UW MEDICINE │ Turkish Society of Perfusionists 3 rd Perfusion Symposium CARDIOPULMONARY BYPASS HOW DO WE KNOW WHAT WE ARE DOING? CRAIG VOCELKA, M.DIV., CCP CHIEF, PERFUSION SERVICES // EXTRACORPOREAL LIFE SUPPORT DIVISION OF CARDIOTHORACIC SURGERY DEPARTMENT OF SURGERY UNIVERSITY OF WASHINGTON SCHOOL OF MEDICINE SEATTLE, WASHINGTON

I have no conflict of interest pertaining to this presentation DISCLOSURE 2

Gibbon 1953 Evolution of CPB Understanding of physiology of CPB INTRODUCTION 3

“Clinical state, secondary to failure of the heart to pump blood into the aorta in sufficient volume and under sufficient pressure to maintain pressure-flow relationship adequate for normal tissue perfusion.” SHOCK 4

“Cardiopulmonary bypass is, in essence, an induced state of controlled, clinical shock” Charles C Reed, Trudi Safford. Cardiopulmonary Bypass 2 nd Ed. Texas Medical Press, Inc CARDIOPULMONARY BYPASS 5

We can directly control Flow Blood gasses Temperature Pressure (to an extent…) Hematocrit WHAT WE CAN VERSUS WHAT WE CANNOT 6

We cannot control Metabolic rate Oxygen consumption Auto regulation WHAT WE CAN VERSUS WHAT WE CANNOT 7

How much is enough? Weight Neonates ml/kg/min Peds ml/kg/min Adults ml/kg/min Body Surface Area 1.6 – 3.2 l/m 2 /min Extreme variable ARTERIAL BLOOD FLOW 8

Where did these numbers come from? Kirkland 1993 Clowes 1958 No recent research ARTERIAL BLOOD FLOW 9

And then… Stanford ‘low flow technique’ 1.0 – 1.2 l/m 2 /min Without neurological complications! ?? IS THERE A MAGIC NUMBER ?? ARTERIAL BLOOD FLOW 10

Consumption – VO 2 – is related to age Infants 7.6 ml O 2 /kg/min (birth to 3 weeks) 2 months 9.0 ml O 2 /kg/min Adults 4.0 ml O 2 /kg/min Studies all done on unanesthetized humans OXYGEN DELIVERY // CONSUMPTION 11

Cardiac Surgery Anesthesia Decrease 25% - 50% Temperature Decrease 7% for each degree Celsius OXYGEN DELIVERY // CONSUMPTION 12

Calculate and monitor blood flow Measure blood gasses Arterial, venous, saturations Oxygen consumption (Fick Equation) Is this telling us all we need to know? Are we adequately oxygenating at the cellular level? BLOOD FLOW AND OXYGEN 13

Basic science review Lactate production results from cellular metabolism of pyruvate into lactate under anaerobic conditions. Blood lactate level in Type A lactic acidosis is related to the total O 2 debt and the magnitude of tissue hypoperfusion LACTATE 14

Outcomes Demmers – a peak blood lactate level >4.0 mmo/L during CPB was identified as a strong independent predictor of mortality and morbidity and suggests tissue hypoperfusion occurred during CPB Basaran – Postoperative morbidity and mortality is increased with higher lactate concentrations LACTATE 15

Problems Blood flow Additional instrumentation / lab testing LA / PVA LACTATE 16

Critical O2 delivery point is associated with Abrupt increase in lactate level Significant increase in A-V pCO 2 gradient Since CO2 is 20X more soluble than O2, it is logical that the A-V pCO 2 gradient may serve as an excellent measurement A-V pCO 2 GRADIENT 17

delta pCO 2 is a valuable parameter for determining the adequacy of CPB to a given metabolic condition delta pCO 2 can help detect changes in O 2 demand A-V pCO 2 GRADIENT 18

We are placing patients in a totally abnormal physiological state As we will discuss in my next presentation, we must understand and treat each patient individually After 60+ years, there is still much to learn and understand about cardiopulmonary bypass CONCLUSION 19

THANK YOU 20