Common challenges and trouble-shooting in ICU

Question 1

What is hypoxia?

Answer 1

Low oxygen supply to bodily tissues

Question 2

Hypoxaemia ?

Answer 2

Low oxygen content of blood

Question 3

What is the definition of hypoxaemia ?

Answer 3

PO2 < 8kPa (Normal 10-13kPa)

Question 4

What is oxygen?

Answer 4

Electron acceptor in mitochondrial matrix

Question 5

What does electron transport drive?

Answer 5

ATP production or synthesis

Question 6

What is the value of pressures at atmospheric air?

Answer 6

760mmHg

Question 7

What is the equivalent of 760mmHg in kPa?

Answer 7

This is equivalent to 100kPa

Question 8

Conversion of mmHg to kPa?

Answer 8

Diving the value of mmHg by 7.5

Question 9

The first stage of reduction of PO2?

Answer 9

Humidification

Subtraction of water vapor pressure 47mmHg

=0.21 x (760mmHg - 47mmHg) = 149mmHg or 20kPa

Question 10

Alveolar air is determined by?

Answer 10

• Alveolar ventilation
• Pulmonary blood flow

Question 11

What is the alveolar gas equation?

Answer 11

PaO2 = PiO2 - pCO2 / R

R = 0.8
pCO2 = usual CO2 concentration 40mmHg

= 149 - 40 /0.8 = 99mmHg or 13kPa

Question 12

Oxygen cascade?

Answer 12

See image attached

Question 13

Hypoventilation will decrease the following values?

Answer 13

Oxygen - Decrease
Carbondioxide - Increase

Question 14

What are the main causes of hypoxia?

Answer 14

• Alveolar hypoventilation
• Limited diffusion capacity
• Shunts - Admixture of venous blood (Bronchial & thebesian veins)
• V/Q mismatch (Most important)

Question 15

What types of shunts do you know?

Answer 15

• Intra-cardiac
• Intra-pulmonary

Question 16

What is an intracardiac shunt?

Answer 16

Blood passes through an abnormal channel in the heart without passing through the lungs

Question 17

What is intrapulmonary shunt?

Answer 17

The blood does not take part in gas exchange

Question 18

What is the only cause of refractory hypoxia?

Answer 18

Shunt

Question 19

What are the causes of intrapulmonary shunts?

Answer 19

• Cardiogenic pulmonary oedema
• ARDS
• Pneumonia
• Pulmonary haemorrhage
• Atelectasis

Question 20

What are the causes of intracardiac shunts?

Answer 20

• Ventricular septal defects
• Congenital heart diseases
• Patent foramen ovale

Question 21

What is the distribution of V/Q?

Answer 21

V/Q is;

• highest at the apices
• Lowest at the bases

Question 22

Increased FiO2 and V/Q mismatch?

Answer 22

Increasing FiO2 will improve V/Q mismatch

Question 23

What are the components of physiological dead space?

Answer 23

Anatomic + Alveolar

Question 24

What are the main causes of V/Q mismatch ?

Answer 24

• Atelectasis
• PE
• Position
• Bronchospasm
• Obstructive airway disease
• Pneumonia
• ARDS
• PTX

Question 25

Pathophysiological mechanisms of hypoxia?

Answer 25

• Low FiO2
• Alveolar hypoventilation
• Diffusion limitation
• Shunt (Main)
• V/Q mismatch (Main)

Question 26

What are the systemic effects of hypoxia?

Answer 26

• CNS - Brain damage & seizures
• CVS - Tachy-arrhythmias & HTN (pul)
• REN - Sodium retention and protenuria

Question 27

Main causes to V/Q mismatch and shunt?

Answer 27

• Mucus plug
• Lung derecruitment
• Worsening underlying pathology

Question 28

What are the aims of lung protective ventilation?

Answer 28

• Pplat < 30
• Vt < 6ml/kg
• Driving pressures < 15

Question 29

Broad complex tachyarrhythmia ?

Answer 29

• QRS > 120ms

Question 30

When does coronary perfusion occur?

Answer 30

During diastole, hence tachycardia will decrease perfusion

Question 31

Bradycardia and extracardiac causes?

Answer 31

• Hypoxia
• Hypothermia
• Drugs

Question 32

What are the adverse features?

Answer 32

• Heart failure
• IHD
• Syncope
• Shock

Question 33

What are the most common causes of AF in the community ?

Answer 33

• Hypertension
• Hyperthyroidism
• IHD
• Pericarditis
• Mitral stenosis

Question 34

What is the dose and half-life of adenosine?

Answer 34

• Half-life = 10s
• Dose = 6+12+18

Question 35

What is class I haemorrhage?

Answer 35

• Blood loss up to 15%
• HR normal or minimally elevated
• BP, RR normal

Question 36

Whats is class II haemorrhage?

Answer 36

• Blood loss between 15-30%
• HR - Elevated
• RR - Elevated
• Pulse pressure reduced
• BP - Minimally decreased
• Sympathetic activation
• Cool peripheries

Question 37

What is class III haemorrhage ?

Answer 37

• Blood loss 30-40%
• Low CO, BP & confusion
• HR - elevated
• Reduced UO
• Reduced CRT

Question 38

What is class IV haemorrhage ?

Answer 38

• Blood loss > 40%
• Low BP
• Confusion
• Reduced pulse pressure < 25mmHg
• Tachycardia
• Reduced UO
• Cold, clammy & delayed CRT

Question 39

What are the potential sources of blood loss? Blood on the floor + four

Answer 39

• Chest
• Abdomen
• Pelvis
• Femur

Question 40

Flow rates for cannula per min?

Answer 40

• 14G - 250
• 16G - 150
• 18G - 100
• 20G - 60
• 22G - 35

Question 41

ROTEM & TEG?

Answer 41

See image

• Clotting factors
• Fibrinogen
• Fibrinogen
• Platelet
• Fibrinolysis

Question 42

Type of blood products to be requested if cross-matched blood is unavailable ?

Answer 42

• O RBC
• AB plasma

Question 43

What is calcium in the classic clotting cascade?

Answer 43

• Factor IV

Question 44

Components of the lethal diamond causing severe blood loss?

Answer 44

• Acidosis - Increased lactic acid in blood
• Coagulopathy - Decreased coagulation
• Hyothermia - Decreased metabolism
• Hypocalcaemia - Citrate makes it worse

Question 45

When should calcium be replaced?

Answer 45

After 3-4 units of blood

Question 46

Time to effect of Vitamin K?

Answer 46

24 hours

Question 47

Anticoagulants and reversal agents?

Answer 47

• Warfarin - Vit K & PCC
• DDirect thrombin inhibitors (Dabigatran) - Idarucizumab or RRT
• Factor Xa (Rivarox, Apixaban & Edoxaban) - PCC (factor 8 inhibitor)
• Heparin - Protamine
• LMHW - Protamine or adexanet alfa

Question 48

Management of anti-platelets reversal ?

Answer 48

• Transfuse if < 50
• Desmopressin (DDAVP)
• Cryoprecipitate