Risk Factors of Ryan et al for Predicting Mortality from Thermal Burns

 

Parameters:

(1) age of the patient in years

(2) percent of body surface area involved by second and third degree burns

(3) inhalation injury

Parameter	Finding	Points
age in years	> 60 years of age	1
	<= 60 years of age	0
percent of body surface area covered by burn	> 40%	1
	<= 40%	0
inhalation injury	present	1
	absent	0

 

percent of body surface area (BSA) covered by burn =

= (percent of BSA involved by second degree burn) + (percent of BSA involved by third degree burn)

 

Inhalation injury is considered present if:

(1) the fire had occurred in a closed space

(2) bronchoscopy on admission showed soot below the level of the vocal cords

(3) blood carboxyhemoglobin was elevated on admission

 

The elevation of blood carboxyhemoglobin is not specified:

• normal nonsmokers have a carboxyhemoglobin of 0.5 - 1.5% saturation of hemoglobin

• average smokers can have levels of 4 - 5% saturation of hemoglobin, while heavy smokers can have levels of 8 - 9% saturation of hemoglobin

• toxic levels are considered > 20% saturation of hemoglobin

• in implementation, used > 10% as elevated

 

number of risk factors present =

= SUM(points for the 3 parameters)

 

logit =

= (2.58 * (number of risk factors present)) - 5.89

 

where :

• logit = natural logarithm ((probability of dying) / (probability of living)) =

= natural logarithm ((probability of dying) / (1 - (probability of dying)))

 

If this is rearranged,

 

probability of dying =

= EXP(logit) / (1 + (EXP(logit)))

 

Number of Risk Factors	Mortality Rate
0	0.3%
1	3%
2	33%
3	87%

 

Limitations:

• The method applies to patients less than 90 years of age. It may not apply to patients 90 years or older due to the presence of "do not resuscitate" directives which limit the level of treatment delivered.