Vasopressors

Question 1

Remember, as epidural blocks climb, the patient’s HR may drop, so giving (Ephedrine/Phenylephrine) may worsen this bradycardia.

Answer 1

Phenylephrine (causes increased BP with reflex drop in HR)

Question 2

(Ephedrine/Phenylephrine) maintains fetal pH.

Answer 2

Phenylephrine

Question 3

(Ephedrine/Phenylephrine) has a faster onset and shorter duration of action.

Answer 3

Phenylephrine`

Question 4

(Ephedrine/Phenylephrine) is good for hypotension post-regional, but doesn’t contain the same antiemetic efficacy.

Answer 4

Phenylephrine

Question 5

(Ephedrine/Phenylephrine) can cause fetal tachycardia and acidosis.

Answer 5

Ephedrine

Question 6

(Ephedrine/Phenylephrine) contains some antiemetic property and is good for hypotension d/t regional anesthesia.

Answer 6

Ephedrine

Question 7

(Ephedrine/Phenylephrine) does NOT decrease blood flow to the uterus.

Answer 7

Ephedrine

Question 8

Phenylephrine dose mixing:

Answer 8

10 mg/cc vial –> 0.1cc (1mg) + 9.9 cc NS = (100 mcg/cc)

Question 9

Phenylephrine dose (conc.):

Answer 9

50-100 mcg
(100 mcg/cc)

Question 10

Vasopressor of choice in OB:

Answer 10

phenylephrine

Question 11

Ephedrine dose mixing:

Answer 11

50 mg/cc vial –> 1 cc (50mg) + 9 cc NS = (5 mg/cc)

Question 12

(Ephedrine/Phenylephrine) is the preferred vasopressor for use in OB.

Why is this?

Answer 12

Phenylephrine is preferred. (maintains fetal pH)

Ephedrine has 2 problems:
- causes fetal tachycardia
- causes fetal acidosis

Only positive of ephedrine in OB is that it increases uterine blood flow, but doesn’t outweigh risks with crossing the placenta.

Question 13

Ephedrine dose (for antiemetic effect):

Answer 13

Ephedrine 25 mg/Vistaril 25 mg IM

given 20 mins before the end of surgery

Question 14

Ephedrine dose (conc.):

Answer 14

5-10 mg at a time to increase BP & HR
(5 mg/cc)

Question 15

With which drug will tachyphylaxis occur with repeated doses?

Answer 15

Ephedrine; because it requires norepinephrine in order to have effect on alpha-1 and beta-1 receptors, repeated dosing will deplete norepi stores and cause tachyphylaxis (rapidly diminishing response to successive doses of a drug).

Question 16

Ephedrine careful with use in which patients:

Answer 16

CAD

Question 17

Ephedrine drug class

MOA:

Answer 17

MIXED ACTING synthetic noncatecholamine sympathomimetic

indirect effect:
- ephedrine endocytosis into alpha-1 and beta-1 presynaptic postganglionic nerve terminals displaces norepinephrine presynaptically
- norepi is released and activates the postsynaptic receptors to cause arterial and venous vasoconstriction and increased myocardial contraction, respectively

direct effect:
- directly stimulates beta-2 receptors
- increases HR, CO, and some SVR

Barash: limits the increases in arterial pressure that occur as a result of alpha-1 stimulation

Question 18

Which of the vasopressors is mixed acting?

Answer 18

ephedrine –> indirect effect on alpha-1 and beta-1; direct effect on beta-2

Question 19

Vasopressors are not a replacement for ___, ___, or ___.

Answer 19

adequate volume
blood
too much anesthesia

Question 20

Which vasoactive drug should you not use for surgeries in the abdomen?

Answer 20

Vasopressin –> it is a potent vasoconstrictor: arterial and mesenteric (will reduce blood flow to mesenteric area)

Question 21

Vasopressin dose:

Answer 21

10/20 units/mL in 10/20 mL syringe

1-2 unit bolus (mix with Saline) –> start low, can always increase

Question 22

Phenylephrine effects:

Answer 22

Causes constriction of cutaneous, mesenteric, splenic and renal blood vessels.

Vasoconstriction
- increases BP and coronary blood flow,
- and causes baroreceptor reflex-mediated decreases in HR

Question 23

Phenylephrine uses:

Answer 23

Hypotension;
Decreased CO in patients with LV dysfunction
Vaso of choice for OB

Question 24

Phenylephrine MOA:

Answer 24

Directly stimulates alpha-1 receptors (minimal effect on alpha-2 or beta receptors) –> this increases venous and arterial vasomotor tone

Question 25

Phenylephrine (___)

Answer 25

___ (Neosynephrine)

Question 26

Ephedrine C/I:

Answer 26

C/I with MAO Inhibitors and in pheochromocytoma

Question 27

Ephedrine effects when used in OB:

Answer 27

can cause fetal tachycardia and acidosis which was associated with lower umbilical artery pH at delivery

Question 28

Ephedrine uses:

Answer 28

increase BP/HR, CO, and contractility
PONV rescue;
bronchodilator effect ( beta-2 agonist)
Used in OB

Question 29

Vasopressin uses:

Answer 29

• Cardiac arrest,
• Sepsis, shock, and
• Hypotension secondary to ACE inhibitors (lisinopril) that is refractory to catecholamines or sympathomimetics

Question 30

Vasopressin drug class and MOA:

Answer 30

Antidiuretic hormone, released by the posterior pituitary

Receptors: V1 (CV effects), V2 (renal), V3 (pituitary)