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Anesthesia > Cardiac Anesthesia > Flashcards

Cardiac Anesthesia Flashcards

1
Q

Trace the coronary blood supply and possible presentation with occlusion

A

Dominance is determined by which artery gives rise to the Posterior Descending Artery (supplies the inferior wall of LV)

(A) Right-sided: right coronary artery
- ~80% of the population
- supplies SA node, AV node, RV –> bradycardia or AV blocks
- ECG: inferior wall - II, III, aVF
(B) Left-sided: left circumflex artery
- supplies AV node, SA node (in 40%), septum
- ECG: septal, anterior, apical, lateral wall

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2
Q

What are the clinical risk factors for a major perioperative cardiac event (MACE)?

A

Revised Cardiac Risk Index (RCRI) - noncardiac sx
- HR surgical procedures: intraperitoneal, intrathoracic, supra-inguinal vascular
- IHD
- CHF
- CVD
- Insulin-requiring DM
- Serum creatinine > 2mg/dl

*Gupta scoring - both cardiac and non-cardiac

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3
Q

What is the metabolic equivalent for adequate cardiac reserve?

A

At least 4 METs:
- able to climb 2-3 flights of stairs without symptoms

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4
Q

What are considered active cardiac conditions?

A

1) Unstable coronary syndromes
2) Decompensated HF
3) Arrhythmia: symptomatic bradycardia/ventricular arrhythmia, high-grade AV block
4) Severe valvular disease: symptomatic MS, severe AS

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5
Q

A patient, S/P PCI, presents for an elective surgery. What are important concerns?

A

S/P PCI patients are on dual anti-platelet therapy
Continue ASA
Hold clopidogrel 5-7 days
Delay elective surgery
- Balloon angioplasty: at least 2 weeks
- BMS: 6 weeks
- DES: 1 year

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6
Q

A patient with a history of MI presents for an elective surgery.

A

Recent - < 30 days
Prior - > 30 days

*ideally hold elective surgery for at least 4-6 weeks d/t risk of reinfarction

*more important to establish functional capacity post-MI
*if symptomatic –> candidate for revascularization prior to elective SX

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7
Q

What information may be derived from the pressure-volume loop?

A

Pressure-volume loop describes heart function; plots LV pressure vs volume in 1 cardiac cycle

EDV
ESV
SV
EF = SV/EDV

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8
Q

How does the Frank-Starling Law apply to the heart?

A

Length-tension relationship in cardiac muscle fibers (force or tension developed in a muscle fiber depends on the extent to which it is stretched) aka more volume more stretching
~ VR = EDV = SV & CO
*until optimal stretch is reached

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9
Q

How does the Laplace Law relate to the heart?

A

Wall tension = intracavitary pressure x radius / wall thickness
a) pressure overload –> concentric hypertrophy –> INC wall tension during systole
b) volume overload –> eccentric hypertrophy –> INC wall tension during diastole

  • increasing wall tension –> increasing myocardial demand
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10
Q

How to balance myocardial demand and supply?

A

Demand
- wall tension: high preload/afterload
- contractility: high HR

Supply
- O2 content: anemia, hypoxemia
- blood supply: high LVEDP, LVH, high HR

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11
Q

Differentiate systolic from diastolic dysfunction

A

SYSTOLIC - ineffective contraction during heartbeats
- low EF, low exercise tolerance –> more symptomatic

DIASTOLIC - ineffective relaxion in between heartbeats
- impaired ventricular relaxation, decreasing LV compliance –> DX relies on 2D echo
- increased LA filling pressures, becomes atrial-dependent, prone to AF
- sensitive to volume-overload ‘flash pulmonary edema’

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12
Q

Which anesthetic agents have the most profound myocardial depression?

A

Barbiturates
Propofol
High dose volatile agents

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13
Q

Considerations for a patient with decompensated HF presenting for emergent surgery

A

Ideally, optimize for a few days w/ IV inotropes, LV assist device (considered full stomach -> RSI)

Invasive monitors: A-line, PA catheter, TEE
Opioid-based +/- low-dose volatile agent
*Ketamine - will act as a negative inotropic agent

Inotrope: dopamine
Inodilator: dobutamine, milrinone

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14
Q

Describe Intra-Aortic Balloon Pump

A

IABP
- temporary invasive hemodynamic support
- uses helium
- inflates during diastole: to increase diastolic pressure –> increase coronary perfusion
- deflates during systole: to decrease afterload and increase SV
- timing is important: inflated at R wave or before dicrotic notch (AV closure –> diastole)

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15
Q

Hemodynamic goals for aortic dissection

A

Lower the shear stress to avoid rupture:

Preload - increase if acute
Afterload - decrease (SBP <100-120 mmHg)
HR < 60-80 bpm
If w/ AF - control VR

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16
Q

A 75/M with a history of syncopal and anginal episodes presents for elective TURP. On PE, he has a systolic murmur radiating to the carotids. What are the appropriate hemodynamic goals?

A

Aortic Stenosis - fixed outflow obstruction
a) adequate preload - for the non-compliant LV
b) maintain afterload - to ensure coronary perfusion
c) low-normal HR, SR

17
Q

Anesthetic concerns during TAVR

A

Invasive monitors: PA catheter, A-line, TEE
Agents with minimal effects on hemodynamics:
- induction: fentanyl, etomidate, rocuronium
- maintenance: volatile agent e.g. sevoflurane
Maintain BP in the normal range
Rapid pacing at 160-180bpm during the repair/replacement

18
Q

Why is there a need for rapid pacing in TAVR?

A

HR 160-180bpm: low MAP with minimal pulsation –> valvuloplasty and valve replacement can be done

‘clear surgical field’

19
Q

A 25/M was diagnosed with HCOM. What are important hemodynamic targets for him?

A

Maintain preload
Maintain or increase afterload
Decrease contractility
Low-normal HR, SR

20
Q

A 60/F has progressive dyspnea. PE shows a diastolic murmur. On 2D echo, there is LVOT. What are hemodynamic goals?

A

Aortic Regurgitation
GOAL: maintain forward flow & decrease regurgitant volume
- high preload (to augment CO)
- lower afterload > > forward flow
- high normal HR > > limits regurgitant time

21
Q

Most common rheumatic-related valvular lesion

A

Mitral Stenosis
- secondary to rheumatic disease in 80-90%
- critical stenosis occurs 10-20 years after

22
Q

What hemodynamic changes occur in MS?

A
  • LV is underfilled (low EDV) –> low CO
  • LA pressure increases –> increasing PVR –> pulmonary hypertension –> eventual RV failure
  • LA overdistention –> prone to AF
23
Q

Anesthetic considerations for MS

A

1) adequate preload to maintain flow
2) low-normal HR to allow for ventricular filling
3) sinus rhythm for adequate filling (atrial systole accounts for 30% of SV)
4) maintain afterload
5) low PVR: avoid/treat hypoxia, hypercarbia, acidosis

24
Q

Why is the anterior spinal cord at risk for ischemia during thoracic aneurysm repair?

A

Single artery to the anterior spinal cord

25
Q

What are considered contraindications for heart transplant?

A

active malignancy
active infection
high, irreversible pulmonary vascular resistance
alcohol or IV drug abuse

26
Q

Anesthesia considerations during organ retrieval

A

Monitor volume status, arterial & CVP
FiO2 1.0 - optimal for organ viability EXCEPT for lungs (lowest FiO2 to maintain PaO2 > 100 mmHg)
NMDR to prevent spinal reflex-mediated movements
Administer heparin
<4 hours ischemia time - for optimal myocardial function

27
Q

CPB vs ECMO

A

CPB - for a bloodless surgical field
ECMO - temporizing support i.e. VV or VA

28
Q

Considerations during cannulation in CPB

A

aortic cannulation - avoid hypertension (SBP 110 mmHg or less)
venous cannulation - low TV

29
Q

Physiologic effects of CPB

A

When blood comes into contact with the CPB circuit:
- release of stress hormones
- activation of: complement cascade, coagulation cascade, systemic inflammatory response
- platelet activation & dysfunction
- hemodilution

30
Q

Why is cardioplegia necessary in CPB?

A

Cardioplegia induces diastolic electromechanical dissociation
- myocardial requirements are lowered to cellular maintenance
- typically a hyperkalemic solution with metabolic substrates

31
Q

What is the purpose of priming solutions in CPB?

A

Either crystalloid, colloid or blood
- ‘prime’ the circuit (avoid air embolism)

*Lower priming volume –> lower inflammatory response and transfusion requirements
(traditionally 1.5 - 2L vs currently <1L)

32
Q

Heparin dose before start of bypass

A

300-400 u/kg

Reversal with protamine: 1 mg/100 u

33
Q

Checklist prior to termination of CPB

A
  • normothermia (rewarm to 37C)
  • correct acid-base & electrolyte, Hgb/Hct
  • evaluate cardiac rate & rhythm, pacing may be required
  • check ECG and TEE
  • complete de-airing of the heart before removal of cross-clamp
  • resume inotropic support
  • initiate lung ventilation

Target (immediate post-CPB):
- HR 100-120 bpm
- MAP > 65 mmHg
- low CVP, PCWP

34
Q

A post-cardiac transplant patient is scheduled for an elective surgery. What important concerns?

A

Transplanted heart is denervated:
- preload-dependent
- high resting HR
- loss of vagal tone
- delayed response to circulating catecholamines
- indirect-acting agents are ineffective e.g. atropine, ephedrine
- must use direct-acting vasoactive drugs: epinephrine, isoproterenol

Anesthesia (8 decks)

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