In this presentation we look at how pediatric population is different from adult and how it aaffects our anaesthetic considerations.

1. ANATOMICALAND
PHYSIOLOGICAL
CHANGES IN
NEWBORNS-
ANAESTHETIC
CONSIDERATIONS
DR-GAURAV PATHAK

2.  Introduction
 Respiratory system
 Cardiovascular system
 Renal system
 Hepatic system
 Haematology
 Glucose metabolism
 Temperature control
 Central nervous system

3. •Pediatric anesthesia involves more than simply adjusting drug doses and
equipment for smaller patients.
• Age groups-
o Neonates (0–1 months)
o Infants (1–12 months)
o Toddlers (12–24 months)
o Young children (2–12 years)
• Risk is generally inversely proportional to age.
 INTRODUCTION

4.  RESPIRATORY SYSTEM
• Pediatric respiratory system is different than adult in many aspects.
• Neonates preferentially breathe through their nose.
• Small diameter of airways-increases resistance.

7. • Narrowest at cricoid rather
than vocal cords
• Tube may be small enough to
pass through cords but not
cricoid
• Larynx is funnel shaped, so
secretions accumulate in
retropharangeal space

9. • Infants and young children ARE NOT SMALL ADULTS.
• "One size fits all" DOES NOT APPLY.
• Neonates preferentially breathe through their nose.
• The airway is funnel shaped & narrowest at level of cricoid
cartilage.
• Neonates& infants have limited respiratory reserve:
–Horizontal ribs prevent the “buckle-handle” action seen in adult
breathing and limit an increase in Tidal volume.
–Ventilation is primarily diaphragmatic.
–Bulky abdominal organ/ stomach filled with gases from poor bag
mask ventilation--impinge chest content.

10. •The ribs are cartilaginous & perpendicular relative to the vertebral column (Horizontal),
reducing the movement of the rib cage
•The infant chest wall is remarkably compliant & compliance decreases with increasing age
•Subsequently the functional residual capacity (FRC) is relatively low.
•FRC ↓ with apnoea & anaesthesia causing lung collapse.

11. • The presence of fewer, smaller airways produces increased airway
resistance.
• The alveoli are fully mature by late childhood (about 8 years of age).
• The work of breathing is increased and respiratory muscles easily fatigue.
• Neonates and infants have fewer and smaller alveoli, reducing lung
compliance; in contrast their cartilaginous rib cage makes their chest wall
very compliant.
• Relatively higher rate of oxygen consumption.
• Muscle of ventilation are easily subject to fatigue d/t low percentage of
Type I muscle fibres in diaphragm

12. • The transformation to neonatal circulation occurs with the
first few breaths, involes 2 major changes:
• A marked increase in systemic resistance.
• A marked decrease in pulmonary resistance.
• Remnants:Patent Foramen Ovale & Ductus Arteriosus.
• The patent ductus contracts in the first few days of life & will fibrose within
2-4 wks.
• Closure of foramen ovale is pressure dependant & closes in the 1st day of life
but may reopen within the next 5 years.
• Neonatal pulmonary vasculature reacts to the rise in PaO2 & pH & the fall in
PaCO2 at birth.
 CARDIOVASCULAR SYSTEM

14. •In neonates Myocardium is less contractile-causing the ventricles to be less
compliant & less ablility to generate tension during contraction.
•HEART RATE DRIVEN CARDIAC OUTPUT.
• Although basal heart rate is greater than in adults , activation of the
parasympathetic nervous system, anesthetic overdose,
or hypoxia can quickly trigger bradycardia and profound reductions in cardiac
output.
•BP is low at birth (approx. 80/50) secondary to a low SVR, due to large
proportion of vessels-rich tissue in children.
•Reaches adult levels at about 16yrs age.

16.  RENAL SYSTEM
• Kidney function approaches normal values by 2 years.
• ↓ GFR/ Renal blood flow
•↓ Concentrating capacity
–U/O 1-2ml/kg/hr
• ↓ Na reabsorption
–Tubular function is immature until 8 months, so infants are unable to
excrete a large sodium load.
• ↓HCO3/H exchange.
• Dehydration

17.  HEPATIC SYSTEM
• Liver function is initially immature with decreased function of hepatic
enzymes.
•Barbiturates & opiods for example have a longer duration of action d/t
slower metabolism.

18.  GLUCOSE METABOLISM
• Neonates have relatively reduced glycogen stores, predisposing them to
hypoglycemia
• Glycogen stores are located in the liver & myocardium

19.  HAEMATOLOGY
• At birth, 70-90% of Hb molecules are HbF.
• HB in newbown ~ 18-20g/dL , HCT ~ 0.6.
• O2 dissociation curve shifts to the right as the level of HbA & 2,3-DPG
rise
• Vit K dependant clotting factor (II, VII, IX, X) & PLT fx are deficient in
first few months.

20.  TEMPERATURE CONTROL
• Factors which promote greater heat loss to the environment in neonates-
 Thin skin.
 Low fat content.
 Greater surface area relative to weight.
• The more important mechanisms for heat production in neonates are—
 Nonshivering thermogenesis by metabolism of brown fat.
 Shifting of hepatic oxidative phosphorylation to a more thermogenic pathway.
• Heat loss during Anaesthesia due to--
 Conduction.
 Convection & evaporation.

21. • Optimal ambient temp to prevent heat loss:
 –Premature infant: 34⁰C
 –Neonates: 32⁰C
 –Adults: 28⁰C
• Effect of low body temp:
 Causes respiratory depression
 Acidosis
 Decreaswd cardiac output
 Increases duration of action of drugs
 Decrease platelet function
 Increases risk of infection

22. • BBB is poorly formed
–Drugs (barbiturates, opioids, antibiotics, bilirubin) cross BBB easily
cause prolong & variable duration of action.
• Cerebral vessels in preterm infant are thin walled & fragile.
–Prone to IVH
–Risk increased with hypoxia, hypercarbia, hypernatraemia, low HCT,
Awake airway manipulation, rapid bicarb administration, & fluctuation
in BP & CBF.
 CENTRAL NERVOUS SYSTEM

23. Be aware of:
• Sudden changes in hemodynamics
• Unexpected responses
• Unknown congenital problem
 CONCLUSION
Different Anatomy
Different Physiology
Different Pharmacology
Different psychology
↓↓↓↓↓
Different approach & preparation

24.  SUMMARY

25. THANK YOU