Understanding Cardiopulmonary Bypass and Arterial Blood Flow in Perfusion Services
Explore the principles of cardiopulmonary bypass (CPB) and the intricacies of arterial blood flow regulation in perfusionist services. Delve into the control and management of physiological parameters during CPB to ensure optimal patient outcomes.
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UW MEDICINE Turkish Society of Perfusionists 3rdPerfusion 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
DISCLOSURE I have no conflict of interest pertaining to this presentation 2
INTRODUCTION Gibbon 1953 Evolution of CPB Understanding of physiology of CPB 3
SHOCK 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. 4
CARDIOPULMONARY BYPASS Cardiopulmonary bypass is, in essence, an induced state of controlled, clinical shock Charles C Reed, Trudi Safford. Cardiopulmonary Bypass 2nd Ed. Texas Medical Press, Inc. 1985 5
WHAT WE CAN VERSUS WHAT WE CANNOT We can directly control Flow Blood gasses Temperature Pressure (to an extent ) Hematocrit 6
WHAT WE CAN VERSUS WHAT WE CANNOT We cannot control Metabolic rate Oxygen consumption Auto regulation 7
ARTERIAL BLOOD FLOW How much is enough? Weight Neonates 100-120 ml/kg/min Peds 80 -100 ml/kg/min Adults 40-60 ml/kg/min Body Surface Area 1.6 3.2 l/m2/min Extreme variable 8
ARTERIAL BLOOD FLOW Where did these numbers come from? Kirkland 1993 Clowes 1958 No recent research 9
ARTERIAL BLOOD FLOW And then Stanford low flow technique 1.0 1.2 l/m2/min Without neurological complications! ?? IS THERE A MAGIC NUMBER ?? 10
OXYGEN DELIVERY // CONSUMPTION Consumption VO2 is related to age Infants 7.6 ml O2/kg/min (birth to 3 weeks) 2 months 9.0 ml O2/kg/min Adults 4.0 ml O2/kg/min Studies all done on unanesthetized humans 11
OXYGEN DELIVERY // CONSUMPTION Cardiac Surgery Anesthesia Decrease 25% - 50% Temperature Decrease 7% for each degree Celsius 12
BLOOD FLOW AND OXYGEN 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? 13
LACTATE 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 O2 debt and the magnitude of tissue hypoperfusion 14
LACTATE 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 15
LACTATE Problems Blood flow Additional instrumentation / lab testing LA / PVA 16
A-V pCO2 GRADIENT Critical O2 delivery point is associated with Abrupt increase in lactate level Significant increase in A-V pCO2 gradient Since CO2 is 20X more soluble than O2, it is logical that the A-V pCO2 gradient may serve as an excellent measurement 17
A-V pCO2 GRADIENT delta pCO2 is a valuable parameter for determining the adequacy of CPB to a given metabolic condition delta pCO2 can help detect changes in O2 demand 18
CONCLUSION 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 19
THANK YOU 20
