Mod2: CARDIAC SURGERY AND ANESTHESIA CONSIDERATIONS Flashcards by Olivier Mba

_{CORONARY ARTERY DISEASE}

What’s the leading cause of death in the US?

Coronary Artery Disease

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CORONARY ARTERY DISEASE

What’s the leading cause of death after anesthesia and surgery?

Perioperative Cardiac morbidity

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_{CORONARY ARTERY DISEASE}

Why is it our goal to either prevent it or to promptly identify it and treat myocardial ischemia?

Because CAD is the leading cause of death in the US and

Cardiac morbidity is the leading cause of death after anesthesia and surgery

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_{CORONARY ARTERY DISEASE}

T/F: When patients do develop CAD, supply and demand becomes a balancing act

True

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_{PATHOPHYSIOLOGY OF ISCHEMIA}

When does Myocardial ischemia occur?

When there is a relative lack of O2 supply to the myocardium and
Reduced metabolite removal for the heart for a given O2 consumption

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_{PATHOPHYSIOLOGY OF ISCHEMIA}

How is Myocardial ischemia Classically noted?

Classically noted as symmetrical T-wave changes

This is a Dynamic state the heart can go in and out of

Occurs at the cellular level

As a result of imbalance between supply and demand

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_{PATHOPHYSIOLOGY OF ISCHEMIA}

Ischemia that causes potentially reversible damage to the myocardium, which causes it to depolarize and repolarize incompletely is also known as:

Myocardial injury

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_{PATHOPHYSIOLOGY OF ISCHEMIA}

How is Myocardial injury classically noted as?

Myocardial injury is Classically noted as ST changes

Also known as “stunned myocardium” or “stoned heart”

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_{PATHOPHYSIOLOGY OF ISCHEMIA}

What event do we have when Myocardial ischemia continues and results in tissue death/necrosis?

Myocardial infarction

Occurs with a reduction in coronary blood flow that persists longer than 20-40 minutes

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_{PATHOPHYSIOLOGY OF ISCHEMIA}

T/F: Ischemia can affect different layers of the heart muscle

True

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_{PATHOPHYSIOLOGY OF ISCHEMIA}

Ischemia that affects the superficial outer layer of the ventricle is known as:

Subepicardial ischemia

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_{PATHOPHYSIOLOGY OF ISCHEMIA}

Ischemia that results in injury or infarction of only the inner half of the heart muscle is known as:

Subendocardial ischemia

As previously mentioned, because autoregulation is lost, this area becomes pressure dependent so it has the highest risk of ischemia

Manisfest as Flipped t-wave* or ST depression
Q-wave will be absent in Subendocardial ischemia?!*
Recent studies suggest that Q-wave could be present in both Subendocardial and Transmural ischemia*

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_{PATHOPHYSIOLOGY OF ISCHEMIA}

How does Subendocardial ischemia manifest on the ECG?

Flipped t-wave, or

ST depression

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_{PATHOPHYSIOLOGY OF ISCHEMIA}

Ischemia that results in injury or infarction of the full thickness of the ventricle is known as:

Transmural ischemia

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_{PATHOPHYSIOLOGY OF ISCHEMIA}

How does Transmural ischemia presents on the ECG?

ST elevation

Some sources say Q-wave

Q-wave will be absent in Subendocardial ischemia?!*
Recent studies suggest that Q-wave could be present in both Subendocardial and Transmural ischemia*

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_{DETECTION OF INTRAOPEARTIVE MYOCARDIAL ISCHEMIA}

What % of patients with CAD may have a normal resting EKG?

25-50%

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_{DETECTION OF INTRAOPEARTIVE MYOCARDIAL ISCHEMIA}

What % of patients have a baseline defect that makes it non-interpretable for ischemia?

25%

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_{DETECTION OF INTRAOPEARTIVE MYOCARDIAL ISCHEMIA}

Why do EKG have increased importance in the postoperative period?

Because 80% of MI’s occur in the postoperative period

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_{DETECTION OF INTRAOPEARTIVE MYOCARDIAL ISCHEMIA}

Why might ST segment changes on the EKG be considered late sign of ischemia?

Because patients with baseline defect (LBB, WPW) make it non-interpretable

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_{DETECTION OF INTRAOPEARTIVE MYOCARDIAL ISCHEMIA}

Which ECG change is seen WPW?

T-wave inversion

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_{DETECTION OF INTRAOPEARTIVE MYOCARDIAL ISCHEMIA}

How does LBB appear in V1?

As a Q-S complex

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_{DETECTION OF INTRAOPEARTIVE MYOCARDIAL ISCHEMIA}

How is intraoperative ischemia detected via PA catheter?

Increased demand, leads to a decreased compliance

Decreased compliance manifests as:

=> Sudden ↑ PA pressure/PCWP (ventricular dysfunction)

=> Large a waves ( ↓ ventricular compliance)

=> Large v waves ( ischemia induced papillary muscle dysfunction)

=> Is Not specific

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_{DETECTION OF INTRAOPEARTIVE MYOCARDIAL ISCHEMIA}

Why is the Intraoperative TEE considered the best choice for detecting ischemia intraoperatively?

Very sensitive and more specific than EKG or PAC

Will detect development of new global and regional wall motion abnormalities

First detectable change in the left ventricle during ischemia

TEE changes are more common and more predictive of MI than ECG

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_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA: OVERVIEW}

What does the QRS complex on the EKG represent?

Ventricular depolarization

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_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA: OVERVIEW} What does the the first downward or negative deflection of the QRS complex represent?

the Q wave

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA: OVERVIEW} What does the First upward or positive deflection of the QRS complex represent?

the R wave

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA: OVERVIEW} What does the negative deflection that occurs after the R wave of the QRS complex represent?

the S wave

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA: OVERVIEW} On the EKG tracing below, what do 4 and 8 represent?

4: ***Q-wave*** 8: ***QS complex*** (Can't tell if it's a Q or an S wave)

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA: OVERVIEW} What happens to the S & R wave amplitudes as the QRS complex progresses in the precordial leads from V1 to V6?

S wave amplitude decreases R-wave amplitude increases

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA: OVERVIEW} Which phase of cardiac action potential does the T wave represents?

Ventricular repolarization

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA: OVERVIEW} In which leads is the T wave normally upright?

In leads I, II, and V3-6

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA: OVERVIEW} In which leads is the T wave normally inverted?

in aVR

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA: OVERVIEW} What's the T wave orientation in leads other than I, II, V3-6, and AVR?

Variable

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA: OVERVIEW} What happens to the T wave amplitude as we progress along the precordial leads V1-6?

Amplitude should increase along with R-wave

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA} Which two changes can ischemic EKG have?

Indicative changes Reciprocal changes

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA} Changes that occur in leads that are facing the ischemic/infarcted area are categorized as:

**Indicative changes**, include: ## Footnote * Inverted T-wave* * Elevated ST segments,* * Abnormal Q-waves or* * Loss of R wave amplitude*

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA} Changes that occur in leads facing away from the ischemic or infarcted area are categorized as:

**Reciprocal changes** They record a mirror image of the indicative changes and provide indirect evidence of ischemia They are sometimes seen first

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA} Given a list of some Reciprocal changes:

Upright, tall or peaked T-waves Depressed ST segments Absence of normal Q-wave in the lateral leads Increased R-wave voltage

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA} Summary table of Indicative/Facing vs Reciprocal changes:

(See table)

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA} What's the signature of an MI on the EKG?

Decreased R-wave amplitude, and Pathologic Q-waves

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA} What causes pathologic Q waves?

Absence of electrical activity

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA} An MI can be thought of as an electrical whole; why is that?

Because scar tissue is electrical death Therefore results in pathological Q wave

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA} When are Q waves considered diagnostic?

It they are more than 0.04 sec in V2-V3, or QS complex in V2

_{IDENTIFICATION OF INTRAOPERATIVE ISCHEMIA} T/F: Q waves in V1-2 are always abnormal

True

_{SELECTION OF ANESTHETIC AGENT} T/F: No “one ideal” anesthetic

True

_{SELECTION OF ANESTHETIC AGENT} Choice dependent primarily on:

Degree of myocardial dysfunction Pharmacological properties of drugs themselves

_{SELECTION OF ANESTHETIC AGENT} Volatile agents might be the anesthetic of choice for a pt with which LV assessment?

Good LV function (meaning EF \>40%, LVEDP \<12, normal CO) Volatile agents will contribute to coronary vasodilation Volatile agents can potentially cause preconditioning which will protect the myocardium from hypoperfusion and ishemia

_{SELECTION OF ANESTHETIC AGENT} High-dose opioid technique might be the anesthetic of choice for a pt with which LV assessment?

Poor LV function (Meaning EF \<40%, LVEDP \>18, Decreased CO, multiple areas of dyskinesia) Opioid-based technique lack myocardial depression so hemodynamics remain stable

_{SELECTION OF ANESTHETIC AGENT} What's a disadvantage of opioid based technique?

Prolonged mechanical ventilation Delayed extubation Whereas the goal is to fastrack (extubate within 6-hrs) most of theses pts

_{SELECTION OF ANESTHETIC AGENT} What's the perfect anesthetic combination for theses patients?

Volatile agents + opioid-based technique = Both together

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA: NITRATES} What's the effect of Nitrates like nitroglycerine on vascular smooth muscles?

Relax vascular smooth muscle ^{Venous > arterial} Reduce venous and arteriolar tone ^{=> reduce circulating blood volume} ^{Reduction in preload and wall tension afterload => reduces MVO2} Dilation of coronary arteries This reduces cardiac oxygen demand by decreasing preload and afterload

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA: NITRATES} Why are Nitrates the drugs of choice for acute coronary vasospasm?

Because they preferentially increases blood flow to Subendocardial layers

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA: NITRATES} How do Nitrates decrease pulmonary HTN?

By reducing pulmonary vascular resistance

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA: NITRATES} Nitrates are great at improving collateral flow to ischemic regions. However, they must be used with caution. Why is that?

Too high doses of Nitrates can cause systemic hypotension and impair coronary perfusion pressure

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA: NITRATES} T/F: High dose Nitrates could cause Methemoglobinemia

True

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA: SNP} Which type of drug is SNP classified as? What are its effects?

Direct-acting nonselective peripheral vasodilator Relaxes both arterial and venous vascular smooth muscles Enhances ventricular function by decreasing impedance to ventricular ejection Reduction in pulmonary vascular resistance (Effective for use against PHTN) Decrease SVR and PVR, preload, and also reduces platelet aggregation

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA: SNP} SNP reduces platelet aggregation. Why would this be a concern?

Reduction of platelet aggregation would be a benefit before surgery but a disadvantage after After surgery, when aggregation is important to reduce post op bleeding, this could potentially cause problems

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA: SNP} SNP could cause the diversion of blood away from ischemic areas. What is this phenomenom called?

Coronary steal

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA: SNP} Which disadvantages of Sodium Nitroprousside make NTG the preferred drug of choice after acute MI?

**Coronary steal**, which results in the diversion of blood away from ischemic areas where blood vessels are already maximally dilated Can also cause **reflex tachycardia** by stimulating baroreceptor-mediated response **Decreases in PaO2** as a result of the *inhibition of hypoxic pulmonary vasoconstriction* **Cyanide toxicity** **Methemoglobinemia** **Thiocyanate toxicity** **Reduces platelet aggregation**

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA - VASOCONSTRICTORS} What role do vasoconstrictors play in the management of intraoperative ischemia?

Maintain diastolic blood pressure Indicated during episodes of systemic hypotension Increase coronary perfusion pressure (alpha-adrenergic) * However, they also increases afterload, preload, and MVO2* * NTG added to counteract increased preload* * More often then not, increased CPP offset increased wall tension*

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA - VASOCONSTRICTORS} Which vasoconstrictors are most commonly used in the intraoperative phase of surgery prior to bypass grafting?

Phenylephrine Norepinephrine Vasopressin

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA - VASOCONSTRICTORS} What makes Phenylepherine is an excellent drug for the treatment of intraoperative ischemia?

It has alpha agonist activity Minimal to no inotropic or chronotrpic stimulation Its administration activates the baroreceptors, reducing heart rate However, the increase in SVR could potentially increase the work of the heart and _reduce_ myocardial O2 demands

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA - VASOCONSTRICTORS} How could Norepinepherine decrease myocardial oxygen supply?

by increasing myocardial contractility via mild stimulation of Beta-1 cells

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA - VASOCONSTRICTORS} Why should Vasopressin be used cautiously in patients with coronary artery disease?

Because of its powerful vasoconstrictor response Could also constrict the coronary arteries

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA - VASOCONSTRICTORS} T/F: although vasoconstrictive agents are effective in treating systemic hypotension during intraoperative ischemia, they should be used with caution

True

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA} A balance of supply and demand involves controlling heart rate and contractility. Which drugs reduce heart rate, and myocardial contractility in hyper-dynamic states?

Beta blockers

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA} Why should Beta blockers be administered prior to CABG (According to quality measures)?

Because they have been shown to reduce the risk of death following surgery They should be administered to all patients who are 18 years of age with no contraindication present *Administration within 24 hours prior to surgery is a quality measure unless contraindicated*

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA} Which drugs selectively relax arterial resistance and thus cause coronary vasodilation?

Calcium channel blockers Also decrease myocardial demand by decreasing contractility

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA} Which Calcium channel blockers have greater effects on cardiac contractility, but should be used cautiously in patients with ventricular dysfunction, conduction abnormalities

Verapamil and Diltiazem

_{TREATMENT OF INTRAOPERATIVE ISCHEMIA} Which calcium channel blocker is frequently used in the operating room and is thought to be the first-line treatment for cardiac patients who have acute hypertension that requires immediate control? and why is it the first-line treatment?

Nicardipine Because of its minimal side effects