Morning Report: 5/7/2013

Today’s Morning Report is courtesy of Dr. Joshi!

Blast Injuries: NEJM 2005

DePalma RG, Burris DG, Champion HR, Hodgson MJ. Blast Injuries. NEJM. 2005 Mar 31;352(13):1335-42. PMID: 15800229.

How to categorize Injuries:

Few bombings in the US –

1995 Okalahoma bombing killed 168, injured 518
2004 Madrid train bombing
Iraq
Israel

Problem – improvised explosive devices are often loaded with metallic objects to cause penetrating injuries in crowded areas.

Types of Bombs: Conventional, Enhanced-Blast

Conventional

Conventional bombs generate blast wave that spreads from point source
Blast wave has two parts: (physics is nonlinear and complex)
- 1. Shock wave of high pressure
- 2. Blast wind aka air in motion

*** Blast wave damage decreases exponentially the further away you are, but there is a reversal of wind back toward the blast and UNDERPRESSURIZATION.

Underpressurization – causes organ damage

Enhanced-Blast Explosive Devices – significantly greater energy dissipated

MORE DAMAGE
- Primary Blast – disseminates explosive and then triggers it to cause a SECOND explosion
  - Therefore, the high pressure wave generated radiates to a MUCH larger area
  - Therefore, prolonging the overpressurization phase
Greater proportion of primary blast injuries than conventional devices

TIP: Blast injuries should be suspected in any pt regardless of the distance the pt was from the blast center and regardless of visible signs of injury.

Types of Blast Injuries:

1 – Different effect of pressure

2 – Effects of projectiles

3 – Effect of Structural damage and being thrown by wind

4 – Burns, asphyxia, exposure to toxic inhalants

Primary Blast Injuries – Barotrauma : over or underpressurization

Mostly organs that are air-filled and airfluid levels
TM membrane, pulmonary damage, air embolis, repture of hollow viscus
Increase in pressure of 5psi is enough to reputure TM
TM neurapraxia – deafness, tinnitus, vertigo
56-76 psi needed to damage other organs
Therefore, if no rupture of TM, then other organs likely fine regarding primary injury
Lungs: pneumo, hemo, subq emphysema, pulm edema, air emboli
Colon: most common hollow viscous perforated; mesenteric ischemia
Eye: rupture of globe, serous retinitis, hyphema
Brain: LOC, TBI

Secondary Blast Injuries – Projectiles / Explosives

Penetrating wounds
- Primary fragments – come from the explosive itself
- Secondary fragments – come from the explosion, ie broken glass from windows

Tertiary Blast Injuries –Structure and Wind

Blast can cause structural damage and fragmentation of buildings/vehicles
Crush Syndrome – metabolic derangement resulting from damage to muscle leads to renal failure
Compartment Syndrome – damaged edematous muscle in inelastic sheath; don’t forget the abdomen
Pts trapped for many hours to days may die from the crush and compartment syndromes
Thrown into other objects by wind

Quaternary Blast Injuries- explosion related injuries from persisting conditions

Burns, problems related to if you are on anticoagulation, or if you are pregnant, toxins
Ex. Resp illness related to 9-11 bombings

General Concepts:

Injuries in closed areas like buildings or buses will have more victims with primary injury than in open areas (Israel bus bomb vs. air bomb)
Injuries are BIPHASIC (high immediate deaths, followed by low early and late mortality rates)
Triage: “greatest good for the greatest number”
Goal – find critically ill with CORRECTABLE conditions among the many people with minor injuries
Up to 28% of blast survivors may have serious eye injuries
The care of a child is more resource intensive than the care of an adult
During pregnancy, direct injury of the fetus is said to be uncommon, due to amniotic fluid, but the attachment to the placenta is at risk and could lead to placental abruption (high density uterine wall and low density placental medium).