Shock

Question 1

Define shock and how quickly can it kill someone ?

Answer 1

• Shock is inadequate organ perfusion leading to inadequate oxygen delivery to tissues and eventually organ failure due to circulatory failure i.e. problem with the heart, blood vessels or flow of blood
• Can lead to death in seconds to hours

SBP <90

MAP <50-60

Question 2

What is MAP and how can it be calculated ?

Answer 2

Mean arterial pressure - is defined as the average pressure in a patient’s arteries during one cardiac cycle

MAP = CO x TPR

MAP = (2 x DBP) + SBP all divided by 3

can be rewrote as 2DBP/3 + SBP/3

Question 3

What is someones MAP a good measure of and what level or MAP would indicate shock?

Answer 3

MAP is a good measure of tissue organ perfusion i.e. the oxygen reaching the organs

For normal tissue perfusion you need a MAP of 50-60mmHg (note if someone has atherosclerosis then this would need to be higher to adequately perfuse there tissues)

So MAP <50-60 would indicate shock

Question 4

What does the inadequate tissue organ perfusion in shock lead to ?

Answer 4

1. Metabolic Acidosis (pH < 7.35) due to ATP hydrolysis and lactic acid formation (due to anaerobic metabolism) further worsening global enzyme function and cellular performance
2. Thrombus formation can occur at a capillary level resulting in patchy tissue injury, or in large vessels, leading to infarction.
3. Eventual cellular necrosis results in mortality

In survivors, a degree of tissue injury may be irreversible, contributing to chronic morbidity

Question 5

What are the 3 main immediate signs of tissue hypoperfusion (shock)?

Answer 5

1. Skin: mottling
2. Brain: confusion, agitation, reduced GCS (<15)
3. Kidneys: oliguria (<0.5ml/kg/h)

Question 6

What 2 things can shock essentially result from ?

Answer 6

Think back to the MAP = CO x TPR (SVR)

CO = HR x SV

So shock can essentially result from inadequate CO or a loss of systemic vascular resistance (TPR), or both

Question 7

After seeing the immediate signs of tissue hypoperfusion (shock) what test is then diagnostic that someone is in shock?

Answer 7

Measure someones arterial blood gases:

• see a metabolic acidosis
• lactate levels >2mmol/L

Question 8

What are the 2 main types of shock which primarily result in inadequate cardiac output?

Answer 8

1. Hypovolaemic shock
2. Cardiogenic shock (has a subtype known as obstructive shock)

Question 9

What are the main types of shock which result in peripheral circulatory failure (decreased SVR)

Answer 9

1. Septic shock
2. Anaphylactic shock
3. Neurogenic shock

These are all grouped as disruptive shock

Question 10

Define stroke volume

Answer 10

The amount of blood pumped by the left ventricle of the heart in one contraction.

Question 11

Describe the mechanism behind cardiogenic shock

Answer 11

• There is sustained decreased cardiac contractility
• This results in reduced force of cardiac contraction and ==> decreased stroke volume
• This reduced SV results in decreased CO and ==> decreased MAP (below 50-60 resulting in inadequate tissue organ perfusion and ==> shock)

Question 12

How do the body try to compensate for the decreased CO in cardiogenic shock and what sign does this result in ?

Answer 12

MAP = CO x TPR

The body tries to compensate by increasing TPR this results in COOL, CLAMY peripheries

Question 13

List the main causes of cardiogenic shock

Answer 13

Pump failure:

• ACS - e.g. MI (most common)
• Arrhythmias
• Aortic dissection
• Acute valve failure e.g. mitral regurg
• Cardiomyopathy
• Myocarditis/pericarditis

Obstruction shock (subtype of cardiogenic):

• PE
• Tension penumothorax
• Cardiac tamponade

Question 14

Along with the 3 general signs of shock what would make you think cardiogenic shock ?

Answer 14

• Cool, clamy peripheries
• Tachycardia
• Normal temp
• Hypoxia
• Hypotension

Question 15

What is the treatment of cardiogenic shock ?

Answer 15

Careful fluid management

Ionotropes e.g. dobutamine or vassopressors e.g. noradrenaline for increasing BP

Question 16

What key sign would make you think of obstructive shock (subtype of cardiogenic)?

Answer 16

Evidence of raised Jugular Venous Pressure (JVP) and Distended Neck Veins may

Note the rest of its symptoms are the same as cardiogenic shock

Question 17

Define what cardiac tamponade is

Answer 17

This is the accumulation of pericardial fluid under pressure.

Question 18

What is the classical traid of cardiac tamponade ?

Answer 18

Classical features - Beck’s triad:

1. Hypotension
2. Raised JVP
3. Muffled heart sounds

Question 19

What are the additional features of cardiac tamponade other than becks triad ?

Answer 19

• Dyspnoea
• Tachycardia
• An absent Y descent on the JVP - this is due to the limited right ventricular filling
• Pulsus paradoxus - an abnormally large drop in BP during inspiration
• Kussmaul’s sign (raised JVP on inspiration)
• ECG: electrical alternans

Question 20

What is the management of cardiac tamponade ?

Answer 20

Urgent pericardiocentesis

Question 21

What is the treatment of obstructive shock ?

Answer 21

Question 22

Describe frank-starling mechanism

Answer 22

The law states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction (the end diastolic volume)

Question 23

Describe the mechanism of hypovolaemic shock

Answer 23

1. Reduced blood volume
2. Lower venous return to the heart (ventricular filling = end-diastolic volume)
3. Reduced force of cardiac contraction and Cardiac Output (Frank-Starling law)
4. Therefore reduced BP (MAP) due to reduced CO which results in inadequate tissue perfusion (shock)

Question 24

What are the causes of hypovolaemic shock ?

Answer 24

• Bleeding - trauma, ruptured aortic aneurysm, GI bleed, ruptured ectopic, femoral pseudoaneurysm rupture
• Fluid loss - D&V, burns, heat exhaustion, pancreatitis

Question 25

What are the main signs/symptoms of hypovolaemic shock along with the 3 initial signs of shock ?

Answer 25

* Tachyponea * Tachycardia * BP decreased but may be compensated for by SVR in smaller haemorrhage * Cool clamy peripheries - due to increased SVR

Question 26

What is the treatment of hypovolaemic shock?

Answer 26

Question 27

What are the 4 classifications of hypovolaemic haemorrhagic shock?

Answer 27

Note - BP normal until \> 30% of blood lost

Question 28

What types of shock are strongly suggested by a patient presenting with the immediate signs of shock plus cold and clamy peripheries ?

Answer 28

Cardiogenic (including obstructive) and hypovolaemic shock is suggested

Question 29

Describe the mechanism behind distributive shock

Answer 29

1. Reduced Systemic Vascular Resistance due to Vasodilatation with WARM, RED PERIPHERIES 2. Reduced Mean Arterial Pressure (MAP = CO x TPR (SVR)) 3. Compensatory increase in Cardiac Output There is pooling of blood in the tissues due to the vasodilation ==\> warm, red peripheries

Question 30

What is the key feature which suggests septic shock ?

Answer 30

Warm and well perfused, with bounding pulse (due to increased CO) Note the other causes of distributive shock also cause this its just sepsis is so much more common

Question 31

What are the main subtypes of distributive shock and which is the most common ?

Answer 31

* Septic - the most common * Anaphylactic * Neurogenic Note - burns can also cause distributive shock

Question 32

What are the causes of neurogenic shock ?

Answer 32

* Spinal cord injury * Epidural or spinal anaesthesia

Question 33

What are the causes of septic shock

Answer 33

Infection

Question 34

what are the causes of anaphlatic shock

Answer 34

* Drugs e.g. penicillin and contrast media in radiology * Latex * Stings e.g. bees, eggs, fish, peanuts, strawberries It is an IgE mediated hypersensitivity reaction caused by mast cell (essentially a basophil) degranulation

Question 35

What signs and symptoms along with the 3 immediate shock signs and patient having an acidosis which suggest septic shock?

Answer 35

* Warm and vasodilated * Bounding pulse * Increased temp \>38 * Cardiac output initially increased * tachycardia and tachyponea * hypotension

Question 36

What is important to remember about the signs and symptoms of anaphylactic & septic shock?

Answer 36

The initial CVS problem is vasodilatation i.e. loss of TPR, but hypovolaemia & cardiac problems will develop rapidly

Question 37

What features would make you think anaphylactic shock ?

Answer 37

* Normal temp * Tachycardia and tachyponea * Hypotension * Urticarial rash * Itching, oedema, erythema * Diarrhoea and vomiting * Sweating * Wheeze, laryngeal obstruction, cyanosis

Question 38

What is the 1st line treatment in anphylactic shock ?

Answer 38

Give adrenaline

Question 39

What is the management of sepsis ?

Answer 39

**BUFALO** * B take bloods, * Measure urine output * Give fluids * Give antibiotics * Measure lactate * Give oxygen

Question 40

What is the treatment of distributive shock ?

Answer 40

Question 41

Describe the initial approach to the management of shock

Answer 41

ABCDE

Question 42

In the treatment of shock when someone is hypotensive what is the rate at which they would be fluid challenged ?

Answer 42

Fluid challenge ¼ or ½ L in less than half an hour

Question 43

Answer 43

* Dx = anaphylactic shock * Tx = as per anaphylaxis guidelines

Question 44

Case: * 82 year old man driven in by wife with central crushing chest pain for last 6 hours * Clammy, sweaty, cool peripherally, grey in colour, agitated * BP 79/45, HR 72, RR 28, SPO2 poor trace * Audible wheeze and crackles in chest bilaterally What is the Dx, initial Mx and Tx?

Answer 44

* STEMI – ST elevation evident in I, aVL and V2-V5, reciprocal changes in II and III * ABCDE approach * Main treatment for this patient is PPCI, may go on to need IABP – they need early discussion and involvement with cardiology team * Cardiogenic shock

Question 45

Case: * 23yo stab wound to right side of chest, jumped over fence while running away * HR 138, BP 82/55, RR 28, SpO2 94% on 15L O2 * Swollen and deformed left thigh, pain left groin * No significant PMH Interpret the images, what is the Dx, Mx and Tx ?

Answer 45

1. CXR = right sided hemothorax 2. Pelvic X-ray = fractures pelvis, Mx = pelvic binder 3. X-ray = mid-shaft femur fracture, Mx = kendrick splint * ABCDE approach – c with haemorrhage control * Senior doctor involvement and major trauma team activation * Early identification of bleeding site – now with CT * Role of interventional radiology * Massive haemorrhage protocol

Question 46

Case: * Collapsed pale and sweaty 24 yo female, BP 67/35, peripherally shut down, taking no medication. What should you beware of? obv there is many potential other causes tho

Answer 46

Beware of a ruptured ectopic pregnancy causing lots of bleeding

Question 47

Case: * 73 yo male sudden onset severe back pain while waving the grandkids off to nursery then collapses on way into house. What should you beware of ? obv serveral other potential causes

Answer 47

Beware of ruptured AAA

Question 48

Case: * 39yo female has had 24 hour history of sharp left sided chest pain worse on inspiration * This morning collapsed after getting out of bed * Just arrived back from Australia, thought her leg was maybe swollen yesterday * Reg meds: COCP * HR 140, BP 70/36, RR 32, SpO2 88% 15 L What is the Dx, Ix and Mx ?

Answer 48

ECG = Sinus tachycardia, atrial flutter or fibrillation, S1Q3T3 pattern, RBBB incomplete or complete, T wave inversion in the right precordial leads, P pulmonale, Right axis deviation * Dx = obstructive shock caused by PE * Ix = PE Ix's * Tx = Pe tx's