Nebulized dexmedetomidine improves pulmonary shunt and lung mechanics during one-lung ventilation: a randomized clinical controlled trial

BACKGROUND: Dexmedetomidine (Dex), a selective a(2)-adrenergic receptor agonist, has been previously reported to attenuate intrapulmonary shunt during one-lung ventilation (OLV) and to alleviate bronchoconstriction. However, the therapeutic effects of nebulized Dex on pulmonary shunt and lung mechanics during OLV have not been evaluated. Here we determine whether nebulized dexmedetomidine improved pulmonary shunt and lung mechanics in patients undergoing elective thoracic surgery in a prospective randomized controlled clinical trial. METHODS: One hundred and twenty-eight patients undergoing elective thoracoscopic surgery were included in this study and randomly divided into four groups: 0.9% saline (Placebo group), 0.5 µg/kg (Dex(0.5) group), 1 µg/kg (Dex(1) group) and 2 µg/kg (Dex(2)group) dexmedetomidine. After bronchial intubation, patients received different nebulized doses of dexmedetomidine (0.5 µg/kg, 1 µg/kg and 2 µg/kg) or 0.9% saline placebo during two-lung ventilation(TLV). OLV was initiated 15 min after bronchial intubation. Anesthesia was maintained with intravenous infusion of cisatracurium and propofol. Bispectral Index values were maintained within 40–50 by adjusting the infusion of propofol in all groups. Arterial blood gas samples and central venous blood gas samples were taken as follows: 15 min after bronchial intubation during two-lung ventilation (TLV(15)), after 30 and 60 min of OLV (OLV(30)and OLV(60), respectively) and 15 min after reinstitution of TLV (ReTLV). Dynamic compliance was also calculated at TLV(15), OLV(30), OLV(60) and ReTLV. RESULTS: Dex decreased the requirement of propofol in a dose-dependent manner(P = 0.000). Heart rate (HR) and mean arterial pressure (MAP) displayed no significant difference among groups (P = 0.397 and 0.863). Compared with the placebo group, Dex administered between 0.5 and 2 µg/kg increased partial pressure of oxygen (P(a)O(2)) significantly at OLV(30) and OLV(60)(P = 0.000); however, Dex administered between 1 and 2 µg/kg decreased pulmonary shunt fraction (Q(s)/Q(t)) at OLV(30) and OLV(60)(P = 0.000). Compared with the placebo group, there were significant increases with dynamic compliance (Cdyn) after OLV in Dex(0.5), Dex(1) and Dex(2)group(P = 0.000). Conclusions. Nebulized dexmedetomidine improved oxygenation not only by decreasing pulmonary shunt but also by improving lung compliance during OLV, which may be effective in managing OLV.