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EMERGENCY OXYGENATOR CHANGEOUT Predisposing Factors and Resulting Incidence

EMERGENCY OXYGENATOR CHANGEOUT Predisposing Factors and Resulting Incidence. Tony Fisher Harefield Hospital U.K. OXYGENATOR PROBLEMS. Leaks in; Membranes Housing Heat Exchanger Grossly contaminated circuit Clots in Oxygenator / Reservoir Oxygenator Failure

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EMERGENCY OXYGENATOR CHANGEOUT Predisposing Factors and Resulting Incidence

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  1. EMERGENCY OXYGENATOR CHANGEOUTPredisposing Factors and Resulting Incidence Tony Fisher Harefield Hospital U.K.

  2. OXYGENATOR PROBLEMS • Leaks in; • Membranes • Housing • Heat Exchanger • Grossly contaminated circuit • Clots in Oxygenator / Reservoir • Oxygenator Failure • Raised trans - oxygenator pressure

  3. LEAKING OXYGENATORS INCIDENCE Stoney I in 23,426 cases Kurusz 2,371 Jenkins 1,932 Fisher 20,781 Housing leaks resulting in EOC Stensved 1,635 Mejak 37,294 Water to blood leaks

  4. CONTAMINATED OXYGENATORS INCIDENCE Stoney 1 in 374,819 cases Kurusz 3,260 Jenkins 6,762 Mejak 23,148

  5. CLOTS IN OXYGENATOR and D.I.C. INCIDENCE Stoney 1979 1 in 787 cases Wheeldon 1981 3,667 Kurusz 1986 1,479 Svenmarker 1991 400 Jenkins 1997 3,005 Mejak 2000 2,283

  6. CLOTS IN OXYGENATOR 1990 - 92 1994 - 96 n= 68,937 97,313 Oxy clotted going back on bypass + aprotinin 6 0 Oxy clotted going back on bypass 0 1 Oxy clotted + aprotinin 3 1 Oxy clotted 1 2

  7. FAILED OXYGENATORS INCIDENCE Stoney 1 in 3,022 cases Wheeldon 2,063 Kurusz 1,134 Mejak 2,458

  8. POSSIBLE CAUSES OF FAILED MEMBRANE OXYGENATORS • Clot formation • Plasma or blood leak • Raised trans-oxygenator pressure gradient (R.T.P.)

  9. CONTRIBUTING FACTORS FOR FAILED OXYGENATORS • Gas supply problems • Metabolic requirements • State of anaesthesia, + + + + • Poor oxygenator design • Large patients • + + +

  10. CHARACTERISTICS OFR.T.P. GRADIENT • A.C.T. is greater than 480 secs • Starts to occur immediately upon going on bypass • Pressure drop across oxygenator increases rapidly • Reaches a plateau • Reduces rapidly back to base line after about 30 minutes or on rewarming

  11. CHARACTERISTICS OF R.T.P. GRADIENT • Effect may be reduced by rewarming • Oxygenation may become inadequate • If the oxygenator is changed out it does not recur

  12. SUGGESTED CAUSES OF RAISED T.O.P. GRADIENT • The blockage is caused by the development of a fibrin - platelet thrombus • This appears to start in the heat exchanger but grows into, or breaks away into the oxygenator fibre bundle

  13. RAISED TRANS-OXYGENATOR PRESSURE GRADIENT INCIDENCE Study Incidence Requiring Size E.O.C. Stensved 11,451 1 in 89 1 in 954 Blomback 1,800 164 600 Wahba 1,959 42 490 Fisher 3,684 228 1,228

  14. MEASUREMENT of TRANS-OXYGENATOR PRESSURE • Reasonably linear relationship between Pressure Gradient and Flow • Therefore can be based on Poiseuille’s Formula Flow =  x p x r4 8 x  x l

  15. MEASUREMENT of TRANS-OXYGENATOR PRESSURE Variations in measurements due to; • Viscosity changes • Haematocrit • Prime constituents • Flow • Temperature + + + + • Site of measurement • OVERALL Variation about 10%

  16. INCIDENCE by HOSPITAL Hospital 1 2 3 4 5 6 7 8 No. cases 602 730 982 498 400 144 87 241 No incidents 1 4 1 2 1 2 2 3 No. of cases per incidence 602 183 982 249 400 72 44 80

  17. INCIDENCE by OXYGENATOR Oxygenator No. Used No.Incidents Terumo SX18 25 0 Terumo SX25 300 1 Medos Hilite 264 0 Affinity 341 0 Sorin Monolyth 128 2 Cobe Duo 986 8 Cobe Optima 208 0 Dideco Avant 982 1 Bard Quantum 371 4 Gish Vision 87 0

  18. Raised Trans-Oxygenator Pressure Gradient can only be seen if it is monitored • Greater awareness of the problem results in more monitoring • If monitoring is not done then the problem presents as a “Failed Oxygenator”

  19. FAILED OXYGENATORS INCIDENCE YEAR Stoney 1 in 3,022 cases 1979 Wheeldon 2,063 1981 Kurusz 1,134 1986 Mejak 2,458 2000

  20. SUMMARY • Happens immediately upon going on bypass • Eventually disappears • Does not recur upon emergency changeout • Incidence varies between different units • At least two different possibly unrelated initiating factors • These factors may always have been present

  21. CONCLUSION • Oxygenators may need emergency replacing due to mechanical failures • A rare event - maybe 1 in 20,000 cases • This can only be improved by better quality control by the manufacturers

  22. CONCLUSION • Oxygenators may need emergency replacing due to clotting problems • Incidence 1 in 3,000 cases • This problem needs to be addressed by improving anticoagulation monitoring

  23. CONCLUSION • Oxygenators may need emergency replacing due to a fibrin - platelet thrombus which may be demonstrated by a raised trans-oxygenator pressure gradient. • Incidence 1 in 1,000 cases • This problem may always have been with us, and needs to be addressed by continuing research into its aetiology.

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