Defining acute aortic syndrome following trauma: are abbreviated injury scale (AIS)

codes a useful surrogate descriptor?

Field ML, Bashir M, Sastry P, Cuerden R, Richens D

Aortic rupture

Intimal tear IMHhttp://www.lightlabimaging.com/gallery/cvpstill.html

http://uk.wrs.yahoo.com

Acute aortic syndrome. Heart 2001;85:365–368

Background

• Vehicle related blunt traumatic aortic injury typically results in exsanguination and fatality

• A small percentage of patients sustain a lesser, partial thickness aortic injury or contained rupture, allowing transfer to hospital

• The spectrum of aortic injuries included in the description of acute aortic syndrome include: intimal tear, intramural haematoma, localised dissection, contained and uncontained rupture

Objective

• To use Abbreviated Injury Scale (AIS) codes, used in trauma data bases, as a surrogate marker for entities within the spectrum of acute aortic syndrome

Hypothesis• The kinematics of injury are distinct for partial

thickness intimal tears and mural haematoma versus full thickness rupture

Results I – Abbreviated Injury Scales (AIS) codes

AIS code AIS Description

420299 4 thoracic aorta, NFS

420202 4 thoracic aorta, intimal tear, no disruption

420204 5 thoracic aorta, intimal tear, with aortic valve involvement

420206 4 thoracic aorta, laceration, NFS, (perforation, puncture)

420208 4 thoracic aorta, laceration, minor

420210 5 thoracic aorta, laceration, major

420212 5 thoracic aorta, laceration, major, with aortic root or valve involvement

420214 5 thoracic aorta, laceration, major, with paraplegia not due to direct spinal cord trauma

420216 5 thoracic aorta, laceration, major, with hemorrhage confined to mediastinum

420218 6 thoracic aorta, laceration, major, with hemorrhage not confined to mediastinum

Intimal injury

Mural injury

Rupture

AAS matched to AIS codes

Methods

• As part of the UK Cooperative Crash Injury Study, which performs detailed vehicle related crash scene analysis, including equivalence test speed (ETS), seatbelt usage, seat position and impact direction, we examined victims with aortic injuries categorised by AIS codes 420200 to 420299

Estimation of combined impact speeds in theLaboratory using vehicle deformation to calculateEstimated Test Speed (ETS)

Results• Of over 16000 analysed crashes in the UK-CCIS database, 132 involved

aortic injuries.• Using AIS codes as surrogate markers there were:

– 9 initimal tears, – 22 intramural haematomas, – 42 localised dissections/ contained ruptures – 41 uncontained ruptures

• Taking this selective group of 132 vehicle related fatalities with BTAI, we were able to relate entities within the spectrum of acute aortic disease to kinematics and mechanism of injury.

• Risk of partial thickness aortic injuries is higher in front and far side impacts while full thickness uncontained ruptures are more likely in near side impacts.

Results: Position in carAIS code AIS Description Front row Second row Unknown Total

420202 4 intimal tear, no disruption 8 1 9

420204 5 intimal tear, with aortic valve involvement 0

420206 4 laceration, NFS, (perforation, puncture) 9 2 1 12

420208 4 laceration, minor 9 1 10

420210 5 laceration, major 29 3 32

420212 5 laceration, major, with aortic root or valve involvement 1 1

420214 5 laceration, major, with paraplegia not due to direct spinal cord trauma 0

420216 5 laceration, major, with hemorrhage confined to mediastinum 17 1 1 19

420218 6 laceration, major, with hemorrhage not confined to mediastinum 36 5 41

420299 4 NFS 7 1 8

    116 11 5 132

Result: Direction of impactAIS code AIS Description Front Side Left Side Right Total

420202 4 intimal tear, no disruption 2 1 3

420204 5 intimal tear, with aortic valve involvement 0

420206 4 laceration, NFS, (perforation, puncture) 2 2

420208 4 laceration, minor 2 3 1 6

420210 5 laceration, major 5 3 5 13

420212 5 laceration, major, with aortic root or valve involvement 1 1

420214 5 laceration, major, with paraplegia not due to direct spinal cord trauma 0

420216 5 laceration, major, with hemorrhage confined to mediastinum 1 5 5 11

420218 6 laceration, major, with hemorrhage not confined to mediastinum 6 6 3 15

420299 4 NFS 1 1 3

    19 19 15 74

Relationship between Estimated Test Speed and Abbreviated Injury Score

AIS versus ETS

40

45

50

55

60

65

70

3 3.5 4 4.5 5 5.5 6 6.5

AIS

ET

S (

km/h

)

Conclusions• AIS codes may be matched to intimal tear, intramural

haematoma, localized dissection and contained/ uncontained rupture

• Mechanism of injury differs for entities within the spectrum of acute aortic syndrome

• Risk of partial thickness injury is higher in frontal and far side impacts while rupture is more common in near side impacts

• Refinement of “Thoracic Vascular” AIS codes in light of our current understanding of acute aortic syndromes would further aid analysis