Combined anticoagulants ameliorate acute lung injury in sheep after burn and smoke inhalation

Burn and smoke inhalation-related multiple organ dysfunction is associated with a severe fall in the plasma concentration of antithrombin. Therefore the aim of the present study was to test the hypothesis that intravenous administration of recombinant human antithrombin in combination with aerosolized heparin will ameliorate acute lung injury in sheep exposed to cutaneous burn and smoke inhalation. Sheep were prepared operatively for study and, 7 days post-surgery, sheep were given a cutaneous burn (40% of total body surface area, third-degree burn) and insufflated with cotton smoke (48 breaths, <40 °C) under halothane anaesthesia. After injury, sheep were placed on a ventilator and resuscitated with Ringer's lactate solution. The animals were divided into three groups: sham group (non-injured and non-treated; n=6), saline group (injured and received saline; n=6) and rhAT.iv.+Hep group [injured and treated with rhAT (recombinant human antithrombin) and heparin; n=6]. In the rhAT.iv.+Hep group, rhAT was infused continuously for 48 h starting 1 h post-injury with a dose of 0.34 mg·h⁻¹·kg⁻¹ of body weight and heparin (10000 units) was aerosolized every 4 h starting at 1 h post-injury. The experiment lasted 48 h. Haemodynamics were stable in sham group, whereas the saline-treated sheep developed multiple signs of acute lung injury, including decreased pulmonary gas exchange, increased inspiratory pressures, extensive airway obstruction and increased pulmonary oedema. These pathological changes were associated with a severe fall in plasma antithrombin concentration, lung tissue accumulation of leucocytes and excessive production of NO. Treatment of injured sheep with anticoagulants attenuated all of the pulmonary pathophysiology observed. In conclusion, the results provide definitive evidence that anticoagulant therapy may be a novel and effective treatment tool in the management of burn patients with concomitant smoke inhalation injury.