Anesthesia Adjuncts (Exam IV) Flashcards
β agonism results in activation of _____ which then produces _______.
Adenylyl Cyclase (AC)
cAMP
Does Ca⁺⁺ influx or efflux during β agonism?
Influx
What type of receptors are β receptors?
GPCR
What types of β receptors are there and where are they primarily located?
- β1 - Heart
- β2 - Lungs
- β3 - Fat/Muscle
Chronic administration of β blockers results in what effect on receptors?
Receptor upregulation (aka ↑ # of receptors)
After β receptor desensitization from prolonged catecholamine exposure, what drug class can restore receptor responsiveness?
β-blockers
How do β blockers protect myocytes from perioperative ischemia?
By ↓O₂ demand on the heart
T/F. β blockers will potentiate renin release.
false. β blockers will inhibit renin release
How will β blockers affect the cardiac foci action potential?
Prolong Phase 4
↓ dysrhythmias during ischemia and reperfusion.
How will β blockers affect diastolic perfusion time?
β blockers will increase diastolic perfusion time.
What type of HTN is a possible indication for β blocker therapy?
Essential Hypertension
What is SCIP?
Describe the protocol and its goals.
- Surgical Care Improvement Protocol
- β-blockers must be given within 24 hrs of surgery for patients at risk for cardiac ischemia and ones already on β-blocker therapy.
What were the three β1 selective agents discussed in lecture?
- Atenolol
- Metoprolol
- Esmolol
What percentage of β receptors in the myocardium are β1 ?
75%
Do cardio-selective β-blockers cause vasodilation?
No
What non-selective β-blocker has active metabolites and is generally shitty for anesthesia?
Propanolol
Differentiate the clearance mechanisms of metoprolol and esmolol.
- Metoprolol = Hepatic
- Esmolol = Plasma cholinesterases
Differentiate the E½ of metoprolol and esmolol.
Metoprolol E½ = 3-4 hours
Esmolol E½ = 9 minutes
When propanolol is given, what effect lasts longer, negative inotropy or negative chronotropy?
Negative chronotropy (bradycardia) lasts longer
What is a possible reason why the heart rate slowing effects of propanolol last longer than the negative inotropic effects?
Possible β1 sub-receptor types (ex. β1A, β1B, etc.)
Propanolol will decrease the clearance of which two important anesthetic drug classes?
- Opioids
- Amide LA’s
What drug is the most selective β1 antagonist?
Atenolol
What are the three benefits of Atenolol?
- Good for non-cardiac sx CAD patients (↓ complications for 2 years)
- No insulin-induced hypoglycemia
- Does not cross the BBB (no fatigue)
What is the dose for Atenolol?
5mg q10min IV
What is the dose of metoprolol?
1mg q5min (Given in 5mg “blocks”)
What two formulations of metoprolol are there?
- Metoprolol Tartate = multiple doses per day
- Metoprolol Succinate = One dose per day
What β blocker would be used for treat intubation stimuli?
Esmolol
What are the onset and offset of esmolol?
Onset: 5 min
Offset: 10-30min
What is the initial dose for esmolol?
20-30mg IV
Caution should be taken when giving esmolol with which two conditions?
Why?
- Cocaine and/or epinephrine
- Can cause pulmonary edema and cardiac collapse
Are the effects of CCBs and β-blockers additive?
No, synergistic
What two scenarios were given in class for a β1 indication over a non-selective β blocker?
- DM: β2 can cause hypoglycemia by insulin potentiation
- Airway: blocking β2 potentiates bronchospasm