Does phenylephrine cause reflex bradycardia?
Learning Objectives: Phenylephrine is a synthetic catecholamine that increases systemic vascular resistance via activation of alpha receptors. A known side effect of phenylephrine is reflex bradycardia due to activation of the baroreceptor.
How does phenylephrine affect heart rate?
Phenylephrine is an α-receptor agonist without β-agonist activity. Its administration causes vasoconstriction and an increase in arterial blood pressure, and a decrease in heart rate. Cardiac output may decrease13,27,28 or increase.
What is the mechanism of action for phenylephrine?
Phenylephrine is an agonist of α1-adrenoceptors. Nasal decongestant action is mediated by activation of α1-adrenoceptors in the arterioles of the nasal mucosa. This causes vasoconstriction, which leads to decreased edema and increased drainage of the sinus cavities.
How does phenylephrine work for shock?
Phenylephrine is a selective alpha1 -adrenergic receptor agonist that is used primarily in anesthesia to increase blood pressure. Although the data are limited, studies have found phenylephrine to increase MAP in patients who were septic and hypotensive with increased oxygen consumption.
What causes reflex bradycardia?
Via the vagus nerve, the parasympathetic nervous system stimulates neurons that release the neurotransmitter acetylcholine (ACh) at synapses with cardiac muscle cells. Acetylcholine then binds to M2 muscarinic receptors, causing the decrease in heart rate that is referred to as reflex bradycardia.
Why does phenylephrine decrease cardiac output?
Most textbooks and review articles contain a table showing a reduction in cardiac output from phenylephrine (example above). The usual explanation is that phenylephrine increases systemic vascular resistance (afterload), which makes it harder for the heart to pump blood forward.
Why does phenylephrine cause decreased cardiac output?
Conclusion: impact of phenylephrine on cardiac output is related to preload dependency. When the heart is preload independent, phenylephrine boluses induce on average a decrease in cardiac output. When the heart is preload dependent, phenylephrine boluses induce on average an increase in cardiac output.
What is the difference between phenylephrine HCL and pseudoephedrine HCL?
Phenylephrine and pseudoephedrine are both adrenergic agonists. Phenylephrine has primarily an affinity to only alpha-adrenergic receptors, while pseudoephedrine has an affinity to both alpha- and beta-adrenergic receptors. Their side effect profiles are very similar.
How does phenylephrine treat hypotension?
Phenylephrine is a selective α1-adrenergic receptor agonist that increases blood pressure mainly by increasing systemic vascular resistance, without an associated increase in myocardial contractility.
How does phenylephrine reduce cardiac output?
As a pure α-agonist, phenylephrine is conventionally considered to solely induce arterial vasoconstriction and thus increase cardiac afterload but not cardiac preload. In specific circumstances, however, phenylephrine may also contribute to an increase in venous return and thus cardiac output (CO).
How does atropine cause reflex bradycardia?
Background: Low-dose atropine causes bradycardia either by acting on the sinoatrial node or by its effects on central muscarinic receptors increasing vagal activity.
What is phenylephrine HCl used for?
Phenylephrine is used for the temporary relief of congestion or stuffiness in the nose caused by hay fever or other allergies, colds, or sinus trouble. It may also be used in ear infections to relieve congestion. This medicine may also be used for other conditions as determined by your doctor.
How does pseudoephedrine HCl work?
Pseudoephedrine works by reducing the swelling of blood vessels in your nose. This helps mucus and air flow more freely in the cavities in your nose (sinuses), helping you to breathe more easily. Pseudoephedrine starts to work in 15 to 30 minutes, but you should feel a lot better after 30 to 60 minutes.
How does norepinephrine cause reflex bradycardia?
A reflex bradycardia results from the infusion of low dose noradrenaline, as the vagal baroreceptor reflex forces a compensatory slowing of the sinus node. However, as the dose increases, the receptor selectivity decreases.
What is atropine mechanism of action?
Mechanism Of Action Atropine competitively blocks the effects of acetylcholine, including excess acetylcholine due to organophosphorus poisoning, at muscarinic cholinergic receptors on smooth muscle, cardiac muscle, secretory gland cells, and in peripheral autonomic ganglia and the central nervous system.
What is the difference between phenylephrine HCl and Pseudoephedrine HCL?
What happens if you take too much phenylephrine HCL?
Symptoms of overdose may include: severe dizziness/fainting, hallucinations, fast/irregular heartbeat, slow/shallow breathing, vomiting, seizures. If this product has been prescribed, do not share this medication with others. This medication is for temporary use only.
Is pseudoephedrine a vasoconstrictor?
1. How it works. Pseudoephedrine is a decongestant that constricts (shrinks) dilated blood vessels within the nose, relieving congestion. It causes vasoconstriction by stimulating primarily alpha-adrenergic receptors.