Vasoactive Pharmacology Flashcards
Volatile anesthetics also depress ______ reflex control of arterial pressure to varying degrees.
- Baroreceptor reflex
* Isoflurane has the least effect
In a normal heart, volatile anesthetics produce dose related: ?
- Depression in myocardial contractility
- Left ventricular diastolic function decreases
- Decrease left ventricular afterload
- Left ventricular -arterial coupling
- Depression of the SA node (Direct negative chronotrope)
* Desflurane exception - tachycardia with rapid increase in dose
Nitrous oxide causes direct negative inotropic effects, but also produces…?
- modest increases in pulmonary and systemic arterial pressure via a sympathomimetic effect
All drugs used in anesthesia cause hypotension except…?
- Ketamine and Etomidate
What is our goal during anesthesia?
- Goal is to maintain organ and tissue perfusion and avoid hypertensive crisis.
- Brain, Heart, Lungs, and Kidneys are the organs we are most concerned about.
What is autoregulation?
- the intrinsic ability of a circulation to maintain a constant blood flow despite changes in perfusion pressure
In anesthesia, where do we try to maintain patients hemodynamically?
- within 20% of baseline
What are the intrinsic factors of blood pressure control?
- Frank-Starling Mechanism (Stroke Volume)
2. SA and AV node (HR and A-V synchronization)
What are the nervous system factors for blood pressure control?
- Sympathetic
2. Parasympathetic
What are the reflexes of blood pressure control?
- Baroreceptor Chemoreceptor
2. Atrial receptor (Bainbridge)
What are the humoral factors that affect blood pressure control?
- Renin-Angiotensin-Aldosterone System
What is vasopressin (ADH)?
- Potent vasoconstrictor
Where is vasopressin produced?
- Posterior pituitary gland, the heart, and adrenal gland
What is the infusion rate of vasopressin (ADH)?
- 0.01 to 0.04
When is vasopressin used?
- Considered in refractory hypotension (shock, hemorrhage) and patient who are on ACE inhibitors
When alpha 2 receptors are activated on presynaptic neurons, what happens?
- They inhibit neurotransmitter release from presynaptic neurons
Where are alpha 1 receptors found and what is their effect?
- Location: Vascular smooth muscle (peripheral, renal and coronary circulation)
- Effect: Vasoconstriction (increase SVR)
Where are Beta 1 receptors found and what is their effect when stimulated?
- Location: Heart
- Effect: Increased heart rate and increased contractility (increasing cardiac output)
Where are Beta 2 receptors located and what is their effect?
- Location: Vascular smooth muscle (peripheral and renal circulation)
- Effect: Vasodilation (reducing systemic vascular resistance)
Where are Beta 3 receptors found and what are their effects?
- Location: Gall Bladder and adipose tissue
- Effect: May play a role in lypolysis and brown fat thermogenesis
What receptors does Phenylephrine work on?
- Mainly Alpha 1
What receptors does Epinephrine work on?
- Alpha 1, Alpha 2, Beta 1, Beta 2
What receptors does Ephedrine work on?
- Alpha 1, Beta 1, mild Beta 2
What receptors does Norepinephrine work on?
- Alpha 1, Alpha 2, Beta 1
What receptors does Dopamine work on?
- Mainly DA 1 and DA 2
- Alpha 1, Alpha 2, Beta 1, mild Beta 2,
Phenylephrine
- Non-catecholamine with predominately Alpha 1 agonist activity
- Primarily a vasoconstrictor used to increase blood pressure due to vasodilator effects of anesthesia agents.
- Reflex bradycardia
Phenylephrine: What is the dose for small intravenous boluses?
- 50-100 mcg (0.5-1.0 mcg/kg)
What is the infusion rate for phenylephrine?
- 0.25 to 1.0 mcg/kg/min
Ephedrine
- Non-catecholamine indirect and direct acting Alpha and Beta agonist
- Works by increasing the release of NE at the synaptic junction and similar direct Alpha and Beta effects as epinephrine
- Increase BP, HR, contractility, CO, and bronchodilator
- Longer duration of action and less potent than epinephrine
- Direct stimulation of the CNS (may increase MAC)
- Tachyphylaxis b/c you deplete NE stores
Ephedrine: What is the IV bolus dose?
- 2.5 to 10 mg (pediatric 0.1 mg/kg)
* Dilute for IV administration
Ephedrine: What is the IM/SQ dose?
- 25-50 mg (Onset may be 10-20 min)
Epinephrine
- Endogenous catecholamine synthesized in adrenal medulla
- Alpha 1 = Alpha 2 ; Beta 1 = Beta 2
- Peripherally vasoconstricts, inotrope, chronotrope, relaxation of peripheral vessels may lead to decrease in diastolic pressure (overall increases MAP)
- Increased oxygen demand on the heart
- Principle treatment in anaphylaxis
Epinephrine: What is the dose in a code?
- 1 mg IV
Epinephrine: What is the IV anaphylaxis dose?
- 0.3 - 0.5 mg IV
Epinephrine: What is the IV gtt dose?
- 0.1 to 1.0 mcg/kg/min
* 1 mg/250 (4mcg/ml)
Norepinephrine
- Direct Alpha 1 stimulation with little Beta 2 activity produces intense vasoconstriction
- Alpha 1 = Alpha 2 ; Beta 1»»Beta 2
- Increased contractility. Increased afterload and some reflective bradycardia
- Does not have the advantages of Beta 2 stimulation (renal and GI blood dilation)
- Extravasation can cause tissue necrosis
Norepinephrine: What is the bolus dose?
- 0.1 mcg/kg (short duration)
Norepinephrine: What is the infusion dose?
- 2-20 mcg/min, or 0.01 to 3 mcg/kg/min (higher rates in septic shock)
Dopamine
- Endogenous non-selective direct and indirect adrenergic and dopaminergic agonist which varies with dosage
Dopamine: What is the Beta 1 dose?
- 2-10 mcg/kg/min
Dopamine: What is the Alpha effects dose?
- > 10 mcg/kg/min
Dopamine: What is the Dopaminergic effects dose?
- 0.5-2 mcg/kg/min
Activation of Alpha 1 and Beta 2 increase….?
- Glucose release into the circulation
Beta 2 activation also…?
- Promotes the uptake of potassium into cells
What are the two Beta selective inotropes?
- Isoproterenol
- Dobutamine
Isoproterenol
- Potent Beta 1 agonist, little effect on Alpha
- Positive chronotrope and inotrope
Dobutamine
- Initially considered as Beta 1 selective, but more complicated than that
- Positive inotrope over chronotrope when compared to isuprel
- Some Alpha 1
Esmolol
- Beta 1 blocker
Esmolol: What is the intermittent dose?
- Up to 1 mg/kg
Hydralazine
- Direct arteriole vasodilation
Hydralazine: What is the intermittent dose?
- 10-40mg IV q4
Labetalol
- Alpha 1 blocker (primarily)
- Beta 1 blocker
- Beta 2 blocker
Labetalol: What is the intermittent dose?
- 10-40 mg IV q4
Metoprolol
- Beta 1 blocker
Metoprolol: What is the intermittent dose?
- 1.25-5 mg IV q6
