36. Child Versus Adult Flashcards
Respiratory system:
17
1
> Relatively larger head,
short neck, large tongue
and narrow nasal passages.
2
> High anterior larynx
(level C2/3 compared to C5/6 in the adult).
3
> Large U-shaped floppy epiglottis.
4
> Narrowest point of the larynx
is at the level of the cricoid cartilage
(in adults it is at the laryngeal inlet).
5 > Trauma to the small airway can easily lead to oedema and airway obstruction. 1 mm oedema can narrow an infant’s airway by 60% (resistance ∝1/radius).
6
> Equal angles of mainstem bronchi
(in adults the right main bronchus is
more vertical).
6
> Obligate nasal breathers.
7
> Compliant chest wall with horizontal ribs.
8
> Diaphragmatic breathing > intercostal breathing.
9
> Diaphragmatic movement
restricted by relatively large liver.
10
> Relatively fixed tidal volume.
Increase in minute ventilation achieved by
increasing respiratory rate.
11
> Higher alveolar ventilation
100–150 mL/kg/min compared with
60 mL/kg/min in adult.
12
> Born with only 10% of the
total number of alveoli as adults.
Alveoli develop over first 8 years.
13 > Closing volume is larger than FRC until 6–8 years of age resulting in airway closure at end-expiration. Consider use of IPPV and PEEP.
14
> Sinusoidal respiratory pattern,
no end-expiratory pause
(inspiratory/expiratory ratio 1:1).
15
> Higher basal oxygen consumption
6 mL/kg/min compared with
3.5 mL/kg/min in the adult.
16
> Higher risk of apnoea.
17
> As a result of all of the above points, hypoxaemia occurs more rapidly.
Cardiovascular system:
10
1
> Circulating blood volume
85 mL/kg compared with 70 mL/kg in adult.
2
> Neonatal myocardium consists of more
non-contractile connective tissue.
3
> Stroke volume is relatively fixed.
4
> Cardiac output is therefore largely
rate dependent and neonates tolerate
bradycardia poorly.
5
> Cardiac output 200 mL/kg/min.
6 > Parasympathetic nervous system better developed than sympathetic, meaning bradycardia occurs frequently with hypoxia or vagal stimulation.
7
> Asystole is the most common
form of cardiac arrest and ventricular
fibrillation is uncommon.
8
> Transitional circulation may revert
to fetal circulation if neonate becomes
hypoxic, acidotic, hypercapnic or hypothermic.
9
> Haemoglobin higher in neonate: 16–20 g/dL.
10
> Right ventricular mass equal to
left ventricular mass until 6 months of
age, resulting in right axis deviation on the ECG.
Central nervous system:
1
> Myelination is incomplete in the first year of life.
2
> Skull non-rigid with open fontanelles.
3
> MAC infant > neonate > adult.
4
> More sensitive to
opiate-induced respiratory
depression and apnoea.
5 > Immature neuromuscular junction that is very sensitive to nondepolarising muscle relaxants but relatively resistant to suxamethonium (use 1.5 mg/kg).
6
Spinal cord ends at L3 (L1 by age 2 years).
Renal system:
8
1
> Higher total body water (80%) at birth.
2
> Increased extracelluar fluid (ECF) resulting
in higher volumes of
distribution of drugs.
3
> Renal immaturity resulting in poor
handling of water excess
or excess sodium.
4
> Poor renal hydrogen ion excretion.
5
> Glucose reabsorption is limited.
6
> Glomerular filtration and
tubular reabsorption reduced
until 6–8 months of age.
7
> Renal blood flow is 6% of cardiac output
at birth rising to 18% of cardiac
output at 1 month (compared with 20% in adult).
8
> GFR at term is 30 mL/min
increasing to 110 mL/min by age 2 years.
Liver:
2
Liver:
1
> Immature liver has fewer
selective pathways to metabolise drugs.
2 > Low hepatic glycogen stores means hypoglycaemia occurs readily with prolonged fasting.
Temperature homeostasis:
1
> Poor temperature regulation in neonates.
2
> Large body surface area/volume ratio.
3
> High heat loss.
4
> Higher thermoneutral temperature
(temperature below which an individual
is unable to maintain core body temperature)
32 °C for a term infant compared with 28 °C for an adult.
5
> Infants <3 months of age cannot shiver.
6
> Utilise non-shivering brown fat thermogenesis.
