Pulmonary gas exchange during intramedullary fixation of femoral shaft fractures.
BACKGROUND
This study was undertaken to determine if the alveolar dead space fraction (Vd/Vt) or the alveolar-arterial oxygen gradient (A-a DO2) increased during intramedullary fixation of femoral shaft fractures.


METHODS
Fifty hemodynamically stable patients with femur fractures were prospectively enrolled. Three serial measurements of Vd/Vt and A-a DO2 were obtained immediately before femoral nailing (Pre), 30 minutes after nailing (+30), and 120 minutes after nailing (+120). Vd/Vt was determined by simultaneously measuring PaCO2 and the steady-state end-tidal CO2 (PetCO2), where Vd/Vt = (1 - PetCO2/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; paired t test, both time points). A-a DO2 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 DO2, however, were both significantly increased in patients with lung contusion (n = 6) before nailing, but neither measurement increased after nailing. One patient developed fat embolism (Vd/Vt of 0.35 at Pre and 0.31 at +120), and another patient experienced postoperative pulmonary thromboembolism (Vd/Vt increased from 0.06 at Pre to 0.17 at +120).


CONCLUSIONS
The process of femoral nailing does not cause enough pulmonary embolization to alter pulmonary gas exchange as measured by Vd/Vt and A-a DO2. If Vd/Vt is increased preoperatively, the likelihood of subsequent pulmonary dysfunction secondary to either preoperative lung injury or fat embolism is increased.
Weresh
M J
MJ
Des Moines Orthopedic Surgeons, West Des Moines, Iowa, USA.
Stover
M D
MD
Bosse
M J
MJ
Jeray
K
K
Kellam
J F
JF
Sims
S H
SH
Kline
J A
JA
D000328:Adult; D002245:Carbon Dioxide / Q000032:analysis; D003288:Contusions / Q000150:complications; D005260:Female; D005264:Femoral Fractures / Q000150:complications / Q000601:surgery*; D005594:Fracture Fixation, Intramedullary / Q000009:adverse effects; D006801:Humans; D007431:Intraoperative Complications / Q000175:diagnosis; D055370:Lung Injury; D008297:Male; D010100:Oxygen / Q000032:analysis; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000175:diagnosis* / Q000209:etiology; D011659:Pulmonary Gas Exchange; D012126:Respiratory Dead Space
D002245:Carbon Dioxide; D010100:Oxygen