Child Vs Adult Flashcards
What are the differences in the respiratory system of the child vs adult?
- larger head, short neck, large tongue, narrow nasal passages
- high anterior larynx (C3-4) instead of C5-6 in adult
- large u-shaped floppy epiglottis
- narrowest point of larynx is at cricoid cartilage (adult = laryngeal inlet)
- trauma to small airway can lead to oedema and airway obstruction (1mm oedema can narrow airway by 60%)
- obligate nasal breathers
- compliant chest wall with horizontal ribs
- diaphragmatic breathing > intercostal breathing
- diaphragm restricted by large liver
- fixed tidal volume - increased minute ventilation achieved by increased RR
- higher alveolar ventilation 100-150 ml/kg/min (60ml/kg/min adults)
- born with only 10% of alveoli - develop over 8yrs
- closing volume is larger than FRC until 6yrs resulting in airway closure at end-expiration
- I:E ratio 1:1 - no end-expiratory pause
- higher basal O2 consumption 6ml/kg/min compared to 3.5 ml/kg/min in adult
- higher apneoa risk
- hypoxaemia occurs more rapidly
What is the alveolar vention in children?
100-150 ml/kg/min
(60 ml/kg/min adults)
What is the I:E ratio in children?
1:1 no expiratory pause
What is the basal O2 consumption of children vs adults?
Higher - 6ml/kg/min
Adults 3.5 ml/kg/min
Where is the larynx level in children?
C3-4
(C5-6 adults)
Where is the narrowest point of the airway in children?
Cricoid cartilage level
What is the circulating blood volume in children?
85ml/kg
What is the circulating blood volume in adults?
70 ml/kg
What is the cardiac output of a child?
200ml/kg/min
What is the Hb in a neonate?
16-20 g/dL
What are the CVS differences in children vs adults?
- higher circulating blood volume (85ml/kg)
- neonatal myocardium is more non-contractile connective tissue
- stroke volume is relatively fixed
- CO is rate depedent and neonates tolerate bradycardia poorly
- CO 200ml/kg/min
- parasympathetic NS more developed than sympathetic - bradycardia more frequent with hypoxia or vagal stimulation
- asystole most common form of arrest
- transitional circulation may revert to fetal circulation if the neonate becomes hypoxic, acidotic, hypercapnic or hypothermic
- Hb conc higher (16-20g/dL)
- right ventricular mass equal to left ventricular mass until 6 months of age (R axis deviation on ECG)
How does the CNS of children differ to adults?
- myelination incomplete until 1yr
- skull non-rigid with open fontanelles
- MAC infant > neonate > adult
- more sensitive to opiate induced resp depression and apnoea
- immature neuromuscular junction that’s very sensitive to NDMRs but relatively resistant to sux (use 1.5mg/kg)
- spinal cord ends at L3 (L1 by age 2)
How does the renal system differ in children?
- higher total body water (80%) at birth
- increased ECF results in higher volumes of distribution of drugs
- renal immaturity results in poor handling of water excess or excess sodium
- poor renal hydrogen ion excretion
- glucose reabsorption is limited
- glomerular filtration and tubular reabsorption reduced until 6-8 months of age
- renal blood flow is 6% of cardiac output at birth - rises to 18% of CO at 1 month (compared to 20% in adult)
- GFR at term is 30ml/min increasing to 110ml/min by 2yrs
How is the child’s liver different to adult?
- immature liver has fewer selective pathways to metabolise drugs
- low hepatic glycogen stores mean hypoglycaemia occurs readily with prolonged fasting
How does temperature homeostasis differ in children vs adults?
- poor temp regulation in neonates
- large body surface area/volume ratio
- high heat loss
- higher thermoneutral temperature (temp below which an individual can’t maintain core body temp) 32°C for term infant compared to 28°C for an adult
- infant <3 months cannot shiver
- utilise non-shivering brown fat thermogenesis
