Impact of pharmacological interventions on intrapulmonary shunt during one-lung ventilation in adult thoracic surgery: a systematic review and component network meta-analysis.

Background: Intrapulmonary shunt is a major determinant of oxygenation in thoracic surgery under one-lung ventilation. We reviewed the effects of available treatments on shunt, Pao ₂ /FiO ₂ and haemodynamics through systematic review and network meta-analysis.
Methods: Online databases were searched for RCTs comparing pharmacological interventions and intrapulmonary shunt in thoracic surgery under one-lung ventilation up to March 30, 2022. Random-effects (component) network meta-analysis compared 24 treatments and 19 treatment components. The Confidence in Network Meta-Analysis (CINeMA) framework assessed evidence certainty. The primary outcome was intrapulmonary shunt fraction during one-lung ventilation.
Results: A total of 55 RCTs were eligible for systematic review (2788 participants). The addition of N ₂ O (mean difference [MD]=-15%; 95% confidence interval [CI], -25 to -5; P=0.003) or almitrine (MD=-13%; 95% CI, -20 to -6; P<0.001) to propofol anaesthesia were efficient at decreasing shunt. Combined epidural anaesthesia (MD=3%; 95% CI, 1-5; P=0.005), sevoflurane (MD=5%; 95% CI, 2-8; P<0.001), isoflurane (MD=6%; 95% CI, 4-9; P<0.001), and desflurane (MD=9%; 95% CI, 4-14; P=0.001) increased shunt vs propofol. Almitrine (MD=147 mm Hg; 95% CI, 58-236; P=0.001), dopexamine (MD=88 mm Hg; 95% CI, 4-171; P=0.039), and iloprost (MD=81 mm Hg; 95% CI, 4-158; P=0.038) improved Pao ₂ /FiO ₂ . Certainty of evidence ranged from very low to moderate.
Conclusions: Adding N ₂ O or almitrine to propofol anaesthesia reduced intrapulmonary shunt during one-lung ventilation. Halogenated anaesthetics increased shunt in comparison with propofol. The effects of N ₂ O, iloprost, and dexmedetomidine should be investigated in future research. N ₂ O results constitute a research hypothesis currently not backed by any direct evidence. The clinical availability of almitrine is limited.
Systematic Review Protocol: PROSPERO CRD42022310313.
Competing Interests: Declarations of interest AH has received speaker fees from Medtronic International (Sàrl, Tolochenaz, Switzerland) regarding an unrelated topic. The other authors have no direct or indirect conflict of interest to report.
(Copyright © 2022 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved.)