Factors Affecting Perioperative Pulmonary Function in Acute Respiratory Failure

To determine the magnitude, duration, and associated factors of perioperative changes in pulmonary function, we retrospectively reviewed the medical records of 145 patients who required preoperative mechanical ventilation for acute respiratory failure before undergoing 200 surgical procedures. Patients were grouped into five pulmonary diagnostic categories: (1) adult respiratory distress syndrome (ARDS) (n = 49); (2) pneumonia (n = 20); (3) atelectasis (n = 65); (4) congestive heart failure (n = 11); and (5) acute ventilatory failure (n = 55). Sixty patients underwent intra-abdominal surgery, 135 patients required surgery on the periphery, and five patients had a thoracotomy. For all patients, Pao2/FIo2 declined significantly from 321 mm Hg (mean) preoperatively to 258 mm Hg intra-operatively, and shunt fraction (Qs/Qt) increased from 0.16 to 0.23 without a significant change in PaCO2. The magnitude of the increase in Qs/Qt did not differ among pulmonary diagnostic groups. Preoperatively, patients undergoing laparotomy had lower PaO2/FIo2 (278 vs 340) and higher Qs/Qt (0.19 vs 0.14) than patients requiring surgery on the periphery. Intra-operatively, Qs/Qt increased more during abdominal procedures than during peripheral procedures. Intra-operative hypoxemia (PaO2/FIo2