Overview :

Cohen et al classified surgical procedures based on the operative complexity. The authors are from the University of Manitoba and University of Saskatchewan in Canada.

Complexity categories:

(1) major

(2) intermediate

(3) minor

Modifications:

• Minimally invasive surgery was not available at the time. One way to incorporate this would be to reduce the complexity rating by one level.

• Organ transplant surgery would qualify from major (heart-lung) to intermediate (renal).

In the paper's analysis of risk for mortality in the week following surgery, the odds ratio for intermediate surgery was 1.8 and for major surgery was 3.8 relative to minor surgery.

Cohen MM, Duncan PG, Tate RB. Does anesthesia contribute to operative mortality? JAMA. 1988; 260: 2859-2863.