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1. Anesthesia in C oronary artery bypass Grafting- ON pump & off PUMP chair person: Dr HV AIRANI MODERATOR: DR PREETHI PRESENTER; DR SHREYA SHETTY

2. History First open heart surgery – performed by John Gibbon in 1952 using CPB First successful OPCAB was performed in 1961 Kolesov (1964) performed the first successful anastomosis of left internal mammary artery (LIMA) to left anterior descending artery (LAD) In 1967 Favalaro and Effler performed reversed saphenous vein grafting

3. History 1990’s - The concept of fast track anesthesia Focusing on : Early extubation (within 6 hours) Mobilization Ambulation Discharge (5 days) The recent concept is ultra fast track cardiac anaesthesia (UFTCA) extubation ( within 2 hours).

4. C lass I - indications Left main coronary artery stenosis > 50% Stenosis of proximal LAD & proximal circumflex > 70% 3 vessel disease: in asymptomatic pts /those with mild or stable angina with proximal LAD stenosis in pt with poor LV function 1 or 2 vessel disease & large area of viable myocardium in high-risk areas in pt with stable angina

5. C lass I - indications >70% proximal LAD stenosis with either EF < 50% or demonstrable ischemia on non-invasive testing Disabling angina Ongoing ischemia in the setting of a non-ST segment elevation MI that is unresponsive to medical therapy Poor LV function but with viable, non-functioning myocardium above the anatomic defect that can be revascularized

6. C lass I - indications A s emergency procedure in the context of ST segment elevation MI (STEMI) in cases where: Percutaneous coronary intervention (PCI) is not possible to perform PCI has failed T here is persistent pain and ischaemia threatening a significant area of myocardium despite medical therapy

7. T ypes of CABG On pump O ff pump T otally endoscopic CABG Hybrid technique (bypass plus stenting)

8. Cardiopulmonary bypass machine

9. Basic CPB circuits A CPB circuit consists of: 1) Tubing ( cannulae ) that drain venous and return arterial blood  2) Oxygenator- gas exchange occurs 3) Mechanical pump that provides systemic perfusion 

10. Basic CPB circuits Prime The fluid contained within the CPB tubing is called prime Prior to use, CPB circuit must be primed with fluid – should be devoid of bubbles(microemboli) Fluid: B alanced salt solution (RL is generalized used) Other components : A lbulmin M annitol (25-50 gm) E lectrolyte H eparin ( 2-2.5 IU /ml )

11. Basic CPB circuits Prime V olume: O n average ~ 1,500 mL Blood ( sanguinous prime) : To prevent excessive dilutional anemia and decrease in oxygen- carrying capacity, Children, small adults, and patients with preoperative anemia. 

12. Basic CPB circuits 1. RESERVOIR – Recieves blood from venous cannula Gravitational drainage

13. Basic CPB circuits 2. OXYGENATOR (artificial lung) – M odern machine has membrane oxygenator P revents destructive blood gas interferece

14. Basic CPB circuits 3. HEAT EXCHANGE- Counter current - cooled or warm H eat transfer occur by conduction

15. Basic CPB circuits 4. PUMP (artificial heart) - Double armed roller/centrifugal pump One major difference between roller head and centrifugal pumps is that from centrifugal pumps flow will vary with changes in pump preload and afterload. Roller pumps- positive displacement through raceway Centrifugal pump – kinetic energy using centrifugal force Vortex effect- pressure differential

16. Basic CPB circuits 5. Arterial filter P articulate matter may enter from carditomy suction F inal filter – reduces systmic emboli F ilter is always in parallel with a bypass limb in case filter becomes clogged and develops increased resistance

17. A ccessory pumps & devices 6. C ardiotomy suction: A spirates blood from the surgical field & returns it directly to the main pump P otential port of entry for fat & other debris

18. A ccessory pumps & devices 7. Left ventricular vent With time blood reaccumulates in LV (residual pulmonary blood from bronchial arteries) Decompress the LV and aspirate air from the heart during de-airing procedures Prevents ventricular distention that may lead to MI and is particularly important in patients with aortic insufficiency.  Site - Via left superior pulmonary vein/ aortic root to LA to LV

19. A ccessory pumps & devices 8. Cardioplegic pump- Procedure to produce asystole by infusing cold cardioplegic solution into coronary arteries Protects myocardium from damage during ischemia Concept – increased K+ extracellularly – reduces transmembrane K+ - cardiac arrest during diastole

20. BASIC COMPONENTS REMARKS 1.POTASSIUM (10-40 mEq/L) Decreases transmembrane potential 2.SODIUM <140 mEq/l (conc<plasma) Ischemia increases intracellular sodium 3.CALCIUM 0.7-1.2 mmol/l Maintain cellular integrity 4.MAGNESIUM 1.5-15 mmol/l control excessive intracellular influxes of calcium 5.BUFFERS- BICARBONATE, HISTIDINE, TROMETHAMINE(THAM) prevent excessive buildup of acid metabolites 6.HYPERTONIC AGENTS-MANNITOL control cellular edema 7. LIGNOCAINE AND GLUCOCORTICOIDS MEMBRANE STABILIZING AGENTS 8.GLUCOSE, GLUTAMATE, ASPARTATE ENERGY SUBSTRATES 9.VEHICLE/SOLVENTS CRYSTALLOIDS OR BLOOD(MORE COMMON)

21. Cardioplegic solution: administration Retrograde – solution introduced via coronary sinus Antegrade – via aortic root Antegrade + retrograde – better

22. P reoperative preparations: History Written informed consent E xaminations Investigations – CXR, ECG, ECHO, Angiography Premedications – Midazolam, Fentanyl, Morphine, Ranitidine, Esmolol Monitorings – 5 ECG, SPO2, IBP, CVP, PA Pressure, Temp, ACT, ABG, Urine Output, TEE, Capnograph Emergency medications – Atropine, Adrenaline, phenylephrine.

23. Cardiac operations usually require general anesthesia, endotracheal intubation & controlled ventilation. High thoracic epidural anesthesia together with lt general anesthesia  used in European countries. Sole thoracic epidural anesthesia  CABG without CPB. Risk of spinal hematoma formation foll : heparinization & medico legal consequences are present. Single pre-op intrathecal morphine .

24. I nduction Goal : to avoid undue hypotension to attenuate hemodynamic response to laryngoscopy and intubation Fall in B.P >20% of baseline - needs use of inotropes. Selected agent - small incremental doses and titrated first against loss of consciousness then to an acceptable fall in BP. Muscle relaxation + controlled ventilation ensures adequate oxygenation and prevents hypercapnia.

25. Volatile agents which produce less myocardial depression (desflurane & sevoflurane) Provide hemodynamic stability & early extubation. Propofol -0.5 -1.5mg/kg Etomidate – 0.1 -0.3 mg/kg OR Thiopental – 1-2mg/kg Midazolam – 0.05mg/kg

26. Opioids – to blunt S ympathtic stimulation response  intermittent or continuou s. Opioids are given intermittently and total dose of fentanyl and remifentanil should not exceed 15 and 5 mcg/kg respectively . Low dose infusion of propofol 25-50 µg/kg/min for maintenance

27. induction Inhalational Volatile agents{ 0.5-1.5 MAC for maintenance of anesthesia and sympathetic response suppressio} Isoflurane , sevoflurane or desflurane are used for maintenance. Preferable in paediatric patients

28. Midline sternotomy with sternal saw. Heart is examined by surgeon. During this time, ventilation is halted to avoid injury to pleura by oscillating screw. High chances of injury in previous sternotomy pt’s or re-do procedure Heparin - before IMA pedicle is clamped 1 end of graft is sutured to coronary artery beyond blockage and other is sutured to Aorta Heart restored. Protamine. Sternum wired

29. cannulation A rterial – ascending aorta, femoral, axillary V enous – RA, IVC, SVC SBP 100 mmHg to minimize risk of aortic dissection during aortotomy : either by increasing the inhaled anesthetic concentration or using vasodilators such as nitroglycerin. After aortic cannulation pressure is raised back Retrograde autologous priming is initiated

30. M anagement of CPB

31. Anticoagulation Heparin A dministered before iniation of CPB – to prevent DIC & formation of clot in pump Dose = 400 units/kg before arterial cannulation Administer in reliable line ( usually central) S ome surgeons administer themselves in RA Activated Clotting Time(ACT): > 480 sec M easure ACT after 3-5 mins I f ACT < 400 sec - additional 100 units/kg Heparin M easured every 30 minutes to 1 hour while on CPB

32. B ypass period L oss of arterial pulsatile waveform Taken up by perfusionist Main concern for anesthesiologist : Cerebral perfusion Default systemic perfusion Aim – MAP 50 – 100 mmHg , 60 mmHg for hypertensive Insulin administration if RBS > 180 mmHg

33. B ypass period Vaporizer – reduce to 1% If problem with vaporizer – IV anesthetics Dose – reduced during hypothermia and increased during rewarming

34. W eaning from CPB machine

35. S eparating from bypass – “CVP” “ C” Cold – temp 36-37°C Conduction – cardiac rate and rhythm. Target rate 80-100 bpm Cardiac output or contractility – estimated from TEE Cells – Hb conc >7-8 gm/dl Calcium – immediately available to treat hyperkalemia and hypocalcemia Coagulation – protamine administration – ACT measured

36. “ CvP ” “V” Ventilation Visualisation of heart directly as well as through TEE – estimate global and regional contractility Vaporizer - re institution of low dose agent immediately after weaning Volume expander – after all products from pump has been exhausted and if BT is not indicated then crystalloid / albumin/ hetastarch – to increase preload

37. “ Cvp ” “P” Predictor of adverse cardiac outcome Pressure- to recognise any discrepancy in central aortic pressure and radial artery pressure Pressors - vasopressors and inotropic agents must be easily available Pacer – an external pacer should be available Potassium – hypokalaemia may contribute to dysrhythmia and conduction abnormalities Protamine

38. P rotamine H eparin reversed when no longer needed for CPB R eversed by protamin D ose 1 -1.3 mg per 100 units of heparin T est dose of 10-20 mg over 60 seconds before full dose

39. Off pump coronary artery bypass surgery

40. off pump CABG(OPCAB) Operation on beating heart
Use of epicardial stabilizer ( octopus, vortex)
Temporary cessation of coronary blood flow ; during anastomosis Avoids :- Cannulation Cross clamping Systemic inflammatory response C oagulation disorders M ultiple organ dysfunctio n

41. 2 O pcab techniques Minimally invasive direct-access coronary artery bypass (MIDCAB) Mini thoracotomy Anteriorly located S ingle or 2 vessel surgery – E g- anastomizing LIMA to anterior descending coronary artery O ff-pump coronary artery bypass (OPCAB) M edian sternotomy M ultivessels grafting

42. indications for opcab Advanced age H/o CVA/TIA/ neuropsychiatric pt Respiratory disease Impaired liver function Impaired renal function Immunosuppression Severe myocardial dysfunction Aortic disease to avoid aortic cannulation and clamping :– - calcified aorta - atherosclerotic aorta

43. Hemodynamic alterations during OPCAB Anastomosis of LAD and branches Positioning requires slight traction on heart Does not cause significant derangements Epicardial stabilizer placed on contracting ant. wall may decrease SV and CO

44. Anastomosis of LCX and branches Runs in left AV groove and continues posteriorly Exposure requires verticalization of heart and causes :– Atrial displacement – atria lies below ventricles, thus requires high filling pressures to maintain CO Distortion of valvular anatomy – MR and TR Reduced amplitude of ECG waveforms Unreliable CVP Management – 1. Trendelenburg position. 2. Fluid bolus to increase filling pressure
3. Vasopressors and inotropes

45. Anastomosis of RCA and branches Runs in rt AV groove and continues posteriorly Exposure requires verticalization Epicardial stabilizer on RV decreases chamber volume Result in decreased RV filling and CO Bradyarrhythmias and CHB Management -
1. Trendelenburg position
2. Fluid bolus to increase filling pressures
3. Vasopressors and inotropes
4. Epicardial pacing

46. A nticoagulation in O p cab surgery Heparin 2mg/kg (200 units/kg) given before division of IMA ACT – 250 to 300 s L ower than CPB – no contact with foreign surface

47. I ntraoperative complications

48. I ntraop complications 1. H ypotension M anagement : V olume loading I notropes therapy – dopamin e, epinephrne, dobutamine infusion P henylephrine I nform surgeon – cotton packs under heart and epicardial stabilizer repositioning I f no improvement – intra aortic ballon pump

49. Vasopressor and inotropes

50. Intraop complication 2. Arrythmias Causes: MI, electrolyte imbalance, hypothermia Use lidocaine (without preservative) infusion if patient has arrhythmia caused by MI Electrolyte imbalance - potassium chloride, magnesium sulfate, calcium, bicarbonate – as suggested by ABG Temperature correction

51. Intraop complication 3. Hypothermia Warm blanket covers OT room temp (22C-25 ° C) Lethal triad – hypothermia, acidosis, coagulopathy

52. Intraop complication 4. Myocardial ischaemia PREVENTION Maintaining systemic blood pressure (+/- 10%), keeping MAP of at least 70 mm Hg at all times avoiding tachycardia using intra operative beta-blockers or calcium channel blockers. Ischaemia during distal anastomosis can be prevented by using intraluminal coronary shunts .

53. Intraop complication 5 . Haemodynamic changes related to heart position During grafting of RCA - bradycardia (reduction in blood supply to the sinus and AV nodes) if required use atropine and atrial pacing.

54. P ostoperative care

55. P ostop management MONITORING • 5 lead ECG monitoring - for any fresh changes like ischemia or MI Rx - LMWH, anti platelet medications, insertion of an intra aortic balloon pump or revision of grafting. • Continuous monitoring of SpO2, ETCO2, Temp., ABG. • Always carry prefilled syringes of diluted adrenaline( 1:2,00,000), 1.2mg of atropine and 100mg of lidocaine to treat a crisis during the transfer phase .

56. P ost op pain management Epidural analgesia : Bupivacaine (0.0625 to 0.125%) with fentanyl 2mcg/ml conc & infuse @10 to 15ml/hr. Intravenous opioids: Fentanyl IV in syringe pump 0.25 to 0.50mcg/kg/hr. It is better to use multimodal analgesia to avoid toxicity of a single drug.

57. I cu management VENTILATION FiO 2 of 0.7 Vt 6-10 ml/kg RR: 12- 15/min I:E ratio of 1:2 Controlled mode of ventilation (CMV). ABG performed after 30 minutes. FiO2 is reduced to 0.4 if oxygenation, carbon dioxide elimination and tissue perfusion maintained

58. ICU management 30 minutes later, assessment of following done: Blood loss (not >10% of blood volume). Fluid balance (not <10-15 ml/kg ) Core temperature ( not < 35 o C ) Arrhythmias U rine O utput (at least 1-2 ml/kg/h) Residual neuromuscular blockade - reversed with Neostigmine and Glycopyrrolate After confirming adequacy of reversal ventilatory mode is switched to the spontaneous modes of ventilation 30 mins after supported ventilation - ABG repeated - satisfactory values of oxygenation, CO 2 elimination and metabolism - extubated

59. F ast track anesthesia (FTCA) Defined as tracheal extubation within 6 hours after cardiac surgery, early mobilization of patient and early discharge (5 days) from the hospital. Use of short acting opioid medications Use of short acting sedatives Early extubation resulted in regaining the cough reflex and thus a lower incidence of atelectasis and pneumonia Patients not suitable - bleeding, dysrhythmias and hemodynamic instability

60. refernces: Miller’s Anesthesia – 9 th Edition. Essentials of Cardiac Anesthesia – Joel.A.Kaplan Clinical Anesthesiology – G. Edward Morgan,Jr . Wylie & Churchill Davidson’s – A Practice of Anesthesia – 7 th Edition.

61. T hank you