What blood pressure response will you see with stimulation of alpha receptors in the blood vessels?
Increased Diastolic BP
What blood pressure response will you see with stimulation of beta receptors in the CV system?
Increased Systolic BP
What beta-2 activation response will you see in the skeletal muscle blood vessels with Epinephrine?
Skeletal muscle vessels dialate
Dosing of Epinephrine?
Asystole = 1mg IV q 3-5min
Hypotension = 1-10 mcg/min IV infusion
Bronchodilator = 0.1-0.5mg IM/SQ q 10-15 min
Why might you see a fall in HR or no increase in HR with Norepi?
The brain senses an increase in BP so it activates the PSNS to stimulate Muscarinic receptors located in the heart - compensatory
What is the RULE OF 6?
6 x weight(kg) x desired dose/desired IV rate = amount of med (mg) to add to 100ml fluid
Isoproterenol's affinity for alpha & Beta receptors?
Potent Beta agonist; Beta-1>Beta-2>>>>>>>>alpha
Response seen in the heart with Isoproterenol?
Increases inotropy & Chronotropy
Increased Cardiac Output
Fall in diastolic with slight increase or decrease in systolic
Dosing of Isoproterenol?
Arrhythmias = 5mcg/min IV infusion initially & titrate
Shock = 0.5-5mcg/min IV infusion & titrate
Dosing for Dopamine?
LOW= 1-3mcg/kg/min (Dopa receptor activation)
INTERMEDIATE= 3-10mcg/kg/min (Dopa & Beta-1)
HIGH= >10mcg/kg/min (Dopa, Beta & Alpha)
Cardiac effects seen with Dobutamine?
Increased Inotropy & Chronotropy by activating selective beta-1 receptors
Why do you see bradycardia with Methoxamine?
Because it is a potent vasoconstrictor, the brain senses the increase in BP and activates the PSNS to stimulate muscarininc receptors in the heart to dec. HR
Why is Midodrine not used clinically?
Used to treat postural HYPOtension, but will see HYPERtension when pt. is supine
MOA of Ephedrine?
Orally active Direct acting sympathomimetic
Releases stored catecholamines
Mimics epinephrine (but doesn't increase BP as much)
Why have we been able to modify ephedrine and come up with new meds?
It has 2 points of chirality allowing for isomers to be derived.
Why do you not want to use Xylometazoline & Oxymetazoline long term?
Can cause rebound congestion b/c alpha receptors that are being stimulated get down regulated
Why may you see a Dec. in BP with increased used of Xylometazoline & Oxymetazoline?
You get good absorption systemically, it crosses BBB and can see effects of Alpha-2 stimulation in the brain leading to a dec. BP (like clonadine)
MOA of Methamphetamine
Indirect acting Sympathomimetic that has a higher ratio of central to peripheral actions
MOA for Methylphenidate & Pemoline and use?
Indirect Sympathomimetic - stimulant used in children for ADHD
MOA of Cocaine?
Sympathomimetic that readily enters CNS and inhibits dopamine re-uptake into pre-synaptic neurons in the pleasure centers- Also alpha stimulation seen causing vasoconstriction
NOT a drug but rather a metabolite of tyrosine
Indirect sympathomimetic (similar to norepi)
Releases stored catecholamines
Effects seen in blood vessels with Alpha receptor stimulation
Vasoconstriction, Inc. SVR & Inc. DBP
Effects seen in blood vessels with Dopamine receptor stimulation
D1 = Vasodilation in renal, coronary, visceral, & Cerebral vessels
Effects seen in the Heart with Beta Receptor Stimulation
Inc. Inotropy & Inc. Chronotropy
Beta 1 - is dominant
Effects seen in the Heart with Alpha receptor stimulation
Not many receptors present = no real effect
Effects seen in the eye with Alpha Stimulation
Pupil dilation via constriction of iris radial muscle & inc. in aqueous humor
Effects seen in the eye with Beta Stimulation
Pupil dilation via relaxing ciliary bodies & decreased in production of aqueous humor
Effects seen in the lungs with Alpha stimulation
Constriction of Bronchial blood vessels in upper airway = decongestants & dec mucus production
Effects seen in the GI tract with Alpha Receptor stimulation
Indirectly as heteroceptor - activates presynaptic alpha site on cholinergic nerve - leads to dec. ACh release and slowing of digestion
Also alpha 1 - contracts smooth muscle sphincters
Effects seen in GI tract with Beta Receptor stimulation
relaxes smooth muscle walls and slows down digestion - Beta -2
Effects seen in GU tract with Alpha Receptor stimulation
constriction of bladder base, urethral sphincter and prostate
Effects seen in GU tract with Beta Receptor stimulation
Relaxation of bladder walls - Beta 2
Uterine relaxation - Beta 2
Effects seen in sweat gland with alpha receptor stimulation
Apocrine - stimulation to release fatty oils
Eccrine - response to cool body off
Beta 2 receptor effects on metabolic functions
Glycogenolysis (breakdown glycogen for glucose)
Gluconeogenesis (protein breakdown for energy)
When do you want to use a direct acting alpha agonist?
- preserve cerebral blood flow
- Severe hemorrhage
- Spinal cord injury
- Anithypertensive OD
- CNS depressant OD
What is an agent used in the OR to achieve Hemostasis?
Also reduces diffusion of local anesthetic away from desired site
MOA for Clonidine in treating hypertension
UNIQUE alpha 2 agonist that can dec. BP by working on alpha receptors in the brain (presynaptic)
Other uses for Clonidine
Diarrhea, dec. appetite cravings, dec. hot flashes, treat hemodynamic instability in the OR