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BCC > Vasoplegia/LV/RV Failure > Flashcards

Vasoplegia/LV/RV Failure Flashcards

1
Q

What is the definition of vasoplegia?

A

Low SVR in the presence of normal or high cardiac output; SVR < 800 dynes with CI > 2.2 L/min/m2

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2
Q

Where does central regulation of vascular tone occur?

A

Locus ceruleus (SNS) and the hypothalamic-pituitary adrenal axis in the paraventricular nucleus

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3
Q

What are the receptors for vascular tone?

A

Adrenergic (epi, norepi, DA, phenylephrine) + vasopressin + angiotensin receptors

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4
Q

What occurs at the cellular level with vasoplegia?

A

Desensitization of the adrenergic, vasopressin, and angiotensin receptors via phosphorylation of the G-protein coupled receptors

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5
Q

How is vascular tone regulated at the intracellular level?

A

Via nitric oxide; NO synthetase expression is enhanced -> increased NO production -> vasodilation

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6
Q

What receptors does epi hit? Norepi? Phenylephrine?

A

Epi = alpha1, beta1, and beta 2; Norepi = alpha1 and beta1; Phenylephrine = alpha1

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7
Q

How does methylene blue work for vasoplegia?

A

Inhibits nitric oxide synthetase (for less NO) and inhibits guanylate cyclase (normally inhibits GMP buildup and promotes smooth muscle vasodilation)

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8
Q

Which patients should you avoid methylene blue in?

A

Patients with G6PD deficiency -> can cause serotonin syndrome when used with other meds that increase serotonin (i.e. SSRI, TCA, fentanyl, tramadol, cocaine)

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9
Q

How does hydroxycobalamin work in vasoplegia?

A

Inhibits NO synthetase, nitric oxide, and hydrogen sulfate

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10
Q

What are the side effects of hydroxycobalamin?

A

Chromaturia (orange/red urine) + erythema + headache + photosensitivity for 2 weeks + abnormal lab values

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11
Q

What abnormal lab values can you see with hydroxycobalamin?

A

Transient hypokalemia (usually in patients with B12 deficiency) + elevated hemoglobin and basophils (12-16 hours) + elevated creatinine, glucose, and alk phos (24 hours) + LDH, PTT, INR/PT are unreliable (24 hours)

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12
Q

How does angiotensin II work with vasoplegia?

A

It inhibits renin; hyperreninemia is associated with hemodynamic instability post bypass and replacing angiotensin II can help with vascular tone

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13
Q

What should you dilute methylene blue with?

A

Anything but normal saline as it can cause precipitation and decreased solubility

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14
Q

How much methylene blue should you give for vasoplegia?

A

1-2 mg/kg bolus followed by 0.25-0.5 mg/kg/hr infusion

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15
Q

How much hydroxycobalamin should you give for vasoplegia?

A

5mg bolus and can repeat if needed

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16
Q

What is dromotropy?

A

Looking at conduction velocity

17
Q

How do catecholamines work?

A

Activates beta1 receptors (increased chronotropy, dromotropy, and release of renin)

18
Q

How does dobutamine work?

A

Beta1 and beta2 agonist + increases myocardial O2 consumption

19
Q

How does dopamine work?

A

Intermediate doses activates beta1 receptors (3-10 mcg/kg/min) while higher doses (10-20 mcg/kg/min) activates alpha1 receptors

20
Q

How does epinephrine work?

A

Alpha1, beta1, and beta2 receptor agonist + increased coronary blood flow (via increased diastolic pressures and local cardiomyocyte vasodilators) + increased pulmonary blood flow (via pulmonary vasoconstriction)

21
Q

How does isoproterenol work?

A

Beta1 and beta2 agonist + potent systemic vasodilation + mild pulmonary vasodilation

22
Q

How does norepinephrine work?

A

Potent alpha1 agonist with some beta1 effects + power vasoconstrictor + increased coronary blood flow (via increased diastolic pressure and local vasodilators in coronaries)

23
Q

What is the mechanism of action for milrinone?

A

Phosphodiesterase inhibitor -> increases cAMP by inhibiting PDE -> increases contractility and CO + decreases SVR/PVR + decreased myocardial wall tension

24
Q

How does levosimendan work?

A

Augments sensitization of troponin C to calcium + increases coronary perfusion via coronary vasodilation + increases contractility without increasing O2 demand

25
Q

What are risk factors for postop low cardiac output syndrome?

A

Age > 65 + LVEF < 50% + on-pump CABG + DM + CKD + CPD duration + emergency surgery + incomplete revascularization

26
Q

What are some echocardiographic findings of RV failure?

A

RV free wall hypokinesia + RV dilation + TAPSE < 16mm

27
Q

What are some causes of chronic RV dysfunction?

A

Left-sided heart disease (most common) + chronic lung disease + pulm HTN + congenital heart disease + right-sided valvular disease + cardiomyopathies

28
Q

How can a properly placed LVAD cause RV dysfunction?

A

The LVAD can uncover preexisting RV dysfunction by increasing venous return to the RV + LV size decreases so the IV septum shifts

29
Q

How does bosentan and ambrisentan work?

A

Endothelin receptor antagonists which can help with pulmonary vasodilation; taken as an oral pill

30
Q

How do inhaled pulmonary vasodilators help with RV function?

A

Reduces RV afterload (decreased PVR) + improved V/Q mismatch (blood flow increases to well-ventilated areas only)

31
Q

How does inhaled nitric oxide work?

A

Increases cellular cGMP -> vasodilates smooth muscle

32
Q

Why does iNO have such a short half life?

A

NO is scavanged by hemoglobin as soon as it diffuses into the blood

33
Q

What are possible side effects of iNO?

A

Methemoglobinemia (inhaled NO combines with hemoglobin to form nitrosylhemoglobin which is oxidized to metHb) + tachyphylaxis + thrombocytopenia (10% of patients) + lung injury from nitrous dioxide formation + increased risk of lung infection

34
Q

Can iNO cause AKI?

A

A meta-analysis suggests only at higher doses (>20ppm) for prolonged periods of time (>7 days)

35
Q

How does inhaled epoprostenol work?

A

Synthetic prostacyclin -> stimulates adenyl cyclase -> vasodilation

36
Q

What is the normal starting dose of iNO? Of inhaled epoprostenol?

A

iNO = 20 ppm; Inhaled epoprostenol = 50 nanograms/kg/min

37
Q

What is the half life of inhaled epoprostenol?

A

2-5 min

38
Q

What pulmonary artery pulsatility index value is concerning for RV failure?

A

PAPi < 1.85

39
Q

What RV stroke work index value is concerning for RV failure?

A

RVSWI < 400 mmHg*mL/m2

BCC (29 decks)

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