Overview :

Aust et al evaluated 30-day mortality in surgical patients using the risk factors from the 1997 Veterans Administration (VA) National Surgical Quality Improvement Program (NSQIP). This can help identify patients who may require more aggressive management or a change in management strategy. The authors are from the University of Texas Health Science Center at San Antonio (UTHSCSA).

Patient data was from the UTHSCSA database, which included women and children. The VA NSQIP data is based largely on male veterans.

Parameters:

(1) serum albumin in g/dL

(2) ASA (American Society of Anesthesiologists) patient classification (from 1 to 5, see above)

(3) age of the patient in years

(4) cancer diagnosis

(5) emergency surgery

(6) VA operative complexity

(7) BUN in mg/dL

(8) low white blood cell count (WBC)

(9) high WBC (using 2 different cutoff values)

where:

• The VA data uses 11,000 as the cutoff for an elevated WBC count (see Table 2, page 1025). This morphed to 14,000 in Figures 4 and 5.

X = data using 1997 VA risk factors =

= (0.9792 * (ASA class)) - (1.0065 * (serum albumin)) + (0.6880 * (points for BUN)) + (1.524 * (points for cancer)) + (0.0379 * (age in years)) + (0.6078 * (points for emergency surgery)) + (0.3898 * (points for low WBC count)) + (0.2953 * (points for high WBC count 1)) - 4.8

probability of 30 day mortality =

= 1 / (1 + EXP((-1) * X))

Y = data using UTHSCSA data without surgical complexity =

= (1.2 * (ASA class)) - (0.87 * (serum albumin)) + (0.65 * (points for cancer)) + (0.023 * (age in years)) + (0.87 * (points for emergency surgery)) - 5.9

probability of 30 day mortality =

= 1 / (1 + EXP((-1) * Y))

Z = data using UTHSCSA data including surgical complexity =

= (1.07 * (ASA class)) - (0.89 * (serum albumin)) + (0.026 * (age in years)) + (0.82 * (points for emergency surgery)) + (0.52 * (points for high WBC count 2)) + (1.2 * (points for VA operative complexity)) - 9.5

probability of 30 day mortality =

= 1 / (1 + EXP((-1) * Z))

Performance:

• The area under the ROC curve (c index)  using the 1997 VA risk factors was 0.902.

• The area under the ROC curve (c index) using the UTHSCSA data without surgical complexity 0.915  and with surgical complexity 0.941.

Aust JB, Henderson W, et al. the impact of operative complexity on patient risk factors. Annals Surgery. 2005; 241: 1024-1028 (Figures 4 and 5, page 1026).