Beta Blockers

Question 1

What does it mean that the selectivity of beta blockers is “dose-dependent?”

Answer 1

The higher the dose, the more broad spectrum the drug becomes-no longer as selective for beta 1 or beta 2

Question 2

What does chronic administration of beta blockers cause?

Answer 2

Upregulation: increases number of receptors

Question 3

What is a benefit of “taking a break” from beta blockers?

Answer 3

restores receptor responsiveness!

Question 4

Cardiac benefit of BB’s:

Answer 4

-protect myocytes from perioperative ischemia and infarction

-prevent consequences after MI for up to 2 YEARS (why CAD pts are on these drugs)

Question 5

What do BB’s do to the cardiac phases?

Answer 5

-Decrease the slope of phase 4
-rate of spontaneous depolarization is decreased
-so decreases dysrhythmias during ischemia
-increases diastolic perfusion time! (this helps increase CO and SV)

Question 6

Indications for BB’s:

Answer 6

-Excessive SNS stimulation
-thyrotoxicosis
-Cardiac Dysrhtyhmias
-Essential HTN
-SCIP!

Question 7

SCIP and BB’s: What are the rules?

Answer 7

-BB’s within 24 hrs of surgery cut time for pts already on BB’s OR at risk for myocardial ischemia (CAD/chest pain/MI hx)

Question 8

Do we use more B1 selective or B2 selective drugs?

Answer 8

Beta 1 selective for sureeee

Question 9

True or false: BB’s cause vasodilation

Answer 9

FALSE: just see effects of chronotrophy, ionotrophy and dromotrophy

Question 10

Propranolol:

Answer 10

-1st BB to be developed, aka Inderal
-Nonselective for B1/B2
-Slows HR more than it affects contractility (inotropy)
-b/c of slower HR and lower CO, hepatic clearance of opioids and amine LAs is REDUCED
-has an active metabolite!

-Dose: 1-10 mg IV
-E1/2 time: 2-3 hours
-PB: high (small VD)

Question 11

Atenolol:

Answer 11

-aka Tenormin
-MOST B1 selective
-useful for pre/post non-cardiac surgery in CAD pts: decreases myocardial ischemia up to 2 years
-does NOT enter CNS (less fatigue)

-Dose: 5-10 mg IV (5 mg every 10 min until you get desired effect)
-renal clearance
-NO active metabolites
-E 1/2 time: 6-7 hours
-PB: low

Question 12

Metoprolol:

Answer 12

-aka Lopressor
-B1 selective
-2 PO formulations: Tartrate and Succinate

-Dose: 1-15 mg IV (1 mg q5min in blocks of 5 mg…5,10, 15, etc)
-Clearance: hepatic
-NO active metabolites
-E 1/2 time: 3-4 hours
-PB: low

Question 13

E 1/2 time of Tartrate:

Answer 13

2-3 hours, BID and QID dosing options

Question 14

E 1/2 time of Succinate:

Answer 14

5-7 hours, usually QD dosing

Question 15

Esmolol:

Answer 15

-aka Brevibloc
-B1 selective, short acting!
-onset 5 min, offset 10-30 min w/ repeated doses
-tx intraop noxious stimuli like intubation-can even decrease opioid use!

-dose: 20-30 mg IV intially, 10-80 mg range
-clearance: plasma hydrolysis
-no active metabolites
-E 1/2 time: 0.15 hours
-PB: low

Question 16

What drug interactions should we look out for with beta blockers?

Answer 16

-synergistic with CCBs
-monitor blood sugars! BBs can interfere with glycogenolysis and potentiate insulin

-potentiates myocardial depression, esp. at >2 MAC, GREATEST with Enflurane, LEAST with Isoflurane (not sig depression b/w 1-2 MAC)

Question 17

Labetolol:

Answer 17

-selective alpha1 and nonselective Beta antagonist (mixed)
-Beta:Alpha blocking-7:1
-lowers BP by decresing SVR (alpha effect)
-reflex tachycardia attenuated by beta blockade

-Dose: 2.5-5 mg IV, can increase to 10 mg IV
-peak: 5-10 min