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Risk Index of Mahmood et al for Intraoperative Blood Transfusion During Endovascular Repair of an Abdominal Aortic Aneurysm

Description

Mahmood et al developed a clinical risk score for predicting the need of intraoperative blood transfusion in a patient undergoing endovascular aneurysm repair. This can help to identify a patient who is likely to need transfusion prior to the surgery. The authors are from Northwestern University, the University of Chicago and Beth Israel Deaconess Medical Center.


Patient selection: endovascular aneurysm repair of an abdominal aortic aneurysm

 

Outcome: intraoperative blood transfusion

 

Parameters:

(1) ASA classification

(2) hemoglobin concentration in g/dL

(3) diameter of the aneurysm in mm

(4) age of the patient in years

 

Parameter

Finding

Points

ASA class

ASA 1

1

 

ASA 2

2

 

ASA 3

3

 

ASA 4

4

 

ASA 5

5

hemoglobin

> 14.5 g/dL

1

 

13.6 to 14.5

2

 

12.3 to 13.5

3

 

< 12.3

4

diameter of the aneurysm

< 52 mm

1

 

52 to 55 mm

2

 

56 to 60 mm

3

 

> 60 mm

4

age in years

< 69 years

1

 

70 to 75 years

2

 

76 to 81 years

3

 

> 81 years

4

 

total score =

= SUM(points for all 4 parameters)

 

Interpretation:

• minimum score: 4

• maximum score: 17

• The higher the score the more likely that the patient will need to be transfused.

 

If the actual outcome in Figure 1 is analyzed:

 

Score

Percent Transfused

4

0

5

0

6

1%

7

2%

8

2.5%

9

3%

10

4%

11

6%

12

8%

13

10%

14

12%

15

21%

16

31%

17

68%

 

Performance:

• The scoring indicates that the risk increase per step is linear, which is arguable for ASA class and aneurysm diameter. This may explain the deviation in Figure 1.

• The area under the ROC curve was 0.73 for the derivation set.


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