Serum IL-6 as a Surrogate Biomarker of Post-operative Complications in Invasive Orthopaedic Surgeries: A Prospective Observational Study.

Background: Interleukin-6 (IL-6) is a cytokine released in response to tissue injury. Elevated serum IL-6 levels in trauma patients have been linked with increased risk of complications such as inapparent hypoxia (SpO < 94%), acute respiratory distress syndrome, fat embolism syndrome (FES), systemic inflammatory response syndrome, multiple organ dysfunction syndrome and sepsis. This study aims to determine the role of serum IL-6 as surrogate biomarker of post-operative complications after invasive orthopaedic surgeries.

Methods: Thirty-seven adults between 18 and 65 years of age undergoing invasive orthopaedic surgeries were included in this hospital-based study. Serum IL-6 levels were estimated serially in the pre-operative period, after 24 h and 7 days post-operatively. Cases were monitored for post-operative complications.

Results: Serum IL-6 levels showed maximum rise in the first 24 h post-operatively especially among older patients (> 60 years). Older patients undergoing bipolar hemiarthroplasty for neck of femur fracture showed highest median post-operative IL-6 level of 258 pg/ml. Serum IL-6 level > 130 pg/ml measured 24 h after surgery was predictive of post-operative complications (sensitivity of 75%). Among the cases with post-operative complications, inapparent hypoxia was the most common complication/event observed. Cases with sub-clinical FES had highest level of serum IL-6 in first 24 h following surgery with median IL-6 level of 300 pg/ml (range 155-444 pg/ml).

Conclusion: Monitoring serum IL-6 level may help in both anticipation and early detection of post-operative complications in patients undergoing invasive orthopaedic surgeries; potentially enhancing patient safety.