Shock

Question 1

What is shock?

Answer 1

Shock is inadequate perfusion to the organ tissues which leads to organ injury

Question 2

What leading factor ofen causes shock?

Answer 2

Hypotension- the blood pressure falls to levels too low to maintain adequate perfusion to the tissues

Question 3

What equation is used to work out mean arterial blood pressure? How does each factor represent a cause of shock?

Answer 3

MABP= CO X SVR

Systemic vascular resistance falls with vasodilation and decreased circulating volume. Cardiac output falls with decreases in stroke volume or heart rate. A number of different causes can therefore be applied to this equation to cause shock.

Question 4

What is stroke volume dependent on?

Answer 4

Preload- the venous return to the heart

Contractility- the pumping action of the myocardium

Question 5

How can the causes of a decreased cardiac output be divided?

Answer 5

Decreased preload
Decreased contractility
Decreased rate or increased rate (too fast for filling)

Question 6

What is the equation for cardiac output?

Answer 6

CO= SV X HR

Question 7

What is the equation for SV?

Answer 7

EDV- ESV

Question 8

What is another name for the end diastolic volume?

Answer 8

Preload

Question 9

What is starling’s law?

Answer 9

Increased the EDV increases the contractility of the myocardium and therefore increases SV

Force of ventricular contraction is dependent on the length of the ventricular muscle fibres in diastole- greater filling= greater stretching of the fibres

Question 10

What factors increase EDV?

Answer 10

Increasing venous return

Increased central venous pressure

Question 11

What 5 factors affect venous return to the heart?

Answer 11

Blood volume
Skeletal muscle pump action
Gravity
Venous tone
Respiratory pump

At rest around 60-70% of the blood volume is found within the venous circulation and this therefore represents a large pool of blood that can be used to increase EDV.

Question 12

What is the preload?

Answer 12

The load of blood to the heart at the end of diastole. This is the EDV.

Due to starling’s law, increases in preload increase the stretch on the muscle fibres which in turn generates greater forces of contraction and greater stroke volumes.

Question 13

What is the afterload?

Answer 13

The load against which the heart must contract to eject the stroke volume.

Aortic or pulmonary artery pressures are the most important in determining this.

Pressure is determined by volume and compliance, compliance reduces with increased vascular tone.

Question 14

What are some causes of a decreased preload/EDV?

Answer 14

Compression of SVC- Tension Pneumothorax
Compression of heart chambers- Pericardial Tamponade
Reduced effective circulating volume- Haemorrhage, Dehydration

Question 15

What are some causes of cardiogenic shock?

Answer 15

Congestive heart failure
MI
Arrhythmia

Question 16

What are some causes of shock that cause shock through reduced SVR?

Answer 16

Anaphylaxis
Sepsis
Neurogenic shock (loss of sympathetic vasoconstriction on peripheral vascular tone)

Question 17

What investigation can confirm the presence of shock?

Answer 17

Lactate- this can be obtained rapidly via an ABG or VBG

Question 18

What are some signs of end organ perfusion?

Answer 18

Altered mental status, agitation, confusion- cerebral hypoxia
Low urine output- Renal hypoperfusion
Prolonged CRT- Decreased skin perfusion

Question 19

What immediate action can be done to investigate for causes of shock/haemorrhage in ED?

Answer 19

FAST Scan

H- Heart, ventricular function and presence of tamponade
I- Inferior Vena Cava for volume status and CVP indication. If dilated it is high and if flat or collapsed it is low.
M- Morrison’s Pouch- Hepatorenal Recess and check other areas in the abdomen and pelvis for any bleeding
A- Aorta- Look for AAA signs and potential for bleeding
P- Pneumothorax

Question 20

What pH change is likely to be seen on an ABG in a shocked patient?

Answer 20

Metabolic acidosis due to the lactate and anaerobic metabolism involved

Question 21

How can the causes of hypovolemic shock be divided?

Answer 21

Hemorrhagic- Bleeding

Non-Haemorrhagic- GI Losses, Vomiting, Diarrhoea, Renal Losses, DKA, Diabetes Insipidus, Dehydration, Third Spacing

Question 22

What are some causes of non-hemorrhagic shock?

Answer 22

GI Losses- Vomiting, Diarrhoea
Renal Losses- DKA, Diabetes Insipidus
Third Spacing- Burns, Pancreatitis
Dehydration

Question 23

Outline the basic management for shock

Answer 23

Resus First- Fluids, Blood etc.

Treat the underlying cause

Question 24

If cause of shock is haemorrhage what needs to be given?

Answer 24

You replace what is lost, therefore use blood products, if they’re bleeding give them blood

Replace in a 1:1:1 ratio of Packed Red Cells, Plasma and Platelets

Question 25

What scan can indicate deficiencies in blood clotting rapidly?

Answer 25

TEG Scan

Question 26

Above what level is a lactate concerning and indicative of shock?

Answer 26

Above 2