounding temperature 22.20±1.30°C, relative humidity <60%; hot and humid environmental temperature 52.60±6.70°C, relative humidity 40-69%, radiant heat intensity >4.184J (cm2.min).; solarization temperature 58.20±6.90°C, relative humidity 39~52 %.Results: 1) The model of craniocerebral firearm wound in dogs is established insuccession. Of 54 individuals who were gunshot by "54" pistol with 7.62 mm bullets, 42 dogs (77.8%) had stable vital signs, and it was consistent with experiment condition that animal survival time was longer than 2 h. 21 dogs (38.9%) occurred breath cessation, of which 9 (16.7%) regained autonomous breathing following emergent treatment. The model of craniocerebral perforating wound in dogs is certified through cranial CT examination and histopathology section. 2) The intracranial hematoma, neuronal degeneration, contusion and laceration of brain, intranuclear heterochromosome decrease, a great deal of axonotmesis and demyelination, the air-containing space in impairment axis zone, glial cellular swelling, vasospasm contraction, vacant space augmentation surrounding blood vessel and subarachnoid haemorrhage pathological change were observed after craniocerebral perforating wound. Intracranial pneumatocele, ballistic curve and fourth ventricle hematoma, bone cips radiate distribution along ballistic curve direction were showed in cranial CT. 3) There was predominant increase in the body temperature, respire and heart rate, decrease in partial pressure of carbon dioxide. The body heat exchange through perspiration and metabolic rate reinforcement resulted in body fluid loss, respiratory alkalosis and internal environment disorder. The subcortex histiocyte structure porosity, neuron manifest decrease, patching hemorrhage and blood vessel erythrocyte edge aggregation were observed in braintissue specimen when the dog died in solarization. 4) The cerebral contusion, neuroglia cells swelling, serious axon injury, perivascular space obviously widen, cerebral angio spasm, subcortex diffluence necrosis band, a great deal of cortex superficial cell vacuolar degeneration or necrosis and traumatic subarachnoid hemorrhage were observed after craniocerebral firearm wound. The body temperature mounted up and PO2, PaCC>2 data and fibrinogen decreased, but the high shear rate, middle shear rate, low shear rate and plasma viscosity had no manifest changes. There were hypoxemia, hypocapnia, hypopotassaemia and internal environment chaos. 5) The far damage effects were studied in craniocerebral firearm wound under hot and humid environment. The respiratory function disorder, lung hemorrhagic infarct and sludged blood in lung small vessels happened after craniocerebral firearm wound. The increased heart rate, cardiac muscle hemorrhage zone, cardiac muscle defibration accompany with bulk erythrocyte, endochylema red dye particle in cardiac muscle cell necrosis zone were observed. The coagulation necrosis damage, renal tubular epithelial cell vesiculation and intracytoplasm red dye particle degeneration and renal tubular necrosis occurred. There were liver swell, hepatic sinusoid extension and hepatic congestion which were filled with a great quantity of erythrocyte. 6) The brain cytoreduction and structure puff happened after solarization under hot and humid environment.Control group's tympanic membrane temperature rose by 5°C and live time was 74 minutes; Urapidil group tympanic membrane temperature rise 3.5 °C and live time was 97 minutes. Compare with control group, the tympanic membrane temperature in Urapidil group fell by 1.5V and the survival time was prolonged by 23 minutes and brain tissue damages were improved, but there was obvious difference in respiration and heart rate between the two groups after solarization. 7) Comparing Urapidil group and Etomidate group with craniocerebral firearm wound group under hot and humid environment, we found that brain tissuedamage was relieved, but the temperature had no obvious descending. However, the temperature in Urapidil+Etomidate group increased on the contrary, and brain tissue damages had not obviously improved.Conclusion: 1) The model of craniocerebral perforating wound in dogs isestablished in succession. The model represented craniocerebral firearm wound impact on brain tissue and throughout the body. It was applied in the study of craniocerebral firearm wound mechanisms under different conditions of peaceful or war times; meanwhile the far damage effects were studied in the internal environment alteration and other organ damages after craniocerebral firearm wound. 2) There were "penetration effect" of primary wound tract, "Cavitation effect" of circumference enlarged, and "Second scatter projection distribution" in bone fragments. The "splash effect" or "Theile's instability" in CSF would have possibly aggravated exhaustion of brain stem. It was an effect factor of 38.9 % dogs that occurred apneic. Among the total, 16.7% the dogs's spontaneous breathing were recovered through rescuing. It suggested the importance of remedy mechanism and early cardiopulmonary resuscitation measure. 3) The body temperature, respiration and heart rate significantly increased, along with excessive ventilation in blood PaCO2 depression, cerebral vessels autoregulation impact, internal environment change and brain tissue damage under hot and humid environment. 4) There was severe axon injury in white matter after craniocerebral firearm wound under hot and humid environment. The extracellular space in white matter was 4-6 times larger than in gray matter; edema expanded mainly in white matter; so brain white matter's injury effected the extent of cerebral edema; and the injury could also effect on cerebral angiospasm, perivascular space, early occurrence of blood vessel cerebral edema, blood brain barrier destroy, great releasing of irritability catecholamines which aggravated cerebral edema extent. The injury caused cortex bounce damage and subcortex crushing destroy as well ashypoxemia, respiratory alkalosis and hidden coagulation disorders, besides prinary wound tract, contusion zone and concussion district. 5) The momentary pressure wave induced the damages of important organs such as heart, lungs, liver and kidneys, and the far damage effects occurred through circulation channel's "blood hammer effect" on the basis of high metabolic rate, hyper consume, internal environment tendency to disequilibrium, greater loading of circulation and respiratory systems. 6) 5-HT1A receptor agonist Urapidil had the protective mechanisms of central hypothermia and survival time prolonging under hot and humid environment. 7) Between craniocerebral firearm wound group and Urapidil group under hot and humid environment after 2 h, the body temperatures had not significant difference, because external heat energy could reach directly thermal equilibrium with cranial cavity temperature through open craniocerebral wound. Even though blood clot closed part path, a great deal of surrounding heat energy influenced local cranial cavity temperature change. 5-HT1A receptor agonist decreased body temperature through hypothalamus, but the cavitation effect in craniocerebral firearm wound inevitably destroyed hypothalamus and effected center hypothermia degrade. Catecholamines factors were released and brain contusion hemorrhage stimulus leaded to cerebral angiospasm and aggravated brain tissue local microenvironment damage and hypoxia extent. Besides the body temperature could go down, Urapidil mitigated brain vasospasm through angiotasis depression of sympathetic nerve to improve valid perfusion of cerebral blood flow and brain cell hypoxia extent. The Urapidil had some brain cell protections, and had no obvious hemorheology changes. 8) In craniocerebral firearm wound group and Etomidate group under hot and humid environment after 2 h, the body temperatures were obviously higher than common temperature group, but the two groups had no significant difference. It was also owing to external heat energy that reached directly thermal equilibrium with cranialcavity temperature through open craniocerebral injury. And Etomidate had not directly degraded histiocyte temperature efficacy, but it could decrease cerebral metabolic rate through relative texture complete chondriosome to maintain cell respiration chain and play membrane repair function at the same time, it had small hemodynamics impact and little myocardial oxygen consumption augment. The Etomidate had some brain cell protections, and have not obviously hemorheology changes. 9) Compared with craniocerebral firearm wound group under hot and humid environment after 2 h, the body temperatures in Urapidil+Etomidate group was obviously higher. It was owing to external heat energy that reached directly thermal equilibrium with cranial cavity temperature through open craniocerebral wound, a great quantity of body fluid loss and relative blood volume deficient, Urapidil's effect of dropping blood pressure, Etomidate's cutting down cerebral blood flow action besides decreasing cerebral metabolic rate, reduction of blood flow due to cerebral vessels constriction in respiratory alkalosis, and hemorrhage stimulus causing vasospasm to induce brain hypoperfusion, which promoted hypoxia and heat cumulation damages. The blood pressure falling affect and Etomidate's cutting down cerebral blood flow action in Urapidil+Etomidate group with craniocerebral firearm wound under hot and humid environment could destroy brain cell protection.