Paediatric anaesthesia Flashcards
1
Q
Definitions?
A
- Prematurity < 37 weeks
- Extreme prematurity < 28 weeks
- Neonate = upt to 44 weeks from date of conception
- Infant = 1 month to 1 year
- Child = 1-12 years
- Adolescent = 13-16 years.
2
Q
Airway anatomy ?
A
- Large head with prominent occiput
- Relatively large tongue
- Short neck and small mandible
- Obligate nose breathers < 5 months - Narrow nasal passages
- Floppy U-shaped epiglottis
- Larynx is anterior and at C4.
- Cricoid ring - Narrowest part of the upper airway.
- Have higher airway resistance for which nasal passages are responsible for 50%
3
Q
Physiological differences ?
A
- The smaller the child the larger the body surface area to mass ratio.
- Increased heat loss due to large body surface area to mass ratio
- Increased metabolic rate
4
Q
High metabolic rate in children?
A
- Higher oxygen demand
- Desaturation occurs quicker
- Higher resting HR and RR
5
Q
CVS?
A
- SV is fixed - Myocardium less compliant and frank-starling curve is flatter
- CO increased by increasing HR
- Relatively vasodilated
6
Q
RESP?
A
- Tidal volume is fixed
- Minute volume increases by increasing RR
- Respiration is diaphragmatic
- Relative deficiency of type 1 muscle firbres (Catch up y the age of 2yo)
- Bronchial tree fully developed at birth
- Very compliant chest wall but reduced lung compliance (poorly developed elastic tissue).
- High oxygen consumption of 15% compared to adults at 5%
- Closing capacity exceeds FRC up to the age of 6 (implications for pre-oxygenation and oxygen reserve)
- Infants have intrinsic peep of 4 cmH2O - Adducting vocal cords during expiration
7
Q
Airway oedema?
A
- Airway diameter in children - 4mm & in adult 8mm
- Resistance to flow is a function of viscosity of gas, length of the tube and radius of the tube to the 4th power.
- Increase in resistance by 16
8
Q
Oxygen consumption and delivery?
A
- About 7ml/kg/min compared to adults 3.5ml/kg/min
- Cardiac output 200ml/kg/min
- Blood volume is 80ml/kg at term and 75ml at age 2yo
- Hb = 16-18 at term, 10 at 3 months and 12-14 at 1 yr
- 80% HbF
9
Q
Nervous system?
A
- PNS is fully developed at birth Hence more susceptible to vagal stimulation.
- SNS continues to mature
- Tolerate neuraxial blockade much better
- BBB is immature - Normal by 6 months
- Increased senstivity to opioids and neuro-depressants
10
Q
Temperature control ?
A
- Increased heat loss
- Rapid onset hypothermia
- No shivering until 3 months
- Use brown fat - up to 6 % of total fat
11
Q
Renal ?
A
- eGFR about 65ml/min
- Reduced tubular function
- Reduced concentrating ability
- Excretory load is decreased by 50% as nitrogen is incoperated into growing tissue
- Maturation by age 2yo
12
Q
GIT?
A
- Reflux common in neonates
2. Coordination of respiration and swallowing matures by 5 months
13
Q
Pharmacokinetic differences?
A
- TBW is proportionately higher
- High volume of distribution of water soluble drugs
- Fat content is lower.
- Lipid soluble drugs dependent on distribution have prolonged effect
- Lower protein binding
- Phase II conjugation reactions are immature
14
Q
Perioperative critical events in children?
A
- Hypoxia
- Laryngospam
- Bradycardia
15
Q
Hypoxia?
A
- Increased work of breathing
- Small FRC
- High BMR
- Diaphragm dependence
