ANAESTHETIC MANAGEMENT OF A PATIENT WITH ISCHAEMIC HEART

DISEASE UNDERGOING NON CARDIAC SURGERY  

PRESENTOR: DR.RAJESH CHOUDHURI PGT, DEPARTMENT OF ANAESTHESIOLOGY

AGMC & GBP HOSPITAL, AGARTALA

INTRODUCTION

•  IHD/CAD -- a group of closely related syndromes resulting from myocardial ischemia—an imbalance between the supply (perfusion) and demand of the heart for oxygenated blood.

The most common form of heart disease. 5% of patients over 35 years of age have asymptomatic ischaemic

heart disease. May be present in up to 30% of older pts undergoing surgery. The overall incidence of CAD in surgical patients is estimated to be

between 5%-10%. Cardiac dysrhythmias[VF] are a major cause of sudden death.

RISK FACTORS FOR DEVELOPMENT OF ISCHEMIC HEART DISEASE

• Male gender   • Increasing age   • Hypercholesterolemia  • Hypertension   • Cigarette smoking• Diabetes mellitus    • Obesity   • Sedentary lifestyle   • Genetic factors• Family history of premature ischemic heart disease (male <55 yrs of age, female <65 yrs)

IHDAngina Pectoris

Stable angina,Prinzmetal angina,

Unstable angina—

Acute MI

STEMINSTEMI

Chronic IHD with

Heart Failure

Sudden Cardiac Death

SPECTRUM OF IHD

ANGINA PECTORIS• Angina Pectoris: symptom complex of IHD characterized by

paroxysmal and usually recurrent attacks of substernal or precordial chest discomfort (variously described as constricting, squeezing,choking, or knifelike) caused by transient (15 seconds to 15 minutes) myocardial ischemia.

• Stable Angina: - Chronic stable angina refers to chest pain or

discomfort that does not change appreciably in frequency or severity over 2 months or longer.

-precipitated by physical activity or emotional upset, relieved by rest or nitroglycerine with in few minutes.

-develops in the setting of partial occlusion or significant (>70%) chronic narrowing of a segment of coronary artery.

- Atherosclerosis is the most common cause .

-Temporary depression of ST segment with no myocardial damage.

Variant Angina/Prinzmetal Angina: -Typical anginal discomfort usually at rest. -Develops due to coronary artery spasm rather than increase myocardial oxygen demand. -The anginal attacks are unrelated to physical activity,heart rate, or blood pressure. - Generally responds promptly to vasodilators. -Transient shifts of ST segment – ST elevation.

Unstable Angina: - defined as angina at rest, angina of new onset, or an increase in the severity or frequency of previously stable angina without an increase in levels of cardiac biomarkers. -is induced by disruption of an atherosclerotic plaque with superimposed partial (mural) thrombosis and possibly embolization or vasospasm (or both). of subsequent acute MI. - lies between stable angina on the one hand and MI on the other hand.

MYOCARDIAL INFARCTION (MI)• Focal disruption of an atheromatous plague triggers the

coagulation cascade with subsequent generation of thrombin and partial or complete occlusion of the coronary artery.• Region of myocardial necrosis due to prolonged cessation of blood supply• Typical symptoms of myocardial infarction include: Sudden Chest Pain,

Shortness Of Breath, Nausea, Vomiting, Palpitations, Sweating,Weakness, Light-headedness,Collapse/syncope .

Diagnosis of Acute MI: At least 2 of the following• Ischaemic symptoms.• Diagnostic ECG changes.• Serum cardiac marker elevations.

Pre-operative Screening & Evaluation

GOALS

•  Identify the risk for heart disease based on risk factors.

•  Identify the presence and severity of heart disease from symptoms, physical findings, or diagnostic tests .

•  Determine the need for preoperative interventions.•  Modify the risk for perioperative adverse events.

PRE-OPERATIVE SCREENING & EVALUATION• HISTORY• Aim-to elicit the severity, progression, and functional limitations

imposed by ischemic heart disease.• Symptoms of IHD. –duration, precipitating factors, associated symptoms, relieving

factors.

• Exercise tolerance. • Risk factors .• H/O MI.• H/O cardiac revascularisation- PCI/CABG

• Co-Existing Noncardiac Diseases: CVA, COPD, DM, Renal insufficiency• Current Medications: Anti-hypertensives, Anti platelet agents, Anticoagulants, Others.

PRE-OPERATIVE SCREENING & EVALUATION

• Physical Examination: Abnormal physical findings are often absent and non-specific.• Quick assessment of patients vital signs• Signs of right and left ventricular dysfunction must be sought.• Jugular venous distention and peripheral edema are signs of right

ventricular failure. • Auscultation of the chest may reveal evidence of left ventricular

dysfunction such as an S3 gallop or rales.• A carotid bruit may indicate cerebrovascular disease.• Orthostatic hypotension may reflect attenuated autonomic nervous

system activity due to treatment with antihypertensive drugs.

SPECIALIZED PREOPERATIVE TESTING• 12-lead ECG: may show no abnormality, old MI, AMI, ST depression, non specific changes.

• Echocardiography: global cardiac function , LV dysfunction, regional wall motion abnormalities , valvular ds, LV thrombus .

• Exercise electrocardiography:C/I- Severe AS, Severe hypotension, Acute myocarditis, Uncontrolled HF, Infective Endocarditis.

• Stress echocardiography : used with pharmacologic induction of cardiac stress (dobutamine) or exercise to look at LV segmental wall function at rest & with stress.

• Nuclear stress imaging: Dipyridamole-thallium testing mimics the coronary vasodilator response associated with exercise.

• Positron emission tomography:to demonstrate regional myocardial blood flow & metabolism, & hence viability.

• Coronary angiography : Provides information about the coronary anatomy & the extent & location of the lesions. indicated in pts w/ unstable angina despite maximal therapy.

• Cardiac enzyme elevation: Troponin is more specific than CK-MB ; increases within 4 hours after AMI & remains elevated up to 1 wk.

RISK STRATIFICATION•AIM: Identify patients at increased risk so as to manage them with

pharmacological and other perioperative interventions that can lessen the risk and severity of perioperative cardiac events.• Lee’s Revised Cardiac Risk Index:

• The ACC/AHA guidelines integrate risk stratification according to:

1. Clinical risk factors & ECG review.

2. Functional Capacity.

3. Surgery specific risk factors.

CLINICAL PREDICTORS OF INCREASED PERIOPERATIVE CARDIOVASCULAR RISK

• MAJOR

• Unstable coronary syndromes• Acute / Recent MI• Unstable/ Severe Angina• Decompensated Heart Failure• High grade AV-block• Symptomatic Ventricular

Dysrhythmias• Severe Valvular Heart Disease

• INTERMEDIATE• Stable Angina• Previous MI (history/ECG)• Compensated or previous heart failure• DM/Renal Insufficiency

• MINOR• Age>70• ECG: LVH,LBBB ST-T abnormalities• Low functional capacity• H/O CVA/HTN

FUNCTIONAL CAPACITY

• The ability to exercise is an excellent indicator of “ cardiovascular fittness”.• Usually expressed in metabolic equivalents of task ( METs) on a scale

defined by the Duke Activity Status Index.• One MET is the resting oxygen consumption of a 40 yr old 70 kg male

( 3.5 ml/kg/min).• Patients who can not sustain 4 METs of physical activity frequently

have adverse outcomes following high-risk surgery.

R I S K F A C T O R S A S S O C I A T E D W I T H S U R G E R Y

PRE-OPERATIVE ASSESSMENT OF PATIENTS WITH IHD

High/ intermediate risk surgery + Moderate-minor clinical risk factors

Prior Revascularization

CABG

<5yrsNo change in

medical condition

Surgery

PCIBMS >30daysMinimal

anti platelet therapySurger

y

DES <12 months

Dual anti platelet therapyCardiol

ogy Opinio

n

High/intermediate risk surgery+ moderate clinical risk factors

No Prior RevascularizationStable CAD

Surgery

Decreased Exercise Tolerance Non Invasive Testing -

ve Surgery

Non Invasive Testing

+ve Coronary

AngiographySignificant CADConsider risk of

coronary revascularization

vs surgery

PREOPERATIVE MANAGEMENT AFTER RISK STRATIFICATION• CABG: Indications are the same as those in the non-operative setting.• PERCUTANEOUS CORONARY INTERVENTION: Poses its own unique set of

problems that need to be considered before elective non cardiac surgery.• PHARMACOLOGIC MANAGEMENT: Perioperative beta-blocker therapy: Patients already

on beta blockers chronically (I) In patients with intermediate- or high-risk preoperative tests (IIb) If used for prophylaxis should be initiated atleast 1 week prior to elective surgery. Nitrates: Prophylactic use of niroglycerin has not been shown to reduce perioperative mortality or morbidity.(III) Perioperative statin therapy: To be continued in patients already taking statins (I) Patients with vascular disease should receive statins regardless of the need of surgery (IIa). Should be started 1-4 weeks prior to surgery and continued perioperatively. Alpha-2 agonists: may be considered in patients who can not tolerate beta blockers. ACE inhibitors: discontinued on the morning of surgery. Restart as soon as clinically feasible postoperatively (IIa ). Antiplatelet agents: Aspirin may be continued throughout the perioperative period. Clopidogrel should however be discontinued for a week prior to surgery…restart as soon as possible after surgery/ removal of epidural catheter.

INTRAOPERATIVE MANAGEMENT• Anaesthetic Goals : 1.Prevent myocardial ischaemia by optimising

myocardial O2 delivery and reducing the O2 demand. 2.To

monitor for ischaemia. 3.To institute appropriate measures to treat

ishaemia if and when it develops.• Causes Of Myocardial O2 Imbalance

Decreased O2 supply Increased O2 demand Decreased coronary flow

• tachycardia (decreased diastolic perfusion time)

• hypotension (esp diastolic BP) • hypocapnia (coronary vaso

constriction) coronary vasospam

Decreased O2 content & availability • anemia • hypoxemia • reduced release from Hb i.e

ODC shift to left

• 1. tachycardia • 2. increased wall tension • 3. increased preload • 4. increased after load • 5. increased myocardial

contractility

ANAESTHETIC CONSIDERATIONS DURING INTRAOPERATIVE PERIOD

• Avoid tachycardia: Increases O2 demand , also shortens diastolic filling time .• Avoid persistent and excessive changes in BP: Keep the HR and

BP within 20 % of the normal awake value. • Avoid hyperventilation: as hypocapnia can cause coronary

artery vasoconstriction.• Maintain normothermia: Intraoperative hypothermia may

predispose to shivering on awakening, leading to abrupt and dramatic increases in myocardial oxygen requirements.• Correct Anaemia : Blood loss to be taken care of – anaemia can

cause critical reduction in myocardial oxygen supply in IHD pt.

GENERAL ANAESTHESIA• PRE-MEDICATION: Morphine, scopolamine, and benzodiazepine , alone or in

combination –for sedation and amnesia without causing deleterious myocardial depression, hypotension, or hypoxaemia. ➣ Continuation or administration of beta blockers . ➣ all pre-medicated patients should receive supplemental oxygen.

• INDUCTION OF ANAESTHESIA: can be accomplished with an intravenous induction drug. ➣ Etomidate is a good choice for patients with poor cardiac reserve. ➣Ketamine is to be avoided as it increases myocardial oxygen demand by increasing HR and BP.

• INTUBATION: To be facilitated by the use of succinyl choline or a NDMR. Blunting of haemodynamic response to tracheal intubation by- 1. Keeping the duration short (<15s). 2.Use of laryngotracheal Lidocaine, intravenous lidocaine, esmolol, fentanyl, dexmedetomidine.

• MAINTENANCE• AHA guidelines recommend volatile anaesthetic agents for maintenance of anaesthesia

in patients with IHD in a haemodynamically stable patient with no evidence of CHF. (Iia)• Halothane has the disadvantage of myocardial depression and potential of dysrhythmias.• The use of N2O in patients with IHD is questionable since it increases PVR, and

predisposes to diastolic dysfunction and subsequent myocardial ischaemia.• Muscle Relaxants : Vecuronium, rocuronium, cisatracurium are attractive choices for

patients with ischemic heart disease.• Atracurium causes histamine release and subsequently fall in blood pressure which

makes it a less desirable agent.• Pancuronium should be avoided to due to its sympathomimetic activity.• For patients with severely impaired LV function: opioids may be selected as the principal

anaesthetic.• REVERSAL: with an anticholinesterase/anticholinergic drug combination can be

safely accomplished . Early extubation is possible and desirable in many patients as long as they fulfill the criteria for extubation.

REGIONAL ANAESTHESIA

Regional anesthesia may be preferred to GA if possible, as it tends to better block the stress response to surgery.

Associated hypotension should be corrected by fluids & sympathomimetic agents

Benefits • excellent pain control.• decreased incidence of deep vein thrombosis. • postoperative analgesia.

However, the incidence of postoperative cardiac morbidity and mortality does not appear to be significantly different between general and regional anesthesia

PERIOPERATIVE MONITORING• ECG: 3 lead monitoring II, V4 & V5 or V3 V4&V5 is recommended. Simplest and most

cost-effective method for detecting perioperative myocardial ischaemia.• PULMONARY ARTERY CATHETER : may be considered when underlying medical

conditions that significantly affect hemodynamics cannot be corrected before surgery (IIa). Intra operative myocardial ischaemia can manifest as an acute increase in

pulmonary artery occlusion pressure.

• CENTRAL VENOUS PRESSURE MONITORING: CVP may correlate with PCWP if EF = 0.5 & there is no evidence of LV dysfunction.

• TRANSESOPHAGEAL ECHOCARDIOGRAPHY: Most sensitive to detect intraoperative myocardial ischemia by detecting new onset of regional wall motion abnormality. Emergency use of perioperative TEE in patients with hemodynamic instability is reasonable in patients undergoing noncardiac surgery if expertise is readily available (IIa).

POST OPERATIVE AND LONG-TERM MANAGEMENT

• patients with IHD can become ischemic during emergence from anesthesia and/or weaning with an increased heart rate and blood pressure. • These hemodynamic alterations must be managed diligently.

Pharmacologic therapy with a β-blocker or combined α- and β-blockers such as labetalol can be very helpful.• pain control.• Continuous ECG monitoring with ST-segment analysis .• Supplemental O2 .• Avoid & treat shivering.• Prevent hypoxemia, hypercarbia hypovolaemia, hypotension in

postoperative period.

PERIOPERATIVE MYOCARDIAL ISCHAEMIA• The risk of perioperative death due to cardiac causes is less

than 1% for patients who do not have ischemic heart disease .The incidence of

perioperative MI in patients who undergo elective high-risk vascular surgery is between 5% and 15%.

PERIOPERATIVE MYOCARDIAL ISCHAEMIA

Intraoperative Diagnosis Complicated by lack of symptomatic presentation in about half of patients with perioperative MI. 75% of Intraop MIs are Silent, present atypically, without ST changes, Q waves or chest pain. • Signs: instability of HR/BP, desaturation, shock refractory to vasopressors,

poor perfusion, new murmur, skin discolored, pulmonary edema ECG: LBBB, arrhythmias, ST changes, T wave inversion, QRS & T wave

axis deviations, and R/U wave changes.ST depression will be 1mm or less in anaesthetized patients.

Biochemistry: Elevated lactate, CK & Troponin levels.

Intraoperative Management of Myocardial Ischemia

• Delay the procedure,- if not possible, expedite surgery while the patient is stabilized by improving coronary blood flow and oxygen delivery and reducing oxygen demand.

Discontinue volatile anaesthetic agents & start 100% O2

Administer 325mg Aspirin via ryles’s tube Tachycardia : Treated with beta blockers. Nitroglycerine is the drug of choice for accompanying hypertension. Morphine is a venodilator that reduces ventricular preload and oxygen requirements

and it is also effective in patients with pulmonary vascular congestion. Hypotension : treated with sympathomimetic drugs / fluid infusion to

restore blood pressure. In an unstable hemodynamic situation, circulatory support with inotropes

or an intra-aortic balloon pump may be necessary.