Conduct of cardiopulmonary bypass in cardiac patient

Conduct of cardiopulmonary bypass

1. CONDUCT OF CARDIOPULMONARY BYPASS 1 Dr. Gunjan Singh

2. Management before CPB Anticoagulation Cannulation Monitoring Cardiac protection Prepartion for CPB 2

3. PHYSILOGICAL PARAMETERS OF CPB Perfusion pressure Pump flow Temperature management CNS monitoring Pulsatility 3

4. Sequence of events Circuit selection and priming Anticoagulation Cannulation Initiation and maintenance of CPB Myocardial protection Weaning and termination from CPB. 4

5. Priming . “Prime volume” is the volume of balanced electrolyte solution necessary to completely de-air the circuit Main cause of the hemodilution associated with CPB This increased volume of distribution dilutes all of the proteins, coagulation factors and formed elements of the blood Dilutes plasma levels of drugs 5

6. Priming solution is selected according to the body surface area, hematocrit , and the volume required. 6

7. priming solution Prerequiste for ideal priming soloution Isosmolar to plasma Should be excreted easily Less hemolysis Should produce no cellular edema Types Balanced salt solution( drawback:interstitial and celluar edema) Colloid (coagulation and allergic reaction) Blood and blood products (old standard for infant and neonate) 7

8. Setting the Occlusion of the Pump For adequate systemic blood flow Outflow tube is held at 30–40 cm height and occluded to hold the fluid in place and then a gradual drop is allowed at the rate of one inch/minute. During induction : CPB machine should be ready Post induction : adequate depth is maintained During sternotomy : tube disconected or low TV ventilation given 8

9. Anticoagulation Heparin is a heterogeneous, heavily sulfated polysaccharide compound derived from pig intestinal mucosa or bovine lung. It binds antithrombin III, profoundly facilitating its native ability to inhibit plasma coagulation, most prominently through inhibition of factors IIa (thrombin) and Xa Initial dose: 3mg/kg or 300units/kg 9

10. Anticoagulation with heparin for CPB can be monitored by measuring clotting times or whole blood heparin concentrations • Most commonly test used for CPB are the ACT • Heparin resistance: AT III concentrate or FFP Reversal Protamine , a polycationic protein derived from salmon sperm contains two active sites – It neutralizes heparin – It exerts a mild anticoagulant effect independently of heparin 10

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12. CANNULATION The cannulas are the catheters which are used to connect the patients circulation to the ECC. There are three types of cannulations involved in CPB. – Arterial( Ascending aorta), – Venous (RA) – Cardioplegia cannulation 12

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14. AORTIC CANNULATION After 3 minutes of heparinization ACT is done. During this period surgeon checks the lines for air bubbles & line pressure(150-200 mm of hg) is checked by the perfusionist to confirm lack of resistance. Any resistance raises the suspicion of aortic dissection or cannula malposition ( innominate artery or left CCA or left SCA ) 14

15. VENOUS CANNULATION Single or bicaval cannulation is done as per requirement Adequate venous return should generate blood flow rate of 2.4 L/min/m2 at a line pressure of 150-200 mm Hg. The venous blood is complelety drained. Ventilation is stopped (full flows). Cardioplegia cannula with a vent is inserted in between aortic root and the cross clamp. 15

16. An LV vent is required in order to prevent warming and distension of LV. Aorta is cross clamped before giving cardioplegia . The duration of cross clamp is noted. All standard monitoring is continued, ET tube is disconnected, and IV fluids and infusions are stopped. 16

17. MONITORING standard monitoring ( ECG,IBP,EtCO2,SPO2) urine output 0.5-1ml/kg temperature at two different sites Blood gas Electrolyte RBS ACT>480 17

18. CPB MAINTAINENCE The oxygen and air attached to the bypass machine are started. The flow of gases is adjusted to meet the oxygenation and removal of carbon dioxide. Anesthesia depth should be sufficient prevent awareness prevent spontaneous movement suppress stress response Vaporizers ( sevo / iso ) can be fixed to oxygentors gas inlet MAP maintained at 60 to 80 mm hg HcT near 22% Reservoir level 18

19. CONCRNS DURING BYPASS Temperature : hypothermia< 34 Glucose : tight sugar control < 180 Ph: Perfusion pressure: Maintenance of anesthesia : 19

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21. Myocardial protection A. Cardioplegia B . Ischemic preconditioning C . Preventing left ventricular distension 21

22. Cardioplegia To provide a motionless field for the surgeon, the heart is arrested in diastole by the administration of a potassium-enriched cardioplegia solution to the heart. • Potassium-induced arrest alone reduces the heart's myocardial oxygen consumption by 90 %. 22

23. The combined influence of potassium arrest and myocardial temperatures lower than 22°C reduces myocardial oxygen consumption by 97% and enables the tissue to withstand complete interruption of blood flow for periods of 20 to 40 minutes. Antegrade and retrograde cardieplagia 23

24. Temperature The advantages of hypothermia (34–28°C). Hypothermia itself reduces minimal alveolar concentration and neuronal activity It reduces o2 requirement by decreasing the metabolic rate; CMRO2 is decreased 6-7 % per degree decline in the temperature. Flow rate of pump can be lowered thus protecting the cells from trauma. Better organ protection especially brain and kidney 24

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26. Temp can be estimated from tympanic, nasopharyngeal , esophageal , rectal, bladder, skin surface, pulmonary arterial, or jugular venous bulb temperature The heater cooler unit commonly known as Haemotherm (or) Temperature control unit Used to warm or cool and to maintain thetemperature during CPB 26

27. Ischemic preconditioning Ischemic preconditioning (IPC) is endogenous myocardial protection triggered by exposure to brief (5 to 15 minutes) periods of ischemia. Ipc is natural defense mechanism 27

28. Mechanism of preconditioning Involves activation/translocation of PKC, tyrosine kinases and mitogen —activated kinases . Isoflurane and sevoflurane aid in IPC. It helps by reducing infarct size—less generation of lactate—decreased rate of fall in ATP while arrhythmias and contractile dysfunction are decreased. 28

29. Venting of heart The purpose is to prevent heart distension, reduce myocardial rewarming , prevent cardiac ejection, and provide a clear field to operate . done by aortic root cardioplegia cannula,RSPV is usually used Complications bleeding , trauma to intima of the chamber, air trapping. 29

30. TERMINATION OF CPB Prerequisite Normothermia is achieved by active rewarming ABG ( Hct > 25%, PaO2>100 ),Electrolyte, Ph ,RBS,ACT Reinflation of lung Targeted HR b/w 70-100 IABP insertion with ongoing MI or unstable HD 30

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32. 32 Temperature gradual rewarming Rate and rhythm 0-100 sinus rhythm Cardiac output TEE Coagulation: After the pump blood is over a test dose of protamine is given , the ratio of heparin protamine reversal is 1:1.3 . given gradually over 10-15 minutes If ACT is less than180, aortic cannula is removed . Hematocrit ( 20 to 25 %) ultra filtration and diuretics helps to increase Blood gas to rule out acidosis Potassium Hyperkalemia causes rhythm disturbances Hypokalemia leaves the heart irritable Calcium for contractility and conduction Resumption of ventilation started just before someload given to heart

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34. SEQUENCE OF EVENTS FOR BYPASS Warm cardioplegia Deairing Unclamping of aorta Filling of heart and add inotrops Increased Venous occlusion and blood flow Cardioplegia -Motionless and bloodless heart Take of bypass and start ventilation Protamine reversal Rewarming Sternum is closed, tranducers are fixed, invasive lines are taped & pt shifted to ICU 34

35. COMPLICATIONS OF CPB Venous cannulation : air lock. Arterial cannulation : dissection OR misplacement Massive air embolism Bleeding disorders Renal dysfunction —: AKI Cerebral dysfunction – neurocognitive disorders to stroke Inflammation APR is initiated by contact with artificial surface of bypasss circuit Cardiac dysfunction and rhythm disturbances Electrolyte disturbances Pulmonary abnormality : ARDS , PE, atlelactsis . 35

36. End Organs That Can Be Adversely Affected by CPB • Heart • Brain • Kidneys • Gastrointestinal tract • Endocrine system 36

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