Pulmonary gas exchange during intramedullary fixation of femoral shaft fractures

Background: This study was undertaken to determine if the alveolar dead spa ce fraction (Vd/Vt) or the alveolar-arterial oxygen gradient (A-a Do(2)) in creased during intramedullary fixation of femoral shaft fractures. Methods: Fifty hemodynamically stable patients with femur fractures were pr ospectively enrolled. Three serial measurements of Vd/Vt and A-a Do(2) were obtained immediately before femoral nailing (Pre), 30 minutes after nailin g (+30), and 120 minutes after nailing (+120), Vd/Vt was determined by simu ltaneously measuring Pace, and the steady-state end-tidal CO2 (Petco(2)), w here Vd/Vt = (1 - PetCO(2)/PaCO2). Results: Vd/Vt before nailing was 0.09 +/- 0.09 (mean +/- SD); at +30 and 120, Vd/Vt was 0.10 +/- 0.06 and 0.08 +/- 0.07, respectively (p > 0.2; pair ed t test, both time points). A-a Do(2) before nailing was 84 +/- 85 mm Hg, and it did not change significantly at +30 (89 +/- 69 mm Hg; p = 0.51 vs. Pre; paired t-test) or at +120 (51 +/- 45 mm Hg). No difference in data was found with analysis by fracture classification or number of reamer passes. Vd/Vt and A-a Do(2), however, were both significantly increased in patient s with lung contusion (n = 6) before nailing, but neither measurement incre ased after nailing, One patient developed fat embolism (Vd/Vt of 0.35 at Pr e and 0.31 at +120), and another patient experienced postoperative pulmonar y thromboembolism (Vd/Vt increased from 0.06 at Pre to 0.17 at +120), Conclusion: The process of femoral nailing does not cause enough pulmonary embolization to alter pulmonary gas exchange as measured by Vd/Vt and A-a D o(2). If Vd/Vt is increased preoperatively, the likelihood of subsequent pu lmonary dysfunction secondary to either preoperative lung injury or fat emb olism is increased.