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

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

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?

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

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

Perfusion Circuit Variation

Perfusion Circuit Variation

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

Perfusion Patient Management

Circuit Prime

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!

Perfusion Flow-Cardiac Index CI During Hypothermia CI During Normothermia 2.4-2.5 2.4-2.8 6/13 reported they increased their flow during rewarming

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

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

Variation in Perfusion % Pulsatile Flow (roller pump) 4 31 DVO2 3 17 Haemofiltration Cerebral Saturation Monitoring Transfusion on CPB Threshold Mean 7.2gdl Range (6.0-8.0gdl)

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)?

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)

Arterial pO2

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?

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;123:2717-22 Liu Y et al. Stroke 1998;29:1679-86 Stub et al Circulation2015;131(24):2143-50

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

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’

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

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%

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%

Evidence Basis of Perfusion Very little, good evidence about bypass management SCPS ‘Recommendations for safety and monitoring during CPB’ do not describe case management www.scps.org AmSECTs International Consortium for Evidence-Based Perfusion: Standards and Guidelines for Perfusion Practice 2013...’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

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?

Thank you