Basic Principle of Cardiopulmonary Bypass (CPB).pptx

Rafiq Sumardi Omar, BSN, RN, G-CVTS, Malaysia-CCP, Level 5 Cardiovascular Perfusionist, MMed, PhD, is a distinguished expert in the field of cardiovascular perfusion. His lecture on the "Basic Principle of Cardiopulmonary Bypass (CPB)" covers essential concepts and techniques critical to the effective management of CPB procedures. This topic is fundamental for understanding how blood circulation and oxygenation are maintained during heart surgery, ensuring patient safety and successful surgical outcomes.

1. Artificial Circulation of Heart Lung Machine : Basic Principles Rafiq Sumardi Omar B.Sc. (Hons) Nursing, M-CCP , M.mEd.(UM)

2. Human circulation HLM circulation

3. How it work’s?

4. Characteristic of ideal blood pump Should be able to move large volume of blood ( up to 7L/min) against significant pressure (perhaps up to 500mmHg proximal to arterial canulla ) Handling of blood should be minimize flow velocity ----minimize blood damaged Pump design, simple and free from dead space (to avoid stagnation and turbulence) should be automatically controlled and manual operated (in the event of power failure) Calibration of the pump should be easy, reliable

5. Pump Occlusive Centrifugal

6. Principle Occlusive pump (roller pump)

7. Flow characteristic Occlusive (roller pump) Flow (output) depends on: Number of rotation rate of the pump head Internal diameter of tubing (in raceway) Length of contact of the roller with tubing (rpm) Blood in Blood out Hagen- Poiseuille

8. Principle Centrifugal pump RPM Resistance DEPENDANT SENSITIVE Flow Resistance

9. Vortex Low pressure Pressure gradient Inlet outlet High pressure High pressure Blood flow depend on: Pressure gradient Resistance (at the outlet) Rotation of impellers Flow characteristic Circuit ( tubing,oxygenator , canulla , filter) SVR

10. Early design create high shear stress, New technology: low shear Reduce hemolysis Gentle blood handling * Although centrifugal pump will reduce the transmission of macroair , microair will still pass- the amount will depend on the design of centrifugal itself

11. Available in IJN Maquet centriMag Rotaflow Terumo EBS

12. Roller pump Centrifugal pump Occlusive (Semi-occlusive) Non-occlusive After load independent After load dependent Advantages Low cost Portable & position insensitive Can used for positive & negative (suction) pressure application Less blood trauma (shear stress, hemolysis ) Less potential for backward flow Safe (from positive pressure) Easy to operate Less potential for pump gross air Biocompatible (coated system) Disadvantages Blood trauma Expensive Spallation Potential passive backward flow (negative pressure) Potential for pump gross air Requires flow meters Necessary occlusion adjustment

13. Selection criteria Cost effectiveness: roller pump > centrifugal pump Advancement in surgery time & skill: side effect less significant Selection on case: Prolonged pump run Complex procedure

14. Safety issues Safety is major aspect considering pump for use in CPB Reported 260 incidences of mechanical failure of one or two pump 150 incidences of electrical / mechanical failure of HLM in a total of 653,621 procedure Mejek et al.2000 A retrospective study on perfusion incidents and safety devices. HOWEVER *most perfusion accidents not caused by device failure but by HUMAN ERROR Kurusz M et al., 1990 Risk containment during CPB

15. Roller pump Device-related incident mainly caused by: Power failure Runaway pump head (rare case) Esper et al. 1994 Human-related incident : improper occlusion setting massive air embolism clamping of the outflow Tayama et.al.2000 centrifugal pump higher incidence of technical failure the complex design device-related malfunction: power failure seal disruption Kolff J et al. 1996

16. Pulsatile vs non- pulsatile flow Pulsatile flow may have physiologic benefits on vital organ function during and after bypass * Continuously controversy between these two technique due to lack of universally accepted and clinical evidence is still debated Early mechanical pump introduction into clinical practice delivered nonpulsatile flow

17. Non-pulsatile flow vs Pulsatile

18. Optimal perfusion during Cardiopulmonary bypass : An evidence-based approach, Glenn et al. 2009 A recent evidence-based review of pulsatile CPB flow concluded the data were conflicting or insufficient to support recommendation for or against pulsatile perfusion to reduce the incidence of mortality, MI, stroke or renal failure. Alghamdi AA et al, 2006

19. Clinical application Primary requirement for CPB is to provide a systemic O2 delivery (DO2) that is sufficient to meet systemic O2 demand (VO2) In ECC circulation, DO2 is not controlled by reflex mechanism like native circulation During CPB, whole body DO2 is a function of pump flow and arterial oxygen content ( Hb ) Major determinants of VO2 are temperature, level of anaesthesia , etc Flow calculated for differing level of metabolic requirement

20. During CPB: systemic DO2 > optimal perfusion In clinical, DO2 can be improved by: increasing pump flow Increasing Hb concentration(transfusion RBC/ hemoconcentration ) Increasing Hb saturation and amount of dissolved O2 (FiO2) DO2 = pump flow x [( Hb . conc. x Hb . Sat x 1.36) + (0.003 x art.O2 tension)]

21. Metabolic needed Pt has lower Vo2 than awake patient

22. To determine pump flow, used formula that utilize BSA or ml/kg/min In paediatric higher CI is used due to higher metabolic rate Our practice, CI 2.4 L/min/m² ( paeds ) or < 10kg 150ml/kg/min CI 2.2 L/min/m² (adult) Systemic Pump CO= SVxHR CO= CPB flow, Q = CIxBSA CI=2.6-4L CI=FI=2.2-3.0 =CO/BSA

23. Hypothermia is used as a technique in order to provide a degree of organ protection and safety margin during CPB Exerts its protective effect by multiple mechanism: Reduction in metabolic rate Reduction in oxygen consumption * Too low a flow may lead under perfusion (*rewarming or at normothermia ) Assessed by : mixed venous O2 tension Return of organ function (urine output) Cerebral oxymetry Spo2

24. * The degree of hypothermia selected depends on the needs for reduction flow to enhance the surgical Temperature Flow index (l/minute/m2) Normothermia 34-37 2.4 Mild hypothermia 32-34 2.2 Moderate Hypothermia 28-32 1.8-2.0 Deep Hypothermia <28 1.6

25. Adequate pressure to drive blood to tissue will provide adequate tissue perfusion Blood flow rate directly proportional to pressure gradient

26. “Vascular” system of HLM Channel for artificial systemic circulation Interconnect all of the main component of the circuit to systemic system The only component of the pump in contact with blood Disposable Variety of material: >polyvinyl chloride (PVC) >silicone >latex rubber

27. Vascular system in Human Vascular system in HLM Venous Arterial

28. Sizes The internal diameter of tubing is a major determinant of the maximum blood flow that can be achieved ½”, 3/8”, ¼”, 3/16” internal tubing diameter

29. Relationship of internal tubing diameter, volume, and resistance Kathy K. Spitzer et al . Tubing diameter (in.) *Blood flow (ml/ Rpm) Tubing priming volume (ml / 100cm) 3/16” 7.2 18 ¼” 12.4 31 3/8” 26 71 ½” 44 126

30. Selection of tubing size Flow Arterial Venous 0.6-1 3/16” 3/16” 0.6-1 3/16” 1 <1.0 ¼” ¼” 1-1.6 ¼” 3/8” 1.6-2.8 3/8” 3/8” >2.8 3/8” ½”

31. Ideal characteristic Transparent Resilient Flexible and Kink Resistance Tolerate to Heat ,Sterilization and Extreme Cold

32. Material PVC silicone Latex rubber Advantages Thermal stability Clear Biocompatibility Resilience (memory) Biocompatibility Disadvantages Stiffness Spallation More hemolysis Hemolysis Lack of thermal stability Fatigue *PVC is the most widely used because of durability and accepted hemolysis rates

33. Coated & non-coated To improve biocompatibility, surface coated was developed Type of coating: Albumin-heparin ( eg : bio-line) Heparin Available in market : X-coating (Terumo) Carmeda (Medtronic) Bio-line ( Maquet )

34. Thank you