Gunshot Wound


 
Background
  1. Wound ballistics determined by characteristics of missile and tissue
  2. Bullets of equal wounding potential may produce wounds of varied severity depending on several variables
    • Mass of bullet
      • Caliber
    • Form of bullet
      • Full metal Jacket
      • Expanding / fragmenting projectile
    • Velocity of bullet
    • Area of target struck
    • Angle target struck from

General principles

  1. Caliber of bullet is not the strongest indicator of wounding potential
    • Does not disclose bullet mass
    • Larger calibers do make bigger holes
  2. Velocity (typical U.S. classification)
    • Not a significant factor
    • Low velocity < 2000 feet/sec
    • High velocity > 2000 feet/sec
  3. Penetration
    • Depth to which bullet enters tissue
  4. Ammunition:
    • Inherent "controllable" characteristics
      • Mass
      • Shape, construction
      • Velocity
    • Conferred "uncontrollable" characteristics
      • Angle of attack at impact
      • Composition of target
    • Civilian rounds
      • Usually deformable - expand on impact
        • Size of injury is increased
        • More tissue is crushed
      • Can potentially cause more damage than military equivalents
    • Military rounds
      • More often have full metal jacket
      • Tend to "tumble" in target
      • May pass through target with little deformation

Pathophysiology

  1. Tissue Damage
    • Permanent cavity
      • Direct crush of tissue
      • Disruption / damage directly caused by projectile
      • Represents destroyed tissue
      • Related to size of projectile
      • Related to degree of yaw (projectile "tumbling") in tissue
    • Temporary cavity
      • Tissue "stretch"
      • Can be 11 times permanent cavity diameter
      • Lasts only few milliseconds
      • Essentially similar to blunt trauma
      • Can disrupt blood vessels, break bone
      • Substantial effects in
        • Minimally elastic tissue (brain, liver)
        • Fluid filled organs
  2. Injury determined by
    • Tissue struck
      • Elasticity, density
      • Physiological importance of the tissue
        • Heart/ brain > hand/arm/gut
    • Amount of tissue injured
      • Bullet size
      • Bullet "tumbling"
        • Sideways bullet injures more tissue
      • Bullet deforming
        • Creates a larger projectile/wound diameter
        • More tissue injured
      • Bullet fragmenting
        • Makes multiple projectiles
        • More damage
    • Velocity
      • May not be a significant factor in wound formation

Diagnostics

  1. Inspect body for hemorrhage and wounds
    • Locate all wounds by inspection; place wound markers for imaging
      • Many wounds get missed
        • Scalp
        • Back
    • Estimate missile path for visualization of possible organ damage
  2. Wound types
    • Be careful classifying "entrance" and "exit" wounds
      • Misclassified > 50% of time by ED, surgeons
      • What matters is path of projectile
      • If there is only 1 wound, then it's clearly an entrance wound
    • Entrance wounds
      • Do not necessarily correlate with bullet caliber
        • May be smaller
        • Elastic tissue contracts around wound defect
      • Contact wounds
        • Weapon in contact with skin
        • Usually see burning of skin around wound
        • May see stellate laceration
      • Close range wounds
        • Weapon 6-12 inches from target
        • Soot deposited around wound
      • Intermediate range wounds - short
        • See "tattooing or stippling" around wound
          • Punctate abrasions
          • From unburned gunpowder
        • Usually weapon < 60cm from tissue
      • Long-distance wounds
        • Usually see "abrasion collar" around bullet hole
        • From friction between bullet and epithelium
    • Exit wounds
      • NOT consistently larger than entrance wounds
      • Skin everted outwards
      • NEVER any abrasion collar, soot or tattooing

General Treatment Principles
(For in-depth treatments, please see specific anatomical area involved)

  1. TREAT THE WOUND - NOT THE WEAPON
    • Base decisions on exam and x-rays - NOT "high-velocity / low-velocity" conjecture
  2. Follow ATLS ABCs
  3. Wound care
    • Conservative debridement of tissue
    • Don't sacrifice viable tissue if you are not sure
  4. Tetanus prophylaxis
  5. Antibiotics
    • A controversial topic
      • Gunshot wounds are contaminated
    • Antibiotics should be prescribed on a case-by-case basis
    • High risk wounds:
      • Contaminated by soil, dirt
      • Open fractures
      • Patient immune status compromised
        • Diabetes
        • HIV
        • Massive transfusion
        • Steroid / immunosuppressant use
    • If chosen:
      • Antibiotics should be initiated early
      • Simple extremity GSWs
        • Cefazolin
        • Ampicillin-sulbactam
        • TMP-SMX
        • Clindamycin