Shock

Question 1

Define shock

Answer 1

A term used to describe the situation when there is insufficient blood supply to the tissues, to meet their demands.

Question 2

4 main shock classes

Answer 2

Cardiogenic
Hypovolaemic
Obstructive
Distributive/normovolaemic

Question 3

Define features of cardiogenic shock

Answer 3

The heart is unable to maintain an adequate blood pressure. This could be due to failure of the heart as a pump (myocardial damage or deterioration), severe alterations in rhythm such that contraction is not co-ordinated, or a mechanical defect (valve damage allowing blood to flow the wrong way)

Question 4

Define features of hypovolaemic shock

Answer 4

There is a decrease in circulatory volume. This could be due to diminished blood volume, loss of whole blood, loss of plasma, loss of extracellular fluid

Question 5

Define features of obstructive shock

Answer 5

There could be an inability of the heart to fill adequately, or obstruction to outflow from the heart (valve damage, aortic stenosis etc.)

Question 6

Define features of distributive shock

Answer 6

Loss of sympathetic vasomotor tone (damage to the CVS centre in the medulla or damage to the sympathetic outflow)
Presence of vasodilator substances in the blood (e.g. histamine)
Shunting of vascular fluid to interstitial spaces
Arterio-venous shunting
Failure of the cells to use oxygen (e.g. poison)

Question 7

Main causes of loss of vessel tone in distributive shock?

Answer 7

A loss of sympathetic-mediated vasomotor tone

The presence of vasodilator substances in the circulation

Consequence of prolonged and severe hypotension

Question 8

3 common forms of distributive shock?

Answer 8

Anaphylactic
Neurogenic
Septic

Question 9

Physiology of anaphylactic shock?

Answer 9

Massive vasodilation
Pooling of blood in the peripheral vessels
Increased capillary permeability

Question 10

Treatment of anaphylactic shock

Answer 10

Adrenaline (constrict blood vessels and relax airways)
Antihistamines
Corticosteroids
Oxygen

Question 11

S/S of septic shock

Answer 11

Fever
Vasodilation
Hyperventilation
Altered cerebral blood flow
Raised WCC
Warm + flushed skin

Question 12

4 stages of shock

Answer 12

INITIAL STAGE – perfusion is decreased but not enough to cause serious effects.

COMPENSATORY – perfusion is reduced, but mechanisms are able to maintain BP and tissue perfusion sufficiently to prevent cell damage.

PROGRESSIVE stage or stage of DECOMPENSATED shock – BP starts to fall, blood flow to the heart and brain becomes impaired, capillary permeability is increased, fluid leaves the capillaries, blood flow becomes sluggish and body cells and their enzyme systems are damaged.

IRREVERSIBLE stage – even if the blood volume is restored and vital signs stabilise, death ensues

Question 13

What is a sympathetic mediated response to shock?

Answer 13

Due to baroreceptor reflex, sympathetic and medullary activity increase –>
Tachycardia
Increase cardiac contractility
Vasoconstriction

AIM: Prioritise blood perfusion to essential areas

Question 14

What are the mechanisms in place to restore blood volume in shock?

Answer 14

Fluid absorption from interstitial spaces

Na and H2O preservation at kidneys

Question 15

Compensatory mechanisms are..

Answer 15

SHORT TERM

Question 16

In severe shock, or if the compensatory mechanisms continue for an extended period, the vascular system ______

Answer 16

In severe shock, or if the compensatory mechanisms continue for an extended period, the vascular system FAILS
There is relaxation of arterioles and venules with a consequent fall in peripheral resistance and hence M.A.P. Venous pooling of the blood occurs.
DUE TO local factors > sympathetic tone

Question 17

S/S of shock

Answer 17

THIRST

COLD and CLAMMY ( sympathetic mediated)

PALE SKIN AND MM (in haemorrhage)

INCREASE HR

REDUCE URINE OUTPUT

RESTLESS –> COMA

Question 18

Complications of shock?

Answer 18

ARDS: Due to increases pulmonary capillary permeability = stiff lung with imparied gas exchange

GI Ulceration: Due to vasoconstriction of blood vessels to the mucosa. Can lead to bleed ulcers and haemorrhage

DIC: formation of small clots in the microcirculation.

RENAL DAMAGE

MULTIPLE ORGAN FAILURE

Question 19

DIC?

Answer 19

Disseminated Intravascular Coagulation

Question 20

Treatment of shock

Answer 20

FLUIDS
First line: Saline
Then colloids (plasma expanders e.g. albumin and dextrans)
In cardiogenic shock, don’t overload the heart with fluid excess

VASOACTIVE DRUGS
Alpha stimulation –> Vasoconstriction
Beta1 stimulation –> Increased HR and contractility
Beta2 stimulation: Vasodilation of skeletal muscle bed and relaxation of bronchiole
Nitrates: Vessel dilation