Objective To investigate the changes of perioperative serum levels of interleukin-6（IL-6）

C-reactive protein （CRP）

and cortisol

as well as gastric intramucosal pH （pHi） and plasma lactate

aiming to compare systemic changes and tissue perfusion during colorectal and orthopaedic surgical procedures. Methods Twenty patients were randomly assigned to two groups

10 cases of operation on vertebral canal

10 cases of colorectal radical operation.Venous blood was drawn at 1 day before operation

2

4

and 6 hours following skin incision

and 1 day after operation

in order to measure serum IL-6

CRP

and cortisol.pHi and plasma lactate were also measured at the same time points.Results Serum concentrations of IL-6 and cortisol increased gradually following operation

reaching the peak value at 6 hours from the beginning of operation.CRP was not detectable until the first day after operation.Peak concentration of IL-6 had positive relationship with CRP.These variables changed more significantly in colorectal group than that in orthopaedic group （P<0.05）.pHi decreased gradually

reaching the lowest level at 4 hours from the beginning of operation

and to more extent in colorectal group than that in orthopaedic group （P<0.05）.Conclusion IL-6 may reflect tissue damage more sensitively than CRP.Colorectal surgery might induce systemic disorder to more extent

in terms of immuno-endocrinal aspect as well as tissue perfusion

reflected with pHi.