31, 32, 36, 37, 39, 42, 58
Run a five-channel surveillance system (visual circuit check, dpMO normalised to blood flow, post-membrane gases, the haemolysis panel, the coagulation panel), read for trend rather than value, and accept that it converts about half of acute clot events into planned procedures rather than abolishing them. Read the pressure drop as a ratio to blood flow, not as a raw number. Put the circuit near the top of the differential for a diffusely bleeding ECMO patient with a rising D-dimer and falling platelets over 3-4 days — a normal fibrinogen does not exclude it and normal gas exchange does not exclude it. Do not require the circuit to be failing before suspecting it. A programme that exchanged circuits in a third of its patients, sometimes up to five times, did not visibly pay for it in survival.
Patients not requiring a system exchange, at comparable support times
DOI 10.1371/journal.pone.0112316; PMID 25464516; PMC4251903
ECMO system exchange (whole circuit except cannulae), acute or elective
Single centre, venovenous only, 2009-2013, retrospective. Six different ECMO systems with differing pumps and coatings but an identical polymethylpentene gas-exchange membrane throughout, so the study cannot speak to membrane material. The 31 percent exchange rate reflects that centre's thresholds, anticoagulation protocol and case mix and is not transferable. D-dimer reported in mg/dL by a local assay, so the absolute numbers do not transfer between laboratories. The mortality comparison is not randomised and not powered — p = 0.113 with a 10-point absolute difference is not evidence of equivalence. Before-and-after design for the reversal findings is uncontrolled. No routine circuit-infection surveillance was performed, so 4 of 83 is a detection rate rather than an incidence. The activated factor VII signal rests on 4 patients. No cut-off is offered for any parameter.
83 of 265 (31 percent) required at least one system exchange: 37 acute, 46 elective. Reasons summing to 83 — mechanical failure 8 (pump 5, membrane lung 2, cannula 1); pump head thrombosis 13; acute oxygenator thrombosis 16; worsening gas transfer 10; device-related coagulation disorder 32 (local fibrinolysis 24, device-induced hyperfibrinolysis 8); suspected circuit infection 4. PUMP HEAD THROMBOSIS: plasma free haemoglobin rose about 10-fold before and fell about 6-fold after exchange (p under 0.001 both); clot documented in every pump head removed; a warning rise on the preceding day in only 6 of 13 (55 [49-60] to 143 [117-266] mg/dL, p = 0.031). ACUTE OXYGENATOR THROMBOSIS: dpMO divided by blood flow rose 2.6-fold (2.1-4.0) before and fell 3.2-fold (2.0-5.2) after exchange (p under 0.001 both), and did not rise in any other acutely exchanged patient; D-dimer elevated beforehand in 11 of 16, with 5 of 16 missed by routine D-dimer testing; gas transfer already worsened in 8 of 11 (53 percent [45-59] fall in outlet pO2; outlet pCO2 40 [32-48] mmHg at gas flows of 10 L/min or more). DEVICE-INDUCED HYPERFIBRINOLYSIS (n = 8): fibrinogen fell below 200 mg/dL with rising D-dimer over 4 days, diffuse unaccountable bleeding, reversible by system exchange, and gas exchange of the respective membrane lungs only minimally affected. LOCAL FIBRINOLYSIS (n = 24): rising D-dimer and falling platelets over 3-4 days with fibrinogen unchanged, yet 40 percent bled. OUTCOME: exchanged patients received a median of 2 (2-3) membrane lungs, range up to 5, with longer support (20 [14-27] versus 8 [6-10] days) and more renal replacement (28 versus 15 percent, p = 0.028), but NO significant mortality difference — weaning 69 versus 79 percent, died on ECMO 31 versus 21 percent, p = 0.113; acute versus elective died on ECMO 17 versus 29 percent, p = 0.320. Acutely exchanged circuits had a shorter first-membrane-lung life (7.0 [5.0-10.3] versus 9.5 [7.0-13.0] days, p = 0.023). SAFETY SIGNAL: 2 of the 4 patients given activated coagulation factor VII developed acute oxygenator thrombosis. INFECTION: 4 exchanges for suspected circuit infection; mycobacteria identified microscopically in one membrane lung, Enterococcus grown from another on long-term ex-vivo incubation; noradrenaline requirement fell 15-fold in one patient after exchange.
265 consecutive adults on venovenous ECMO, single centre (Regensburg), January 2009 to December 2013. Retrospective analysis of prospectively collected data. Age 50 (36-60); SOFA 11.0 (8.0-14.3); Murray score 3.33 (3.33-3.67); primary lung failure 68 percent. Cumulative support 3,411 days, median 9 (6-15) days.