TABLE 2

Summary of findings and certainty of evidence for randomised controlled trials

Participants/studies [references]Pooled event rate (%) or pooled mean±sd#Mean posterior relative effect (95% CrI)Posterior probability of harm from ECCO2R+Certainty of the evidence (GRADE)
ECCO2RStandard care
Primary outcome
 Mortality up to day 30 (or latest)§ 524/3 [8, 17, 18]97/261 (37.2)91/263 (34.6)Relative risk 1.19 (0.70–2.29)0.73⊕⊕◯◯ Low##
Secondary outcomes
 90-day mortality  405/1 [8]83/200 (41.5)81/205 (39.5)
 Hospital mortalityƒ 119/2 [18]21/61 (34.4)17/58 (29.3)⊕◯◯◯ Very low¶¶
 28-day ventilator-free days (days) 484/2 [8, 18]7.6±8.79.2±9.2MD −1.4 (−3.6–0.9)0.90⊕⊕⊕◯ Moderate++
 ICU length of stay (days) 531/3 [8, 17, 18]17.4±16.615.2±11.5MD 0.9 (−1.3–3.1)0.79⊕⊕◯◯ Low§§
 Hospital length of stay (days) 513/3 [8, 17, 18]24.1±25.822.1±19.2MD 0.8 (−2.2–3.9)0.70⊕⊕◯◯ Low§§
 Haemorrhage 452/2 [8, 17]38/223 (17)3/229 (1.3)⊕⊕◯◯ Lowƒƒ,###,¶¶¶
 Intracranial haemorrhage452/2 [8, 17]11/223 (4.9)3/229 (1.3)Relative risk 3.00 (0.41–20.51)0.88⊕⊕◯◯ Low###

Data are presented as n/N, n/N (%) or mean±sd, unless otherwise stated. ECCO2R: extracorporeal carbon dioxide removal; 95% CrI: 95% credible interval; GRADE: Grading of Recommendations, Assessment, Development, and Evaluations; ICU: intensive care unit; MD: mean difference. #: calculated as per the Cochrane Handbook [39]; : relative risk for binary outcomes or mean difference for continuous outcomes; +: set for relative risk >1 or MD <0 days; §: Morris et al. [17] reported 30-day mortality, Bein et al. [18] reported hospital mortality and McNamee et al. [8] reported 28-day mortality; ƒ: all models failed to converge, probably due to low sample sizes and imprecision; ##: downgraded one point due to indirectness (given the differing outcome measures) and one point for imprecision (as the number of participants did not reach the optimal information size); ¶¶: downgraded one point for risk of bias and two points for serious imprecision (as the number of participants did not reach the optimal information size); ++: downgraded one point for imprecision (as the number of participants did not reach the optimal information size); §§: downgraded one point for imprecision (as the number of participants did not reach the optimal information size) and one point for indirectness (given the time elapsed between studies and differences in practice relating to ICU and hospital admission and discharge); ƒƒ: no study offered a consistent definition of major haemorrhage. Haemorrhage was not reported as an adverse event by Bein et al. [18]. Bleeding adverse events reported by McNamee et al. [8] are included. These were defined as bleeding events (excluding intracranial bleeding) that were possibly, probably or definitely related to the intervention; ###: downgraded two points for serious imprecision (as the number of participants did not reach the optimal information size and the event rate is low); ¶¶¶: could not be pooled due to the absence of events in the Morris et al. [17] standard care arm.