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Problems in Cardiopulmonary Bypass

Problems in Cardiopulmonary Bypass. Introduction. Perfusion Incident frequency Identify possible problems during CPB Outline remedial action. Incident Frequency. Incident distribution. Topics for Discussion. Mediation of Patient’s immune system response Unusual syndromes

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Problems in Cardiopulmonary Bypass

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  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

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

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

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

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

  21. 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

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

  23. 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

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

  25. 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

  26. 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

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

  28. 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

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