Interleukin-6 and Hospital Length of Stay after Open-heart Surgery.

BACKGROUND

Interleukin-6 (IL-6) is a multi-function, pro-inflammatory cytokine that is chronically elevated in heart diseases. Research suggested that IL-6 may play an important role in the development of systemic inflammatory response syndrome (SIRS) following cardiopulmonary bypass (CPB) used in major open-heart surgery. The present study capitalized on a previous report that used non-laboratory preoperative data of 235 patients undergoing open-heart surgery to predict their length of hospitalization (LOH) following open-heart surgery.

METHODS

All patients underwent cardiac surgery (e.g., CABG, valve repair or valve replacement surgery), requiring CPB. Two weeks prior to their scheduled operation, trained research assistants blinded to cardiac indices and laboratory data recruited patients for a psychosocial study and conducted interviews. Key cardiac indices were obtained from a national database: the Society of Thoracic Surgeons' (STS) Adult Cardiac Database at the hospital. Blood samples were collected three days postoperatively for biomarker assays. Plasma was stored within 30 minutes of acquisition. Plasma IL-6 was measured using a sandwich enzyme immunoassay kit, Quantikine High-Sensitivity IL-6 (R&D Systems, Minneapolis MN) with no modification of the manufacturer protocol.

RESULTS

Univariate analysis shows that significantly correlated with LOH were older age, more medical comorbidities, perfusion time and postoperative IL-6. Results from the regression model predicting LOH [F (10, N=215)=8.042, p<.001, R=.282], showed that, among known predictors in the previous report and other STS cardiac indices, only age, perfusion time and postoperative IL-6 were significantly associated with LOH (p<.01).

CONCLUSION

Besides the replication of the previous finding in linking postoperative IL-6 and perfusion time, the study demonstrated the link between postoperative plasma IL-6 and LOH.