2. Angela Beatson and Lorna Davidson Clinical Perfusion Scientists
Quality and Variation
Angela Beatson
and Lorna Davidson
Clinical Perfusion Scientists

3. Do we provide the best quality perfusion practice within our restraints?

4. Perfusion Quality How do we measure the quality of our practice?
Why do we make the choices we do about our equipment and methods?
Is perfusion an evidence based science?
Can we share and learn more from each other?
For better accountability should we be more consistent?

6. How do different units approach the same (theoretical) patient?
Phone Survey
Over 3 days we attempted to telephone all NHS perfusion units
18 responses (36 listed on SCTS website)
Hypothesis:
How do different units approach the same (theoretical) patient?
Circuit choices
Case management
Variation perception

7. The ‘Ideal’ Patient Male patient requiring CABGx3 or ASD surgery
80kg, BSA 2.0 m2
No co-morbidities (cerebral, pulmonary, renal, GI) good LV function, fit and well
Hb =14.5gdl, Hct 45%
Urea =6.7mmol/l,
Creatinine =82μmol/l

8. Perfusion Circuit Variation

9. Perfusion Circuit Variation

10. Perfusion Circuit Variation
22%
28%
89%
78%
17%

11. Perfusion Patient Management

12. Circuit Prime

13. No two units in the UK and Ireland used the same prime.
The overlying message was:
No two units in the UK and Ireland used the same prime.
Not a lot has changed!

14. Perfusion Flow-Cardiac Index
CI During Hypothermia
CI During Normothermia
6/13 reported they increased their flow during rewarming

15. Perfusion Flow
Numerous studies looking at MAP and flow on CPB with few conclusive outcomes
Potential Advantages of Higher CPB Flow
Enhanced tissue perfusion
Improved collateral flow
Normothermic surgery
Potential Advantages of Lower CPB Flow
Less blood trauma
Less blood in surgical field
Less cardiotomy suction
Smaller cannulae
Enhances myocardial protection (less collateral flow)
Reduced embolic load

16. Perfusion Flow Studies comparing low and high flow bypass are variable
Many performed in era of hypothermia with different acid-base, Hb and glucose management
Cerebral autoregulation appears to maintain cerebral flow
No evidence from large scale RCT supporting minimal safe flow rate

17. Variation in Perfusion%
Pulsatile Flow (roller pump) 4 31
DVO2 3 17
Haemofiltration
Cerebral Saturation Monitoring
Transfusion on CPB
Threshold Mean
7.2gdl
Range
( gdl)

18. Transfusion Many studies correlate low Hct to poor outcome
Authors
Study
Conclusion
Habib et al
J Thorac Cardiovasc Surg (2003)
5000 pts
↑ Early and late mortality, major morbidity
DeFoe et al
Ann Thorac Surg 20010
6980 pts
↑mortality, IABP need, 2nd bypass need
Karkouti et al
J Thorac Cardiovasc Surg (2005)
10,949 pts
↑ stroke rate
Ranucci et al Tex Heart Inst J (2006)
1766 pts
↑Acute renal injury
But as the majority of these patients would have been transfused is it the anaemia or the blood that caused the injury (or both)?

20. Transfusion Low Hct has been associated with post-op renal dysfunction
BUT ALSO
Transfusion of PRBCs on CPB increased the risk of renal failure
Dilution v Transfusion v Outcome
TITRe2 study attempted to address this but only during post-op period
‘Efforts should be made to reduce dilution, including reduction of prime volume to avoid allogenic transfusions’ (Class I, Level A)

21. Arterial pO2

22. DVO2 and VO2
Hyperoxemia was traditionally a consequence of bubble oxygenators.
Whilst insufficient DO2 is harmful, should we maintain higher than physiological pO2
Hyperoxygenation increases generation of reactive oxygen species which cause oxidative damage, particularly after ischaemia
With membrane oxygenators and continuous inline monitoring is it necessary, beneficial or perhaps harmful?

23. Demonstrated intraoperative quantifiable oxidative damage independently predicts AKI after cardiac surgery
Hyperoxic reperfusion of ischaemic tissues is associated with tissue damage and poor outcomes in various situations1,2,3
Kilgannon et al. Circulation 2011;123:
Liu Y et al. Stroke 1998;29:
Stub et al Circulation2015;131(24):

24. Arterial pO2 Hyperoxemia Excessive DO2 Safety margin
Hyperbaric benefits
Oxygen pressure field theory
Near physiological pO2
Inkeeping with normal physiology
Realtime monitoring
Reduced ROS production
Oxygen toxicity
Gas generation risk

25. Circuit Choices
What factor(s) are important in making your circuit the best it can be within your restraints? What are important considerations to your circuit design? ‘RAP’ ‘Pre-bypass filters’ ‘Centrifugal pumps’ ‘DvO2’ ‘Electronic patient records’ ‘Minimised prime volume’ ‘Cost’

26. Perception of Variance
Do you think there would be variation in the answers to these questions within your dept?
0- No difference
10- Completely different
Within my dept I would score this as high variation ≈ 6
Range
0-7
Mean 2

28. Evidence Basis of Perfusion
What proportion of your practice do you feel is evidence based?
Variable response, some very definite, others struggled to define
‘0% evidence is recent and reviewed, approx 70% is historical’
‘Always done that way’ ‘Everything is evidence based’
‘90% should be evidence based but in reality approx 20%’
‘You would receive different responses within dept’
‘Recently less variability due to increased accountability’
Range
0-100%
Mean
63%

29. Evidence Basis of Perfusion
Does this perception of evidence basis vary with experience?
Does this suggest the younger generation are doing something different?
Have us ‘older guys’ forgotten all our evidence basis?
Perfusionist <10years
88%
Perfusionist >20years
62%

31. Evidence Basis of Perfusion
Very little, good evidence about bypass management
SCPS ‘Recommendations for safety and monitoring during CPB’ do not describe case management
AmSECTs International Consortium for Evidence-Based Perfusion: Standards and Guidelines for Perfusion Practice ’focuses attention on the role of institutional protocols to dictate practice’
Society of Thoracic Surgeons and Cardiovascular Anesthesiologists describes evidence to some aspects of patient management but large gaps

32. Conclusion Variation is standard practice
Does it make a difference to outcome?
Probably not in low-risk patients….but as complexity increases??
Is it safe?
Is it cost effective?
Is it accountable?
Does it ensure quality?

33. Thank you