Problems in Cardiopulmonary Bypass

1. Problems in Cardiopulmonary Bypass

2. Introduction • Perfusion Incident frequency • Identify possible problems during CPB • Outline remedial action

3. Incident Frequency

4. Incident distribution

5. Topics for Discussion • Mediation of Patient’s immune system response • Unusual syndromes • Oxygenator problems • Embolic events  Protocol for Gross Air Embolism

6. Systemic Inflammatory response • Platelet adhesion, activation of Factor XII • Cascade activation : • kallikrein • kinin-bradykinin • Fibrinolytic • Complement -  C3a + C5a leucocyte activation  oxygen free radicals

7. Mediation of Inflammatory response 1. Biocompatible materials • Albumin in priming fluid • Heparin coating - ionic - benzalkonium heparin • surface grafting - • covalent - Carmeda • Endothelial-like surfaces - phosphorylcholine • trillium

11. Mediation of Inflammatory response • Leucocyte depletion 3. Isolation of Cardiotomy suction

12. Anti-thrombin III deficiency • In the absence of adequate circulating AT-III heparin has little or no effect retarding blood coagulation. • Congenital AT-III deficiency • Acute venous thrombosis • DIC • Liver cirrhosis

13. AT III - Diagnosis & action • ACT still low after Heparin bolus • Repeat bolus ( 30 - 40mg / Kg ) • ACT still low – give 2 units FFP • Recheck ACT • On bypass add further FFP as reqd

14. Microaggregates - Cold agglutinins • gp1 : Immunoglobulin M class directed against erythrocyte I antigen – wide thermal range 4 to 32C • gp2 : narrow thermal range 0 - 10C • Clotting / grainy appearance • Interfere with cardioplegia distribution &  myocardial protection.

15. Cold agglutinins – management strategy • Rewarm pat to 320C • Switch to warm blood cardioplegia • Sample to haematology to determine thermal amplitude • Pre-op plasmapheresis for patients with known agglutinins will remove most of the serum antibodies.

16. Malignant Hyperthermia • Inherited disorder – rapid temp to 42°C in response to volatile anaesthetic agents • Abnormal calcium metabolism - myoplasmic ionic calcium • Metabolic rate, resp + met acidosis, K+ ,  lactate + pyruvate, tachycardia,  temp • Massive muscle swelling, Pul oedema, DIC & acute renal failure   70% mortality

17. M.H. - remedial action • Stop all volatile anaesthetic agents • FiO2 to meet metabolic demand • Administer Dantrolene sodium IV • Correct acidosis + hyperkalaemia • Use IV and surface cooling to control temp • Give mannitol + frusemide to maintain urine output of at least 2ml/Kg/hr

18. Sickle Cell Disease • Low O2 sat +/- hypothermia will cause sickle cells to clump + precipitate • Disease : Pats with 50% Haemoglobin S cells will sickle @  85% O2 sat • Trait : Pats with 45% Haemoglobin S cells will sickle @  40% O2 sat

19. Sickle Cell Disease – management strategy • Disease : • Trait : Divert venous blood to cell salvage / plasmapheresis to separate plasma and platelets Replace with RBC, FFP, colloid + crystalloid Keep O2 saturations high Avoid acidosis Avoid hypothermia Warm blood cardioplegia

20. Methaemoglobinaemia • Severe cyanosis of arterial blood ( often appears chocolate brown rather than blue ) in spite of high pO2 • Haem ion oxidised from ferrous (Fe 2+) to ferric (Fe 3+) state • Hereditary deficiency in control enzymes • Drug reaction – e.g. nitroglycerine, isosorbide dinitrate, sodium nitrate

21. Remedial Action • Withdraw all possible causative agents • Administer 1% methylene blue infusion 1 – 3mg/kg over 5 min • Doses > 7mg/kg are toxic • High dose Vitamin C and/or exchange transfusion in severe cases

22. Oxygenator Problems • Physical attrition •  Gas exchange capability • Inadequate anticoagulation • Heparin resistance • AT III deficiency • Administration of Protamine !

23. Sources of Emboli Particulate • Oxygenator - Polypropylene / polycarbonate • CPB circuit - PVC / silicone (spallation) • Patient - plaque • calcium • platelet / fibrin aggregates • lipid globules • muscle / connective tissue fragments

24. Sources of Emboli • Gaseous • Cannulation • Venous air entrainment – (VAVD?) • Inadequate de-airing of the heart • Inappropriate vent suction • Centrifugal pump – retrograde flow • IABP deflation during aortotomy • Temperature Gradients • Catastrophic gross air embolism

25. Protection Against Embolic Events ( 1 ) • Particulate 0.5 micron Pre-bypass filter 40 micron Arterial line filter 120 micron cardiotomy reservoir filter

26. Protection Against Embolic Events ( 2 ) • Gaseous • Microemboli - arterial line filter + purge line • - elimination of entrained venous air • - vent line – one-way pressure relief valves • Macroemboli - oxygenator resevoir level sensor • - arterial line filter + purge line - ultrasonic bubble detector in art line • - anti-siphon valve / software for centrifugal pumps • - CO2 insufflation

27. Gross Air Embolism Incident - Protocol • Perfusion • Surgical • Anaesthetic • Post operative care

28. Perfusion • Discontinue bypass – clamp art + ven lines • Identify origin of problem • Reprime CPB circuit & art cannula • Retrograde SVC perfusion 1-2 LPM • Reinstitute bypass -  temp (22 – 30o C) Systemic pressure FiO2 = 100% • Off bypass @ 34o C

29. Surgical • Clamp & remove aortic cannula • Cannulate SVC or connect to SVC cannula • Retrieve blood/air exiting aorta via vent • When no more air is visible at aortotomy -- Re-cannulate aorta – reinstitute bypass • Bleed air from coronary arteries • Complete Surgical procedure

30. Anaesthetic • Place patient in steep Trendelenberg position • Compress carotid arteries • Consider administering : • Steroids • Mannitol • Antiplatelet agents

31. Post Bypass Management • Ventilate patient on 100% oxygen • Institute slight hyperventilation • Rewarm to normothermia over 24hrs • Place patient in reverse trendelenberg posn • Avoid hyperglycaemia + hyponatraemia • Consider Hyperbaric oxygen treatment