j o u r n a l o f s u r g i c a l r e s e a r c h x x x ( 2 0 1 5 ) 1 e9
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.JournalofSurgicalResearch.com
Establishment of swine-penetrating craniocerebral gunshot wound model Huchen Lu, MD,a Lian Wang, MD, PhD,b Wuzhao Zhong, MD,a Rongfeng Qi, MD, PhD,c Ning Li, MD,a Wanchun You, MD, PhD,a Xingfeng Su, MD, PhD,a Zong Zhuang, MD, PhD,a Huilin Cheng, MD, PhD,a,* and Jixin Shi, MD, PhDa,* a
Department of Neurosurgery, Jingling Hospital, Medical School of Nanjing University, Nanjing, China Department of Thoracic Surgery, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China c Department of Medical Imaging, Jingling Hospital, Medical School of Nanjing University, Nanjing, China b
article info
abstract
Article history:
Background: Bullet-induced brain wounds are common among military personnel in war
Received 12 June 2014
zones and among civilians with gun accidents or crime-related gun injuries. The goal of
Received in revised form
this study was to develop a nonfatal porcine model of penetrating craniocerebral gunshot
17 December 2014
wound (PCGW) by firing a projectile in live swine to induce PCGW in such a realistic
Accepted 7 January 2015
manner as to reconstruct their physical characteristics.
Available online xxx
Materials and methods: We established a nonfatal porcine model of PCGW based on a customdesigned experimental gun that emulates the shooting of a 5.56-mm NATO standard rifle at
Keywords:
800 m (317 m/s; 200.9 J). Commercial swine (n ¼ 20) were subjected to a ballistic wound to the
Animal models of injury
bilateral frontal lobe, and four swine were used as controls. Surviving swine were used in sub-
Bullet wound
sequent first-aid, management, and monitoring experiments for neurosurgeons. Various
Penetrating brain injury
physiological variables were measured continuously. After computed tomography (CT) scanning
Gunshot wounds
and three-dimensional CT reconstructions, all pigs underwent primary lifesaving emergency
Damage control
interventions, including emergency decompressive craniotomies and hemorrhage control. Results: In our nonfatal porcine model of PCGW, injuries were comparable in their morphology to real gunshot wounds, as evidenced by analysis of wound characteristics and CT scan images. The survival rates of the pigs were 100% within 2 h, 95% within 6 h, 85% within 12 h, and 85% within 24 h (P < 0.01). Hemodynamics, hematology, blood routine biochemistry, coagulation, and other physiological parameters also exhibited significant changes in the PCGW pigs. Conclusions: This model makes possible the laboratory reproduction of real ballistic wounds in a live large animal model that is close to humans. ª 2015 Elsevier Inc. All rights reserved.
1.
Introduction
Penetrating craniocerebral gunshot wounds (PCGWs) are the most devastating type of projectile injuries to the head [1e3].
They are usually caused by gun projectiles or by bomb shrapnel. Much experience in PCGW treatment was gained during the First and Second World Wars [4,5], as well as during subsequent large-scale global conflicts [6], but PCGWs
* Corresponding authors. Department of Neurosurgery, Jingling Hospital, Medical School of Nanjing University, Nanjing 210000, China. Tel.: þ86 15195982516; fax: þ86 21 64085785. E-mail addresses: [email protected] (H. Cheng), [email protected] (J. Shi). 0022-4804/$ e see front matter ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jss.2015.01.006
2
j o u r n a l o f s u r g i c a l r e s e a r c h x x x ( 2 0 1 5 ) 1 e9
still have high mortality and morbidity rates [7]. PCGWs are rarer in civilian practice; nevertheless, the mortality rate is >50% [8,9]. The complicated injury patterns created by gunshots, either by military weapons in war zones or by civilian weapons (e.g., handling or hunting accidents, crimes), present a great challenge to conventional diagnosis and treatment. The approach to PCGW has undergone significant evolution and offers unique challenges. As a result, research focusing on the pathophysiological mechanisms is necessary. For almost a century, a number of animal PCGW models [10e13] have been developed and have helped to understand the mechanisms of the physiological response and cerebral edema formation. However, more in-depth studies are difficult to carry out because of the short survival time following PCGW due to the high energy of military cartridges and bullets. Carey et al. [13] established a model of penetrating injuries to the cerebral hemispheres in cats, based on the release of pressurized helium propellant. Recently, Williams et al. [14] successfully developed a right frontal lobe gunshot wound model in rats using air pressure needle, which primarily recreates the temporary cavity found around a penetrating bullet injury. Another rat model used the implantation of a small lead pellet in the brain [15]. However, these models might be impaired because of the differences in the brain size compared with humans and to the method used to induce PCGW. The aim of this study was to develop a nonfatal porcine model of PCGW by firing a projectile in live animals to induce PCGW in such a realistic manner as to reconstruct their physical characteristics. In addition, swine surviving the gunshot were used for first-aid, management, and monitoring experiments. Our goal was to lay the groundwork for the expected clinical wound patterns and for the subsequent realcase surgical procedures in a large animal model that is close to humans in size and brain morphology. This article presents model making, autopsy, and radiologic assessments of 24 pigs with PCGW caused by gunshot wounds from an experimental gun.
2.
Materials and methods
2.1.
Animal preparation
A total of 24 3-mo crossbred commercial swine (35.9 2.8 kg) were used for all experiments (Chinese Academy of Science, Nanjing University Animal Center, Nanjing, China). All animals received humane care in compliance with “The Principles of Laboratory Animal Care” formulated by the National Society of Medical Research and “The Guide for the Care and Use of Laboratory Animals” from the U.S. National Institutes of Health (Publication No. 85e23, revised 1996). The experimental protocol was approved by the Nanjing University Animal Care and Use Committee. The pigs were housed at the Animal Center of Jinling Hospital for at least 7 d before experiments to allow them to adjust to the environment. Pigs were fed a standard diet ad libitum and were housed at 21 C with a 12h lighte dark cycle.
2.2.
Experimental gun
The experimental gun was composed of a stereotaxic head holder, a barrel, a firing device, and an electronic control device (Fig. 1A), and was co-developed by our hospital and the Sichuan Nanshan Powder Actuated Fastening System Co, Ltd (Nanxi, China), which is a company specialized in the conception and building of powder-powered fastening tools such as nailers. The stereotactic head holder fixed the gun to the animal’s head allowing the precise determination of the firing position and to adjust the shooting distance. The barrel was a 60-cm-long hollow steel tube with an inside diameter accommodating the test bullet. The firing device was composed of a breech-loaded barrel coupled to a solenoid valve (Fig. 1B and C), which was used to remote-control the firing pin. Powering of the electromagnetic solenoid via a wired remote-control generated an electromagnetic force that moved the firing pin forward to hit the priming, firing the powder.
2.3.
Ammunition
The most important advantage of the experimental gun was the separation of the gunpowder and projectiles, which allowed adjusting the initial velocity by either increasing or decreasing the amount of gunpowder. The projectiles emulated the 5.56-mm NATO ammunition, characterized by a 3.7 g mass and an initial velocity of 309.3e321.6 m/s. Gunpowder was purchased from Sichuan Nanshan Powder Actuated Fastening System Co, Ltd. Data about the actual velocity and energy of the projectile were provided by the manufacturer. The bullet velocity was obtained using a military ballistic chronograph. The energy of the bullet at the muzzle was then calculated using: E0 ¼ (1/2) mV20. The velocity at impact (V1) is derived by: V1 ¼ V0 (Br) (distance from target to muzzle), where V1 is the velocity available at impact after a period of free flight, V0 is the muzzle velocity, and the constant Br is a derived constant, based on free flight data. Then, the energy at impact (E1) is: E1 ¼ (1/2) m V1, where m is the mass of the projectile. The initial velocity and energy of all ammunition projectiles are well documented and these data were used as the basis of free flight performance (air). At a distance of 15 cm between the muzzle and the target, the initial velocity is almost equivalent to the impact velocity. All pigs were wounded by a projectile having a mean velocity of 309.3e321.6 m/s (172.1e186.1 J), which is equivalent to the speed of a standard 5.56-mm NATO rifle at 800 m (317 m/s, 200.9 J [16].
2.4. CT scanning and three-dimensional CT reconstructions The swine brain was scanned and reconstructed using dynamic and multiplane scans (Volume Zoom Spiral CT, Siemens, Germany). The baseline was the orbitomeatal line. The head was scanned from the skull base to the top of the skull with 1.0-mm slice thickness and 3.0-mm slice interval. Two radiologists with specific experience in neuroimaging independently assessed all images; discrepancies were discussed to reach a consensus. Independent observations by the
j o u r n a l o f s u r g i c a l r e s e a r c h x x x ( 2 0 1 5 ) 1 e9
3
two examiners were compared with each other, as well as with the autopsy reports and circumstantial medical imaging evidence. The two radiologists were asked to note the number of holes detected in the skull; to distinguish the bullet entry and, if present, exit wounds to locate in the three spatial planes the final position of the bullet and bone fragments and to describe tissue lesions so as to trace the bullet’s likely course within the pig’s brain.
to cover the surgical wounds. If a swine became apneic after wounding and if spontaneous breathing did not resume within 1 min, the animal was ventilated until spontaneous breathing resumed or for a maximum of 30 min. Control pigs (n ¼ 4) were randomly selected from the 24 pigs before procedures. They underwent anesthesia, craniotomy, and placement in the stereotactic frame but were not wounded. The number and causes of death were recorded.
2.5.
2.7.
Surgical procedures
The swine were fasted overnight but had free access to water on the day before operation. All subsequent invasive procedures were performed under aseptic conditions. Swine were premedicated with droperidol (5 mg intramuscular) and atropine (0.01 mg/kg intramuscular) 1 h before surgery. Anesthesia was induced with ketamine (20 mg/kg intramuscular) and maintained with propofol (2e4 mg/kg intravenous). Ringer solution (2 mL/kg/h) was administered throughout the experiment. Tracheal intubation and mechanical ventilation were used. Bilateral groin incisions were made for femoral artery cannulations. One femoral artery was cannulated for monitoring mean arterial blood pressure and heart rate (HR) using a pressure transducer, whereas the other femoral artery catheter was used for blood sampling. A central venous catheter was inserted into the exposed right jugular vein. Vitals were monitored using a PiCCO device (Pulsion Medical Systems AG, Mu¨nchen, Germany). A 12-Fr Foley catheter was inserted in the urinary bladder. All incisions were closed. Prophylactic antibiotic (ceftriaxone disodium) treatment was given to all pigs. Famotidine injections were given intravenously to prevent damage to the stomach mucosa.
2.6.
Physiological assessment
Rectal temperature, urine volume per hour, hemodynamics (mean arterial pressure, HR, and central venous pressure), and hematologic (hemoglobin, hematocrit, white blood cell, and neutrophils) indexes were recorded 10 and 30 min after gunshot, and 4 mL blood was sampled from the carotid artery. After anticoagulant treatment with heparin, the samples were used for blood routine biochemistry (lactic acid, pH value, and base excess) analysis by an FC-717 blood routine analyzer (CIS Inc, Tokyo, Japan) and for coagulation parameters (prothrombin time and partial thromboplastin time) analysis using an ACT TOP automatic coagulation analyzer (Beckman Coulter Inc, Brea, CA).
2.8.
Statistical analysis
All analyses were performed using SPSS 17.0 (SPSS Inc, Chicago, IL). Continuous variables are presented as mean standard deviation and were analyzed using a oneway repeated-measures analysis of variance followed by Tukey post hoc test to assess the difference between time points (baseline, and 10 and 30 min after the shot). P values
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.JournalofSurgicalResearch.com
Establishment of swine-penetrating craniocerebral gunshot wound model Huchen Lu, MD,a Lian Wang, MD, PhD,b Wuzhao Zhong, MD,a Rongfeng Qi, MD, PhD,c Ning Li, MD,a Wanchun You, MD, PhD,a Xingfeng Su, MD, PhD,a Zong Zhuang, MD, PhD,a Huilin Cheng, MD, PhD,a,* and Jixin Shi, MD, PhDa,* a
Department of Neurosurgery, Jingling Hospital, Medical School of Nanjing University, Nanjing, China Department of Thoracic Surgery, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China c Department of Medical Imaging, Jingling Hospital, Medical School of Nanjing University, Nanjing, China b
article info
abstract
Article history:
Background: Bullet-induced brain wounds are common among military personnel in war
Received 12 June 2014
zones and among civilians with gun accidents or crime-related gun injuries. The goal of
Received in revised form
this study was to develop a nonfatal porcine model of penetrating craniocerebral gunshot
17 December 2014
wound (PCGW) by firing a projectile in live swine to induce PCGW in such a realistic
Accepted 7 January 2015
manner as to reconstruct their physical characteristics.
Available online xxx
Materials and methods: We established a nonfatal porcine model of PCGW based on a customdesigned experimental gun that emulates the shooting of a 5.56-mm NATO standard rifle at
Keywords:
800 m (317 m/s; 200.9 J). Commercial swine (n ¼ 20) were subjected to a ballistic wound to the
Animal models of injury
bilateral frontal lobe, and four swine were used as controls. Surviving swine were used in sub-
Bullet wound
sequent first-aid, management, and monitoring experiments for neurosurgeons. Various
Penetrating brain injury
physiological variables were measured continuously. After computed tomography (CT) scanning
Gunshot wounds
and three-dimensional CT reconstructions, all pigs underwent primary lifesaving emergency
Damage control
interventions, including emergency decompressive craniotomies and hemorrhage control. Results: In our nonfatal porcine model of PCGW, injuries were comparable in their morphology to real gunshot wounds, as evidenced by analysis of wound characteristics and CT scan images. The survival rates of the pigs were 100% within 2 h, 95% within 6 h, 85% within 12 h, and 85% within 24 h (P < 0.01). Hemodynamics, hematology, blood routine biochemistry, coagulation, and other physiological parameters also exhibited significant changes in the PCGW pigs. Conclusions: This model makes possible the laboratory reproduction of real ballistic wounds in a live large animal model that is close to humans. ª 2015 Elsevier Inc. All rights reserved.
1.
Introduction
Penetrating craniocerebral gunshot wounds (PCGWs) are the most devastating type of projectile injuries to the head [1e3].
They are usually caused by gun projectiles or by bomb shrapnel. Much experience in PCGW treatment was gained during the First and Second World Wars [4,5], as well as during subsequent large-scale global conflicts [6], but PCGWs
* Corresponding authors. Department of Neurosurgery, Jingling Hospital, Medical School of Nanjing University, Nanjing 210000, China. Tel.: þ86 15195982516; fax: þ86 21 64085785. E-mail addresses: [email protected] (H. Cheng), [email protected] (J. Shi). 0022-4804/$ e see front matter ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jss.2015.01.006
2
j o u r n a l o f s u r g i c a l r e s e a r c h x x x ( 2 0 1 5 ) 1 e9
still have high mortality and morbidity rates [7]. PCGWs are rarer in civilian practice; nevertheless, the mortality rate is >50% [8,9]. The complicated injury patterns created by gunshots, either by military weapons in war zones or by civilian weapons (e.g., handling or hunting accidents, crimes), present a great challenge to conventional diagnosis and treatment. The approach to PCGW has undergone significant evolution and offers unique challenges. As a result, research focusing on the pathophysiological mechanisms is necessary. For almost a century, a number of animal PCGW models [10e13] have been developed and have helped to understand the mechanisms of the physiological response and cerebral edema formation. However, more in-depth studies are difficult to carry out because of the short survival time following PCGW due to the high energy of military cartridges and bullets. Carey et al. [13] established a model of penetrating injuries to the cerebral hemispheres in cats, based on the release of pressurized helium propellant. Recently, Williams et al. [14] successfully developed a right frontal lobe gunshot wound model in rats using air pressure needle, which primarily recreates the temporary cavity found around a penetrating bullet injury. Another rat model used the implantation of a small lead pellet in the brain [15]. However, these models might be impaired because of the differences in the brain size compared with humans and to the method used to induce PCGW. The aim of this study was to develop a nonfatal porcine model of PCGW by firing a projectile in live animals to induce PCGW in such a realistic manner as to reconstruct their physical characteristics. In addition, swine surviving the gunshot were used for first-aid, management, and monitoring experiments. Our goal was to lay the groundwork for the expected clinical wound patterns and for the subsequent realcase surgical procedures in a large animal model that is close to humans in size and brain morphology. This article presents model making, autopsy, and radiologic assessments of 24 pigs with PCGW caused by gunshot wounds from an experimental gun.
2.
Materials and methods
2.1.
Animal preparation
A total of 24 3-mo crossbred commercial swine (35.9 2.8 kg) were used for all experiments (Chinese Academy of Science, Nanjing University Animal Center, Nanjing, China). All animals received humane care in compliance with “The Principles of Laboratory Animal Care” formulated by the National Society of Medical Research and “The Guide for the Care and Use of Laboratory Animals” from the U.S. National Institutes of Health (Publication No. 85e23, revised 1996). The experimental protocol was approved by the Nanjing University Animal Care and Use Committee. The pigs were housed at the Animal Center of Jinling Hospital for at least 7 d before experiments to allow them to adjust to the environment. Pigs were fed a standard diet ad libitum and were housed at 21 C with a 12h lighte dark cycle.
2.2.
Experimental gun
The experimental gun was composed of a stereotaxic head holder, a barrel, a firing device, and an electronic control device (Fig. 1A), and was co-developed by our hospital and the Sichuan Nanshan Powder Actuated Fastening System Co, Ltd (Nanxi, China), which is a company specialized in the conception and building of powder-powered fastening tools such as nailers. The stereotactic head holder fixed the gun to the animal’s head allowing the precise determination of the firing position and to adjust the shooting distance. The barrel was a 60-cm-long hollow steel tube with an inside diameter accommodating the test bullet. The firing device was composed of a breech-loaded barrel coupled to a solenoid valve (Fig. 1B and C), which was used to remote-control the firing pin. Powering of the electromagnetic solenoid via a wired remote-control generated an electromagnetic force that moved the firing pin forward to hit the priming, firing the powder.
2.3.
Ammunition
The most important advantage of the experimental gun was the separation of the gunpowder and projectiles, which allowed adjusting the initial velocity by either increasing or decreasing the amount of gunpowder. The projectiles emulated the 5.56-mm NATO ammunition, characterized by a 3.7 g mass and an initial velocity of 309.3e321.6 m/s. Gunpowder was purchased from Sichuan Nanshan Powder Actuated Fastening System Co, Ltd. Data about the actual velocity and energy of the projectile were provided by the manufacturer. The bullet velocity was obtained using a military ballistic chronograph. The energy of the bullet at the muzzle was then calculated using: E0 ¼ (1/2) mV20. The velocity at impact (V1) is derived by: V1 ¼ V0 (Br) (distance from target to muzzle), where V1 is the velocity available at impact after a period of free flight, V0 is the muzzle velocity, and the constant Br is a derived constant, based on free flight data. Then, the energy at impact (E1) is: E1 ¼ (1/2) m V1, where m is the mass of the projectile. The initial velocity and energy of all ammunition projectiles are well documented and these data were used as the basis of free flight performance (air). At a distance of 15 cm between the muzzle and the target, the initial velocity is almost equivalent to the impact velocity. All pigs were wounded by a projectile having a mean velocity of 309.3e321.6 m/s (172.1e186.1 J), which is equivalent to the speed of a standard 5.56-mm NATO rifle at 800 m (317 m/s, 200.9 J [16].
2.4. CT scanning and three-dimensional CT reconstructions The swine brain was scanned and reconstructed using dynamic and multiplane scans (Volume Zoom Spiral CT, Siemens, Germany). The baseline was the orbitomeatal line. The head was scanned from the skull base to the top of the skull with 1.0-mm slice thickness and 3.0-mm slice interval. Two radiologists with specific experience in neuroimaging independently assessed all images; discrepancies were discussed to reach a consensus. Independent observations by the
j o u r n a l o f s u r g i c a l r e s e a r c h x x x ( 2 0 1 5 ) 1 e9
3
two examiners were compared with each other, as well as with the autopsy reports and circumstantial medical imaging evidence. The two radiologists were asked to note the number of holes detected in the skull; to distinguish the bullet entry and, if present, exit wounds to locate in the three spatial planes the final position of the bullet and bone fragments and to describe tissue lesions so as to trace the bullet’s likely course within the pig’s brain.
to cover the surgical wounds. If a swine became apneic after wounding and if spontaneous breathing did not resume within 1 min, the animal was ventilated until spontaneous breathing resumed or for a maximum of 30 min. Control pigs (n ¼ 4) were randomly selected from the 24 pigs before procedures. They underwent anesthesia, craniotomy, and placement in the stereotactic frame but were not wounded. The number and causes of death were recorded.
2.5.
2.7.
Surgical procedures
The swine were fasted overnight but had free access to water on the day before operation. All subsequent invasive procedures were performed under aseptic conditions. Swine were premedicated with droperidol (5 mg intramuscular) and atropine (0.01 mg/kg intramuscular) 1 h before surgery. Anesthesia was induced with ketamine (20 mg/kg intramuscular) and maintained with propofol (2e4 mg/kg intravenous). Ringer solution (2 mL/kg/h) was administered throughout the experiment. Tracheal intubation and mechanical ventilation were used. Bilateral groin incisions were made for femoral artery cannulations. One femoral artery was cannulated for monitoring mean arterial blood pressure and heart rate (HR) using a pressure transducer, whereas the other femoral artery catheter was used for blood sampling. A central venous catheter was inserted into the exposed right jugular vein. Vitals were monitored using a PiCCO device (Pulsion Medical Systems AG, Mu¨nchen, Germany). A 12-Fr Foley catheter was inserted in the urinary bladder. All incisions were closed. Prophylactic antibiotic (ceftriaxone disodium) treatment was given to all pigs. Famotidine injections were given intravenously to prevent damage to the stomach mucosa.
2.6.
Physiological assessment
Rectal temperature, urine volume per hour, hemodynamics (mean arterial pressure, HR, and central venous pressure), and hematologic (hemoglobin, hematocrit, white blood cell, and neutrophils) indexes were recorded 10 and 30 min after gunshot, and 4 mL blood was sampled from the carotid artery. After anticoagulant treatment with heparin, the samples were used for blood routine biochemistry (lactic acid, pH value, and base excess) analysis by an FC-717 blood routine analyzer (CIS Inc, Tokyo, Japan) and for coagulation parameters (prothrombin time and partial thromboplastin time) analysis using an ACT TOP automatic coagulation analyzer (Beckman Coulter Inc, Brea, CA).
2.8.
Statistical analysis
All analyses were performed using SPSS 17.0 (SPSS Inc, Chicago, IL). Continuous variables are presented as mean standard deviation and were analyzed using a oneway repeated-measures analysis of variance followed by Tukey post hoc test to assess the difference between time points (baseline, and 10 and 30 min after the shot). P values
