LAUSR

OBJECTIVES To characterize and quantify accumulating immunological alterations, pre- and post-operatively in patients undergoing elective surgical procedures. SUMMARY BACKGROUND DATA Elective surgery is an anticipatable, controlled human injury. Although the human response to injury is generally stereotyped, individual variability exists. This makes surgical outcomes less predictable, even after standardized procedures, and may provoke complications in patients unable to compensate for their injury. One potential source of variation is found in immune cell maturation, with phenotypic changes dependent on an individual's unique, lifelong response to environmental antigens. METHODS We enrolled 248 patients in a prospective trial facilitating comprehensive biospecimen and clinical data collection in patients scheduled to undergo elective surgery. Peripheral blood was collected pre-operatively, and immediately upon return to the post- anesthesia care unit. Postoperative complications that occurred within 30 days after surgery were captured. RESULTS As this was an elective surgical cohort, outcomes were generally favorable. With a median follow-up of 6 months, the overall survival at 30 days was 100%. However, 20.5% of the cohort experienced a postoperative complication (infection, readmission, or system dysfunction). We identified substantial heterogeneity of immune senescence and terminal differentiation phenotypes in surgical patients. More importantly, phenotypes indicating increased T-cell maturation and senescence were associated with postoperative complications and were evident pre-operatively. CONCLUSIONS The baseline immune repertoire may define an immune signature of resilience to surgical injury and help predict risk for surgical complications.