Session 12: Shock

Question 1

Decribe the essential characteristics of shock

Answer 1

no actual definition of shock, but it is used to describe acute circulatory failure with either inadequate/inappropriately distributed tissue perfusion leading to generalised lack of oxygen supply to cells

Question 2

Types of shock

Answer 2

Cardiogenic: inability of heart to eject enough blood eg in arrhythmias, ischaemic damage

Mechanical: due to a) restriction of filling of heart eg cardiac tamponade, with the pressure outside the heart impairing filling or b) obstruction to blood flow through the lungs eg pulm. emb., so the R/ventricle cannot empty and reducing the return to the L/atrium

Hypovolaemic: loss of circulating blood volume eg haemorrhage, where the ven. press. drops causing the CO to fall, trated by infusing fluid, colloid/blood

Normovalaemic: an uncontrolled dec. in peripheral resistance, caused by a) a dramatic fall in arterial pressure, b) sepsis (endotoxins are released by circulating bacteria causing profound periph. vasodilation, trated w/ adr. to vasoconstrict and by antibiotics) and c) anaphylaxis (release of histamines from mast cells -> profound vasodilation, treated w/ adr. for vasoconstriction)

Question 3

cardiogenic shock

Answer 3

inability of heart to eject enough blood eg from arrhythmias, ischaemic damage

Question 4

mechanical shock

Answer 4

a) due to restriction of filling of heart (eg cardiac tamponade, so the pressure outside the heart prevents filling) or b) obstruction of the the blood flow through the lungs/pulmonary circulation (eg pulm. emb., so r/ ventricle cannot empty and there is a reduced return to the l/atrium)

Question 5

hypovolaemic shock

Answer 5

caused by a loss of circulating blood volume eg haemorrhages, ven press. and CO drops, treated by infusing fluid, colloid/blood

Question 6

normovolaemic shock

Answer 6

an uncontrolled drop in peripheral resistance

cause: a) dramatic fall in art. press.
b) sepsis: circulating bacteria release endotoxins that cause profound peripheral vasodilatation, treated w/ adr. to cause vasodilation and antibiotics
c) anaphylactic: mast cells release histamine which causes profound vasodilation, trated w/ adr. -> vasoconstriction