Anesthesia for coronary artery bypass grafting

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1. ANESTHESIA FOR CORONARY ARTERY BYPASS GRAFTING Presenter -Dr A parna J ayara (pg- Iiyr ) Moderater –Dr U rmila P alaria (professor ) Dept. of anesthesiology and critical care Govt. medical college haldwani uttarakhand

2.    THE BEGINNING  F irst open heart surgery - performed by John Gibbon in 1952 using cardiopulmonary bypass   First successful OPCAB was performed in 1961    and Kolesov in 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.   In 1968 , Green performed anastomosis of the internal mammary artery to the coronary artery   . In 1998, Jansen and coworkers clinically used novel suction based mechanical CA stabilizing system ( medtronic octopus system)

3. Indications of CABG CABG is performed for both symptomatic and prognostic reasons. Indications for CABG have been classified by the American College of Cardiology (ACC) and the American Heart Association (AHA) according to the level of evidence supporting the usefulness and efficacy of the procedure [1, 2] : Class I - Conditions for which there is evidence and/or general agreement that a given procedure or treatment is useful and effective Class II - Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness or efficacy of a procedure or treatment Class IIa - Weight of evidence or opinion is in favor of usefulness or efficacy Class IIb - Usefulness or efficacy is less well established by evidence or opinion Class III - Conditions for which there is evidence and/or general agreement that the procedure/treatment is not useful or effective, and in some cases it may be harmful

4. Indications of CABG Class I indications for CABG from the American College of Cardiology (ACC) and the American Heart Association (AHA) are as follows [1, 2] : Left main coronary artery stenosis >50% Stenosis of proximal LAD and proximal circumflex >70% 3-vessel disease in asymptomatic patients or those with mild or stable angina 3-vessel disease with proximal LAD stenosis in patients with poor left ventricular (LV) function 1- or 2-vessel disease and a large area of viable myocardium in high-risk area in patients with stable angina >70% proximal LAD stenosis with either ejection fraction < 50% or demonstrable ischemia on noninvasive testing Other indications for CABG include the following: Disabling angina (Class I) Ongoing ischemia in the setting of a non–ST segment elevation MI that is unresponsive to medical therapy (Class I) Poor left ventricular function but with viable, nonfunctioning myocardium above the anatomic defect that can be revascularized CABG may be performed as an emergency procedure in the context of an ST-segment elevation MI (STEMI) in cases where it has not been possible to perform percutaneous coronary intervention (PCI) or where PCI has failed and there is persistent pain and ischemia threatening a significant area of myocardium despite medical therapy.

5. contraindications CABG is not considered appropriate in asymptomatic patients who are at a low risk of MI or death. Patients who will experience little benefit from coronary revascularization are also excluded. Although advanced age is not a contraindication, CABG is less commonly performed in the elderly. Because elderly patients have a shorter life expectancy, CABG may not necessarily prolong survival. These patients are also more likely to experience perioperative complications after CABG

6. Types of cabg It is usually conducted with the use of a cardio- pulmonary by-pass. Alternative techniques include surgery on the beating heart without bypass aka off pump cabg It can be done through a median sternotomy or left anterolateral thoracotomy and laser re- vascularisation Alternative approaches to CABG include the following: Totally endoscopic CABG Hybrid technique (bypass plus stenting

7. Basic circuit of cardiopulmonary bypass

8. Prior to use , CPB circuit must be primed with fluid that is devoid of bubbles. A balanced salt solution such as RL is generally used RESERVOIR- recieves blood from the patient via one or two venous cannulaes placed in RA, the svc and ivc or a femoral vein. OXYGENATOR-drains blood by gravity from the bottom of the resevoir . It contains a blood gas interface which that allows blood to equilibriate with gas mixture (primarily o2)

9. HEAT EXCHANGER- blood can be cooled or warmed depending on the temperature of the exchanger. Heat transfer occurs by conduction. Pump- double armed roller or centrifugal pump. Arterial filter- particulate matter may enter the cbp from cardiotomy suction line . Final in line arterila filter helps to reduce systemic embolism The filter is always in parallel with a bypass limb in case the filter becoms clogges and develops an increased resistance

10. Accessory pumps and devices 1. cardiotomy suction – aspirates blood from the surgical field during CPB and returns it diirectly to the main pump reservoir Potential port of entry for fat and other debris to the pump that could embolize to the organs Cell saver suction device may also be used to aspirate blood from surgical field.it is sent to separate resevoir and when enough amt is accumulated , its is cenrifuged , washed and sent back to the patient.

11. 2.left ventricular vent- with time even with total CPB , blood reaccumulates in LV as a result of residual pulmonary flow from the bronchial arteries . Via rt superior pulonary vein to LA to LV Cardioplegic pump- for the administration of cardioplegic solution ( cardioplegia – the m.c . procedureto accomplish asystoleby infusing cold cardioplegic solution into coronary arteries, it protects myocadiumfrom damage during ischemia. It containspotassium (10-40meq), sodium(less tha 140 meq ), calcium (0.7-1.2meq), magnesium(1.5-15meq),buffers( histidine and THAM..concept- potassium when increased extracellularly , reduces transmembrane pot. And heart is arrested in diastole. THAM-proton acceptor

12. On pump cabg Advantages The surgeon is provided with the still heart Absence of blood in the anastomotic area Empty flaccid heart can be manipulated easily to expose all coronary branches Adverse effects Initiation of CPB associated with marked increased in stress hormone including catecholamine, cortisol , argenine , vasopressin, angiotensin Complement and neutrophil activation- increase in cappillary permeability- increase risk of micro-emboli Haemo dilution Electrolyte and acid base disturbances Metabolic disturbances

13. The contact activation with the extracorporeal circuit, shear forces, activation of compliment system, fibrinolysis and extrinsic factors all contribute to platelete dysfunction Hypothermia can lead to platelete dysfunction reversible coagulopathy , potentiation of citrate toxicity, altered glucose transport and depression of myocardial contractility Alteration in cardial function- decrease cardiac output, cardiac arrythmias , hypoxic subendocardial necrosis, release of myocardial enzymes and compromised cardiac performance Neurologic complications- 40%. changes in cognitive function to organic brain damage and stroke. Results mainly from embolic gas, atheromatous debris, fat or ischaemic events

14. Post op lung dysfunction- pulmonary edema, ARDS, atelectasis , anoxia GI dysfunction- splanchnic vasoconstriction leading to bowel ischaemia and bleeding

15. Off pump cabg Development of advanced epicardial stabilizers such as octopus has facilitated CABG withot the use of CPB, also known as OPCAB Low morbidity , low mortality with faster recovery and reduced procedural costs. Midline sternotomy -traditional approach Source of bypass grafts – rt and lt mammary arteries, saphenous v. and radial arteries Pericardium incised, reflected and secured to the edges of mediastinum Special sternal retractors allows the placement of adjustment of flexible fixation devices that work by direct surface pressure on myocardium.. These devices stabilize and verticalize the apex of heart When the targeting vessel and surrounding myocardium are stabilized elastic ligature is placed on coronary artery as arteriotomy is performed then distal anastomosis is performed

16. Off Pump CAB Surgery Indications- Single as well as multivessel CAD or as a hybrid procedure with PTCA contra indications/ increased risk for CPB- 1. severe myocardial dysfunction 2. Immuno suppression 3. H/O TIA/CVA 4. Heavily calcified aorta 5. Aortic dissection 6. Impaired renal function/need for dialysis 7. H/O previous cardiac surgery

17. Pts who are Jehovah/s witnesses High risk patients eg . Advanced age, respiratory problem, other systemic ds .

18. COMPARING ON AND OFF PUMP CABG Systemic inflammatory response syndrome (SIRS) -A combination of non pulsatile flow, myocardial ischaemia , hypothermia and contact of the patient blood with the artificial surface of the extra corporeal circuit is responsible for the inflammatory process. Coagulopathy - disruption of the coagulation system and haemodilution after cardiopulmonary by­pass is avoided in OPCAB Less blood loss in OPCAB Ascine – Eur. J. Cardioth . Surg. 1999 Puskas – Ann. Thor. Surg. 1998 DR GEETANJALI S VERMA

19. Neurologic dysfunction- due to embolization , inflammation, hypoperfusion and hyperthermia . Type 1 -   Death either due to stroke or hypoxic encephalopathy, stupor & coma. (Risk factors are DM, atherosclerosis in the proximal aorta and pre existing impairment of cerebral blood flow) Type 2 -   I ntellectual dysfunction - memory deficits, confusion or agitation - due to small micro emboli and inadequate perfusion The incidence of stroke after OPCAB is about 1% when compared to 9% after ON pump CABG   DR GEETANJALI S VERMA

20. Neurological Outcome Only few prospective Randomized Trials showed superiority of OPCAB Vs CABG. 1. Sedrakan - Stroke 2006 41 randomized trials – 50% reduction of stoke in OPCAB 2. Glenville – Ann. Thor. Surg. 2004 Elderly P. Stroke CABG – 3% OPCAB 1% 3. Mohr – Ann. Thor. Surg. 2003 16,184 p. Stroke CABG - 3.8% OPCAB 1.9% Others 1. Alamanni – Eur. J. Cardioth . Surg. 2007 No difference stroke rate 2. Lund – Ann. Thorac . Surg. 2005 No difference in long term cognitive function or MRI evidence of brain injury On the Other Hand Puskas – Ann. Thor. Surg. 2000 In series of 10,800 p. found 3 independent variables for prediction of stroke – age, previous Tia, carotid bruit DR GEETANJALI S VERMA

21. MYOCARDIAL INJURY as assessed by biochemical markers is much less after OPCAB when compared to CABG. Rastan – Eur. J Cardioth . Surg. 2005 PULMONARY DYSFUNCTION caused by atelectasis , inflammation, increased shunting and volume infusion. Reddy. Eur. J. Cardthor . Surg. 2006 6. RENAL DYSFUNCTION - lower in patients undergoing OPCAB. DR GEETANJALI S VERMA

22. Preop optimization Before CABG, the patient’s medical history should be carefully examined for factors that might predispose to complications, such as the following: Recent MI Previous cardiac surgery or chest radiation Conditions predisposing to bleeding Renal dysfunction Cerebrovascular disease including carotid bruits and TIA Electrolyte disturbances that might predispose the patient to dysrhythmias Infection, including urinary tract infection and dental abscesses Respiratory function, including the presence of COPD or infection [3] Routine preoperative investigations include the following [3] : Full blood count (abnormalities corrected) Clotting screen Creatinine and electrolytes (abnormalities corrected and discussed with the anesthetist) Liver function tests Screening for methicillin -resistant Staphylococcus aureus Chest radiography ECG Echocardiography or ventriculography (to assess LV function) Coronary angiography (to define the extent and location of CAD)

23. PRE MEDICATION Ideally two large bore (16 gauge or larger) intravenous catheters should be placed.one of these should be in a large central vein. Anti aspiration prophylaxis: Ranitidine (150mg) / P antoprazole (40mg) + prokinetic ( Metochlopramide 10 mg) Anti anxiety: tab Alprazolam 0.5-1mg oral 0.05mg.kg  -1  of midazolam + 1µg.kg  -1  of fentanyl IV 30minutes prior to surgery with supplemental oxygen. Regular medn : Beta blockers should be continued in same dosage Anti platelet medications - stopped atleast 1 week prior to surgery ACE inhibitors may be stopped 24 to 36 hours prior to surgery (substituted with calcium channel blockers) For DM patients – conversion to short acting Insulin DR GEETANJALI S VERMA

24. INTRA OP MONITORING ECG – 5 lead electrode system.an electrode is placed on each extremity and 1 precordial lead is placed in V5 position (on lt ant axillary line at 5 th intercoastal space) ischemia detection is greatest(75%)with v5 lead. This sensitivity is increased to 80%when lead II is paired with a V5 lead .hence continuous monitoring with lead II and V5, the addition of a second precordial lead V4 can detect 100% ischemic episodes. well visualized 'P' wave and QRS complex prior to commencing the surgery Invasive blood pressure (IBP) monitoring – Cont. real time , beat to beat assesment of arterial perfusion pressure and waveform throughout suurgery Most comonly assesed site- radial artery but femoral artery, brachial, ulnar , dorsalis pedis , posterior tibial and axillary artery can also be used.If radial artery cannulation is planned the Allen's test must be performed prior to performing cannulation.if radial artery graft is to be harvestedthe arterial line will be placed in dominant hand. The cannulation of the femoral artery not only permits access to the central arterial tree  but provides access to quick insertion of an intra aortic balloon pump.  DR GEETANJALI S VERMA

25. Central venous pressure Monitoring of CVP Portal for intravascular volume replacement, pharmacologic therapy and insertion of other invasive monitors such as pulmonary artery catheters. To measure the filling pressure of rt ventricle and estimate intravascular volume status. It gives an estimate of lt. sided pressures in patient with good lt. ventricular fn. IJV is most commonly selected one (ease of approach and distance from operative field) Femoral or subclavian vein can also be used but subclavian can get obstructed during sternal retraction.. And Groin assess can be challenging in obese patients and may be inappropriate if femoral bypass cannula placement or vein grafting is necessary.

26. Pulmonary artery catheter (PAC)   U sually placed via the right internal jugular vein. Indications: Ejection fraction < 0.4 Significant abnormality of the left ventricular wall motion. LVEDP > 18 mm Hg at rest. Recent MI and unstable angina. DR GEETANJALI S VERMA

27. Transesophageal echocardiography (TEE) Advantages: Identify myocardial ischaemia early by detecting regional wall motion abnormalities. Assess left ventricular dysfunction intra operatively. Assessing the improvement in myocardial function after the completion of revascularization. Disadvantage Inability to image the required part of the heart during grafting . DR GEETANJALI S VERMA

28. SpO2, ETCO2 Temperature monitoring Urinary output monitoring ACT- normal range is 80-120 seconds , heparin dosing for extracorporeal circulation is targeted to maintain ACT values longer than 480 seconds.

29. INDUCTION Induction should be slow By  intravenous ( Propofol / Etomidate / Thiopentone + Opioids ( fentanyl / morphine) +BZD) or inhalational method ( Sevo / Iso in 1-2 MAC) Neuromuscular blockade - 0.7 mg/kg   R ocuronium IV or Vecuronium 0.08-0.1 mg/kg IV (Pan/ atrac – tachy ) An endotracheal tube is inserted and secured and mechanical ventilation is started. MAINTENANCE I nfusion of fentanyl , atracurium +/- Midazolam Isoflurane / O2/ air continuous very slow injection of Propofol . DR GEETANJALI S VERMA

30. The chest is opened via a median sternotomy with the sternal saw and the heart is examined by the surgeon. Ventilation of the lung is halted during sawing to avoid injury to pleura.(oscillating saw in previous sternotomy (redo)), if it’s a redo 2 units of blood must be arranged because of perforation of RV, damage to existing v. grafts. Heparin administration usually occurs before the IMA pedicle is clamped

31. In the case of "off-pump" surgery, the surgeon places devices to stabilize the heart. If the case is "on-pump", the surgeon sutures cannulae into the heart and instructs the perfusionist to start cardiopulmonary bypass (CPB).Anticoagulation is established before CPB ,heparin given through central line.ACT longer than 400-800s is achieved Once CPB is established, the surgeon places the aortic cross-clamp across the aorta and instructs the perfusionist to deliver cardioplegia (a special potassium-mixture, cooled) to stop the heart and slow its metabolism. Usually the patient's machine-circulated blood is cooled to around 84 °F (29 °C) After heparinization,aortic cannulation done first in ascending aorta 1 or two venous cannulae are put in RA. ( hypotenssion can occur this time) Before aortic cannulation TEE or epiaortic echocardiography or both provides critical information regarding the presence and precise location of calcification and mobile atheromas in aortic arch

32. One end of each graft is sewn on to the coronary arteries beyond the blockages and the other end is attached to the aorta. The heart is restarted; or in "off-pump" surgery, the stabilizing devices are removed. In cases where the aorta is partially occluded by a C-shaped clamp, the heart is restarted and suturing of the grafts to the aorta is done in this partially occluded section of the aorta while the heart is beating. Protamine is given to reverse the effects of heparin. Chest tubes are placed in the mediastinal and pleural space to drain blood from around the heart and lungs. The sternum is wired together and the incisions are sutured closed.

33. Brief overview of cabg

34. OPCAB tissue stabilization and heart positioning devices. Verma S et al. Circulation. 2004;109:1206-1211 Copyright © American Heart Association, Inc. All rights reserved. Genzyme Immobilizer utilizes a stabilization platform and silastic vessel loops the Medtronic Octopus4 tissue stabilizer and Starfish2 heart positioner utilize vacuum suction to stabilize and position the heart. Coro- Vasc System ( CoroNeo Inc) illustrates silastic snares that are looped around the target coronary vessel and then fixed to a small immobile plate, thus directly immobilizing the target vessel.

35. Weaning from cardiopulmonary bypass TERMINATION OF CPBRewarming , evacuation of air from heart and graft,removal of aortic cross clampand lung ventilation is resumed MNEMONIC CVP C- COLD , temp should be 36-37 degree celsius C-CONDUCTION, cardiac rate and rhythm , target rate 80-100 per minute, C-CO or contractility, estimated from TEE or PA catheter C-CELLS , hb conc shud be equal or more tha 7-8 gm% C-CALCIUM, Immediately available to treat hyperkalemia and hypocalcemia C-COAGULATION, after protamine admin. ACT is measured

36. V-VENTILATION of the lungs V- VISUALIZATION of the heart directly as well as through TEEto estimate global and regional contractlity V-VAPORIZER, reinstitution of low dose of volatile agent immediately after weaning. V-VOLUME EXPANDERS, after all products from pump has been exhausted and and if BT is not indicated , crystalloid/albumin/ hetastarch should be available to increase preload

37. P-PREDICTORS OF adverse cardiovascular outcome, P-PRESSURE,TO RECOGNIZE ANY DISCREPANCY IN CENTRAL AORTIC PRESSURE AND RADIAL ARTERY PRESSURE P-PRESORS, vasopressors and ionotropic agents must be easily available P-PACER an external pacer shold be readily available P-POTASSIUM, hypokalemia may contribute to dysrhytmiasand hyperkalemai may cause conduction abnormality P- PROTAMINEsugeon , anesthesiologist and perfusionist should decide when to administe rprotamine .

38. INTRAOP PROBLEMS 1. HYPOTENSION treated with volume loading Maintain adequate heart rate in sinus rhythm. increasing afterload to maintain systemic perfusion pressures. Inotrope therapy - dopamine, epinephrine, dobutamine infusion. Phenylephrine Inform surgeon - cotton packs can be placed under the heart and the epicardial stabilizers should be repositioned. resting the heart in the pericardial cavity. If there is no improvement, an intra aortic balloon pump support can be instituted.  DR GEETANJALI S VERMA

39. ARRYTHYMIAS Rule out causes: MI, electrolyte imbalance, hypothermia Use lidocaine (without preservative) infusion if patient has arrhythmia caused by myocardial ischaemia . Electrolyte imbalance - potassium chloride, magnesium sulfate , calcium, bicarbonate – as suggested by ABG Temperature correction DR GEETANJALI S VERMA

40. HEPARINIZATION Dose of heparin is 2mg.kg  -1  (200 units.kg  -1  ) intravenously. ACT performed 3 minutes after administration. The goal is to keep the ACT between 250 - 300 seconds. ACT repeated hourly and repeat bolus of 5000 units Heparin is essential if ACT <250 seconds. Heparin is reversed with protamine sulfate (1 mg/1mg of heparin. ) Acceptable ACT – upto 140 seconds after protamine administration. A high ACT will require additional protamine in a dose of 25 to 50 mg. DR GEETANJALI S VERMA

41. HYPOTHERMIA Warm blanket covers O T room temp The time taken for sterile preparation by painting and draping by sterile sheets should be kept to the minimum. Warm IV fluids Low fresh gas flows DR GEETANJALI S VERMA

42. MYOCARDIAL ISCHEMIA PREVENTION Maintaining systemic blood pressure (+/- 10%), keeping MAP of at least 70 mm Hg at all times Reduction in myocardial oxygen consumption by avoiding tachycardia using intra operative beta-blockers or calcium channel blockers. Ischaemia during distal anastomosis can be prevented by using intraluminal coronary shunts . DR GEETANJALI S VERMA

43. 6. Haemodynamic changes related to heart position Lifting and rotating the heart during OPCAB can alter the haemodynamics such as cardiac output, stroke work, left ventricular end diastolic pressure and right atrial pressure. During grafting of right coronary artery, bradycardia can occure due to reduction in blood supply to the sinus and AV nodes, so if required use atropine and atrial pacing During grafting of the right coronary artery and obtuse marginal branches " verticalization " of the heart is required, so posterior pericardial stitches and a gentle retracting socket will greatly facilitate haemodynamics Reduction in the dose of intravenous vasodilators can increase the haemodynamic changes. During such times it may be essential to reduce the dose of the vasodilator and add a vasoconstrictor. DR GEETANJALI S VERMA

44. POST OP MGMT MONITORING 5 lead ECG monitoring - for any fresh changes like ischaemia or myocardial infarction - treated with LMWH, anti platelet medications, insertion of an intra aortic balloon pump or revision of grafting. SpO2, ETCO2, IBP, Temp., ABG Always carry prefilled syringes of diluted 1:200,000 adrenaline , 1.2mg of atropine and 100mg of lidocaine (preservative free) to treat a crisis during the transfer phase. DR GEETANJALI S VERMA

45. POST OP PAIN MGMT Epidural analgesia: epidural fentanyl infusion with   Fentanyl 3000 mcg (60 ml), 0.5% bupivacaine 55ml and saline 155ml are added to make a final total volume 265 ml & start at a rate of 2ml.hour  -1 Intravenous opioids : Fentanyl 3000mcg and saline 215ml are added to make a final con­centration 11 mcg.ml  -1  of fentanyl . DR GEETANJALI S VERMA

46. ICU MGMT VENTILATION FiO2 of 0.8 Vt 6 -10 ml/kg  RR: 12- 15/min I:E ratio of 1:2 controlled mode of ventilation. ABG performed after thirty minutes.   FiO2 is reduced to 0.4  if oxygenation, carbon dioxide elimination and tissue perfusion maintained DR GEETANJALI S VERMA

47. Thirty minutes later, assessment of foll done: blood loss (not more than 10% of blood volume) fluid balance (not more than 10-15 ml.kg-  1  body weight) core temperature ( not less than 35 deg Celsius ), arrhythmias urine output (at least 1-2 ml.kg  -1  .hr  -1  ) If the residual neuro­muscular blockade is present then reversed by injecting a combination of neostigmine and glycopyrrolate . After confirming adequacy of reversal ventilatory mode is switched to the spontaneous modes of ventilation , such as pressure support, or continuous positive airway pressure. Thirty minutes after supported ventilation, ABG analysis is repeated and if the analysis shows satisfactory values of oxygenation, carbon dioxide elimination and metabolism, the patients are extubated . DR GEETANJALI S VERMA

48. FAST TRACK ANESTHESIA Defined as tracheal extubation within 8 hours after cardiac surgery, early mobilization of patient and early discharge from the hospital. Use of short acting opioid medications Long acting sedatives should be avoided Early extubation resulted in regaining the cough reflex and thus a lower incidence of atelectasis and pneumonia. Patients not suitable - bleeding, dysrryhtmias and haemodynamic instability DR GEETANJALI S VERMA

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