Protective effects of dexmedetomidine combined with lung-protective ventilation on lungs in patients undergoing thoracic surgery

Objective To evaluate protective effects of dexmedetomidine combined with lung-protective ventilation on lungs in patients undergoing thoracic surgery. Methods Eighty patients with normal pulmonary function, aged 40-64 yr, of American Society of Anesthesiologists physical status Ⅰ or Ⅱ, with body mass index of 20-25 kg/m2, scheduled for elective right lobectomy for lung cancer performed via a thoracoscope, were divided into 4 groups (n=20 each) using a random number table: conventional ventilation group (group C), dexmedetomidine combined with conventional ventilation group (group DC), lung-protective ventilation group(group P) and dexmedetomidine combined with lung-protective ventilation group (group DP). In DC and DP groups, dexmedetomidine was intravenously infused as a loading dose of 0.5 μg/kg (over 10 min) starting from 10 min before anesthesia induction, followed by an infusion of 0.6 μg·kg-1·h-1 until the end of surgery.In C and DC groups, the tidal volume was set at 9 ml/kg, positive end-expiratory pressure 0 cmH2O, fraction of inspired oxygen 100%, respiratory rate 10-12 breaths/min, inspiratory/expiratory ratio 1∶2, and end-tidal pressure of carbon dioxide was maintained at 35-45 mmHg during both two-lung ventilation (TLV) and one-lung ventilation (OLV). In P and DP groups, the tidal volume was set at 6 ml/kg, positive end-expiratory pressure 5 cmH2O, fraction of inspired oxygen 70%, respiratory rate 14-16 breaths/min, inspiratory/expiratory ratio 1∶2, and end-tidal pressure of carbon dioxide was maintained at 35-45 mmHg during TLV and OLV.Airway peak pressure (Ppeak), airway plateau pressure (Pplat), dynamic lung compliance and airway resistance (Raw) were monitored and recorded immediately before OLV (T1), at 30 min, 1 h and 2 h of OLV (T2-4) and at 15 min after restoration of TLV (T5). Arterial blood samples were collected at 10 min before induction of anesthesia (T0) and T1-5 for blood gas analysis, and oxygenation index was calculated.At T0, T1, T3, T4 and 2 and 24 h after surgery (T6, 7), blood samples were taken from the right internal jugular vein for determination of the concentrations of serum tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and high-mobility group box 1 protein (HMGB1) by enzyme-linked immunosorbent assay. Results Compared with group C, Raw was significantly decreased at T2-4 in group DC, Ppeak, Pplat and Raw were significantly decreased at T2-4 in P and DP groups, oxygenation index was significantly increased at T5 in DC and P groups, oxygenation index was significantly increased at T2-5 in group DP, the concentrations of serum TNF-α and IL-6 were significantly decreased at T3, 4 and T6, 7 in P, DC and DP groups, and the concentrations of serum HMGB1 were significantly decreased at T6, 7 in DC and DP groups (P 0.05). Conclusion The combination of dexmedetomidine and lung-protective ventilation provides protective effects on lungs and exterts better efficacy than either alone, and the mechanism may be related to inhibiting systemic inflammatory responses of patients undergoing thoracic surgery. Key words: Dexmedetomidine; Respiration, artificial; Respiratory distress syndrome, adult