Pulmonary Injury in Patients Undergoing Complex Spine Surgery

Introduction: After sequential anterior-posterior spinal fusions (AP) for spinal deformities a significant number of patients demonstrate pulmonary injury in the form of elevated pulmonary vascular resistance and hypoxemia. We reported that the bronchoalveolar lavages (BAL) of these patients revealed increases in neutrophils and lipid laden macrophages (LLM). This report includes the analysis of the BAL for cytokine levels: TNF-± and IL-6.

Methods: With IRB approval, 15 adult patients for elective AP fusions underwent BAL. Following induction of general anesthesia BAL was performed prior to surgery (baseline), after insertion of the posterior spinal instrumentation (PSF), and the morning after surgery prior to extubation (POD1). The BAL was 3-washes of 60cc of 0.9% saline from a fiberoptic bronchoscope wedged in the right middle lobe and lingual. BAL fluid was concentrated via centrifugation and assayed for IL-6 and TNF-± using commercially available ELISA kits.

Results: As a group, patients exhibited increases in BAL cytokine levels with surgery. Increases in TNF- ± correlated with increases in IL-6. There was also a strong correlation with the concentration of IL-6 and the number of LLM. Patient 8, who had the highest levels of BAL lipid laden macrophages and acute lung injury, also had high levels of IL-6 and TNF- ± on POD1. Six patients exhibited significantly elevated TNF- ± and IL-6 levels and 3 of the 6 had evidence for acute lung injury.

Conclusion: Acute lung injury is a diffuse pulmonary response to direct injury to lung tissue. There are multiple possibilities for the cause of direct lung injury during AP spine fusions including the embolization of fat and bone marrow debris. This probably triggers the release of acute phase reactants including cytokines. Cytokines are known to amplify inflammatory responses in the lungs, and an elevated IL-6 level has been found in the BAL of patients at risk for adult respiratory distress syndrome. We have demonstrated that the BAL fluid of patients undergoing AP fusions has elevated cytokine levels and in some of the patients this may be the cause of acute lung injury. Reference: Urban MK et al. Spine. 2001;26:387-390.