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Anesthesia Pharmacology > Vasopressors > Flashcards

Vasopressors Flashcards

1
Q

What are the three endogenous catecholamines?

A

Epi, Norepi, Dopamine

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2
Q

Where is epinephrine synthesized, stored, and released from?

A

Adrenal Medulla

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3
Q

What are Epi’s natural regulatory functions on the heart?

A

Increases Myocardial Contractility and HR

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4
Q

What are Epi’s effects on the lungs?

A

Bronchial smooth muscle dilation due to activation of the Beta-2 Gs Protein.

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5
Q

What is the series of events when Epi binds to the Beta-2 Gs Receptor in the lung?

A

finish…….Protein Kinase A inhibits MLCK (myosin light chain kinase) MLCK is needed for smooth muscle contraction

Inhibiting MLCK = relaxation

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6
Q

MOA of Epinephrine

A

Beta 1= Beta 2 Agonist @ lower doses
@ higher doses Alpha 1, 2(b) Agonist

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7
Q

Why can’t epinephrine be taken PO

A

Rapid Metabolism - significant first pass metabolism in liver and GI mucosa

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8
Q

Does epi cross the blood-brain barrier?

A

Normally, no, has poor lipid solubility. Maybe could at very high concentrations. But overall, lacks cerebral effects.

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9
Q

Epinephrine can be given via?

A

IV, IO, IM, SQ

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10
Q

Clinical uses for epinephrine?

A

-Tx for anaphylaxis
-Tx for severe asthma or bronchospasm (Beta-2)
-CPR 1mg q3-5min
-Hemodynamic Support (Inotropy, HR, SVR, SV)
-Added to local anesthetics to decrease systemic absorption.

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11
Q

Natural functions of epinephrine upon release into circulation include:

A

-Regulation of myocardial, contractility and heart rate
-Vascular and bronchial smooth muscle tone
-Glandular secretions
-Metabolic processes, such as glycogenolysis and lipolysis

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12
Q

What are the effects of Alpha-1 Gq stimulation in the vasculature?

A

Arterial and Venous Constriction
Smooth muscle within the blood vessels constricts.

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13
Q

What are the effects of Beta-1 Gs stimulation in the heart?

A

Increase HR, Inotropy,

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14
Q

What does epinephrine do to pulse pressure? Why?

A

Increases pulse pressure.
Beta 1 stimulation increases SBP
Beta 2 stimulation decreases DBP (skeletal muscle vessel dilation)
Widening/increasing the pulse pressure

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15
Q

How does Cardiac Beta-1 (Gs) Activation increase HR?

A

Accelerates rate of spontaneous phase 4 depolarization (leaky sodium and calcium channels-automaticity)

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16
Q

Which endogenous catecholamine has the most metabolic effects?

A

epinephrine

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17
Q

Bolus and Infusion dose of Epinephrine

A

Bolus: 5-10mcg

Infusion: 1-16mcg/min ;
0.1-1mcg/kg/min

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18
Q

What are Epinephrine’s effects on Beta-2 (Gs) receptors in the vasculature?

A

Beta-2 Activation via Epi promotes VasoDilation of skeletal muscle vessels. [NOT vascular smooth muscle]
(AKA more CO to skeletal muscle to run away)

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19
Q

How does Epinephrine increase the contractility of the heart?

A

Through Beta-1 (Gs) receptor activation of the cardiac myocytes.

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20
Q

What are sympathomimetics (sympathomimetic drugs)?

A

Drugs that mimic the actions of the sympathetic nervous system, so drugs the mimic endogenous epinephrine, norepinephrine, and dopamine.

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21
Q

The endogenous catecholamines are synthesized in a series of reactions from which amino acid?

A

Phenylalanine

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22
Q

The endogenous catecholamine chemical structure is derived from / shares a core with what chemical?

A

Beta-Phenylethylamine

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23
Q

What are epi’s effects on myocardial oxygen consumption?

A

Increase

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24
Q

What are epinephrine’s metabolic effects?

A

NET EFFECT: Increase glucose levels and Lipolysis. At first there is decrease insulin levels to allow glucose to accumulate. Then increased insulin levels so muscles can use that glucose. There is transient hyperglycemia.

Through Beta-1 receptor stimulation: cardiac muscle does minimal glycogenolysis.

Through Beta-2 in the Liver: there is an increase in glycogenolysis.
Through Beta-2 in the Pancrease: there is an increase in insulin production.

Through Beta-3 receptor stimulation: in the adipose tissue, there is an increase in lipolysis. (Increase Protein Kinase A leads to increase Lipase activity)

Through Alpha-2 in the Pancrease: Inhibit insulin release to allow glucose to accumulate.

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25
What is epinephrine's effect on the GI system?
Smooth muscle relaxation - decreased gastric motility via Beta-3 (Gs) receptor activation
26
Does Norepi activate Beta 2 receptors?
NO. So it behaves more like an alpha agonist with Beta-1 activity.
27
What is the precursor to norepinephrine and epinephrine in the peripheral nervous system during catecholamine synthesis?
Dopamine
28
Endogenous and low-dose exogenous Dopamine activates what receptor in the renal system? What is its effect?
Renal Vasodilation via the D1 (Gs) receptor
29
Does epinephrine have a higher, lower, or equal affinity to beta-1 and beta-2 receptors?
Equal!
30
IV and IM epinephrine dose for anaphylaxis/allergic reaction?
0.1-0.25mg IV (100-250mcg) 0.3mg IM (300mcg)
31
Pediatric epinephrine dosing?
Cardiac Arrest: 0.01mg/kg Infusion: 0.1-1mcg/kg/min Bolus: 1-2mcg IVP common starting dose
32
At what dose of epinephrine does skeletal muscle, beta-2 activation, predominate over alpha-1 activation?
Low doses ~ 10mcg/min
33
If cardiac ischemia is occurring, how will the administration of epinephrine affect this?
If given to a patient suffering from cardiac ischemia, it may worsen this ischemia and paradoxically decrease cardiac output due to myocardial depression. Caution should be used when using epinephrine in patient with active cardiac ischemia.
34
The increase in contractility with epinephrine will not lead to increased cardiac output if the heart does not have adequate ________?
Preload
35
What are epinephrine effects on coagulation?
Coagulation is accelerated via increase platelet aggregation and Factor 5 (cofactor that converts Prothrombin to Thrombin). A hypercoagulable state present during the intraoperative and postoperative period may reflect stress associated release of epinephrine.
36
Ocular effects of epinephrine
Pupil dilation - mydriasis
37
Where is norepinephrine synthesized and stored?
Predominately in post – ganglionic sympathetic nerve endings. Released with sympathetic nerve stimulation. ~20% comes from the adrenal medulla. (80% Epi from adrenal medulla)
38
What receptors does norepinephrine stimulate?
Alpha-1 Alpha-2 Beta-1
39
The primary utility of norepinephrine, is as a potent _________, to increase total peripheral vascular resistance, and mean arterial pressure
Vasoconstrictor
40
What medication is the first line agent in the treatment of refractory hypotension during severe sepsis?
Norepinephrine
41
Why is the use of norepinephrine as an inotropic agent limited?
Potent vasoconstrictor which increases the SVR, which reduces the Beta-1 contractility effects.
42
Large amounts of epinephrine can lead to?
Excessive vasoconstriction and decrease perfusion of renal, splanchnic, and peripheral vascular beds which may lead to end-organ hypoperfusion and ischemia.
43
Adult IV dosing for Norepinephrine
Bolus: 8-16mcg Infusion: 0.02-1mcg/kg/min 1-30mcg/min (non-weight based)
44
IV Pediatric (off-label) dosing for Norepi
0.05-2mcg/kg/min
45
Which drug, epinephrine or norepinephrine, would be more useful in a patient with RV failure that needs more inotropy?
Epinephrine. It has more Beta 1 activity and less Alpha 1 activity. Norepi has more alpha-1 activity - this creates an increase in Pulmonary vascular resistance, more SVR, and increased preload which can have negative effects in a failing RV. But there is little to no increase in CO because of the increased SVR.
46
If epinephrine and norepinephrine have equal potency to the beta-1 cardiac receptors, why does the one medication over the other have a more pronounced increase in cardiac output/ contractility?
Because epinephrine does not have as strong of an Alpha-1 effect, so it's increasing contractility against less resistance compared to Norepi.
47
What are some side effects of high concentrations of epinephrine?
-Arrhythmias due to excessive beta one activation -End-organ ischemia
48
Dopamine is an endogenous catecholamine that regulates?
Cardiac, vascular, and endocrine functions It is an important neurotransmitter in the central and peripheral nervous system
49
Despite identical IV infusion rates, there may be a ___-_____ fold variability in plasma dopamine concentrations produced even in healthy individuals with normal drug metabolism
10-75 fold variability !
50
Between Epi and Norepi: which causes a greater increase in systemic vascular resistance and diastolic blood pres- sure, mean arterial pressure, and systolic blood pressure
Norepi
51
What are the relative receptor affinities for Dopamine?
= affinity for D1 and D2 > Beta > Alpha
52
Where is dopamine released?
Released from the post-ganglionic, sympathetic nerve
53
Which drug is associated with more dose related sinus tachycardia, and potential to cause ventricular arrhythmias than dobutamine or epinephrine?
Dopamine May predisposed to myocardial ischemia by precipitating tachycardia, increasing contractility, increasing afterload, and precipitating coronary artery vasospasm
54
Adult and Pediatric IV Dosing For Dopamine
Adult: 2-20mcg/kg/min Peds: 2-20mcg/kg/min Same Same!
55
What are the effects of D-1 (Gs) receptor activation in the renal system?
Renal vasodilation can stimulate urine production, despite a shock state. Not beneficial in oliguric patients.
56
Why does dopamine require a continuous infusion?
Rapid metabolism of dopamine with a elimination half-life of 1-2min mandates its use as a continuous infusion to maintain therapeutic plasma concentrations.
57
Clinical uses for dopamine?
To increase cardiac output in patients with decrease contractility, low systemic, blood pressure, and low urine output that might be present after cardio, pulmonary bypass or with chronic heart failure. (Less used nowadays)
58
Dopamine is unique among the catecholamine because it is able to simultaneously:
Increase myocardial contractility (Beta-1 Gs) Increase renal blood flow (D-1 Gs) Increase glomerular filtration rate (D-1 Gs) -Increase sodium excretion and Increase urine output (D-1 Gs) due to inhibiting Aldosterone.
59
Do patients have better outcomes using "renal dosing" of Dopamine?
No. That practice and theory has not been supported.
60
One instance in which dopamine is often still used is? why?
Hypotension with bradycardia. Has greater positive chronotropic effects than other vasopressors. It's beta-1 activity is greater than its alpha-1 activity.
61
What are two common synthetic catecholamines?
Isoproterenol (Isuprel) and Dobutamine (Dobutrex)
62
What is the most commonly used Direct Alpha-1 Agonist?
Phenylephrine (Neosynephrine)
63
Phenylephrine mimics the effects of Norepinephrine but is _____ potent and _____ lasting.
Less potent and longer lasting
64
What is the mechanism of action of Phenylephrine?
Primary effect - Stimulates Alpha-1 Adrenergic Receptors by a direct effect. Small indirect effect due to its ability to evokle the release of norepinephrine.
65
According to Dr. C's powerpoint, Phenylephrine primarily causes ______ rather than ______ constriction
Venoconstriction rather than arterial constriction. (But it does do BOTH).
66
IV Dosing for Phenylephrine
Bolus: 50-200mcg IV Infusion: 0.5-1.4mcg/kg/min or 20-100mcg/min
67
How long does a bolus of Phenylephrine last for?
5-20 minutes
68
Phenylephrine is believed to be particularly useful in patients with coronary artery disease and in patients with aortic stenosis because?
it increases coronary perfusion pressure without chronotropic side effects, unlike most other sympathomimetics. (Remember, in Aortic Stenosis - afterload is fixed on the stenotic lesion. Increasing SVR down steam of the lesion will not drastically further impede output. And if you do get reflexive bradycardia, AS, thats not a bad thing, gives heart more time to full.)
69
What is a PO Alpha-1 Agonist?
Midodrine!
70
What medication is a nasal alpha-1 agonist we might use prior to a nasal intubation?
Oxymetozoline
71
What cardiac reflex can become activated when using phenylephrine?
Baroreceptor Reflex. Senses higher blood pressure and results in decreasing HR via vagus nerve.
72
Phenylephrine keeps the heart rate stable or lowers it, so therefore it can be helpful for hypotensive patients in which increased heart rate would be detrimental. What are two clinical situations where this would be desirable?
Patients who are hypotensive due to rapid heart rate such as Afib RVR and Patients with Aortic Stenosis
73
What is the MOA of Isoproterenol?
Potent Non-Selective Beta Agonist. (Beta-1 & Beta-2)
74
Isoproterenol Beta Receptor activity is ______ more potent than epinephrine and at least _____ time more active than norepinephrine
2-3x more potent than Epi 100x more active than Norepi
75
Like Phyenylephine, does Isoproterenol cause compensatory baroreceptor reflex activation?
No. Isoproterenol has very little Alpha-1 activity - MAP does not increase much, if at all, which would stimulate the baroreceptor reflex.
76
Effects of Phenylephrine on pulse pressure?
No change in Pulse Pressure. Alpha only stimulation.
77
Effects of Isoproterenol on pulse pressure?
Increase. Like Epi, stimulates Beta-1 which increases SBP and stimulates Beta-2 which decreases DBP leading to widened pulse pressure.
78
How does pulse pressure relate to mean arterial pressure?
Pulse Pressure contributes directly to MAP, but only one-third of it (because diastole lasts longer than systole) A widened pulse pressure (e.g. 160/60 = PP of 100) may only modestly increase MAP. MAP=93 A narrow pulse pressure (e.g. 90/70 = PP of 20) means a lower MAP, even if DBP is okay. MAP=76 Even though 160/60 looks weird with a low diastolic, the MAP is still higher than 90/70—thanks to that large pulse pressure.
79
In general, what is a normal pulse pressure range?
30-50mmHg
80
While MAP tells us about organ perfusion, pulse pressure tells you more about?
Stroke volume and vascular compliance -Systolic BP is strongly influenced by stroke volume (how much blood is ejected from the left ventricle per beat) -Diastolic BP reflects vascular tone and how well the arteries can maintain pressure during diastole
81
When using Isoproterenol, Cardiac Output might increase but the MAP may decrease. Why?
B1 activation increases HR and Contractility. CO = HR x SV Beta 2 activation decreases DBP via skeletal muscle vasodilation. MAP = (SBP + 2xDBP)/3
82
Why does isoproterenol require a continuous infusion?
Liver metabolism by COMT (catechol-O-methyltransferase) is rapid.
83
IV dose for Isoproterenol
Infusion: 1-5mcg/min
84
Clinical uses for Isoproterenol
Used less often now that we have Dobutamine. Effective in increasing the heart rate in adults, experiencing heart block can also increase heart rate before insertion of temporary or permanent pacemaker.
85
Dobutamine is a synthetic catecholamine derived from?
Isoproterenol, consisting of a 50:50 racemic mixture of the two stereoisomers
86
MOA of Dobutamine
Beta Agonist Potent Cardiac Beta-1 effects with weaker Beta-2 effects. Effect on receptors increases as the dose increases. Its effect on alpha receptors increases at higher doses.
87
Why does Dobutamine require an infusion? What is the dose for the infusion?
Rapid metabolism of dobutamine (half-life of 2 minutes) necessitates its administration as a continuous infusion of 2 to 10 mg/kg/minute to maintain therapeutic plasma concentrations.
88
While Dobutamine primarily effects contractility by stimulating Beta-1 Cardiac Myocytes, how does it increase HR as well?
Beta-1 Receptors in the cardiac conduction cells are also stimulated. Stimulates Sinoatrial Node Automaticity as well as AV and Ventricular Conduction (like epi).
89
Clinical uses of Dobutamine. Can it be paired with Vasodilators?
Used to improve CO in patients with CHF and for weaning from CPB. Good choice for pts with decreased HR fxn who have high or normal blood pressure. Can be combined with vasodilators to reduced afterload and optimize CO
90
Adverse effects of Dobutamine
Use may be limited by the occurrence of tachyarrhythmias (Occur more frequently at higher doses, pts with underlying arrhythmias, or HF)
91
What kind of sympathomimetic is Ephedrine?
Mixed - Direct and Indirect Acting Sympathomimetic
92
MOA of Ephedrine
Direct: Nonselective Alpha and Beta Agonist Indirect: Stimulate the release of endogenous Norepinephrine from post-synaptic nerve terminals
93
IV Adult Dose of ephedrine
5-10mg IV
94
Clinical uses of Ephedrine
To increase systemic blood pressure in the presence of sympathetic nervous system blockade produced by regional anesthesia or hypotension due to inhaled or injected anesthetics.
95
Why does ephedrine have a longer duration of action than catecholamines? What is its duration of action?
Because it is not a catecholamine - which makes it resistant to Monoamine Oxidase metabolism DOA: 15-1.5 hours depending on dose
96
Cardiovascular effects of Ephedrine
Beta-1 Activation: Increased SBP, HR, Contractility -> increased CO Alpha-1: Vasoconstriction
97
Cardiovascular effects of Ephedrine are similar to Epinephrine but its systemic blood pressure elevating effects are _____ intense and last ~10 times ______
Less intense but last ~10x longer
98
In the presence of Beta Blockade, the CV effects of ephedrine may resemble?
Alpha Adrenergic Stimulation
99
A second dose of Ephedrine produces a less intense systemic blood pressure response than first dose, why?
Tachyphylaxis. Decreased effectiveness with each dose.
100
What is a patient population ephedrine may not be as effective in?
Patients in catecholamine depleted states such as sepsis, CHF, or someone who uses chronic stimulants. Ephedrine partially uses the body's own catecholamine stores.
101
Which electrolyte disturbance might you expect to see after epinephrine administration?
Hypokalemia. Epinephrine stimulates β2 receptors on skeletal muscle cells This activates the Na⁺/K⁺-ATPase pump Result: K⁺ is pumped from the blood into cells (especially muscle) K⁺ (extracellular)⟶K⁺ (intracellular) ➡️ This causes a drop in serum potassium (hypokalemia), even though total body potassium hasn’t changed.

Anesthesia Pharmacology (23 decks)

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