ObjectiveTo examine whether surgical stress causes blood cells to lose their responsiveness to endotoxin during surgery.DesignProspective case series.SettingA university hospital.PatientsSixteen volunteers classified as American Society of Anesthesiologists physical status I–II who were scheduled for elective distal partial gastrectomy.InterventionsWe studied nine patients who underwent elective distal partial gastrectomy. Blood samples for tumor necrosis factor (TNF) and interleukin (IL)-10 assay were obtained before anesthesia, preincision, 2 hrs and 4 hrs postincision, postextubation, and 24 hrs postincision. The rest of each blood sample was diluted with 5 volumes of endotoxin-free saline, incubated for 4 hrs in the presence of lipopolysaccharide (LPS), centrifuged to remove cells, and assayed for TNF. In another seven patients, antihuman IL-10 antibody was added into the diluted whole blood sample before LPS stimulation.Measurements and Main ResultsTNF activity was not detected in the blood of any patient throughout the study. In contrast, plasma cortisol and IL-10 levels increased rapidly during surgery (p< .01,p< .05, respectively). LPS-induced TNF activity in whole blood decreased significantly during surgery (p< .01) and recovered to control levels by 24 hrs postincision. The peak suppression of LPS-induced TNF and the peak value of plasma IL-10 levels occurred postextubation. Treatment with anti-IL-10 antibody partially restored the ability of LPS to induce TNF activity postextubation (p< .05).ConclusionsSurgical trauma rapidly induces a transient hyporesponsiveness of blood cells to endotoxin. Plasma IL-10, which increases during surgery, participates in this hyporesponsiveness.