Anaesthetics

Question 1

What is the oxygen cascade?

Answer 1

flow of oxygen from air to mitochondria
as move down from air there is a physiological decrease in PaO2

Question 2

O2 moves from areas of _____

Answer 2

high partial pressure to low partial pressure - hence pulmonary capillaries have low PaO2 compared to alveoli so it moves across

Question 3

What is V/Q mismatch?

Answer 3

idea that perfusion and ventilation does not completely match

Question 4

Define deadspace? What conditions can increase it

Answer 4

areas that are ventilated but not adequately perfused

PE and hypotension
anatomically the mouth, pharynx and large areas are deadspcare

Question 5

Why do you not give too much oxygen in COPD?

Answer 5

those with COPD have developed over time to only perfuse the areas of lungs that are not diseased, adding O2 can result in increased perfusion to areas that are not well ventilated and result in hypercapnia as the haemoglobin picks up the CO2 there instead as has higher affinity

Question 6

What is shunt? Causes?

Answer 6

areas that are perfused but not adequately ventilated

alveolar collapse, pneumonia, pulmonary oedema, COPD

Question 7

What is the oxygen dissociation curve?

Answer 7

sigmoidal curve
binding to O2 to one HB subunit causes a conformational change making other subunits more likely to bind

means O2 collection is maximised in areas of high concentration and easy to offload in areas of low O2

acidosis and temp increase can shift curve to right making O2 more likely to be released (exercising tissues produce heat and lactic acid so need more O2)

Question 8

Cardiac output =

Answer 8

HR x SV

Question 9

MAP =

Answer 9

CO x SVR

Question 10

Conditions that too much O2 can be bad?

Answer 10

COPD / type 2 resp failure
post MI ( new research)

Question 11

List 4 types of oxygen masks and use?

Answer 11

Nasal cannula - on ward with low O2
Hudson face mask - when in recovery and cannot nose breathe
Venturi - gives targeted fio2 if risk of type 2 respiratory failure
15l/min non rebreather mask - acutely unwell patient

Question 12

What do you need to do with non-rebreather mask?

Answer 12

occlude valve before putting on and ensure bag filled

Question 13

What is important to consider with oxygen therapy?

Answer 13

it is very drying, makes it difficult to cough up secretions and damages alveoli and surfactant, need to consider humidification

Question 14

Define sepsis?

Answer 14

Dysregulated host response to infection
can be considered as patient with signs of infection and NEWS > 5

Question 15

Fluid requirements for maintenance in adults?

Answer 15

25-30ml/ kg/ day of water
1mmol/kg/day of Na, K, Cl
50-100 g glucose

Question 16

Paediatric fluid reuquirements?

Answer 16

100mls/kg/day for first 10kg
50mls/kg/day for next 10kg
20mls/kg/ day for remaining weight

Question 17

Fluid resuscitation?

Answer 17

500mls bolus of crystalloid given over less than 15 minutes

if no response continue giving bolus of 250mls-500mls until given 2000mls, if still no response, need expert help

Question 18

How many mmol/l of Na and Cl in 0.9% saline?

Answer 18

154

Question 19

In acid base derangement compensation by the lungs is ____ but by kidneys is ______

Answer 19

compensation by lungs is fast but by kidneys is slow
so if there is HCO3 compensation then this is a chronic condition

Question 20

What is base excess?

Answer 20

indicates how much acid required to return the blood to a normal ph

so negative = too much acid
positive = too much alkali

normal base excess is -2 to +2

Question 21

When assessing a patient with COPD - what do you want to know about co2 retention?

Answer 21

is it acute or chronic
check if bicarb is raised - if it is this suggest chronic retention

Question 22

Why is temperature control in anaesthesia important?

Answer 22

patients autonomic reflexes are blocked by anaesthetic so they cannot shiver etc. and cannot adjust their own temperature. When patients become colder their coagulation is affected making surgery more risky, at even colder temperatures the heart rate will be slowed.

Question 23

How can you check you are ventilating someone appropriately/ correct placement of airway adjunct?

Answer 23

misting of mask
chest rising and falling
capnography trace

Question 24

3 common presentations in SHDU? (explain)

Answer 24

nausea and vomiting - need to rule out it is not being caused by a bowel obstruction
post op ileus - could be due to abdominal surgery or opioids or a combination
basal atelectasis - partial collapse of base of lung, usually due to inadequate respiratory effort as do not have enough analgesia

Question 25

When under anaesthetic what BP is okay? Why?

Answer 25

Anaesthetic drops the BP but generally not too worried about this.

Usually aiming for a systolic around 80. Aim for 90 in older people or those who are normally hypertensive.

You do not need as high a BP with anaesthetic because your kidneys and brain which usually need the higher BP are resting. Having a lower BP also makes surgery easier because there is less bleeding in the surgical field.

Question 26

Where do you have to be to receive inotropes or vasopressors?

Answer 26

HDU or ICU

Question 27

What do vasopressors do and what is indication?

Answer 27

They cause vasoconstriction by stimulating vascular smooth muscle contraction. Given to increase MAP.
Often given in cases of shock where patients have not responded to fluids.

Question 28

MOA of Metaraminol?

Answer 28

alpha agonist

Question 29

MOA of Noradrenaline?

Answer 29

Alpha agonist

Question 30

MOA of adrenaline?

Answer 30

Alpha agonist

Question 31

MOA of vasopressin?

Answer 31

hormone that causes vasoconstriction

Question 32

MOA of ephedrine?

Answer 32

alpha and beta agonist

Question 33

MOA of phenylephrine?

Answer 33

alpha agonist

Question 34

List 6 vasopressors?

Answer 34

metaraminol
noradrenaline
adrenaline
vasopressin
ephedrine
phenylephrine

Question 35

Adrenaline and noradrenaline need given through?

Answer 35

central venous line as very irritant

Question 36

What is a central venous line/ catheter?

Answer 36

essentially a large cannula put into a large central vein e.g. internal jugular, subclavian, or femoral

Question 37

How do you give TPN?

Answer 37

Ideally through a central venous line as very irritant

Question 38

What is an art line? Indications?

Answer 38

arterial line, catheter/ cannula inserted into an artery - often the radial artery

Continuous blood pressure monitoring.
Continuous mean arterial pressure monitoring.
Frequent arterial blood gas specimens.
Frequent blood sampling for diagnostic testing

Question 39

What are inotropes?

Answer 39

drugs that increase the contractility of the heart to increase cardiac output and therefore MAP

Question 40

Inotrope use vs vasopressors?

Answer 40

inotropes and vasopressors will both increase MAP but use depends on why MAP is low, if you have low MAP cause of cardiogenic shock then you want inotropes so heart pumps better, but if you have low MAP cause of vasodilation e.g. septic shock you want vasopressors so that systemic vascular resistance increases

Question 41

Examples when inotropes are given?

Answer 41

given when cardiac output is low, for example in heart failure, post MI or following heart surgery

Question 42

Examples of inotropes?

Answer 42

mainly catecholamines

adrenaline
dobutamine
isoprenaline