Physiology in Anaesthesia: Part 3

Question 1

Aetiological factors in the development of retinopathy of prematurity

Answer 1

1. prematurity
2. hyperoxia
3. hypocarbia
4. vitamin E deficiency
5. acidaemia

Question 2

Preferred trimester for non-obstetric surgery in obstetric patients

Answer 2

second

Question 3

What factors cause the increased in maternal intravascular fluid volume

Answer 3

1. increased production of renin, angiotensin, and aldosterone
2. promotion of sodium absorption and water retention
3. progesterone circulation

Question 4

Haematological changes in maternity

Answer 4

1. increased intravascular fluid volume
2. relative reduction in plasma protein concentration
3. physiologic anaemia due to greater increase in plasma than RBC
4. mild thrombocytopaenia
5. mild leukocytosis
6. increased fibrinogen and factor 7
7. decreased factors 6, 8, and antithrombin 3
8. decreased PT and PTT (20%)

Question 5

What accounts for the large increase in cardiac output immediately after delivery

Answer 5

1. autotransfusion after delivery
2. reduced vascular capacitance from loss of placenta
3. decreased lower extremity venous pressure from release of aortocaval compression

Question 6

Do the following increase, decrease, or stay the same in pregnancy:
1. systemic blood pressure
2. central venous pressure
3. pulmonary capillary wedge pressure
4. venous capacitance

Answer 6

1. decrease
2. stay the same
3. stay the same
4. increase

Question 7

Signs of aortocaval compression

Answer 7

nausea, vomiting
diaphoresis
dizziness

Question 8

Cardiac auscultation in pregnancy

Answer 8

S1: accentuated, increased splitting
S3: common
S4: minority
EJS: 2/6

Question 9

Acid-base changes in pregnancy

Answer 9

1. PaCO2 reduced to 30mmHg
2. Mild increase in arterial pH
3. HCO3 reduced to 20-21 (increased renal excretion)

Question 10

Lung volume changes in pregnancy

Answer 10

1. FRC reduced 20%
2. Equal reductions in RV and ERV
3. Closing capacity unchanged
4. Vital capacity not significantly changed

Question 11

Reasons for increased risk of aspiration in pregnancy

Answer 11

1. upward movement of oesophageal sphincter
2. reduced oesophageal sphincter tone
3. gastrin secreted by placenta stimulates gastric acid secretion
4. gastric emptying unchanged unless in labour
5. increased residual gastric volume

Question 12

Why do pregnant women require smaller volumes of local anaesthetic for neuraxial blockade

Answer 12

1. decreased size of epidural space
2. decreased volume of CSF in subarachnoid space
3. engorgement of epidural veins
4. hormonal changes

Question 13

Causes of decreased uterine perfusion pressure

Answer 13

1. maternal hypotension
2. hypovolaemia
3. aortocaval compression
4. anaesthesia
5. increased uterine pressure
6. hypocapnoea
7. valsalva
8. endogenous catecholamines, exogenous vasopressors

Question 14

Why is foetal haemoglobin left shifted

Answer 14

HbF does not interact with 2,3-DPG

Question 15

GA at which FHR monitoring is acceptable

Answer 15

25 weeks

Question 16

Molecular weight below which drugs diffuse through placenta to foetus

Answer 16

1000 Daltons

Question 17

Rate of diffusion of drugs to foetus depends on:

Answer 17

1. maternal-foetal concentration gradients
2. maternal protein binding
3. molecular weight of drug
4. lipid solubility
5. degree of ionisation

Question 18

What contributes to increased in size of the elderly heart

Answer 18

fibrosis and endothelial damage
lead to increased arterial stiffness
and decreased nitric-oxide induced vasodilation;
thus afterload is increased.
This causes concentric left ventricular hypertrophy.

Question 19

Diseases in elderly associated with diastolic dysfunction

Answer 19

1. systemic hypertension
2. coronary artery disease
3. cardiomyopathy
4. aortic stenosis
5. atrial fibrillation
6. diabetes
7. chronic kidney disease

Question 20

In elderly, the following values are (increased/unchanged/decreased) compared to young adults:
1. systolic blood pressure
2. diastolic blood pressure
3. pulse pressure
4. left ventricular afterload

Answer 20

1. increased
2. decreased
3. increased
4. increased

Question 21

What is age-related endothelial dysfunction

Answer 21

In the elderly, a decreased in the ability of the endothelium to dilate or contract blood vessels in response to physiologic and pharmacologic stimuli.

Question 22

Changes to the heart’s conduction system in the elderly

Answer 22

1. decreased proportion of pacemaker cells
2. conductive tissue becomes infiltrated with fibrous and fatty tissue

Question 23

Intrinsic ageing factors that influence the respiratory system

Answer 23

1. decreased bronchiolar calibre
2. decreased alveolar surface area
3. increased lung collagen
4. decreased lung elastin
5. kyphoscoliosis
6. increased thoracic cage rigidity
7. decreased diaphragmatic strength

Question 24

Extrinsic factors affecting the elderly lung

Answer 24

1. pollution
2. smoking
3. general deconditioning
4. coexisting disease

Question 25

Functional consequences of respiratory ageing

Answer 25

1. decreased lung elastic recoil 2. increased lung compliance 3. decreased oxygen diffusion capacity 4. premature airway closure - VQ mismatch - increased A-a gradient 5. small airway closure and gas trapping 6. decreased expiratory flow rates

Question 26

What happens to lung volumes in the elderly (increase/decrease/no change)

Answer 26

Vital Capacity: decrease Residual Volume: increase Total lung capacity: no change FRC: increased Closing capacity: increased

Question 27

How does smoking affect upper airway reflexes

Answer 27

1. depletion of neuropeptide of airway sensory nerves 2. inhibition of C-fibre transmission in the lower respiratory tract

Question 28

What are morbidities associated with sleep disordered breathing

Answer 28

1. systemic hypertension 2. pulmonary hypertension 3. dysrhythmias 4. myocardial infarction 5. stroke 6. sudden death 7. car accidents 8. post-operative delirium

Question 29

How is the functional capacity of the liver affected in old age

Answer 29

1. protein synthesis diminished 2. a1-acid glycoprotein increased 3. plasma cholinesterase diminished

Question 30

Factors associated with reduced resting core temperatures in the elderly

Answer 30

1. neurologic disease 2. diabetes 3. low body weight 4. lack of self-sufficiency 5. consumption of less than two meals per day 6. smoking 7. alcohol consumption

Question 31

Factors that predispose to GORD in the elderly

Answer 31

1. sliding hiatal hernias 2. shortened intra-abdominal segment of lower oesophageal sphincter 3.impaired clearance of refluxed acid 4. medications that reduce lower oesophageal sphincter pressure 5. decreased oesophageal peristalsis

Question 32

Medication that reduces lower oesophageal tone

Answer 32

anticholinergics antidepressants nitrates calcium channel blockers theophylline

Question 33

Why do the elderly lose lean muscle mass

Answer 33

1. decreased motor neurone innervation 2. decreased physical activity 3. decreased caloric intake 4. endocrine shift towards catabolism 5. decreased androgen production 6. decreased protein consumption and synthesis 7. raised inflammatory mediators

Question 34

Perioperative consequences of having reduced lean muscle mass

Answer 34

1. impaired mobilisation 2. reduced cough efficiency 3. reduced shivering thermogenesis 4. altered drug disposition 5. reduced functional reserve 6. prolonged recovery and hospitalisation

Question 35

Define post-operative delirium

Answer 35

Syndrome of fluctuating consciousness, inattention, memory impairment, and perceptual abnormalities, that typically occurs after a lucid interval of 1-3 days after emergence from anaesthesia.

Question 36

How is morphine metabolised

Answer 36

glucuronidation

Question 37

What are the metabolites of morphine

Answer 37

morphine-3-glucuronide morphine-6-glucuronide