Halothane and isoflurane do not decrease PaO2 during one-lung ventilation in intravenously anesthetized patients

We examined the effect of the inhalational anesthetics halothane (H) and isoflurane (IF) on arterial oxygenation during one-lung ventilation. Twenty consenting patients who required thoracotomy and one-lung ventilation were initially anesthetized only with the intravenous agents, diazepam, fentanyl, pancuronium, metocurine, and infusions of either ketamine or methohexital. A double lumen endotracheal tube was inserted, and each patient's lungs were mechanically ventilated (two-lung ventilation, step 1) with 100% O2 while the patient was in the lateral decubitus position. After the pleura was opened, the nondependent lung was collapsed while the dependent lung continued to be ventilated with 100% O2. After serial PaO2 measurements indicated achievement of stable one-lung ventilation conditions (step 2), intravenous anesthetic agents were discontinued, and either H (n = 10) or IF (n = 10) was administered (step 3) so that PETH = 7.70 +/- 0.61 mm Hg and PETIF = 9.89 +/- 1.08 mm Hg for more than 15 min; at the end of step 3, PaH/PETH = 0.82 (n = 5), PaIF/PETIF = 0.75 (n = 5), PvH/PETH = 0.64 (n = 3), and PvIF/PETIF = 0.68 (n = 3). The inhalational anesthetics were then discontinued, and intravenous agents were reinstituted, allowing PETH and PETIF to decrease below 0.50 mm Hg (step 4). Two-lung ventilation was resumed at the end of the surgical procedure (step 5). PaO2 decreased from 441 +/- 64 to 252 +/- 70 mm Hg when one-lung ventilation was achieved (steps 1-2), and PaO2 increased from 258 +/- 72 to 395 +/- 65 mm Hg when two-lung ventilation was resumed (steps 4-5).(ABSTRACT TRUNCATED AT 250 WORDS)