Cardiogenic shock

Question 1

What are the end effect of impaired tissue perfusion

Answer 1

Initially compensated for in shocked states
if prolonged poor perfusion
1) reduced fucntionality of cell membrane pumps due to change in Ph
2) intracellar odema
3) leakage of intracellular contents into the extracellular space
4) inadequate regualtion of intravellular PH

Question 2

What are the determinants of tissue perfusion

Answer 2

Cardiac output and arterial blood pressure

CO = SV x HR

SV is affected by preload, afterload and contractiliy

Contracility: 
increased
-inotropic drugs 
Decreased
-B blocker 
-hypoxia, hypercapinia, acidemaia

Question 3

Discuss the stages of shock

Answer 3

Preshock (compensated)
-bodies homeostatic mechanisms are able to maintain perfusion (RAS, vasopressin, catecholamines)

Progressive
-Regulatory mechanisms have become overwhelmed and signs and symptoms of organ damage beign to appear

Irreversible

• Progressive end organ dysfunction leads to irreversible organ damage and eventual death
• urine output declines and renal failure
• resp muscles fatigue leading to hypercapnia
• multiple organ failure

Question 4

Discuss management of cardiogenic shock (drug therapy)

Answer 4

Sympathetic amines
Typically drugs such as norad and dopamine are used to provide inotropic and vasopressor support when severe hypotension is present. All of these drugs increase mycocardial o2 demand and may worsen ischaemia so should be used as a temporising measure

Vasodilators
Drugs with vasodilator properties such as dobutamine, milrinone, nitroprusside and GTN increase output by reducing afterload when hypotension is not present

Question 5

Discuss milrinone

Answer 5

is a phosphodiesterase inhibitor which leads to a decrease in destruction of cAMP

Inoptropy and vasodilation – leading to decrease afterload and increased output. Reduces pulmonary vascular pressure

Question 6

Discuss intra aortic balloon counterpulsation

Answer 6

A ballon pump is placed in the descending aorto trans-femorally. This inflates during diastole and deflates during systole causing a vacuum effect and reducing afterload

Reduces mortality if used with fibrinolytics

Question 7

Discuss failure with right ventricular impairment

Answer 7

Occurs in 7% inferior MI and is associated with high mortality
Right dysfunction causes an acute drop in left preload and stroke volume.
Initial treatment of right heart dysfunction is fluid loading because high filling pressures are needed to maintain left preload
GTN needs to be avoided as it may cause severe hypotension

If refractory to fluid should be treated with inotropes such as dobutamine or milrinone (as these reduce pulmonary vascular resistance)

Drugs such as dopamine or norad which increase pulmonary resistance should be avoided

Question 8

List other causes of cardiogenic shock apart from MI

Answer 8

Arrythmias
myocarditis
cardiomyopathies