Objective: To find out if there was any local activation of complement in the vicinity of a colonic cancer, and any fluctuation in the function of the complement system during operation.
Design: Prospective study.
Setting: One university and two district hospitals in Denmark.
Subjects: 29 selected patients undergoing emergency and elective operations for colonic cancer.
Interventions: Measurements of systemic and local complement fixation capacity and complement activation in samples of serum or plasma taken before, during, and after operation.
Main outcome measures: Changes in complement fixation capacity and complement activation during operation.
Results: Haemodilution during operation caused a significant reduction in the complement fixation capacity of serum and in the activation of the complement system as measured by generation of C3c. We were unable to confirm the presence of complement inhibitors during operation. Haemodilution caused a 30% reduction in fixation capacity of C3b (12/29 samples of serum had values more than 2SD below the mean of the reference range compared with 4/29 before operation). The activity of C4 was reduced by 25% during operation and the capacity of the complement system to fix C3b and C4b was restored to baseline nine days postoperatively. Concentration of C3d was significantly higher in serum from tumour venous blood compared with that from peripheral blood during operation.
Conclusion: The presence of complement activation products in the general circulation reflects local activation of the complement system in the vicinity of the tumour, but this may have been influenced by tissue necrosis or subclinical infection. Haemodilution causes a significant reduction in the capacity of the complement system during operation, whereas inhibitory factors associated with the cancer or operation and anaesthesia could not be demonstrated. We found no correlation between complement activity and clinical data.