Increased permeability-oedema and atelectasis in pulmonary dysfunction after trauma and surgery: a prospective cohort study

Abstract

Background: Trauma and surgery may be complicated by pulmonary dysfunction, acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), but the mechanisms are incompletely understood.

Methods: We evaluated lung capillary protein permeability non-invasively with help of the 67Ga-transferrin pulmonary leak index (PLI) technique and extravascular lung water (EVLW) by the transpulmonary thermal-dye dilution technique in consecutive, mechanically ventilated patients in the intensive care unit within 24 h of direct, blunt thoracic trauma (n = 5, 2 with ARDS), and within 12 h of indirect trauma by transhiatal oesophagectomy (n = 8), abdominal surgery for cancer (n = 6) and bone surgery (n = 4). We studied transfusion history, haemodynamics, oxygenation and mechanics of the lungs. The lung injury score (LIS, 0-4) was calculated. Plain radiography was also done to judge densities and atelectasis.

Results: The PLI and EVLW were elevated above normal in 61 and 30% of patients, respectively, and the PLI directly related to the number of red cell concentrates given (rs = 0.69, P < 0.001), without group differences. Oxygenation, lung mechanics, radiographic densities and thus the LIS (1.0 [0.25-3.5]) did not relate to PLI and EVLW. However, groups differed in oxygenation and airway pressures and impaired oxygenation related to the number of radiographic quadrants with densities (rs = 0.55, P = 0.007). Thoracic trauma patients had a worse oxygenation requiring higher airway pressures and thus higher LIS than the other patient groups, unrelated to PLI and EVLW but attributable to a higher cardiac output and thereby venous admixture. Finally, patients with radiographic signs of atelectasis had more impaired oxygenation and more densities than those without.

Conclusion: The oxygenation defect and radiographic densities in mechanically ventilated patients with pulmonary dysfunction and ALI/ARDS after trauma and surgery are likely caused by atelectasis rather than by increased permeability-oedema related to red cell transfusion.

Figure 1

A healthy volunteer with two cesium iodide scilliation probes positioned over the lung apices, for collecting ⁶⁷Ga and ^99mTc radioactivity data for calculating the pulmonary leak index (PLI).

Figure 2

Relation between number of red cell concentrates administered and the pulmonary leak index (PLI, × 10^-3.min^-1) in the patient groups: r_s = 0.69, P < 0.001. The upper limit of normal PLI is 14.1 ×10^-3.min^-1.

Figure 3

Relation between number of plain radiographic quadrants with densities versus venous admixture: r_s = 0.55, P = 0.007. Similar relations were present with P_aO₂ and P _aO₂/F_IO₂ (r_s = -0.52, P = 0.011).