Relationship between PaO₂/FiO₂ and number of regions with B-line on transthoracic lung ultrasound: a prospective, observational study

ABSTRACT

BACKGROUND: Aeration of the lungs must be monitored during general anesthesia because of the possibility of postsurgical pulmonary complications. The aim of this study was to compare PaO₂/FiO₂ and the number of regions with B-line on transthoracic lung ultrasonography (TLU) between the postinduction and postsurgical periods. METHODS: Twenty-six adult patients undergoing major abdominal surgery were enrolled. Arterial blood gas analysis and TLU were performed 30 min after the induction of anesthesia (postinduction) and after skin closure (postsurgical period) while patients were under mechanical ventilation. TLU was performed in 12 regions (anterior, lateral, and posterior in the upper and lower regions of both lungs). The number of regions with B-line was counted. RESULTS: Compared with postinduction values, the number of regions with B-line on TLU was increased in the postsurgical period (0.3 ± 0.5 to 1.3 ± 1.2, P < 0.001); however, PaO₂/FiO₂ did not significantly differ (421.3 ± 95.8 to 425.2 ± 86.0, P = 0.765). The change in PaO₂/FiO₂ (postinduction-postsurgical period) was significantly higher in Group B than in Group A (P = 0.028). CONCLUSIONS: Although the number of regions with B-line on TLU was increased in the postsurgical period, lung oxygenation did not differ, based on the main assessment in this study. In contrast, patients with an increased number of regions with B-line tended to show a reduction in PaO₂/FiO₂ during the postsurgical period. Further study seems necessary to establish the number of regions with B-line on TLU as a tool for evaluation of perioperative oxygenation.