Final Exam Anesthesia Adjuncts Flashcards
What occurs when agonists bind to one of the 3 beta receptor subtypes? (3)
- Activates adenylyl cyclase to produce caMP
- Enhances Ca++ influx
- Chronotropic, inotropic, and dromotropic effects
What is the selectivity of beta-antagonists dependent on?
Selectivity is dose dependent, which is lost at high doses of antagonists
Can competitive antagonists be displaced by higher doses?
yes
4 general benefits of beta blockers?
- May restored receptor responsiveness such as after desensitization from catecholamines (tachyphylaxis)
- Protect myocytes from perioperative ischemia and infarction
- Some may decrease arterial vascular tone and reduce afterload
- Decrease CO and inhibit renin release
Where do beta blockers delay conduction speed through?
The AV node
Which phase of depolarization do beta blockers effect?
decrease phase 4 depolarization
What would be the benefit of increasing diastolic perfusion time?
Gives more time for the perfusion of coronary arteries
4 Indications for Beta blocker administration?
- Excessive SNS stimulation from things such as noxious stimulus or acute cocaine ingestion
- Thyrotoxicosis
- Cardiac Dysrhythmias
- SCIP
Surgical Care Improvement Protocol (SCIP) for beta blockers
Beta blockers should be administered within 24 hours to all patients who are at risk for myocardial ischemia and patients who are already on beta-blockade therapy
3 examples of b1 selective agents?
- Atenolol
- Metoprolol
- Esmolol
Are all B1 receptors in the myocardium?
No, 75% of them are
Do B1 selective agents cause vasodilation or increased diastolic filling time?
No vasodilation but they do increase diastolic filling time
Cardiac selectivity, clearance route, active metabolites, elimination half time, protein binding and adult iv dose of propranolol?
Cardiac Selectivity: no Clearance: hepatic E 1/2: 2-3 hours Protein binding: highly (small Vd) IV dose (mg): 1-10mg Active metabolites: yes
Cardiac selectivity, clearance route, active metabolites, elimination half time, protein binding and adult iv dose of metoprolol?
Cardiac Selectivity: yes Clearance: hepatic E 1/2: 3-4 hours Protein binding: low IV dose (mg): 1-15 mg Active metabolites: no
Cardiac selectivity, clearance route, active metabolites, elimination half time, protein binding and adult iv dose of atenolol?
Cardiac Selectivity: yes Clearance: renal E 1/2: 6-7 hours Protein binding: low IV dose (mg): 5-10 mg Active metabolites: no
Cardiac selectivity, clearance route, active metabolites, elimination half time, protein binding and adult iv dose of esmolol?
Cardiac Selectivity: yes Clearance: plasma hydrolysis E 1/2: .15 hours (~9min) Protein binding: low IV dose (mg): 10-80 mg Active metabolites: no
What receptor effect does propranolol (inderal) have?
Pure beta (B1=B2),there is no sympathomimetic activity
What is the difference per person of plasma concentration with inderal?
20x difference per person, oral doses range from 40mg-800mg/day
What other drugs does inderal have an effect on?
decreases clearance of amide LA’s and opioids
Which beta antagonist is the most B1 selective?
Atenolol (Tenormin)
What patients is tenormin useful for in the pre and postoperative setting?
Non-cardiac surgery in CAD patients, reduces complications for 2 years
Does tenormin potentiate insulin-induced hypoglycemia?
no
Why does tenormin show less fatigue than other beta blockers?
it does not enter the CNS
How is tenormin usually given?
5mg every 10 minutes IV
What are the two po forms of metoprolol
- Tartrate elimination 1/2 time is 2-3 hours, bid, qid dosing
- Succinate elimination 1/2 time is 5-7 hours, qd dosing
How is lopressor usually dosed?
1mg q 5 min IV in blocks of 5mgs
What does the selectivity of metoprolol (loppressor) give us?
bronchodilator, vasodilation and keeps metabolic effects of B2 receptors intact
Therapeutic effect and offset of esmolol (brevibloc)?
TE: 5 minutes
Offest: 10-30 minutes
What is esmolol useful in treating?
intraoperative noxious stimulu
Initial dosing of brevibloc?
20-30mg IV
Drug interactions with cimetidine?
decreases 1st pass metabolism of metoprolol, causing it to last much longer
Drug interaction of beta blockers when concurrently administered with Ca++ channel blockers?
bradyarrhythmias and heart failure
Drug interaction of beta blockers and insulin?
Potentiate insulin effects and prevents glycogenolysis (B2 agonist activity), want to administer B1 antagonists instead of B2
Interaction of beta antagonists with anesthesia? (3)
Potential additive myocardial depression, greatest with enflurane, least with isoflurane, not significant between 1-2 MAC
2 examples of mixed beta/alpha antagonists
- Labetolol
2. Carvedilol
Receptors that labetalol effects?
selective alpha 1, non-selective b1 and b2 antagonist effects