Physiology in Anaesthesia Part 2

Question 1

pH 7.0 = how many hydrogen ions

Answer 1

100nmol/L

Question 2

what is the effect of alkalosis on calcium ions

Answer 2

encourages calcium to bind with proteins;
lowers free ionised fraction of calcium;
may lead to tetany

Question 3

What is myoglobin

Answer 3

A single ferroprotein chain, can bind only one molecule of oxygen, releasing it at only extremely low PO2 levels.

Question 4

Factors in the neonate that can cause dilation of the ductus arteriousus

Answer 4

hypoxia
hypercarbia
acidosis
pulmonary vasoconstriction

Question 5

Causes of persistent pulmonary hypertension in neonates

Answer 5

prematurity
diaphragmatic hernia
meconium aspiration
infection
congenital heart disease
polycythaemia

Question 6

Neonatal myocardium is more sensitive to (inotrope);
and less sensitive to (inotrope);
because:

Answer 6

noradrenaline;
dopamine;
sympathetic innervation of the myocardium is incomplete

Question 7

Neonatal haemotocrit should be maintained at ____% or higher;
because:

Answer 7

30%;
neonates have a marginal cardiovascular reserve, and the foetal haemoglobin dissociation curve is left-shifted.

Question 8

Conducting airways are fully developed at ____ weeks of gestation;
but alveoli begin to develop from distal saccules at ____ weeks.

Answer 8

16;
24-28

Question 9

Complete alveolar maturation occurs at:

Answer 9

8-10 years

Question 10

The primary neonatal respiratory muscle:

Answer 10

diaphragm

Question 11

Production of surfactant begins at ____;
and reaches maturity at ______.

Answer 11

23-24 weeks gestation;
35 weeks gestation

Question 12

Cause of ventilation-perfusion mismatch in the neonate:

Answer 12

distal airway closure during normal tidal breathing

Question 13

Prevention of respiratory distress syndrome in preterm infants:

Answer 13

1. maternal coritcosteroids before delivery;
2. intratracheal exogenous surfactant

Question 14

Why does the neonatal lung have a greater tendency to collapse

Answer 14

1. greater compliance;
   less outward recoil

Question 15

Neonatal active mechanisms to maintain normal lung volumes

Answer 15

1. rapid breathing rate shortens duration of expiration;
2. utilises intercostal muscle activity during expiration to stabilise the chest wall;
3. exhalation through a partially closed glottis in order to slow expiratory flow and maintain an end-expiratory lung volume.

Question 16

Explain the rapid wash-in and wash-out of inhaled gases in neonates

Answer 16

high ratio of minute ventilation to FRC

Question 17

Why does the neonate have an altered response to hypoxia and hypercarbia

Answer 17

immature function of peripheral chemoreceptors

Question 18

Respiratory differences in neonates (cf. adults)

Answer 18

1. decreased ratio of alveolar surface area to body surface area;
2. alveolar minute ventilation is doubled;
3. diaphragm has fewer high-oxidative muscle fibres and his more fatiguable;
4. increased alveolar-arterial oxygen tension gradient;
5. chest wall is more compliant and has less outward recoil;
6. greater V/Q mismatch;
7. greater tendency for airway collapse;
8. altered response to hypoxia and hypercarbia;
9. low airway resistance;
10. narrow airways more vulnerable to obstruction.

Question 19

Neonatal thermogenesis relies on:

Answer 19

non-shivering;
chemical thermogenesis by brown fat metabolism

Question 20

Define: thermoregulatory range

Answer 20

the ambient temperature range;
within which an unclothed subject;
can maintain a normal body temperature

Question 21

What stimulates thermogenesis in brown fat

Answer 21

sympathetic system: noradrenaline

Question 22

What is the lower limit of the thermoregulatory range in:
1. term infant
2. preterm infant

Answer 22

1. 23C
2. 28C

Question 23

Causes of accelerated heat loss in the paediatric patient

Answer 23

1. decreased thermoregulatory threshold due to anaesthesia;
2. low ambient temperature in the OR;
3. cold skin preparation solutions;
4. infusion of cold solutions;
5. anaesthesia-induced vasodilatation;
6. dry gases at high flows in nonrebreathing systems

Question 24

Measures to prevent loss of heat in paediatric anaesthesia

Answer 24

1. raising OR temperatures to 28-30C;
2. radiant heat lamps;
3. wrapping peripheries in insulating material;
4. warmed, non-volatile skin preparation solutions;
5. warmed IV fluids/blood products;
6. heated and humidified inhaled gases;
7. forced-air warmers

Question 25

The neonatal renal tubules have a decreased ability to reabsorb:

Answer 25

sodium
bicarbonate
glucose
amino acids
phosphates

Question 26

Causes of insensible fluid losses in the neonate

Answer 26

radiant heat lamps
fever
phototherapy
increased ambient temperature
decreased humidity

Question 27

Glucose requirements in:
1. term infants
2. preterm infants

Answer 27

1. 3-5mg/kg/minute
2. 5 mg/kg/minute

Question 28

Somatosensory evoked potentials can be recorded from the foetal cerebral cortex at _____ weeks gestation

Answer 28

29

Question 29

Most neonatal nociceptive impulses are transmitted by:

Answer 29

unmyelinated C-fibres;
poorly-myelinated A-delta fibres

Question 30

non-pharmacologic behavioural interventions as analgesia for the neonate

Answer 30

1. sucrose administration
2. suckling

Question 31

Origin of intraventricular haemorrhage in premature infants

Answer 31

1. germinal matrix
2. choroid plexus

Question 32

Factors in the pathogenesis of neonatal intraventricular haemorrhage

Answer 32

1. abrupt changes in cerebral haemodynamics;
2. changes in ICP;
3. disturbances in osmotic equilibrium;
4. coagulopathy