18, 13, 26, 30
The reference synthesis for VA ECMO weaning. Two transferable lessons beyond the parameter list. First, load dependence explains why ejection fraction performs poorly as a single-timepoint discriminator while its trajectory carries signal. Second, the end-tidal CO2 rule is free, continuous and was met by every successfully weaned patient in its source study - the highest-value non-echo signal available.
Successfully weaned versus not successfully weaned
DOI 10.1186/s13054-022-04249-w
Not applicable - synthesis of biomarkers, haemodynamic and echocardiographic parameters associated with successful weaning
Most studies at moderate or high risk of bias; 15 of 47 were conference abstracts without protocols; most observational, unblinded, retrospective and small. Heterogeneity in methods, timing and conditions of measurement PRECLUDED ANY META-ANALYSIS. Critically, the review notes that LVEF, LVOT VTI, LV systolic velocity, strain and strain rate are ALL LOAD-DEPENDENT - decisive in a patient whose preload and afterload are both being manipulated by the circuit. Thresholds and the conditions under which they are measured vary significantly across studies.
Definition used: survival after complete removal of the circuit without further mechanical support or heart transplant, though definitions varied across studies. Reported weaning success ranged from 30 to 75%. BIOMARKERS: peak CK-MB under 183 U/L predicted weaning with sensitivity 86% and specificity 71%; lactate clearance in the first 12 hours AUROC 0.72; lactate at 24 hours independently associated OR 0.52, p=0.018; higher AST at 48 and 72 hours associated with failure; initial and pre-weaning lactate inconsistent. HAEMODYNAMICS: MAP at weaning independently associated OR 1.05, p=0.009; pulse pressure under 30 mmHg independently associated with failure; systolic pressure 120 versus 103 mmHg in survivors, p=0.04; lower right atrial to wedge pressure ratio and higher pulmonary artery pulsatility index at 48 and 72 hours. END-TIDAL CO2: an increase of 5 mmHg or more above previous mean values across two consecutive 12-hour periods occurred in ALL successfully weaned patients, rising from 9 to 21 mmHg at 24 hours, p=0.04. MICROCIRCULATION: skin blood flow at or above 34 perfusion units AUROC 0.93; higher perfused small vessel density p=0.002. ECHO: LVOT VTI is the most widely used parameter, common threshold above 9.5 cm, AUROC 0.85 and 0.74 in different studies; ratio of VTI from cannulation to weaning OR 2.80, p=0.01; LVEF rose 9.0% at 24-48 hours in weaned patients, p=0.001, with both absolute value and change independently associated at 48 hours; improvement in lateral e-prime and tricuspid annular S-prime during a flow reduction trial AUROC 0.93; total isovolumic time improvement in the first 48 hours the strongest single predictor; corrected LV ejection time to wedge pressure ratio above 15.9 AUROC 0.82.
Adults on VA ECMO for cardiogenic shock in whom weaning was attempted. Critical Care 2022;26:375. 14,578 records screened, 47 studies included, study sizes 12 to 258 patients. Retrieved in full. FIRST AUTHOR DISPUTED: a bibliographic index returns Charbonneau; the retrieved article named Cavayas as lead author. No author list asserted. ECPR-only studies and bridge-to-VAD or transplant studies were deliberately excluded, the latter because such patients are by definition never successfully weaned.