The Effect of Increased F_IO₂before Removal of the Laryngeal Mask Airway on Postanesthetic Arterial Partial Oxygen Pressure

Abstract

Background:The administration of 100% oxygen at the end of general anesthesia before tracheal extubation has been shown to worsen postanesthetic pulmonary gas exchange. Because the laryngeal mask airway (LMA) and the endotracheal tube (ETT) are very different, it remains uncertain whether emergence on oxygen has the same results on lung function as ETT. Therefore, the aim of this study was to evaluate whether the use of 100% oxygen before LMA removal worsens gas exchange after inhalation or total intravenous general anesthesia.Methods: Eighty ASA physical status I-II patients scheduled for elective surgery of the extremities were randomly assigned to receive either sevoflurane or propofol during general anesthesia with LMA. At the end of surgery, patients were randomized to an inspiratory fraction of oxygen of 0.3 in sevoflurane (n = 20), of 0.3 propofol (n = 20) or of 1.0 in sevoflurane (n = 20) or of 1.0 in propofol (n = 20) during emergence from anesthesia and LMA removal. Postoperative blood gas measurements were taken immediately and 60 min after arrival in the recovery room.Results: No significant differences in PaO2 (propofol groups: 87.5 ± 14.4 vs 88.5 ± 10.5 mmHg, sevoflurane groups: 86.7 ± 11.3 vs 90.7 ± 9.9 mmHg) or alveolar -arterial oxygen tension difference (AaDO2) were found between the two groups at 30 min after LMA removal (propofol groups: 12.0 ± 12.4 vs 10.3 ± 8.3 mmHg, sevoflurane groups: 8.6 ± 7.1 vs 7.1 ± 9.4 mmHg). No differences were observed between the sevoflurane and propofol groups when FIO2 levels were similar.Conclusions: Breathing 100% oxygen during emergence from general anesthesia does not worsen postanesthetic pulmonary gas exchange when an LMA is used.

The Effects of Intraoperative Inspired Oxygen Fraction on Postoperative Pulmonary Parameters in Patients with General Anesthesia: A Systemic Review and Meta-Analysis

“…AaDO 2 AaDO 2 was reported in 4 studies including 211 patients (Figure 4A) [17,21,22,24]. AaDO 2 was significantly higher in the high FiO 2 group than the low FiO 2 group (MD 3.42 mmHg, 95% CI 0.95 to 5.89, p = 0.007).…”

“…After evaluating full-text articles, 17 records were excluded because they reported no outcomes related to this study ( n = 7), performed arterial blood gas analysis during intervention ( n = 5), did not compare between high FiO 2 and low FiO 2 ( n = 4) or included lung cancer surgery ( n = 1). Finally, a total of 10 RCTs [17,18,19,20,21,22,23,24,25,26], with 787 patients, were included in final analysis (Figure 1). Among them, 391 patients were assigned to high FiO 2 group and 396 patients to low FiO 2 group.…”

“…A moderate level of heterogeneity among the studies was observed (I 2 = 62%, p = 0.01). In subgroup analysis, there were 5 studies in the endotracheal tube group [17,18,21,22,23] and 2 studies in the laryngeal mask airway group [24,25]. Each group included 213 and 142 patients, respectively.…”

“…Another reason for the heterogeneity may be attributable to ABGA being performed at different times in each study. Blood samples for ABGA were drawn at 30 min [18,24,25] or 60 min [21,25] after extubation in some studies, whereas in other studies, it was performed on the first postoperative day [17,22,23].…”