Critical Care

Question 1

Vasoactive infusions

Answer 1

Inotropes
● Act by increasing the force of myocardial contractility

Vasopressors
● Mimic sympathetic nervous system to cause vasoconstriction

Question 2

Common Indications

Answer 2

● Cardiac arrest
● Hypotension
● Shock refractory to fluid resuscitation
● Cardiac disease
○ Acquired
○ Congenital

Answer 3

a1 - Adrenergic Receptors
● Primarily found in vascular smooth muscle
● Peripheral ● vasoconstriction ●
● Increased SVR

b1-
Found in heart and intestinal smooth muscle
Increase contractility ● Increase SV, HR, and CO

b2
●Primarily found in bronchial vasculature ●Bronchodilation
●Coronary artery vasodilation

Question 4

Norepinephrine

Answer 4

Shock, hypotension
● Acts on alpha-1 receptors
● Causes peripheral vasoconstriction → increases BP
○ Increases cardiac output

a1 - Adrenergic Receptors
● Primarily found in vascular smooth muscle
● Peripheral ● vasoconstriction ●
● Increased SVR

Question 5

Epinephrine

Answer 5

Shock, cardiac arrest, asystole
● Low doses act on beta-1 receptors ○ Increase the cardiac output

b1-
Found in heart and intestinal smooth muscle
Increase contractility ● Increase SV, HR, and CO

● High doses act on alpha-1 receptors
○ Increase systemic vascular resistance → increase BP

a1 - Adrenergic Receptors
● Primarily found in vascular smooth muscle
● Peripheral ● vasoconstriction ●
● Increased SVR

Question 6

Phenylephrine

Answer 6

Anesthesia-induced hypotension; Second line agent in some shock clients
● Only acts on alpha-1 receptors
● Causes only vasoconstriction - no inotropy
● Vasoconstriction → Increased BP

a1 - Adrenergic Receptors
● Primarily found in vascular smooth muscle
● Peripheral ● vasoconstriction ●
● Increased SVR

Question 7

Dopamine

Answer 7

Shock, hypotension, trauma
● Low doses used in kidney failure to increase renal blood flow
○ ‘Renal dopa’

● Low doses increase contractility → Increase CO
● Higher doses cause vasoconstriction → Increase SVR → Increase BP
Acts on DOPAMINE receptors!

Question 8

Vasopressin

Answer 8

● Antidiuretic hormone (ADH)
● ANTI-diuresis…. Less diuresis → more volume IN the vascular system
○ More volume → more pressure!
○ Raises BP
● Second line in vasodilatory shock
● Third line in septic shock
○ 1st: Dopa or norepi
○ 2nd: Epi or phenylephrine
○ 3rd: Vaso

Answer 9

Complications and Side Effects
Arrhythmias - due to stimulation of beta-1 receptors

Hypoperfusion to extremities, kidneys, and GI tract - due to excessive vasoconstriction
Peripheral tissue necrosis - due to hypoperfusion of
the skin

Myocardial ischemia -
due to increased myocardial oxygen demand secondary to increased chronotropy