Increased Alveolar Damage After Mechanical Ventilation in a Porcine Model of Thoracic Surgery

Objective

Mechanical stress during one-lung ventilation (OLV) results in lung injury. This study compared the effects of mechanical ventilation, OLV, and surgical manipulation on diffuse alveolar damage (DAD) after application of different anesthetic regimens.

Design

Prospective, randomized, controlled, blinded animal experiment.

Setting

University hospital.

Objects

Twenty-one piglets.

Interventions

Animals (27.5 kg) were randomized into 4 groups: spontaneous breathing (SB, n = 3), two-lung ventilation (TLV, n = 6), OLV during desflurane (n = 6), and propofol anesthesia (n = 6). SB pigs were killed after the induction of anesthesia. Lung tissue samples were analyzed to obtain reference values for alveolar damage. TLV pigs underwent standard TLV (tidal volumes [V_T] = 10 mL/kg, F_IO₂ = 0.40, positive end-expiratory pressure = 5 cmH₂O). In OLV pigs, after lung separation by a bronchial blocker, OLV (V_T = 10 mL/kg) and thoracic surgery were performed. After the procedure, the pigs were killed. Lung tissue samples were harvested for histologic examination. Lung injury was quantified by DAD score; sequestration of leukocytes was assessed by the recruitment of CD45⁺ cells into the lungs.

Main Results

TLV resulted in increased DAD scores in both lungs (TLV v SB: 6.9 v 2.7, p < 0.05); the number of CD45⁺ cells was not increased (TLV v SB: 8.7 v 5.0 cells per view). OLV and surgical manipulation increased DAD and leukocyte sequestration without differences between the ventilated and manipulated lungs. Leukocyte recruitment was not differently affected by the anesthetic regimen (propofol v desflurane: CD45⁺ cells per view: 13.5 v 11.3).

Conclusions

TLV resulted in increased DAD scores in the lungs as compared with SB. OLV and thoracic surgery further increased lung injury and leukocyte recruitment independently of the administration of propofol or desflurane anesthesia.

Key Words: one-lung ventilation, open thoracic surgery, ventilator-induced lung injury, diffuse alveolar damage, pulmonary leukocyte recruitment, general anesthesia