Pilot Study on the Effect of Dexmedetomidine on Inflammatory Responses in Patients Undergoing Lumbar Spinal Fusion

Surgical injury to tissue causes a variety of profound physiologic reactions which are essential for the restoration of an organisms' homeostasis. The inflammatory response involves a surge of stress hormones (i.e. ACTH, cortisol, catecholamines), activation of the complement system, migration of leukocytes to the site of injury, the release of cytokines (i.e. interleukins, tumor necrosis factor), as well as other cellular products (i.e. superoxide radicals, proteases, growth factors) (1-3). An appropriate inflammatory cascade is essential for tissue reconstitution and infection control. The associated impairment of multiple organ function is generally mild, because of the physiological reserve of the biological systems. However, a systemic inflammatory response may also lead to postoperative complications in the elderly, neonates, and patients with significant co-morbidity (4, 5). Indeed, mediators of inflammation may induce fatigue and prolong convalescence in healthy patients. On the other hand, dysregulation or suppression of the inflammatory process may lead to improper wound healing, infection and, as demonstrated recently, even an increase in cancer recurrence due to reduction in natural killer cell activity (6, 7).

Anesthetic management may affect both immunostimulatory and immunosuppressive mechanisms either directly by modulating functions of immune cells or indirectly by attenuating the stress response. For example, inhalational anesthetics inhibit neutrophil function and depress lymphocyte proliferation while increasing pro-inflammatory cytokine levels (8, 9)). Propofol also inhibits neutrophil and monocyte function, and has strong anti-inflammatory and anti-oxidative effects (10). Opioids attenuate the direct cell immune response, but have only minimal effects on systemic inflammatory responses (11). It is expected that the choice of anesthetic technique may disturb the balance between pro- and anti-inflammatory responses thus affecting clinical outcomes. A most advantageous anesthetic choice would enhance or have a neutral effect on cellular immunity while minimizing contribution to the systemic inflammatory response.