Gunshot Wounds

Concept

 

Treat the wound, not the gun velocity

 

Management based on gun velocity old fashioned because

1.  Only 1/3 guns are known 

2.  High velocity guns can produce low energy transfer wounds

 

Wound Ballistics

 

Kinetic Energy = 1/2mv²

- important factor is tissue interaction

- energy transfer

 

Two mechanisms of tissue injury

 

1. Permanent cavity

- tissue actually hit by the bullet

- increases with distance travelled through tissue

 

2. Temporary cavity

- tissue stretched by the bullet passage

- as vacuum created, microbes can be sucked in at exit or entry

- increased with distance travelled through tissue

 

Microbes

 

Bullets are not sterile

- suck microbes in as well

- clothing fabric gets pulled in too

- wadding also gets into wound

 

Pathology

 

Amount of tissue damage depends on

 

1. Bullet type 

- partially jacketed fall apart

- Dum Dum - soft nosed bullets deform and start to spin earlier

 

2. Target tissue

- inelastic brain worse than elastic muscle

- bone fragments can produce their own injury

 

3. Tissue width 

- bullets really cause damage after they spin 180°

- occurs when hit tissue

- has to be > 12cm tissue thickness for this to start

- hence calf may have low energy transfer wound

- thigh / abdomen have high energy transfer

- energy transfer can increase as travel along wound

 

4. High velocity bullets

- have more kinetic energy to transfer

- much worse if start to spin / > 12 cm tissue

- better outcome if already exited prior to spin or fragmentation

 

Management

 

Initial

 

ATLS

- secondary survey

- entry wound / exit wound

- NV injury

- history gun type & range

- cover wound

- ADT & antibiotics

- splint 

 

Abdomen

- all GSW that pass through the abdomen become infected without 2/52 antibiotic treatment

 

Lumbar spine

- all bullets retained in the lumbar spine should be removed acutely

- the cauda equina involves multiple levels & LMN have a better chance of recovery

- better if < 48/24 or > 2/52 to avoid oedema

 

Operative Management

 

 

First OT

- scrub

- large incisions to explore wound

- excise all devitalised tissue 

- washout +++

- skeletal stabilisation

- always leave wound open

 

Remove bullet if

- easy to do so

- danger of later migration causing injury

- likely to cause later pain (i.e. hand / foot)

 

Second OT

- 48 hours

- DPC if wound clean

- SSG / muscle flaps as needed

 

Non-Operative Management

 

In USA good success with non-op management of low energy transfer wounds