Gunshot Wounds
Marcelo Devaud
Outline
Gunshot Wounds
Marcelo Devaud
Trauma Service
Auckland City Hospital
Introduction
• Understand the mechanisms: nature of firearms / projectiles
• Ballistics : scientific study of projectile motion
– internal
– external
– terminal à Wound ballistics: physician to understand
Civilian injuries
• Types of Firearms : handguns, rifles, airguns, and shotguns
• Wounding potential : KE = 1/2 mv2 ( joules )
• Type of projectile
• Type of tissue injured à energy dissipation
• Distance (range)
Handguns and rifles
• bullet strikes tissue à ceases spinning
• looses directional stability à “tumble”
• 180° tumble: mass concentrated at base
– permanent cavity elliptical-shaped tunnel
– temporary cavity shockwave compresses adjacent tissue.
Bullets
• Caliber : diameter (decimals of inch, millimeters)
• Construction
– low-velocity : entirely of lead
– medium- / high-velocity : metal jacket ( copper )
• full metal jacket
• semi-jacketed : deform on impact + fragmentation
hollow-point bullets -> mushroom shape
• Deformation:
– deliver more energy -> ↑ tissue damage
Bullet injuries
• Friable solid organs
– most severe : temp cavitation remote from bullet track
• Dense and loose tissues
– more resistant
– Alter course, slow down,↑ deformity and fragmentation
• straight trajectory à deflected (tissue density ) à straight trajectory
Airguns
• pellets
• air pressure from pumps, springs, or gas canisters
• low muzzle velocity à low wounding potential
• longer barreled à more kinetic energy
• close-range injuries can be fatal
• path of least resistance : fail to penetrate the fascia
Shotguns
• shotgun shells :
– Cartridge size : gauge (↑ gauge à↓ diameter)
– plastic : brass cap at base ( primer )
– wadding ( paper or plastic ): separates charge from pellets
• pellets : ( wounding potential )
– do not spin
– separate after leaving barrel
– velocity rapidly ↓
– many sizes : buckshot, birdshot
Injuries
• Close range ( <15 ft ): greater energy available
– massive destruction: combined mass of multiple pellets over small area
• Intermediate range :
– less predictable: severity function of anatomic location and pellet density
• long range : wider spread / lower velocity
– multiple, widely separated, superficial injuries
– painful but rarely life threatening
Pellet injuries
• Clinical practice : most involve birdshot
• Vascular injuries à embolization more likely
• shotgun pellets : lead / steel
• Steel pellets : move if exposed to magnetic field
– MRI : additional damage (contraindicated)
– Xray : can usually distinguish one from another
• Lead pellets : deformed and fragmented
• Steel pellets : remain round.
Gunshot Injury Assessment
• Prompt and accurate assessment
• entrance - exit wound : unreliable
à Surface wounds : characterize appearance – location
• Xray :
– surgical approach + additional imaging
– paths of the projectiles
– Metallic markers beside each surface wound
– Two projections of injured area
– additional radiographs : If projectile not found - no exit wound
Gunshot Injury Assessment
• Hemodynamically unstable
– Time only for Xray :
• Organs at risk à formulate action plan
• bullet quality, fragmentation, pathway, or other unsuspected foreign bodies
• “lead snowstorm”
– fragments deposited in soft tissues
– conical distribution : apex pointing toward entry site
Hemodynamic instability from presumed hemorrhagic shock precludes detailed imaging
Gunshot Injury Assessment
• Hemodynamically stable :
– CT scan :
• more accurate road map of injury
• better surgical approach: fragment crossed body cavities
– Xray + CT : direction of projectile travel and tissues injured
– CT - Angio :
• bullet or pellets close to major vessels
• significant injuries even when peripheral pulses are normal
– MRI :
• may not be safe : nature of bullet construction unknown
Gunshot Injury Assessment
• bullets not causing mechanical problems can be left in the tissues
• synovial joints : should always be removed
– slow leeching of lead by the synovial fluid
– chronic ↑ serum levels: lead arthropathy - poisoning
Pellet Emboli
• Arterio-arterial and veno-venous
• Prerequisites:
– very little kinetic energy
– diameter of vessel greater than projectile
• arterial circulation à embolize to the upper or lower extremities, intracranial circulation
• Management : dictated by whether symptomatic or asymptomatic
Shotgun wounds
Management
• Symptomatic embolus à peripheral ischemia
– remove as soon as possible ( tissue or neurologic function loss )
• Asymptomatic: may be left alone
– removal is technically difficult
– risk of further embolization or migration
– thrombosis, potential delayed arterial insufficiency
– pseudoaneurysm
Intracranial circulation emboli
• 50% from wounds to the neck and 50% to chest
• Entrance site : carotid - cardiac - pulmonary vein and vertebral artery
• Survivors : neurologic impairment
• Treatment :
– arteriotomy with removal of missile
– repositioning of pellet with clip to prevent migration
– supportive measures
• change in the neurologic examination : suspicion for delayed arterial migration
Extrathoracic veno-venous pellet emboli
• lodged in the right ventricle and in the pulmonary artery
• can be left in situ without risk of complications
• can be retrieved via percutaneous techniques with fluoroscopic guidance
• Acute setting: presence suggests major venous injury at entrance site that needs immediate exploration to prevent further embolization
Extremity arterio-arterial pellet emboli
• If no compromise to distal circulation à left without risk.
– ↓ patient morbidity without risk of late complications
• Exploration :
– Embolectomy catheters or direct arteriotomy (milking)
– Proximal and distal arterial control
– Numerous pellets and wadding usually found
– soft tissue defect : ( type III )
aggressive debridement - local flap coverage of vital structures - delayed closure of defect
Nonoperative Management of Abdominal
Gunshot Wounds
• Mandatory surgical exploration for GSW to abdomen has been a surgical dictum (WWII)
– hemodynamic instability
– Peritonitis
• Selective nonoperative treatment is gaining acceptance: HD stable patients without peritonitis
– Physical examination
– CT, DPL, Laparoscopy
Nonoperative treatment GSW
• avoids complications of unnecessary laparotomy
– 41.3% : atelectasis, prolonged ileus and UTI
– 2.5% : small bowel obstruction
– increases hospital length of stay and cost of care
• no significant increase in complications from delayed operative procedure in patients initially lacking positive clinical signs (<24 hours).
Clinical examination
• reliable and sensitive in dg intra-abdominal injury
• 1° Survey (ABC)
– HD unstable à OT
• 2° Survey : (HD stable)
– Peritoneal irritation à OT
– Retroperitoneum: ? Signs
– Distracting injuries: head trauma / intoxication
– hidden wounds :axilla, groin, perineum, gluteal folds
Determination of Trajectory
• determine whether bullet has entered peritoneal cavity
• Diagnostic Peritoneal Lavage :
– blood in the peritoneum : 10,000 RBCs/mm3
– bedside procedure, quick and accurate
– no information on specific injuries
– PPV: 96.7% , Sens: 87.5%
Determination of Trajectory
• Abdominal CT :
– valuable information in HD stable patients
– 3-D determination of missile trajectory
– defines injuries that may not need laparotomy
– missed injury : diaphragm
Determination of Trajectory
• Laparoscopy :
– limiting the need for full laparotomy
– Examination of anterior intra-abdominal structures
– Advantage over laparotomy :
• incision size , recovery time, pain, and shorter LOS
– Limitations : retroperitoneum - posterior diaphragm
aspects of small and large bowel
– indication : determining peritoneal penetration
Thoracoabdominal Wounds
• thoracic and abdominal contents
• motion of the diaphragm
• injuries treated differently, depending on side :
– Right : (7%) nonoperative
– Left: diaphragm and hollow visceral injury
• 31% : no signs of peritonitis
• 40% : normal chest radiograph
à Diagnostic laparoscopy
The Back and Flank
• paucity of literature : small numbers of patients
• Evaluating patients is especially difficult :
– Retroperitoneum : peritoneal irritation delayed or missing
– laparoscopy and DPL have limited value
• CT : test of choice à “triple contrast”
• selective nonoperative management appropriate and safe
The Pelvis
• restricted space with densely crowded internal structures
• transpelvic injuries : 85% organ injury
• selective nonoperative approach :
– adjuncts : urinalysis + rigid proctoscopy
• clinical examination :100% sensitive and 95.3% specific
Patient Selection
• ED physician : active role in initial resuscitation
• surgeon must always be involved with decision
• factors to be considered :
– clinical examination + determination of trajectory
– repeated reliable examinations
– Type of Weapon : tissue destruction
Conclusions
• studies are small and have wide confidence intervals
• larger studies : few groups of Level I trauma centers
• Small census of GSW may not allow practitioners to develop the mature judgment
• Level II and III trauma centers need to determine universality of this type of management
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