Adrenergic

Question 1

Norepinephrine

Answer 1

Primary neurotransmitter 
Alpha and beta 
Used primarily for alpha 1, main effect = increased SVR 
-reflex Brady  
-Vado-C; pulmonary, renal, mesenteric
t1/2 2.5min 
Dose 
3 ug/min (titrated)  
0.01-0.1 ug/kg/min

Question 2

Epinephrine

Answer 2

a/B
Dose dependent effects
B1; (+) inotrope, chronotrope, enhanced conduction
B2; smooth muscle relaxation- vascular and bronchial
a1; Vaso-C
Endocrine/metabolic; increased blood glucose, lactate, free fatty acid
Doses:
1-2 ug/min (B2)
2-10 ug/min (B1)
>10 (a1)
Bronchospasm; 300ug SC q20 min x3 dose (croup?) tx via direct broncho-d and mast cell stabilization
Decreased refractory period in myocardium- risk of arrhythmias

Question 3

Dopamine

Answer 3

a/B/D 
Direct plus indirect (release of NE from storage vesicles)  
D1; improved renal and mesenteric blood flow in shock-like states?  
t1/2 1min 
Dose
(D1) 0.5-2 ug/kg/min  
(B1) 2-10 
(a1) >10

Question 4

Dobutamine

Answer 4

Synthetic dopamine analog
Predominantly B1, inotropy > chronotropy
Less B2 and a1
Dose
Low; 20ug/kg/min (usually no tachy)
Direct B1 - can be good in catacholamine depleted state (chronic CHF)
Tachyphilaxis

Question 5

Ephedrine

Answer 5

Increased BP and (+) inotrope
No detrimental effect on uterine blood flow. Previously used but now phenyl for decreased fetal acidosis
B1 - tx moderate hypo-tn esp w/ brady
Dose
2.5-25mg
Tachyphilax to indirect effect; NE release as stores deplete

Question 6

Phenylephrine

Neo-Synephrine

Answer 6

Selective a1 
Great for hypo-tn with good CO, ex: spinal anesthesia 
Maintain afterload in aortic stenosis - coronary profusion compromised by decreased SVR 
Rapid, short duration 5-10min 
Dose 
Bolus 40-100 ug 
Infusion start at 10-20 ug/min
1mg - can slow SVT reflexively