Title: Neonatal and Paediatric Anatomy and Physiology
1Neonatal and Paediatric Anatomy and Physiology
- Dr Alison Chalmers
- Consultant Anaesthetist
- Queen Victoria Hospital
2What you need to know
- Fetal circulation and changes at birth
- Anatomical differences in the airway, head and
spinal cord from the adult - Physiological differences from the adult
- Haematological and biochemical changes with age
- Estimation of blood volume
3Fetal circulation
- Ductus venosus
- Foramen ovale
- Ductus arteriosus
4Changes at birth
5Changes at birth
- First breath generates negative pressure
- ? FRC ? PVR
- Blood flows from right ventricle through lungs
- ? SVR with clamping of umbilical vessels
- Reversal of right to left flow through DA
- Oxygen and ? PGE2 stimulates ductal constriction
- ? LAP and ? SVR cause closure of the FO
- DV closes passively as flow ceases
6Fetal haemoglobin
- 2 ? chains and 2 ? chains
- Binds 2,3-DPG less avidly than HbA
- Shifts ODC to left (P50 2.4KPa)
- Favours O2 transfer from mother to fetus
- Gives up more O2 to fetal tissues than HbA
- 80 circulating Hb at birth
- Replaced within 3-5months by HbA
7Neonatal physiology
- CVS
- RVLV at birth
- ? ratio of connective to contractile tissue
- Flat Starling curve
- Fixed SV
- Lungs
- Bronchial tree fully developed
- Alveoli develop fully after birth
- Compliant chest wall
- Diaphragmatic breathing
- Less ventilatory responses to PaO2 and PaCO2
8Neonatal physiology
- Kidneys
- No of nephrons complete by birth
- RBF increases from 5 CO at birth to 20 at 1
month - Low GFR adult by 2 years
- Liver
- Immature enzymes
- CNS
- Pathways complete at birth
- Temp control
- High SA to body weight ratio
- Less SC fat
- Non shivering thermogenesis
9Paediatric anatomy and physiology
- Airway
- Lungs
- CVS
- BMR
- CNS
- Temp regulation
- Fluid balance
- Pharmacology
10Paediatric Airway
11Paediatric respiratory system
- Diaphragmatic
- Neonates obligate nasal breathers
- Increased respiratory rate
- Very compliant chest wall horizontal ribs
- CC gt FRC in normal breathing
- Ventilatory response to CO2 reduced
- BMR/O2 consumption high
12Paediatric cardiovascular system
AGE SYSTOLIC BP (mmHg) DIASTOLIC BP (mmHg) HEART RATE
Preterm 45 25 gt120
Birth 60 35 gt120
Neonate 70-80 40-50 120-150
3-6 months 80-90 50-60 120-140
1 year 90-100 60-80 110-130
5 years 95-100 50-80 90-100
12 years 110-120 60-70 80-100
13Paediatric nervous system
- Spinal cord ends L3 recedes by adolescence
- Immature BBB
- Pronounced vagal reflexes
14Fluid balance
- Blood volumes
- Birth 90ml/kg
- Child 80ml/kg
- Teenager 70ml/kg
- Maintenance fluid requirements
- 4ml/kg/h for first 10kg
- 2ml/kg/h for next 10kg
- 1ml/kg/h for each kg after
15Pharmacokinetics/dynamics
- Lower plasma albumin levels up to 1 year
- Renal and hepatic immaturity
- MAC increased in neonates
- Neonates sensitive to NMB more resistant to sux
16Haematological changes with age
- Hb
- Birth 14-22g/l, 3-6 months 11-14, 6-12 years
11.5-15.5 - WCC
- Birth 10-26 x109/l, 3-6 months 6-18, 6-12
years 5-13 - Platelets fairly stable between 150-500 x109/l
- All vit K dependant clotting factors are low at
birth reach adult values by 6 months
17Biochemical changes with age
- Albumin low up to 1 year
- Bilirubin high at birth (17-170umol/l), normal
adult levels by 1 month - Ca2 low neonate (1.9-2.8mmol/l), normal adult
levels by 1 year - T4 high neonate, falls to adult range steadily
up to 10 years
18Any questions?
19Summary
- Fetal circulation and changes at birth
- Anatomical differences in the airway, head and
spinal cord from the adult - Physiological differences from the adult
- Haematological and biochemical changes with age
- Estimation of blood volume