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SECTION 4 Pre-, intra-, and postoperative management ofthe coronary artery bypass graft patient158

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Risk stratiﬁcation and scoringsystems

Dening independent risk factors for major adverse cardiac and cerebrovascular events in the era of big datasets is statistically easy. New risk factors are frequently published which correlate with increased or decreased risk in cardiac surgery, and it seems that no patient characteristic is statistically neutral in this regard. Integrating this knowledge into accurate prognostic tools, which can be reliably used to inform decision- making and counsel patients, is more difcult. However, as comorbidity levels continue to increase, and patients demand accurate risk information as active decision- makers in their care, a reliable risk scoring system would be extremely useful.

e STS risk models are based on analysis of a national (United States) database that has been collecting data since 1989. Currently, more than 90% of cardiac centres in the United States submit their data, and 5.8million records have been accumulated. is enables prediction of a large number of outcomes including stroke, prolonged ventilation, deep sternal wound infection, renal failure, reoperation, length of stay, and mortality. e EuroSCORE was derived from 20,000 patients from 128 hospitals in eight European countries, and predicts 30- day mortality only. It was corrected with logistic analysis for high- risk patients in 2003, and updated in 2011 (EuroSCORE II).

e predictive value of both EuroSCORE II and STS scoring systems is roughly equivalent, and they have been cross- validated

Table18.3 Template fora preoperative enhanced recovery service

Morbidity Risk factors Investigations Threshold for

Stroke Age >65years

Delirium Age

Respiratory dysfunction

Renal impairment

Metabolic status

Frailty Age

Anaemia Hb <135 g/ L

Left main stem disease Peripheral vascular disease Transient ischaemic attack Cerebrovascular accident Diabetes Hypertension Carotid bruit

Cognitive impairment Depression Anaemia Atrial ﬁbrillation

Smoking Age

Age Diabetes Hypertension Poor left ventricular function Redo surgery

Diabetes Obesity

Multiple comorbidities Poor subjective performance status

Weight <77kg Female sex Age >65years Emergency surgery Creatinine >120 µmol/ L Redo surgery Multiple procedures

Carotid Doppler

None established

Pulmonary function tests

Baseline creatinine in all

HbA1c in all HbA1c >7% Refer to endocrinology for better

Frailty scoring in clinic: Grip strength Sit- to- stand time etc.

Calculate TRUST score (or similar)

intervention

Bilateral 70% stenosis in men (50% stenosis if symptomatic)

None established Rationalize medications

FEV1 <75% predicted

GFR <60 mL/ min Eliminate nephrotoxic drugs and

Variable Discuss long hospital stay with patient

>60% risk of red cell transfusion (local factors dependent)

Intervention Beneﬁt

Consider carotid endarterectomy, before or simultaneously to CABG

Consider dexmedetomidine infusion Consider cerebral oximetry Treat depression

Refer to respirology for potential

chronic obstructive pulmonary disease diagnosis, optimization of medical therapy

Refer to physiotherapy for inspiratory

muscle training

Discuss prolonged ICU/ hospital stay

with patient and caregivers.

interventions

If GFR <25 mL/ min, discuss long- term

renal replacement therapy

glucose control

Refer to dietician for nutrition and

weight- loss advice

and caregivers

Discuss reduced independence with

patient and caregivers Warn discharge coordinator Warn social services, physical/

occupational therapy department Prehabilitation

Refer for course of erythropoietin/ intravenous iron at least 4 weeks before surgery

Reduction in stroke rate

Reduction in postoperative cognitive impairment

Reduction in pneumonia Reduction in sternal wound infection

Reduction in acute kidney injury

Reduction in deep sternal

wound infection

Reduction in acute

kidney injury

Reduction in postoperative

atrial ﬁbrillation

Avoidance of delayed

discharge

Avoidance of hospital

readmission

Reduction in red cell transfusion and associated complications

FEV1, forced expiratory volume in 1 second; Hb, haemoglobin.

18 Preoperative assessment in coronary bypasssurgery 159

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against other large national databases. However, the statistic that matters to patients is their potential individual mortality, which is locally determined at institutional or possibly individual surgeon level. e United Kingdom has a system for mandatory risk and outcome reporting with publication of individual surgeon survival rates, compared to the national average. However, when all surgeons are within a 99.8% condence interval of the predicted mortality rates, the utility of this measure in decision- making is not clear.

Enhanced recovery programmes forcardiacsurgery

Fast- track recovery from cardiac surgery is well established and includes a philosophy of withholding sedation in ICU, aiming for extubation within 2 hours of the completion of surgery, rapid removal of chest drains, and transfer to the ward within 24 hours. Enhanced recovery from cardiac surgery includes minimizing barriers to restoration of diet and mobility, and minimizing the duration of harmful interventions such as positive pressure ventilation, vasoactive drug infusions, and invasive monitoring.

e enhanced recovery philosophy borrows heavily from the work begun 20 years ago by Kehlet in reducing physiological stressors in colorectal and cardiac surgery. e process includes minimization of fasting periods and uid restriction with carbohydrate drinks, pre- emptive multimodal, systemic, non- opioid analgesia in the preoperative waiting area, regular postoperative antiemetics, rapid discontinuation of opioid infusions, and mobilization out of bed by the rst morning postoperatively.

e key to the eective introduction of such a programme is patient preparation: changing expectations for recovery including pain control, participation in physiotherapy, lifestyle change (e.g. smoking cessation), and active mobilization.

Conclusion

e preoperative assessment of the patient for CABG surgery has the potential to overwhelm care providers with the knowledge of hundreds of interdependent risk factors, and conicting evidence as to ecacy of interventions. However, as the scrutiny increases on healthcare providers to demonstrate that they are providing the safest possible care, and the ‘aggregation of marginal gains’ available, the preassessment clinic is an ideal place to set patients up for success before they even arrive at the hospital on the day of surgery.

A schema for the operation of such a clinic is presented in Table 18.3.

REFERENCES

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2. Schwann TA, Habib RH, Wallace A, Shahian DM, O’Brien S, Jacobs JP, etal. Operative outcomes of multiple- arterial versus single- arterial coronary bypass graing. Ann orac Surg. 2018;105(4):1109– 19.

3. Hillis DL, Smith PK, Anderson JL, Bittl JA, Bridges CR, Byrne JG, etal. ACCF/ AHA guideline for coronary artery bypass gra surgery:a report of the American College of Cardiology Foundation/ American Heart Association Task Force on Practice Guidelines. Circulation. 2011;124(23):e652– 735.

4. Neumann FJ, Sousa- Uva M, Ahlsson A, Alfonso F, Banning AP, Benedetto U, etal. 2018 ESC/ EACTS Guidelines on myocardial revascularization. Eur Heart J. 2019;40(2):87– 165.

5. Newman MF, Kirchner JL, Phillips- Bute B, Gaver V, Grocott H, Jones RH, etal. Longitudinal assessment of neurocognitive function aer coronary artery bypass surgery. N Engl J Med. 2001;344(6):395– 402.

6. Murkin JM, Newman SP, Stump DA, Blumenthal JA. Statement of consensus on assessment of neurobehavioral outcomes aer cardiac surgery. Ann orac Surg. 1995;59(5):1289– 95.

7. Witlox J, Eurelings LS, de Jonghe JF, Kalisvaart KJ, Eikelenboom P, van Gool WA. Delirium in elderly patients and the risk of postdischarge mortality, institutionalization, and dementia:a meta- analysis. J Am Med Assoc. 2010;304(4):443– 51.

8. Djaiani G, Silverton N, Fedorko L, Carroll J, Styra R, Rao V, etal. Dexmedetomidine versus propofol sedation reduces delirium aer cardiac surgery:a randomized controlled trial. Anesthesiology. 2016;124(2):362– 8.

9. Hudetz JA, Patterson KM, Iqbal Z, Gandhi SD, Byrne AJ, Hudetz AG, etal. Ketamine attenuates delirium aer cardiac surgery with cardiopulmonary bypass. J Cardiothorac Vasc Anesth. 2009;23(5):651– 7.

10. Avidan MS, Maybrier HR, Abdallah AB, Jacobsohn E, Vlisides PE, Pryor KO, etal. Intraoperative ketamine for prevention of postoperative delirium or pain aer major surgery in older adults:an international, multicentre, double- blind, randomised clinical trial. Lancet. 2017;390(10091):267– 75.

11. Ng KT, Shubash CJ, Chong JS. e eect of dexmedetomidine on delirium and agitation in patients in intensive care:systematic review and meta- analysis with sequential trial analysis. Anaesthesia. 2019;74(3):380– 92.

12. Peng K, Ji FH, Liu HY, Zhang J, Chen QC, Jiang YH. Eects of perioperative dexmedetomidine on postoperative mortality and morbidity:a systematic review and meta- analysis. Clin er. 2019;41(1):138– 54.

13. Wu M, Liang Y, Dai Z, Wang S. Perioperative dexmedetomidine reduces delirium aer cardiac surgery:a meta- analysis of randomized controlled trials. J Clin Anesth. 2018;50:33– 42.

14. Siddiqi N, Harrison JK, Clegg A, Teale EA, Young J, Taylor J, etal. Interventions for preventing delirium in hospitalised non- ICU patients. Cochrane Database Syst Rev. 2016;3:CD005563.

15. Pilarczyk K, Marggraf G, Dudasova M, Demircioglu E, Scheer V, Jakob H, etal. Tracheostomy aer cardiac surgery with median sternotomy and risk of deep sternal wound infections:is it a matter of timing? J Cardiothorac Vasc Anesth. 2015;29(6):1573– 81.

16. Bernardi MH, Schmidlin D, Schiferer A, Ristl R, Neugebauer T, Hiesmayr M, etal. Impact of preoperative serum creatinine on short- and long- term mortality aer cardiac surgery:a cohort study. Br J Anaesth. 2015;114(1):53– 62.

17. Cho JS, Shim JK, Soh S, Kim MK, Kwak YL. Perioperative dexmedetomidine reduces the incidence and severity of acute kidney injury following valvular heart surgery. Kidney Int. 2016;89(3):693– 700.

18. Tran DTT, Tu JV, Dupuis JY, Bader Eddeen A, Sun LY. Association of frailty and long- term survival in patients undergoing coronary artery bypass graing. J Am Heart Assoc. 2018;7(15):e009882.

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19. Hung M, Ortmann E, Besser M, Martin- Cabrera P, Richards T, Ghosh M, etal. A prospective observational cohort study to identify the causes of anaemia and association with outcome in cardiac surgical patients. Heart. 2015;101(2):107– 12.

20. Alghamdi AA, Davis A, Brister S, Corey P, Logan A. Development and validation of Transfusion Risk Understanding Scoring Tool (TRUST) to stratify cardiac surgery patients according to their blood transfusion needs. Transfusion. 2006;46(7):1120– 9.

21. Kehlet H. Multimodal approach to control postoperative pathophysiology and rehabilitation. Br J Anaesth. 1997;78(5): 606– 17.

22. Cheng DCH, Karski J, Peniston C, Asokumar B, Raveendran G, Carroll J, etal. Morbidity outcome in early versus conventional tracheal extubation aer coronary artery bypass graing:a prospective randomized controlled trial. J orac Cardiovasc Surg. 1996;112(3):755– 64.

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Anaesthetic management of on- and oﬀ- pump coronary artery bypassgraing

Elvera L. Baron, Menachem M. Weiner, and David L. Reich

Introduction

While the overall number of patients presenting for coronary artery bypass gra (CABG) surgery has declined over the past 20years, primarily due to the growth of percutaneous coronary interventions, the complexity of the patients presenting for CABG as well as the procedures themselves has increased. Patients who are not eligible for percutaneous interventions typically have an increased risk of perioperative morbidity and mortality and depend more than ever on optimal anaesthetic management. Anaesthesiologists are involved in all aspects of perioperative management for these patients presenting for CABG surgery, including pharmacological risk reduction and intraoperative anaesthetic management. While cardiopulmonary bypass (CPB) remains a critical part of many CABG surgeries, many are performed without CPB. Specic considerations need to be taken into account prior to institution of CPB and subsequent successful weaning. O- pump CABG (OPCAB) has a number of unique anaesthetic management considerations as well. Perioperative and especially intraoperative transoesophageal echocardiography (TOE) is oen utilized for surgical guidance, assessment of cardiac function, and evaluation of any iatrogenic complications. is chapter reviews monitoring modalities for CABG surgery, induction and maintenance of general anaesthesia, important considerations involved in initiation and weaning from CPB, as well as implications of quality metrics for CABG surgery.

Monitoring

It is recommended that standard American Society of Anesthesiologists monitors including pulse oximeter, non- invasive blood pressure, and a ve- lead electrocardiogram be placed upon arrival to the operating room prior to administration of any medications for any patient presenting for CABG surgery. It is well established that 90%

of cardiac ischaemic episodes can be detected by monitoring leads V5 and II, while rhythm assessment is best assessed using lead II.

In most cases, a combination of both patient and surgical factors require placement of an arterial line prior to induction of anaesthesia. is allows for careful titration of anaesthetic induction and vasoactive medications. Prior to placement, it is prudent to discuss the site of placement to facilitate surgical needs:whether radial gra(s) is (are) planned, whether two arterial lines may be required, and whether central or peripheral arterial cannulation for CPB is planned. Most commonly, the radial artery is cannulated; however, at some centres bilateral arterial cannulation is used, or a more central artery such as the brachial, axillary, or femoral artery is chosen to ensure accurate pressure reading aer CPB, when peripheral vasoconstriction may make a radial arterial line temporarily unreliable.

Central venous cannulation, performed under ultrasound guidance, is performed routinely for CABG surgery and is used for both central venous pressure measurements and for central delivery of vasoactive medications. In patients with pulmonary hypertension or those with severely reduced le ventricular (LV) function (LV ejection fraction <30%), pulmonary artery catheter (PAC) placement may be indicated. Although PAC use has not been shown to improve mortality outcomes, trends in the generated physiological parameters may help guide medical treatment both intraoperatively and postoperatively in the intensive care unit. Most recently, several reports suggested lack of eectiveness of PAC use in cardiac surgery, with some even reporting increased mortality and higher risk of severe end- organ complications. Additionally, cost– benet analysis studies demonstrate increased costs associated with use of PACs without any clear benet.

TOE is recommended by the American Society of Anesthesiologists and the Society of Cardiovascular Anesthesiologists practice guidelines for CABG surgery, and is routinely used for both on- pump and o- pump CABG surgery. Real- time assessment of cardiac function pre- , intra- , and postoperatively has the potential to aect surgical

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decisions. TOE can provide specic details on regional wall motion abnormalities, any associated valvular lesions, burden of aortic atherosclerotic disease, detection of patent foramen ovale, and other congenital anomalies. Intraoperatively, TOE can also be used to help determine the optimal site of aortic cannulation, site of aortic cross- clamping, and the ability to provide retrograde cardioplegia

dysfunction. More recently, remote ischaemic preconditioning was preliminarily shown to prevent deterioration of short- term postoperative cognitive function aer cardiac surgery CPB. ere is, however, no denitive set of techniques or drugs that are known to prevent transient or permanent neurocognitive dysfunction aer

coronary surgery. safely and eectively. Following release of the aortic cross- clamp, TOE assists with de- airing of the heart, assesses volume status, ventricular function, including monitoring for any changes in regional wall motion, and can demonstrate the eects of inotropic support

Induction and maintenance ofgeneral anaesthesia

on cardiac function. Furthermore, TOE contributes to the safety prole of CABG surgery, as detection of associated iatrogenic complications, such as aortic dissection and malpositioned cannulae, are quickly recognized and addressed. ough TOE placement is not without risk (such as oesophageal perforation or bleeding), the American Society of Echocardiography also recommends a comprehensive TOE examination pre and post CPB or pre and post revascularization in patients undergoing CABG.

Neurophysiological monitoring during CABG with non- invasive monitors, such as cerebral oximetry and bispectral index (BIS) analysis, is oen used during CABG. Cerebral oximetry, a continuous monitoring device (which works during non- pulsatile ow states), is based on the principle of transcranial transmission of near- infrared light to estimate regional tissue oxygenation and may help identify and correct regional cerebral ischaemia. BIS monitoring is based on fast Fourier transformation and bispectral analysis of one- channel electroencephalographic data obtained from electrodes on the patient’s forehead, represents global cerebral electroencephalographic activity, and may provide benet in decreasing intraoperative awareness or recall.–  Additionally, BIS could be useful in achieving burst suppression or isoelectric states during cooling in situations where hypothermic circulatory arrest is required.

Postoperative cognitive dysfunction is a recognized complication aer cardiac surgery. Intraoperative cerebral microembolism and hypoperfusion have been proposed to be the major mechanisms of cognitive dysfunction. Neuroprotective strategies include reduction of plaque disruption and macroemboli via careful and appropriate aortic cannula placement, judicious temperature regulation for cooling and rewarming, with special attention to avoid hyperthermic perfusion. While large database studies have reported reduced perioperative stroke with OPCAB versus CABG on CPB, these results have not been replicated in randomized controlled trials with smaller sample size enrolling lower- risk patients. Arecent meta- analysis of more than 37,000 patients found that avoidance of aortic manipulation altogether, by use of a no- aortic- touch OPCAB technique, was associated with dramatic reduction in stroke risk; however, this technique is technically challenging and has not been widely adopted.

Glucose control is also considered a best practice for neuroprotection, but likely within ranges specied in the NICE SUGAR trial. Several studies examined intraoperative administration of magnesium or lidocaine on neurocognitive function aer cardiac surgery., Administration of intraoperative magnesium was not shown to confer protection against postoperative cognitive decline, while preliminary data suggest that lidocaine administration decreased the occurrence of early postoperative cognitive

Induction and maintenance of general anaesthesia for CABG surgery can be safely achieved in several ways, as long as haemodynamic goals are met. Most standard induction agents, including hypnotics, opioids, muscle relaxants, and volatile anaesthetics, have been safely used for CABG surgery. e specic anaesthetic agent choices are determined by LV function and coronary pathology, with a focus on primary haemodynamic goals: maintaining adequate coronary perfusion pressure without increasing myocardial oxygen demand. Avoidance of tachycardia and hypotension are particularly important to ensure adequate lling time and to decrease the risk of intraoperative ischaemia. is is achieved by titration of drugs, such as phenylephrine and/ or nitroglycerine, and avoidance of excessive myocardial depression, especially in patients with severe ow- dependent coronary stenosis.

It is also prudent to anticipate and plan for fast- tracking and early tracheal extubation in appropriately selected patients. is includes use of shorter- acting medications during induction and maintenance, limited administration of muscle relaxants and opioids, as well as adequate rewarming and postoperative analgesia. Although many neuromuscular agents can be used for induction and maintenance, agents must be administered such that uncomplicated CABG patients may be extubated within 6 hours aer arrival in the intensive care unit.

Induction agents, such as etomidate, propofol, and ketamine, are all acceptable. For patients with severe LV dysfunction, etomidate or ketamine are preferred, although the catecholamine depletion in severe congestive heart failure may predispose towards more hypotension with ketamine, since the catecholamine- releasing effect of ketamine is diminished. Maintenance of anaesthesia with volatile anaesthetics, total intravenous techniques, and balanced techniques should all be managed to optimize haemodynamics so as to avoid intraoperative myocardial ischaemia. Additionally, midazolam is used extensively. As noted previously, the choice and dosing of neuromuscular blocking agents is targeted to facilitate early extubation, such that intermediate- acting agents, such as rocuronium, vecuronium, and cisatracurium, are preferred.

Inhalational anaesthetics are also thought to protect the myocardium against ischaemia by their ability to elicit protective cellular responses similar to what is seen with ischaemic preconditioning. Successful preconditioning has been shown to reduce myocardial infarction size aer periods of ischaemia, reduce post- ischaemic LV dysfunction, and reduce the incidence of arrhythmias. Additionally, opioids have also been shown to trigger benecial eects of preconditioning. e literature on rates of mortality and myocardial infarction in those patients who received preconditioning has shown mixed results.

19 Anaesthetic management of on- and off-pump coronary artery bypassgrafting 163

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Since both myocardial ischaemia time and reperfusion are known to contribute to myocardial damage, the role of postconditioning is now becoming an area of investigation. ere is preliminary evidence that postconditioning improves contractile function and decreases the incidence of post- ischaemic arrhythmias., e choice of anaesthetics may have an impact on postconditioning. For example, volatile agents are thought to have a blunting eect on the harmful eects of post- ischaemic reperfusion injury aer CABG, supporting their use in these surgeries.

Intraoperative detection and treatment

Box 19.1 Checklist forinitiation ofCPB

• Adequate anticoagulation

• Properly positioned vascular cannulae:arterial and venous

• Quick survey of major organ function (cerebral, pulmonary, renal)

• Functional vascular access and monitors

• No evidence of iatrogenic injuries to the aorta, coronary sinus, superior

vena cava, or inferior vena cava

• Inspection of head and neck

• Adequate anaesthetic depth and muscle relaxation

• Vaporizer available for the CPB circuit

• Discontinue ventilation once CPB initiated.

ofmyocardialischaemia

be routinely utilized to identify portions of the ascending aorta that Although the incidence of perioperative myocardial ischaemia for patients undergoing CABG has been reported to be 10– 50%, no dierence in the relative risk of postoperative myocardial ischaemia has been attributed to choice of anaesthetic medications. Anaesthesiologists must, however, be able to promptly recognize and treat intraoperative myocardial ischaemia. In addition to electrocardiogram changes, tachycardia with hypotension, increased LV lling pressures, or development of new regional wall motion abnormalities point to early signs of ischaemia. TOE is the most sensitive method of detecting myocardial ischaemia in patients undergoing CABG. Furthermore, new onset of mitral regurgitation or worsening of pre- existing mitral regurgitation, either of which can occur in association with developing myocardial ischaemia or surgical manipulation of the heart, is easily detected and characterized by TOE monitoring. Early detection and mitigation of worsening or new- onset ischaemic mitral regurgitation may be especially important during OPCAB; in this setting, TOE is especially valuable.

Intraoperative management of a patient with coronary artery disease relies on tight haemodynamic control and prompt correction of any haemodynamic abnormalities. e main goal is to maintain coronary perfusion pressure— both by maintaining adequate diastolic pressure and normalized heart rate. Useful agents for treatment of acute perioperative or intraoperative myocardial ischaemia include intravenous beta blockers (e.g. esmolol, metoprolol), nitrates (e.g. nitroglycerine), calcium channel blockers (e.g. nicardipine, nifedipine, clevidipine), or increased delivery of volatile anaesthetics for those patients presenting with hypertension and/ or increased heart rate. For those patients presenting with hypotension with or without heart rate changes, useful agents may include intravenous phenylephrine, norepinephrine, ephedrine, atropine, or lightened inhalational anaesthesia. e overall goal is to optimize myocardial oxygen supply and demand by decreasing determinants of myocardial oxygen consumption and maintaining coronary perfusion pressure.

Speciﬁc anaesthetic considerations togo oncardiopulmonarybypass

Prior to initiation of CPB, adequate preparation is essential. Anticoagulation is normally achieved using heparin, with measurement of in vitro heparin level and activated coagulation time prior to cannulation. Also, prior to cannulation, epiaortic scanning should

would be appropriate and safe for arterial cannulation and aortic cross- clamping. ese locations are ideally distant from signicant atherosclerotic plaques to decrease the incidence of thromboembolic events. Depending upon the specic surgical approach, either one ‘two- stage’ cannula is inserted through the right atrium extending into the inferior vena cava, or two separate venous cannulae are placed in the superior and inferior vena cavae. TOE guidance is utilized in ensuring proper positioning of the inferior vena cava cannula, so as to avoid malposition of the cannula tip in the hepatic venous circulation. e proper placement of these cannulae ensures adequate drainage of the venous blood into the CPB circuit once CPB is instituted. Additionally, internal jugular venous pressure and the patient’s head and neck are checked for any evidence of obstruction to superior vena cava drainage. TOE is also used to survey for any evidence of iatrogenic injuries to the great vessels, such as aortic dissection. It is also recommended that the anaesthesiologist reassess the patient’s anaesthetic depth, administering opioids, muscle relaxants, or benzodiazepines, as necessary.

Once CPB is instituted, delivery of volatile anaesthetic agents can continue through a vaporizer attached to the CPB circuit. e anaesthesiologist also plays a role in myocardial protection during CPB, ensuring that there is electrical silence on the electrocardiogram, assuring that LV distension does not occur during antegrade cardioplegia, and monitoring myocardial temperature if a probe is placed by the surgeons. Additionally, the TOE can ensure that retrograde cardioplegia cannulae, if present, are placed correctly. Achecklist for safe initiation of CPB is shown in Box 19.1.

Speciﬁc anaesthetic considerations for separation fromcardiopulmonarybypass

Planning for separation from CPB begins as early as preoperative assessment and anaesthetic induction. During CPB, specic preparations are made for successful weaning. Weaning from CPB is generally considered only aer the patient’s core temperature is rewarmed to at least 35°C, electrolyte abnormalities are corrected, a stable cardiac rhythm is present (with or without assistance of a pacemaker), and ventilation is reinstituted. Furthermore, cardiac function is generally assessed by TOE while still on CPB aer the coronary anastomoses have been completed. Specically, ventricular function and, in cases of concomitant valve surgery, the integrity of the surgical repair or replacement are assessed. Inotropic, vasopressor,

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Box 19.2 Checklist forweaning fromCPB

• Reinstitute ventilation and delivery of inhalational agent

• Monitoring alarms turned on, monitoring devices properly functioning

• Presence of cardiac rhythm, intrinsic or paced (deﬁbrillate as needed)

• Pacing wires and generator readily available

• Optimize metabolic parameters, including correcting pH and electro-

lyte abnormalities

• Complete rewarming, such that the patient’s core temperature is at

least 35°C

• Haemostasis in the surgical ﬁeld

• Assessment of ventricular function by TOE

• Perform manoeuvres to eliminate intracardiac air

• Inotropic and vasopressor medications readily available to optimize

rate, rhythm, contractility, preload, and afterload

• Ensure adequate anaesthetic depth

• Consider need for intra- aortic balloon pump for patients with poor

LV function and/ or severe myocardial ischaemia to aid in weaning from CPB

• Gradual weaning from CPB

• Once venous cannula is removed, transfuse blood remaining in CPB

reservoir via arterial cannula into the patient; remainder of pump circuit blood may be haemoconcentrated or processed by a cell salvaging device.

More specically, cardiovascular eects could be due to distortion of cardiac chambers by the surgical equipment or ischaemia induced by vessel occlusion during the anastomoses. Signicant reductions in most haemodynamic parameters (cardiac output, stroke volume, mean arterial pressures, heart rate, and coronary ow) may be seen during surgical manipulation. Additionally, altered right ventricular and LV geometry and chamber sizes that are seen on TOE during vertical retraction of the heart will aect haemodynamic stability.

Anaesthetic techniques for OPCAB are similar to those used in on- pump procedures, including extensive monitoring and use of intraoperative TOE and warming devices. Although interest has steadily risen in thoracic epidural anaesthesia and analgesia for cardiac surgery, this practice is limited (especially in the United States) due to safety concerns related to neuraxial access in anticoagulated patients, many of whom also receive antiplatelet agents. Some OPCAB patients are eligible for fast- tracking and early extubation, again requiring advanced planning with limited intraoperative use of opioids and muscle relaxants. Haemodynamic uctuations due to heart positioning are managed with uids, positional changes, and vasopressor medications, as needed. CPB is always readily available for emergencies related to haemodynamic decompensation. Instability due to new or ongoing myocardial ischaemia can also be managed with judicious use of vasodilators and inotropes.

and/ or vasodilator medications are used to optimize preload, contractility, and aerload. As a general rule, patients with worse myocardial function preoperatively will require more gradual weaning from CPB so as to avoid major haemodynamic instability and to allow careful titration of medications and/ or surgical intervention. Myocardial stunning, which is common immediately following

Haemodynamic goals are dierent at dierent points in the surgical intervention: lower mean arterial pressures (approximately 60 mmHg) are preferred during proximal (aortic) anastomoses, while higher mean arterial pressures (approximately 80mmHg) are preferred during distal ones. erefore, eective ongoing communication between anaesthesiologists and surgeons is crucial.

CPB, is responsive to positive inotropic support with low- dose positive inotropic agents. Additionally, as right ventricular dysfunction contributes to perioperative morbidity and mortality, optimization of right ventricular function is critical. Careful titration of vasodilators, such as nitroglycerine, may be needed in patients with elevated

Implications ofquality metrics and adverse outcomes aftercoronary artery bypassgrafting

preload. Finally, in some patients, use of an intra- aortic balloon pump, which increases coronary blood ow during diastole and unloads the le ventricle during systole, may be needed to aid in successful weaning from CPB. Achecklist for safe weaning from CPB is shown in Box 19.2.

As discussed in Chapter15, cardiac surgical programmes are assessed in several ways by external groups. State- mandated reporting of complications and mortality, with or without risk adjustment, is perhaps the most common means by which United States programmes are assessed by individual departments of health. Typically,

Anaesthetic considerations foroff- pump coronary artery bypassgrafting

individual states will publish the raw and risk- adjusted results for mortality for cardiac surgical programmes in their jurisdiction. e Society of oracic Surgeons National Database was established in 1989 as an initiative for quality improvement and patient safety

e o- pump approach to CABG (OPCAB) is preferred by some surgeons. Recent meta- analysis of clinical outcomes, comparing conventional on- pump versus o- pump approaches, demonstrated that both are safe and comparable in terms of early mortality and late survival. OPCAB surgery is thought to confer an advantage over the conventional approach in preventing perioperative myocardial infarction and reducing overall blood loss. Unique anaesthetic considerations are present for OPCAB due to frequent potential for haemodynamic lability. ese haemodynamic changes may be induced not only due to patient factors, such as the severity of coronary artery disease and its eect on the myocardium, but also due to surgical factors, particularly during positioning, mobilization, and retraction of the heart to aid in adequate surgical exposure.

among cardiothoracic surgeons. e large size, and robust statistical modelling, is helpful to CABG programmes in assessing their performance against national benchmarks, which may help to put other results into perspective.

Among the most robust set of standards has been established by the National Quality Forum. Ameasure that anaesthesiologists are particularly able to inuence by anaesthetic techniques is prolonged postoperative intubation. Prolonged intubation is dened as the percentage of patients aged 18years and older undergoing isolated CABG who require intubation for more than 24 hours. e full set of voluntary consensus metrics is presented in Box 19.3.

Value- based purchasing is a programme initially started by the United States Centers for Medicare and Medicaid Services to reward

19 Anaesthetic management of on- and off-pump coronary artery bypassgrafting 165

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Box 19.3 National voluntary consensus standards forcardiacsurgery

1. Participation in a systematic database for cardiac surgery

2. Surgical volume for isolated CABG surgery, valve surgery, and CABG plus valve surgery

3. Timing of antibiotic administration for cardiac surgery patients

4. Selection of antibiotic administration for cardiac surgery patients

5. Preoperative beta blockade

6. Use of internal thoracic artery

7. Duration of prophylaxis for cardiac surgery patients

8. Prolonged intubation

9. Deep sternal wound infection rate

10. Stroke/ cerebrovascular accident

11. Postoperative renal insufﬁciency

12. Surgical re- exploration

13. Antiplatelet medications at discharge

14. Beta blockade at discharge

15. Anti- hyperlipidaemia treatment at discharge

16. Risk- adjusted inpatient operative mortality for CABG

17. Risk- adjusted operative mortality for CABG

18. Risk- adjusted operative mortality for aortic valve replacement

19. Risk- adjusted operative mortality for mitral valve replacement/ repair

20. Risk- adjusted operative mortality for mitral valve replacement/ repair plus CABG

21. Risk- adjusted operative mortality for aortic valve replacement plus CABG.

or punish hospital- based programmes for quality metrics. In the United States, commercial insurance payers also mirror portions of the Centers for Medicare and Medicaid Services programme. Currently, value- based purchasing includes hospital- acquired infections, specically supercial and deep sternal wound infections, catheter- associated urinary tract infections, central line- associated bloodstream infections, and patient satisfaction metrics. As of 2017, failure to achieve these quality metrics could result in a penalty as high as 2% of total Medicare payments to a hospital. Again, anaesthesiologists have signicant potential to inuence these results based upon care provided intraoperatively and in the intensive care unit.

Conclusion

Anaesthesia for CABG has evolved over the decades along with the increased role of the anaesthesiologist in perioperative care. e current trends towards transparency in reporting outcomes and in valuebased purchasing nancial incentives are changing the landscape of cardiac surgical programmes. Cardiac anaesthesiologists have a key role to play in developing protocols and quality programmes to assure the success of their institutional CABG programmes.

REFERENCES

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Arnett DK, Blaha MJ, etal. Heart disease and stroke statistics— 2016 update:a report from the American Heart Association. Circulation. 2016;133(4):e38– 360.

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5. Shanewise JS, Cheung AT, Aronson S, Stewart WJ, Weiss RL, Mark JB, etal. ASE/ SCA guidelines for performing a comprehensive intraoperative multiplane transesophageal echocardiography examination:recommendations of the American Society of Echocardiography Council for Intraoperative Echocardiography and the Society of Cardiovascular Anesthesiologists Task Force for Certication in Perioperative Transesophageal Echocardiography. Anesth Analg. 1999;89(4):870– 84.

6. Barr G, Anderson RE, Samuelsson S, Owall A, Jakobsson JG. Fentanyl and midazolam anaesthesia for coronary bypass surgery:a clinical study of bispectral electroencephalogram analysis, drug concentrations and recall. Br J Anaesth. 2000;84(6):749– 52.

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8. Myles PS, Leslie K, McNeil J, Forbes A, Chan MT. Bispectral index monitoring to prevent awareness during anaesthesia:the B- Aware randomised controlled trial. Lancet. 2004;363(9423):1757– 63.

9. Meybohm P, Gruenewald M, Höcker J, Renner J, Graesner JT, Ilies C, etal. Correlation and agreement between the bispectral index vs. state entropy during hypothermic cardio- pulmonary bypass. Acta Anaesthesiol Scand. 2010;54(2):169– 75.

10. Puskas JD, ourani VH, Kilgo P, Cooper W, Vassiliades T, Vega JD, etal. O- pump coronary artery bypass disproportionately benets high- risk patients. Ann orac Surg. 2009;88(4):1142– 7.

11. Lamy A, Devereaux PJ, Prabhakaran D, Taggart DP, Shengshou H, Paolasso E, etal. O pump or on pump coronary artery bypass graing at 30days. N Engl J Med. 2012;366(16):1489– 97.

12. Zhao DF, Edelman JJ, Seco M, Bannon PG, Wilson MK, Byrom MJ, etal. Coronary artery bypass graing with and without manipulation of the ascending aorta:a network meta- analysis. J Am Coll Cardiol. 2017;69(8):924– 36.

13. NICE- SUGAR Study Investigators, Finfer S, Chittock DR, Su SY, Blair D, Foster D, etal. Intensive versus conventional glucose control in critically ill patients. N Engl J Med. 2009;360(13):1283– 97.

14. Klinger RY, unberg CA, White WD, Fontes M, Waldron NH, Piccini JP, etal. Intraoperative magnesium administration does not reduce postoperative atrial brillation aer cardiac surgery. Anesth Analg. 2015;121(4):861– 7.

15. Wang D, Wu X, Li J, Xiao F, Liu X, Meng M. e eect of lidocaine on early postoperative cognitive dysfunction aer coronary artery bypass surgery. Anesth Analg. 2002;95(5):1134– 41.

16. Hudetz JA, Patterson KM, Iqbal Z, Gandhi SD, Pagel PS. Remote ischemic preconditioning prevents deterioration of short- term

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postoperative cognitive function aer cardiac surgery using cardiopulmonary bypass:results of a pilot investigation. J Cardiothorac Vasc Anesth. 2015(2);29:382– 8.

17. Kloner RA, Jennings RB. Consequences of brief ischemia:stunning, preconditioning, and their clinical implications:part2. Circulation. 2001;104(25):3158– 67.

18. Ishii H. Cardioprotection with opioids— trusted old friends– clinical science. Curr Pharm Des. 2014;20(36):5794– 8.

19. Sardar P, Chatterjee S, Kundu A, Samady H, Owan T, Giri J, etal. Remote ischemic preconditioning in patients undergoing cardiovascular surgery:Evidence from a meta- analysis of randomized controlled trials. Int J Cardiol. 2016;221:34– 41.

20. Vinten- Johansen J, Zhao ZQ, Corvera JS, Morris CD, Budde JM, ourani VH, etal. Adenosine in myocardial protection in on- pump and o- pump cardiac surgery. Ann orac Surg. 2003;75(2):S691– 9.

21. Zhao ZQ, Corvera JS, Halkos ME, Kerendi F, Wang NP, Guyton RA, etal. Inhibition of myocardial injury by ischemic postconditioning during reperfusion:comparison with ischemic preconditioning. Am J Physiol Heart Circ Physiol. 2003;285(2):H579– 88.

22. Smith JS, Cahalan MK, Beneel DJ, Byrd BF, Lurz FW, Shapiro WA, etal. Intraoperative detection of myocardial ischemia

in high- risk patients:electrocardiography versus twodimensional transesophageal echocardiography. Circulation 1985;72(5):1015– 21.

23. Chaudhry UA, Harling L, Sepehripour AH, Stavridis G, Kokotsakis J, Ashraan H, etal. Beating- heart versus conventional on- pump coronary artery bypass graing:a meta- analysis of clinical outcomes. Ann orac Surg. 2015;100(6):2251– 60.

24. e Society of oracic Surgeons. STS Adult Cardiac Surgery Database [Internet]. Available from:http:// www.sts.org/ sts- national- database/ database- managers/ adult- cardiac- surgery- database

25. National Quality Forum. National Voluntary Consensus Standards for Cardiac Surgery [Internet]. National Quality Forum; 2005. Available from:https:// www.qualityforum. org/ Publications/ 2005/ 01/ National_ Voluntary_ Consensus_ Standards_ for_ Cardiac_ Surgery.aspx

26. Centers for Medicare and Medicaid Services. Value based programs [Internet]. Available from:Centers for Medicare and Medicaid Services; 2020. https:// www.cms.gov/ Medicare/ Quality- Initiatives- Patient- Assessment- Instruments/ ValueBased- Programs/ Value- Based- Programs.html

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Postoperative management aer coronary artery bypass grasurgery

Jason Chui and John M. Murkin

Introduction

Patients presenting for coronary artery bypass gra (CABG) surgery are increasingly older and sicker, while the usage of newer surgical techniques (o- pump CABG, minimally invasive CABG, and robotic- assisted CABG), coupled with alterations in anaesthetic approach (fast- track recovery), have added to the complexity and variability in the postoperative management of CABG patients.

Fast- track cardiacsurgery

Most cardiac surgical centres have adopted a fast- track recovery protocol aimed at minimizing length of stay and resource utilization. Incorporation of a standardized handover procedure in the cardiac recovery unit minimizes miscommunication and enhances patient safety by providing a continuum of anaesthetic and surgical care.

Fast- track recovery for cardiac surgery was rst introduced in mid- 1990, and has been widely implemented in most cardiac surgical centres, mainly driven by strong economic incentives for shortening mechanical ventilation times, lengths of stay in the intensive care unit (ICU), and resource utilization. A2016 Cochrane review involving 4438 patients in 28 trials concluded fast- track could signicantly reduce extubation times and ICU stay without increasing mortality and major perioperative complications in low- and moderate- risk cardiac surgical patients. e targets of fast track are extubation within 3– 6 hours and discharge from the ICU within 18– 24 hours.

e key components of fast track include use of low- dose, shortacting, opioid- based anaesthesia and sedatives perioperatively, and a time- directed protocol for early extubation and discharge from the ICU. Initially, high- dose opioid- based anaesthesia (e.g. morphine) was used for cardiac surgery because of its minimal myocardial depressive eect, but at the expense of prolonged mechanical ventilation. e introduction of newer opioids such as remifentanil and sufentanil, having much shorter elimination half- lives, reduces the risks of over- narcotization but may require supplementary analgesia postoperatively. e substitution of a short- acting propofol infusion, in lieu of longer- acting benzodiazepines in the

rst few postoperative hours, is a further key component. Usage of dexmedetomidine- based sedation has now been reported to further shorten extubation time yet with higher patient satisfaction compared with propofol in postcardiac surgical patients.

Adherence to a time- based extubation protocol, evaluated and modied in haemodynamically unstable or bleeding patients, along with adequate physician and nurse- to- patient ratios, are further keys for successful implementation. Increased age, female sex, and atrial arrhythmias are risk factors for failed fast- track protocol. Aggressive management of bleeding, active rewarming to ensure normothermia, as well as prompt diuresis and maintenance of normoglycemia and uid and electrolyte balance are further important guidelines which have the added benet of improving overall quality of care in postcardiac surgical patients.

Adequacy ofperfusion

A degree of haemodynamic instability is found in almost all postcardiac surgical patients. is is oen a result of transient myocardial dysfunction (stunning or hibernation) with associated reductions in ventricular compliance (diastolic dysfunction), and is frequently accompanied by varying degrees of intravascular depletion.

e ultimate goal of postoperative haemodynamic management is to maintain adequate distal organ perfusion to meet metabolic demand. erefore, apart from optimizing cardiac output (preload, aerload, contractility, and heart rate) and perfusion pressure, maintenance of normothermia and correction of anaemia and optimization of gas exchange are additional factors to consider.

Systemic blood pressure alone is a poor indicator of end- organ perfusion. Cardiac output coupled with mixed venous oxygen saturation is the most direct index of global metabolic supply/ demand ratio; however, it is less commonly monitored in post- CABG patients because of a decline in usage of pulmonary artery catheters (PACs). e role of pulse contour devices to determine pulse pressure and stroke volume variation- derived parameters based on percentage alteration of phasic arterial pressure during positive- pressure ventilation has demonstrated utility in assessment of uid responsiveness and when associated with protocol- driven goal- directed therapy,

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