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Lindsays Flashcardlet > RE4: Chapter 24: Anesthesia for Cardiac Surgery Part 2 > Flashcards

RE4: Chapter 24: Anesthesia for Cardiac Surgery Part 2 Flashcards

0
Q

Patients with CAD can develop _________ ischemia vs. patient with ACS or perioperative ischemia is usually caused by _________ ischemia.

A

demand ischemia

Supply ischemia

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1
Q

True or False. Coronary oxygen extraction is maximal at rest.

A

True. The only way to increase oxygen delivery to the tissues is to increase coronary flow!!!

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2
Q

What are some anesthetic considerations in the management of CABG?

A
  1. Relatively HIGH MAP to maintain coronary perfusion
  2. Keep the HR and LVEDP LOW to maintain coronary perfusion
  3. Decrease preload - LIMIT FLUIDS to decrease LVEPD because this will increase MVO2 supply and decrease demand
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3
Q

What is the preferred drugs to control HR and and preferred vasodilator for CABG?

A

Beta-blockers to control HR

Preferred vasodilator is nitroglycerin

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4
Q

What are the most commonly used conduits for a CABG?

A

Internal thoracic arteries (LITA) (formerly internal mammary arteries (LMA)) and the greater saphenous veins

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5
Q

What are anesthetic considerations with off-pump CABGs compared to on-pump CABGs?

A
  1. These patients require crystalloid and/or colloid solutions to correct fluid deficit. There is no hemodilution from the CPB priming fluid.
  2. Amicar is not routinely used because the blood is not exposed to CPB.
  3. Hypothermia is a concern and must be treated.
  4. Anticoagulation is necessary and ACTs should be checked q 30 min
  5. CPP must be maintained by keeping a high MAP (90-100mmHg) during distal anastomosis.
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6
Q

What is the most common valvular defect requiring surgical intervention?

A

Aortic Stenosis

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7
Q

What three factors determine valvular flow?

A
  1. Valve area
  2. Pressure gradient across the valve
  3. Duration of flow in systole or diastole
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8
Q

With AS, what valve size is considered severe?

A

Stenosis is considered severe when valve area decreases to 1 cm2 and critical when it is 0.7cm2 or less

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9
Q

What type of LV hypertrophy is associated with AS?

A

Concentric hypertrophy. The LV becomes thicker attempting to generate enough to pressure to push the blood forward past the stenosis.

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10
Q

With AS, what is characteristically seen on an arterial waveform?

A

The pressure drop (secondary to the Venturi effect) results in a characteristic slow upstroke and high dicrotic notch on the A-line with a classic narrow pulse pressure.

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11
Q

Atrial kick contributes ____% of LVEDV with patients with AS?

A

40%

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12
Q

What is the classic triad of AS symptoms?

A

Angina
Syncope
Dyspnea

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13
Q

What are the anesthetic considerations in the management of AS?

A
  1. AVOID HYPOTENSION and TACHYCARDIA!!!!
  2. INCREASE PRELOAD - this will reduce gradient across the LVOT (Pts with AS have at least a 40 -50mmHg mean pressure gradient between the LV and aorta)
  3. HR SLOW TO NORMAL
  4. NSR - atrial kick contributes 40% of LVEDV
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14
Q

What is the primary problem in hypertrophic cardiomyopathy compared to AS?

A

Concentric hypertrophy as opposed to AS, in which the LVH is secondary to stenosis

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15
Q

What is SAM?

A

Systolic anterior motion (SAM) of the mitral valve. SAM increase LVOT obstruction and causes mitral regurg.

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16
Q

What must be avoided with SAM?

A

Any reduction in ventricular volume will increase the degree of SAM. Therefore, any increase in HR and contractility and/or decrease in preload and afterload must be avoided!!!

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17
Q

What are the anesthetic considerations in the management of HOCM?

A
  1. Increase preload - stretches non compliant LV, reduces gradient across LVOT and prevents SAM and MR
  2. HR LOW TO NORMAL
  3. NRS - atrial kick contributes to LVEDV
  4. AVOID REDUCTIONS IN SVR - hypertension is better tolerated than hypotension
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18
Q

What is the difference between Acute AI vs. Chronic AI?

A

Acute AI results in rapid deterioration because the LV cannot compensate the increased volume

Chronic AI is better tolerated because the LV remodels to tolerate the increased volume.

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19
Q

What type of LVH is associated with AI?

A

Eccentric hypertrophy due to the increased LVEDV

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20
Q

What are some characteristic findings do you with AI especially on an arterial waveform?

A
  1. Widened pulse pressure due to the rapid systolic ejection and diastolic run-off
  2. Bound pulse
  3. Arterial waveform with a rapid rise in systolic pressure and low dicrotic notch. Sometimes a double systolic peak called a pulsus bisferiens
21
Q

What are some anesthetic considerations in the management of AI?

A
  1. ENHANCE FORWARD FLOW AND MINIMIZE REGURG VOL.
  2. PRELOAD INCREASED - maintain forward flow
  3. HR HIGH TO NORMAL - minimizes diastolic time
  4. SVR DECREASED - maintains forward flow/reduces regurg.
22
Q

With AI, what type of cardioplegia flow is required to achieve diastolic standstill?

A

Retrograde

23
Q

What is the pathophysiology of MS?

A

As the MV narrows, diastolic filling of the LV is limited, a pressure gradient develops across the MV. LA pressure increase which results in PHTN.

24
Q

What MV size is considered severe?

A

When the valve area is less than 1.0cm2

25
Q

Is AFib common with patients with MS?

A

Yes, approx. 40% of patients develop AF.

The rapid HR is the primary cause of hemodynamic instability rather than the loss of atrial kick!!!

26
Q

What are some anesthetic considerations in the management of MS?

A
  1. HR SLOW TO NORMAL - maximizes diastolic time to fill LV
  2. NSR - AF occurs in 40% of patients
  3. REDUCE PRELOAD - adequate preload needed to maintain flow across gradient but too much vol. can lead to pulmonary congestion.
  4. AVOID INCREASES IN PVR - (hypercarbia, hypoxemia, nitrous oxide, and trendelenburg)
27
Q

True or False. With MR, there is no isovolumetric relaxation phase of systole because the LA acts as a low resistance vent for ventricular ejection.

A

FALSE - there is no isovolumetric contraction!

28
Q

What type of LVH is common with MR?

A

Eccentric hypertrophy because the LA and LV compensate for chronic volume.

29
Q

With acute MR, what is a classic finding in the PCWP?

A

Enlarged V wave, but the size does NOT correlate with the degree of MR

30
Q

What are some anesthetic considerations in the management of MR?

A
  1. PRELOAD MAINTAINED - enhance forward flow
  2. HR HIGH TO NORMAL - minimizes diastolic time
  3. DECREASE SVR - enhance forward flow
  4. AVOID INCREASES IN PVR
31
Q

What are some anesthetic considerations for minimally invasive surgical approaches?

A
  1. Consider a fast-track approach
  2. Closely monitor level of muscle relaxation esp. with robotic procedures
  3. Maintain normothermia
  4. External defibrillator pads should be placed on all patients because the use of internal defibrillator pads is not possible.
  5. With a mini-thoracostomy, DLT may be possible for lung isolation
32
Q

What are advantages and disadvantages of robotic cardiac procedures?

A

Advantages: reduction in surgeon tremor, increased mobility with instrumentation and three-dimensional vision

Disadvantages: higher cost, increased complexity, longer cross-clamp times due to learning curve

33
Q

What is a TAVI?

A

Transcatheter Aortic Valve Implantation

It is a minimally, invasive percutaneous procedure for the correction of severe AS. It does not require sternotomy or CPB. A retrograde approach (transfemoral) via the femoral artery or an antegrade (transapical) approach via the LV apex is used to implant a bioprosthetic valve.

34
Q

What are some anesthetic considerations in the management of a TAVI patient?

A
  1. Excellent communication between all disciplines
  2. Muscle relaxation is required to prevent movement during the valve deployment
  3. During valve deployment, apnea is required and anticipate a low CO (hypotension) induced by a rapid pacing of the ventricle at a rate of 200bpm.
  4. TEE and fluoroscopy is required throughout the procedure
  5. AV block is common following procedure, thus defibrillator pads must be placed on patient prior to start of procedure.
  6. Plan to extubate following procedure
35
Q

What does an intra-aortic baloon pump (IABP) do?

A

IABP is an mechanical circulatory-assist device that reduces afterload and increases diastolic coronary perfusion to the heart.

36
Q

Where is the IABP positioned?

A

IABP is positioned 2cm distal to the origin of the left subclavian artery so the tip of the baloon is situated at the junction of the aortic arch and descending aorta.

37
Q

Describe the timing of the IABOP.

A

The IABP should be timed with the dicrotic notch of the arterial waveform so that the baloon inflates once the aortic valve closes and diastole begins.

The deflation of the baloon is timed immediately before the onset of systole at the beginning of the R wave of the ECG.

38
Q

What does the inflation and deflation the IABP assist with?

A

Inflation of the baloon enhances coronary artery perfusion and ultimately myocardial oxygen delivery improves

Deflation of the baloon creates a vacuum effect, reducing afterload, facilitating ventricular ejection, and reducing myocardial oxygen demand.

KNOW FIGURE 24-23!

39
Q

What is the only definitive treatment for end-stage heart failure?

A

Heart transplantation

40
Q

What are some anesthetic considerations in the management of LVAD candidates?

A
  1. Decreases in preload and increases in afterload are poorly tolerated
  2. Extremely dependent on HR due to a fixed CO with an inability to increase SV
  3. RSI - considered full stomachs
  4. Etomidate is the agent of choice
41
Q

What is a major cause of short-term morbidity after transplantation?

A

Right ventricular failure due to fixed pulmonary hypertension in the recipient causes an acute right heart failure in the donor heart.

42
Q

True or false. The transplanted heart becomes extremely preload dependent.

A

TRUE - once the heart is denerved or loss of normal vagel tone and sympathetic/parasympathetic innervation, the transplanted heart responds to hypovolemia and hypotension by initially increasing SV.

43
Q

What are the inotropic agents of choice to used with a transplanted heart?

A

Only pharmacologic agents such as epi and isoproterenol that have direct-acting effects on catecholamines will be effective in increasing HR. (Ephedrine and anticholinergics such as atropine are ineffective)

44
Q

Surgery is indicated with ascending thoracic aneurysms that are dilated to _____cm for congenital lesions or ______cm for acquired lesions.

A

5cm

5.5cm

45
Q

What technique is used to protect the brain with aortic arch aneurysms?

A

Deep hypothermic circulatory arrests (DHCA)

46
Q

What are some anesthetic considerations in the management of aortic arch aneurysm?

A
  1. Possibility of a difficult airway if aneurysm is large
  2. Consider that AI may be present
  3. Maintain forward flow with low SVR and high HR
  4. Keep SBP less than 120mmHg to minimize chance of dissection
47
Q

Why is it recommended to have multiple arterial lines with aortic arch aneurysms?

A

Due to pressure differences between the A-lines indicates inadequate flow and potential ischemia

48
Q

What is the goal HR and BP with aortic dissections?

A

HR and BP are controlled with beta-blockers first to achieve a HR or 60bpm followed by cautious vasodilation to achieve a SBP lower than 120mmHg

49
Q

With DHCA, what are the recommended temps and arrest times?

A

Generally, a nasopharyngeal temp is measured and the patient is cooled to 15 - 22C. Arrest periods of less than 25 minutes are generally considered safe.

Lindsays Flashcardlet (27 decks)

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