Shock

Question 1

What is shock?

Answer 1

A state of cellular and tissue hypoxia due to either reduced oxygen delivery, increased oxygen consumption, inadequate oxygen utilisation or a combo

Question 2

How is MAP calculated?

Answer 2

CO x SVR

DBP + 1/3 (pulse pressure = SBP - DBP)

Question 3

What are the causes of shock?

Answer 3

Hypovolaemia
Cardiogenic
Distributive - septic, anaphylactic, neurogenic
Obstructive 
Endocrine

Question 4

Mechanism behind hypovolaemic shock

Answer 4

Volume depletion - reduced SVR

Reduced pre-load = reduced CO

Question 5

What mediates cardiogenic shock?

Answer 5

Ischaemia induced myocardial dysfunction mainly
But can be caused by cardiomyopathies, valvular problems, dysrhythmias
If cardiogenic shock due to MI; suggests that >40% of LV involved, mortality of >75%

Question 6

Mechanism of distributive shock

Answer 6

Disruption of normal vascular autoregulation and profound vasodilation
Poor perfusion; despite increased CO
Regional perfusion differences
Alteration of oxygen extraction

Question 7

What can cause endocrine shock?

Answer 7

Myxoedema coma
Addisonian crisis
Thyrotoxicosis crisis

Question 8

What is the effect of the sympathetic nervous system on the heart?

Answer 8

Positive chronotropy and inotropy

Increased vasoconstriction

Question 9

What is the role of cortisol in shock?

Answer 9

Fluid retention

Antagonises insulin to maintain adequate sugar levels

Question 10

What inflammatory response is involved in shock?

Answer 10

Activation of complement cascade; attraction and activation of leukocytes
Cytokine release; interleukins, TNF-alpha
Platelet activating factor; increased vascular permeability, platelet aggregation
Lysosomal enzymes; myocardial depression
Adhesion molecules; damaged vessel walls
Endothelium derived mediators; NO
Imbalance between antioxidants and oxidants

Question 11

What haemodynamic changes are seen in shock?

Answer 11

Vascular abnormalities; vasodilation or constriction. Often massive venodilataion
Maldistribution of blood flow
Microcirculatory abnormalities
Inappropriate activation of coagulation system
DIC
Reperfusion injuries

Question 12

What mediates the loss of vascular reactivity seen in shock?

Answer 12

Massive release of NO; vasodilation

Question 13

What myocardial dysfunction will result from shock?

Answer 13

Reversible biventricular systolic and diastolic dysfunction
Circulating cytokines have a direct myocardial effect
Beta-receptor down regulation
Decreased cardiac myofilament calcium sensitivity

Question 14

Class 1 hypovolaemia

Answer 14

<15% blood loss
HR, BP, pulse pressure, RR, urine, GCS and base deficit normal
Monitor

Question 15

Class 2 (mild) hypovolaemia

Answer 15

15-30% blood loss
Tachycardic, decreased pulse pressure 
BP, RR, urine, GCS normal 
Base deficit -2 to -6 
Possible need for blood transfusion

Question 16

Class 3 (moderate) hypovolaemia

Answer 16

31-40% blood loss
Tachycardic, hypotensive, decreased pulse pressure, tachypnoeic, decreased urine output, decreased GCS
Base deficit -6 to -10
Blood transfusion required

Question 17

Class 4 (severe) hypovolaemia

Answer 17

> 40% blood loss
Tachycardic, hypotensive, decreased pulse pressure, tachypnoeic, anuric, low GCS
Base deficit -10 or less
Massive Transfusion Protocol required

Question 18

How can BP be measured?

Answer 18

Cuff

Arterial line

Question 19

What is CVP useful for?

Answer 19

Assessment of fluid responsiveness

Look at trend

Question 20

What is the gold standard for monitoring cardiac output?

Answer 20

Thermodilution with pulmonary artery catheter

Question 21

What MAP is aimed for?

Answer 21

65-70 mmHg

Question 22

How is oxygen delivery calculated?

Answer 22

CO x (1.39 x Hb x SpO2) + (PaO2 x 0.003)

Question 23

What is the goals with fluid resuscitation in shock?

Answer 23

Increase preload

Fine balance between rapid volume replacement and fluid overload (pulmonary oedema)

Question 24

How is a fluid challenge given?

Answer 24

500ml over 15 mins

Want to see increased MAP, decreased HR, increased urine output

Question 25

What fluid can be given?

Answer 25

Crystalloids (saline, hartman’s) - good, cheap, safe BUT rapidly lost from circulation to extravascular spaces so significant volumes required
Colloids - reduced volumes required but can cause anaphylaxis
Blood; probs best
NEVER use dextrose

Question 26

What pharmacological management options are available for management of BP?

Answer 26

Adrenaline; alpha/beta adrenergic agonists. At low dose primarily beta (positive chronotropy and inotropy, vasodilation. Alpha has vasoconstrictive effects) 
NA; alpha agonist
Vasopressin 
Dopamine
Dobutamine/ dopexamine

Question 27

What is a massive haemorrhage?

Answer 27

50% blood volume within 3 hours
Blood loss of 150ml/min
Obstetrics; minor (500-1000ml), major (<1000ml)

Question 28

What blood samples are required in a major haemorrhage protocol?

Answer 28

FBC
Coag screen
Fibrinogen 
Crossmatch 
U+Es
Calcium

Question 29

What will the blood bank supply in a major haemorrhage protocol?

Answer 29

4 units red cell
4 units FFP
1 unit platelets

Question 30

What markers do you want to aim for in blood transfusionn?

Answer 30

Hb 80 g/L
APTT and PT ratio <1.5
Platelets >50
Fibrinogen >1.5 g/L (obstetric >2 g/L)

Question 31

When should you transfuse cryoprecipitate (factor 7, fibrinogen, von Willebrand factor)?

Answer 31

Fibrinogen <1 g/L or <2g/L in obstetric haemorrhage

Question 32

What is important to think about post blood transfusion?

Answer 32

Thromboprophylaxis