Inotropic (vasopressor) drugs

Question 1

Inotrope

Answer 1

• can change the force of cardiac muscle contraction - increase or decrease
• alpha and beta agonists - very tight narrow window (intensive care units)

Question 2

Shock

• hypovolemic
• cardiogenic
• distributive
• obstrucive

Answer 2

inadequate oxygen perfusion to meet tissues oxygenation demand leading to organ dysfunction

• hypovolemic - haemorrhage, dehydration
• cardiogenic - heart failure
• distributive - sepsis, anaphylaxis
• obstructive - pulmonary embolsim

Question 3

Features of shock

Answer 3

• hypotension, hyovolemia
• LV impairment
• Changes in vascular resistance
• poor renal/peripheral perfusion
• confused, sedated

Question 4

How do we manage shock ?

Answer 4

• resotre blood pressure (euvolemci) - increase preload
• normalise systemic perfusion - inotropes nad vasopressors
• perserve organ function - renal perfusion
• treat underlying cause - anitibotics

Question 5

Inotropic agents

Answer 5

-want to improve contractility to increase cardiac output

Question 6

Alpha and bet adrenoreceptor agonists

Answer 6

• norepinephrine- a1 agonist - mostly in blood vessles - increase resistance (vasopressor)
• epinephrine
• dobutamine - B1 agonist - mostly in heart - increase contractility and heart rate (vasodilator)
• dopamine

Question 7

-norepinephrine

Answer 7

a1 agonist - mostly in blood vessels - increase resistance (vasopressor)

• increases peripheral resistance, and increase systolic and diastolic blood pressure
• first line use for someone with shock
• short half life
• works by g coupled proteins, increase phosphate levels - get calcium - onstriciotn

Question 8

Epinephirne (adreanline)

Answer 8

• mixed alpha and beta adrenergic effects
• can vasoconstrict and vasodilate
• used for cardiac arrest situations
• increases myocardial oxygen consumption - particularly in coronary heart disease
• also for anaohylaxis - will stop blood pressure block - dilates bronchi, and is a potent vasopressor

Question 9

Dobutamine

Answer 9

• dobutamine - B1 agonist - mostly in heart - increase contractility and heart rate (vasodilator)
• adenylate cyclase - increase cAMP

Question 10

Dopamine

Answer 10

• low dose - will specifically agonise renal vasodilatation to increase renal vasdoilation and blood flow
• if increase this it becomes a beta agonist -intropy and heart rate
• if turn it up more- then becomes alpha agonist

_Dose dependent - not much clinical relevance
-dont realyl use this

Question 11

Vasopressor side effects

Answer 11

In shock, there is already a very high SNS and if we increase this, then get increase amount of this activity - need to be careful
-dont want ischemia of arms or legs, gut, brain, heart

• increase cardiac work - cardiac ischemia due to increasing heart work
• arrhythmia

Question 12

Vasopressin

Answer 12

• IV agent
• increase tone in vascular smooth muscle
• not much effect compared to noradrenaline, only use if its not working

Question 13

Digoxin

Answer 13

• slows heart down and increases inotropy
• very lipofillic - long half life
• 1. cardiac myocytes - blocks sodium potassium atpase channel - normally get sodium out of cell and potassium in - increase of intracellular sodium - activates sodium calcium channel - and gets increase in calcium in cell - increase contractility
• potassium also competes for this - can get more side effects for hypokalemia - need to test to see if this is okay
• increase vagus nerve at AV node
• slows conduction through here

Is used in acute heart failure- with fast atrial fibrillation
-AF rate control - 3rd line (first line - beta blockers, calcium channel blocker) - sometimes need a combo of 2 of these 3

• need to give loading dose first
• can cause gi upset, can cross blood brain barrier
• many drug interactions