Effect of ischemic preconditioning combined with dexmedetomidine on lung injury induced by limb ischemia-reperfusion in patients undergoing orthopedic surgery

Yiliu YANG; Jianli LI; Junfang RONG

ABSTRACT

Objective:

To evaluate the effect of ischemic preconditioning combined with dexmedetomidine on lung injury induced by limb ischemia-reperfusion (I/R) in patients undergoing orthopedic surgery.

Methods:

Seventy-five patients of both sexes, aged 50-89 yr, with body mass index of <35 kg/m 2, of American Society of Anesthesiologists physical status Ⅱ or Ⅲ, scheduled for elective lower extremity surgery with tourniquet, were divided into 4 groups using a random number table

method:

control group (group C, n=17), ischemic preconditioning group (group IP, n=19), dexmedetomidine group (group D, n=19) and ischemic preconditioning combined with dexmedetomidine group (group IPD, n=20). The patients underwent three cycles of 5 min ischemia which was induced by a tourniquet placed on the upper extremity and inflated to 200 mmHg, followed by 5 min deflation at 24 h before surgery in group IP and group IPD.In D and IPD groups, dexmedetomidine was intravenously infused at a loading dose of 0.5 μg/kg over 15 min starting from the time point after the patients were in the supine position, followed by an infusion of 0.5 μg·kg -1·h -1 until the end of surgery, while the equal volume of normal saline was given instead in group C. Before using the the tourniquet (T 0), immediately after loosing the tourniquet (T 1) and at 24 h after surgery (T 2), mean arterial pressure and heart rate (HR) were recorded.Arterial blood samples were collected for blood gas analysis at T 0 and T 1, and pH value, arterial oxygen partial pressure (PaO 2), arterial carbon dioxide partial pressure (PaCO 2) and lactic acid concentration (Lac) were recorded.Alveolar-arterial oxygen partial pressure difference (P A-aDO 2), oxygenation index (OI) and respiratory index (RI) were calculated.The occurrence of acute lung injury (ALI) was recorded from T 1 to T 2.The serum concentrations of Clara cells secrete proteins 16 (CC16) and malonyldialdehyde (MDA) were determined by enzyme linked immunosorbent assay from T 1 to T 2.

Results:

Compared with group C, HR was significantly decreased and PaCO 2 was increased in D and IPD groups, PaO 2 and OI were increased and RI was decreased in IP and IPD groups, and CC16 and MDA concentrations were decreased ( P<0.05), and no significant change was found in the incidence of ALI in IP and D groups ( P>0.05). Compared with group IP or group D, no significant change was found in the parameters mentioned above in group IPD ( P>0.05).

Conclusion:

For the patients undergoing orthopedic surgery, both ischemic preconditioning and dexmedetomidine can reduce lung injury induced by limb I/R, but the effect of the combination is not enhanced significantly.