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Advanced Pharmacology: Inotropes & Vasopressors

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Angela Corry

on 31 May 2017

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Transcript of Advanced Pharmacology: Inotropes & Vasopressors

Advanced Pharmacology: Inotropes & Vasopressors
RAH Emergency Dept
March 2016

What is an inotrope?
drugs that affect the force of contraction of the heart
influence how effective the heart can pump
Positive Inotrope:
stimulate & increase the strength of the heart muscle contraction causing the heart rate to increased
Negative Inotrope:
drugs that weaken the force of myocardial contractions
Key Points of Inotropic Drugs:

Extremely short half life

Caution in hypovolemia

Titrate to desired effect

Administration has to be accurate & infusion pump required

Dedicated infusion line

Caution in peripheral lines, can cause extravasation

Caution if patient is volume overloaded

Ensure oxygen demands are continually being met
What is a Chronotrope?
drugs that may change the hearts ability to increase its rates with increased activity or demand
Positive Chronotrope:
drugs that increase heart rate
Negative Chronotrope:
drugs that reduce the heart rate
What is a Dromotrope?
drugs that affect the heart rate by affecting the conduction speed at the AV junction

they are often, but not always, inotropic and chronotropic as well

Ex.) Calcium Channel Blockers
What is a Vasopressor?
drugs that induce vasoconstriction

elevates the mean arterial pressure (MAP)

differ from inotropes, however many drugs have both vasopressor and inotropic effects
Adrenergic Receptors
Dopaminergic Receptors
Predominant catecholamine neurotransmitter in the brain

Controls a variety of functions including locomotor activity, cognition, emotion, positive reinforcement, food intake and endocrine regulation

Plays multiple roles as a modulator of cardiovascular function, catecholamine release, hormone secretion, vascular tone, renal function and gastrointestinal motility
Alpha Receptors:
Found in blood vessels, heart, CNS
positive inotrope

negative chronotrope

Beta-1 Receptors
Found in the heart
Positive inotropic

Positive chronotropic

Increases automaticity

Increases rate of conduction
Beta-2 Receptors
Found in blood vessels, bronchioles,
GI tract & uterus


Relaxation of smooth muscle
(GI & uterus)

Increases renin release

Drives K+ intracellularly (hypokalemia)

positive inotropic & chronotropic effects

releases norepi from storage, thus increases heart rate and contractility

alpha effects with vasoconstriction & increases blood pressure
How does it work?
What's the
1 - 4 mcg/kg/min
primarily dopaminergic receptors are activated
decreases vascular resistance
mild increase in cardiac output
no vasopressor effects below 5 mcg/kg/min
5 - 10 mcg/kg/min
B-1 affects increase cardiac output
increase in heart rate noted
inotropic & chronotropic effects
> 10 mcg/kg/min
alpha effects are predominant
increase in vascular resistance
vasopressor effects evident
Clinical Implications
Caution in tachycardia & any tachydysrhythmias

Prolonged use with high doses can result in severe vasoconstriction leading to gangrene of extremities

MUST be diluted before giving (who cares, it's premixed!)

Central line is preferred
How does it work?
pure alpha

direct vasoconstriction with little effect on the coronary circulation

no effect on heart rate

MAP is augmented by raising SVR
What's the dose?
can be given as an infusion or direct IV push
Direct IV Push:
Add 10 mls of phenylephrine to 100mls NS bag

100mcg/ml or 0.1mg/ml


Add 1 ml (10 mg) Phenylephrine to 9 ml NS of D5W (1 mg/1 ml). Mix well.

Discard 9 mL of mixed solution, and add 9 ml NS to further dilute phenylephrine

100 mcg/ml or 0.1 mg/ml

Give in doses of 0.1 - 0.5 mg over 20 - 60 seconds, repeat every 10-15 minutes
Continuous Infusion:
Add 50 mg to 250 ml D5W or NS
Initiate rate is 100mcg/min

200 mcg/ml

Clinical Implications
observe for adverse effects
reflex bradycardia (bolus doses)
ventricular arrhythmias (rare)
infuse into large veins to prevent extravasation
How does it work?
potent sympathomimetic

stimulates both alpha and beta

enhances the release of norepi

Inotropic and chronotropic

Increases myocardial oxygen demand
What is the dose?
5-25mg IV push

add 1ml (50mg) Ephedrine to 9ml NS


do not exceed 10 mg/min

Direct IV
How does it work?
potent alpha and beta 1 & 2 effects

inotrope and chronotrope


increases SVR, SV and CO

potent bronchodilator
What is the dose in cardiac arrest?
What is the dose in anaphylaxis?

begin at a rate of 2-10 mcg/min

titrate every 2-5 min to desired blood pressure

do NOT stop abruptly, must be weaned down

Continuous Infusion:
Standard concentration (16mcg/ml)
4mg in 250mls NS
High concentration (60mcg/ml)
15mg in 150mls NS
How does it work?
endogenous catecholamine

combined alpha and beta effects
More beta 1 than beta 2
prominent alpha effect on vascular beds

potent vasopressor & inotrope

Minimal chronotrope
less effect on heart rate than epinephrine

increases MAP and SVR

causes a decrease in renal, splanchic, muscular and skin blood flow
What's the dose?

dose usually starts at 0.5-1 mcg/min

titrate to blood pressure effect, increasing q 2-5 min

max dose is usually 30 mcg/min
No direct IV push!
Continuous Infusion:
Standard Concentration (16mcg/ml)
4mg in 250mls NS or D5W
High Concentration (64mcg/ml)
16mg in 250mls NS or D5W
Positive Inotropes
How does it work?
synthetic analog of dopamine

primarily beta agonist

beta 1 more than beta 2

more inotropic effects than chronotropic

increases contractility

moderately increases heart rate

improves renal and mesenteric blood flow

increases stroke volume and cardiac output

decreases afterload
What's the dose?
is a weight based infusion

usual rate is 2 - 20mcg/kg/min

titrate in small increments until desired effect
No direct IV push!
Standard Concentration (2mg/ml)
500mg in 250mls NS or D5W
Remove 40mls from 250mls and add 40mls (500mg) of dobutrex
High Concentration (4mg/ml)
1000mg in 250mls NS or D5W
Remove 80mls from 250mls and add 80mls (1000mg) of dobutrex
Clinical Implications
must be diluted before administration

central line is preferred

observe for adverse effects
increased HR and SBP
PVCs, tachycardia
angina, shortness of breath
hypokalemia & hypotension
How does it work?
is a phospodiesterase inhibitor (huh?)

intracellular shift of calcium into the cardiac muscle cells

increases contractility (positive inotrope)

increases heart rate

dose dependent vasodilation

decreases vascular resistance (reduced preload and afterload)

increases cardiac output and stroke volume

long half life
What's the dose?
No direct IV push!
dose is weight based
loading dose followed by continuous infusion
dose is adjusted for renal function
50 mcg/kg administered over 10 minutes
Loading Dose
Continuous Infusion
0.125 to 0.75 mcg/kg/minute
MAX recommended total daily dose is 1.13 mg/kg
Clinical Implications
correct fluid and electrolyte status before initiating

caution with severe obstructive aortic or pulmonic valvular disease

central line is preferred

observe for adverse effects
ventriular arrhythmias, SVT
angina/chest pain
How does it work?
positive chronotrope, dromotrope and inotrope

beta 1 and 2 effect

low affinity for alpha receptors

decreases vascular resistance by causing vasodilation and venous pooling
What's the dose?
Continuous infusion
2 to 10 mcg/minute or 0.01 to 0.2 mcg/kg/minute, and titrate to response
The odd one out....
How does it work?
antidiuretic hormone

synthesized in the hypothalamus

stored in the posterior pituitary

potent stimuli for release includes hypotenion, hypovolemia and hyperosmolality

interacts with different receptors (V1-2-3)

No inotropic or chronotropic effects

causes vasocontriction, increases MAP

results in net water retention

increases insulin secretion
What's the dose?
0.01 - 0.04 units/min
Low Dose
High Dose
0.2 - 0.4 units/min up to 1.5 units/min
Clinical Implications
higher doses (> 0.04 units/min) associated with cardiac ischemia

use cautiously in patients with cardiac dysfunction

monitor for extravasation

monitor for water intoxication

can cause bronchial constriction
Let's put it into practice....
Before initiating vasopressor or inotropic support, it is crucial to correct what state?

Case Studies
Sue is a 24 year old female who is 12 wks pregnant. Her husband brought her to the ED when she passed out at home. On route she began vomiting and complaining of severe RLQ pain radiating to her suprapubic area and Rt shoulder.

General Appearance: diaphoretic, cool, clammy skin, she is moaning and guarding her abdomen. Restless, GCS 15

Vital Signs: 37.2, 28 (shallow), 126 (regular), 90/70, 95% RA

Exam: S1/S2 present, no murmurs, A/E clear and equal to lungs, nail beds are dusky, Abd firm (pain with palp)
IV access
1 L Ringers bolus, then 200mls/hr
CBC-D, lytes, crea, urea, BHCG, VBG
X-match for 4 units PRBCs
CT abdomen
Considering Sue's presenting symptoms, what orders are the priority?
Hbg = 130 (135-175)
WBC = 15.9 (4.0-11.0)
RBC = 5.3 (4.3-6.0)
HcT = 0.48 (0.41-0.52)
Na+ = 146 (133-146)
K+ = 3.5 (3.3-4.8)
Cl = 95 (96-109)
Ca+ = 2.14 (2.10-2.60)
Glucose = 8.5 (3.3-11.0)
BHCG = pending...
CT Abdomen = Scan positive for diffuse abdominal bleeding
What is the significance of the lab and CT results?
Sue diagnosed her pregnancy with OTC test
They have been trying for 2 years to get pregnant
Before trying, she was taking BCPs
LMP 86 days ago, P0G1

The past 2 days, Sue has had nausea, vomited only today, gradual onset & intensity of abd pain. Syncopal episode when trying to get off the couch to answer the phone.

No past medical history
No allergies
Last meal was 6 hours ago
Sue returns from CT....
remains orientated, but restless
diaphoretic, cool & clammy
cap refill sluggish
abdomen firm and tight
no bowel sounds auscultated
increased pain to abd and Rt shoulder
foley inserted (light, yellow urine) 40mls/hr output
Vital Signs: 38.2, 32, 145, 78/51, 96% 2L
Sue's condition deteriorates...
SBP 60mmHg
No peripheral pulses palpable, thready carotid noted
GCS drastically drops to 5
Resistant to IV fluid replacements

Besides surgical intervention, what would be the appropriate treatment & why?
1. Levophed infusion
2. Dopamine infusion
3. Epinephrine infusion
4. Milrinone infusion
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