Acute respiratory distress syndrome and shunt detection with bubble studies: a systematic review and meta-analysis

Abstract

ABSTRACTObjectivesAcute respiratory distress syndrome (ARDS) is a life-threatening respiratory injury with multiple physiological sequalae. Shunting of deoxygenated blood through intra and extra-pulmonary shunts is one consequence that may complicate ARDS management. Therefore, we conducted a systematic review to determine the prevalence of sonographically detected shunt and its association with oxygenation and mortality in patients with ARDS.Data SourcesWe searched MEDLINE, EMBASE, Cochrane Library and DARE databases on March 26, 2021Study SelectionArticles relating to respiratory failure and sonographic shunt detection.Data ExtractionArticles were independently screened and extracted in duplicate. Data pertaining to study demographics and shunt detection were compiled for mortality and oxygenation outcomes. Risk of bias was appraised using the Joanna Briggs Institute and Newcastle-Ottawa Scale tools with evidence rating certainty using GRADE methodology.Data SynthesisFrom 4,617 citations, 10 observational studies met eligibility criteria. Sonographic detection of right-to-left shunt was present in 21.8% of patients (range:14.4-30.0%) amongst included studies using transthoracic, transesophageal and transcranial bubble Doppler sonography. Shunt prevalence may be associated with increased mortality (risk ratio: 1.22, 95% CI: 1.01-1.49, p=0.04, very low certainty evidence) with no difference in oxygenation as measured by PaO2:FiO2 ratio (mean difference -0.7, 95% CI: -18.6 to 17.2, p=0.94, very low certainty evidence).ConclusionsIntra- and extra-pulmonary shunts are detected frequently in ARDS with ultrasound techniques. Shunts may increase mortality amongst patients with ARDS, but its association with oxygenation is uncertain. Future research should explore the role of shunt in ARDS, their association with mortality, and whether targeted precision medicine interventions can improve outcomes.PROSPERO Registration Number: CRD42021245194 (March 26, 2021)Key PointsQuestion: In adult critically ill ARDS patients, what is the prevalence of right-to-left shunts, and what are their effects on mortality and/or oxygenation?Findings: In this systematic review and meta-analysis, shunts be may prevalent in ∼1 in 5 ARDS patients. They may be associated with a statistically significant increase in mortality, with no difference in oxygenation parameters.Meaning: Intra- and extra-pulmonary shunts are detected frequently in ARDS with ultrasound techniques, and may increase mortality amongst patients with ARDS (although its association with oxygenation is uncertain).