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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

EMERGENCY OXYGENATOR CHANGEOUTPredisposing Factors and Resulting Incidence

Tony Fisher

Harefield Hospital

U.K.

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

contaminated oxygenators
CONTAMINATED OXYGENATORS

INCIDENCE

Stoney 1 in 374,819 cases

Kurusz 3,260

Jenkins 6,762

Mejak 23,148

clots in oxygenator and d i c
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

clots in oxygenator
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

failed oxygenators
FAILED OXYGENATORS

INCIDENCE

Stoney 1 in 3,022 cases

Wheeldon 2,063

Kurusz 1,134

Mejak 2,458

possible causes of failed membrane oxygenators
POSSIBLE CAUSES OF FAILED MEMBRANE OXYGENATORS
  • Clot formation
  • Plasma or blood leak
  • Raised trans-oxygenator pressure gradient (R.T.P.)
contributing factors for failed oxygenators
CONTRIBUTING FACTORS FOR FAILED OXYGENATORS
  • Gas supply problems
  • Metabolic requirements
    • State of anaesthesia, + + + +
  • Poor oxygenator design
  • Large patients
  • + + +
characteristics of r t p gradient
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
characteristics of r t p gradient13
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
suggested causes of raised t o p gradient
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
raised trans oxygenator pressure gradient
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

measurement of trans oxygenator pressure
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

measurement of trans oxygenator pressure19
MEASUREMENT of TRANS-OXYGENATOR PRESSURE

Variations in measurements due to;

  • Viscosity changes
    • Haematocrit
    • Prime constituents
    • Flow
    • Temperature + + + +
  • Site of measurement
  • OVERALL Variation about 10%
incidence by hospital
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

incidence by oxygenator
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

slide29
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”
failed oxygenators30
FAILED OXYGENATORS

INCIDENCE YEAR

Stoney 1 in 3,022 cases 1979

Wheeldon 2,063 1981

Kurusz 1,134 1986

Mejak 2,458 2000

summary
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
conclusion
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
conclusion34
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
conclusion35
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.