Overview & Vital Signs
How are paediatric patients classified by age?
Neonate
Within 44 weeks of age from the date of conception
Infant
Up to 12 months of age
Child
Child 1 to 12 years
Adolescent
13 to 16 years
What are the normal values for vital signs in children & infants?
Normal vital sign values vary significantly with age:
APLS Normal Values
APLS Normal Values
APLS Normal Values
ACC Threshold Values
(Used in Shock)
(Used in Shock)
ACC Threshold Values
(Used in Shock)
(Used in Shock)
Age
Respiratory Rate
Heart Rate
Systolic BP
Heart Rate
Mean BP
Newborn
40-60
90-180
60-90
120–180
≥ 55
1 - 3 mo
30-50
110-180
70-104
120–180
≥ 60
3 - 6 mo
30-45
110-180
70-104
120–180
≥ 60
6 - 12 mo
25 -35
110-180
72-110
120–180
≥ 60
1 - 2 yrs
20-30
80-160
72-110
120–160
≥ 65
2 - 4 yrs
20-28
80-140
74-110
100–140
≥ 65
4 - 6 yrs
20-26
80-120
78-112
100–140
≥ 65
6 - 8 yrs
18-24
75-115
82-115
100–140
≥ 65
8 - 10 yrs
18-22
70-110
86-118
100–140
≥ 65
10 - 12 yrs
16-20
70-110
90-121
100–140
≥ 65
12 - 14 yrs
16-20
60-110
90-126
90–140
≥ 65
>14 yrs
16-20
60-110
92-130
90–140
≥ 65
A: Airway
What are the features of the paediatric airway that differ from adults and what implications do these have?
Features
Implications
- Large head, short neck and a prominent occiput.
- ‘Sniffing the morning air’ position will not help bag mask ventilation or visualisation of the glottis
- Head needs to be in a neutral position.
- Epiglottis is long, stiff and U-shaped. It flops posteriorly
- A straight blade laryngoscope may be advantageous to place underneath and lift up the epiglottis
- Tongue is relatively large
- Inadequate displacement of the tongue may impede visualization of the glottis during laryngoscopy
- Larynx is high, anterior (at the level of C3 - C4) and more acutely angled
- Vocal cords are angled more anteriorly rather than a right angle (90°) to the trachea.
- Typically does not affect laryngoscopic view but can make insertion of the endotracheal tube more challenging or traumatic
- Airway is funnel shaped and narrowest at the level of the cricoid cartilage
- Allows uncuffed tube to form an acceptable seal potentially reducing risk of mucosal damage associated with an inflated cuff
- Trachea is shorter in length than adult's
- Tubes must be carefully inserted to the correct length to sit at least 1cm above the carina
- Tubes should be taped securely to prevent tube dislodgement or endobronchial intubation with head movement
- Trachea is smaller in diameter than adult's
- Epithelium is loosely bound to the underlying tissue
- Trauma to the airway easily results in oedema:
- One millimetre of oedema can narrow a baby’s airway by 60% (resistance ∝ 1/radius)
- A small leak should be present around an uncuffed tube to prevent development of subglottic oedema
- Neonates preferentially breathe through their nose
- May be blocked easily by secretions
- Careful suctioning of the nose is important
B: Respiratory System
What are the features of the paediatric respiratory system that differ from adults and what implications do these have?
Features
Implications
- Limited respiratory reserve due to fatigable muscles, differing respiratory mechanics, increased dead space and reduced functional residual capacity (FRC)
- ‘Sniffing the morning air’ position will not help bag mask ventilation or visualisation of the glottis
- Head needs to be in a neutral position.
- Ventilation is primarily diaphragmatic
- Diaphragm is relatively horizontal rather than dome shaped
- Bulky abdominal organ which can easily splint the diaphragm
- FRC decreases with apnoea and anaesthesia
- Stomach insufflation due to poor bag-mask ventilation can splint the diaphragm - nasogastric tube decompression can significantly improve ventilation
- Contributes to limited respiratory reserve
- Horizontal ribs prevent the ‘bucket handle’ action seen in adults
- Limits ability to increase tidal volume
- Important to vary ventilatory rate according to age of the child
- Contributes to limited respiratory reserve
- Chest wall is significantly more compliant than that of an adult
- FRC is relatively low
- Closing volume is larger than FRC until 6-8 years
- Reduced time to desaturation during apneoa
- Prone to atelectasis - PEEP increases increases lung volumes and reduces the risk of atelectasis during anaesthesia
- Contributes to limited respiratory reserve
- Work of respiration may be up to 15% of oxygen consumption
- Muscles of respiration contain low levels of type 1 muscle fibres when immature
- Easily prone to fatigue
- Contributes to limited respiratory reserve
- Physiological dead space is around 30% and may be significantly increased by anaesthetic equipment
- CPAP improves oxygenation and reduces work of breathing during spontaneous ventilation
- Prone to rebreathing during invasive ventilation - apparatus dead space and resistance should be kept to a minimum
- Respiratory centre is relatively immature
- Neonates and young infants have irregular respirations and are at a greater risk of apnoea
- Apnoeas may be a manifestation of significant systemic disease in neonates and young infants
- Apnoeas are common postoperatively in premature infants - vigilant monitoring required
C: Cardiovascular System
What are the features of the paediatric cardiovascular system that differ from adults and what implications do these have?
Features
Implications
- Myocardium less contractile
- Ventricle is less compliant and less able to generate tension during contraction
- Limits size of and changes in stroke volume
- Cardiac output becomes rate dependent
- Bradycardia associated with reduced cardiac output and in the neonate external compression should be started if the rate is <60 bpm
- Myocardium less contractile
- Ventricle is less compliant and less able to generate tension during contraction
- Limits size of and changes in stroke volume
- More prone to developing low cardiac output ('cold') shock during sepsis
- Vagal parasympathetic tone is most dominant
- Sinus arrhythmia is common
- Prone to bradycardia with hypoxia, which should should be treated with oxygen and ventilation initially
- Vagal parasympathetic tone is most dominant
- Sinus arrhythmia is common
- Prone to bradycardia with hypoxia, which should should be treated with oxygen and ventilation initially
- Resting and maximal heart rate values decrease spontaneously with age
- Age dependent parameters should be targeted during resuscitation
- Cardiac output is 300-400 ml/kg/min at birth and decreases to 200 ml/kg/min within a few months
- Age dependent parameters should be targeted during resuscitation
- Ductus arteriosus contracts in the first few days of life and fibroses within 2-4 weeks
- Closure is pressure dependent with neonatal pulmonary vasculature reacting to the rise in PaO2 and pH and the fall in PaCO2 at birth
- Alterations in pressure and in response to hypoxia and acidosis can lead to reversion to the transitional circulation in the first few weeks after birthv
D: Central Nervous System
What are the features of the paediatric central nervous system and psychology that differ from adults and what implications do these have?
Features
Implications
- Cerebral metabolic requirement for oxygen (CMRO2) and cerebral blood flow are higher in young children
- Brain forms higher % of body weight (10–15% of body weight at birth, but only 2% of body weight by the age of 8 years)
- More susceptible to periods of hypoglycaemia, hypoxia and decreased cerebral blood flow
- Blood brain barrier is poorly formed
- Drugs such as barbiturates, opioids, antibiotics and bilirubin cross the blood brain barrier easily causing a prolonged and variable duration of action
- Entry of ammonia into the brain can leads to hyperammonaemic encephalopathy
- Head is large and heavy relative to the size of the body
- Balanced on a neck poorly supported by weak muscles and ligaments
- Both head and cervical spine are easily injured
- Cerebral vessels in the preterm infant and neonate are thin walled and fragile
- Prone to developing intraventricular haemorrhages
- Anxiety related to separation, unfamiliar people and environments becomes marked over the age of 6 months
- Parental anxiety readily perceived and reacted by children
- Anxiety and associated behavioural change can lead to a significant impact on outcomes such as pain and length of stay
- Reducing child and parent anxiety important in optimising outcomes from anaesthesia and intensive care
E: Endocrine System & Metabolism
What are the features of the paediatric endocrine system & metabolism that differ from adults and what implications do these have?
Features
Implications
- Young children have an undeveloped hypothalamus
- Ability to regulate temperature is impaired
- Large surface area to weight ratio
- Increased thermal conductance
- Subcutaneous tissue is 20-30% thinner than adults
- Poorly developed shivering, sweating and vasoconstriction mechanisms
- Prone to excessive heat loss and thermoregulation easily overwhelmed by environmental conditions
- Requires higher optimal ambient temperature in neonates and young infants
- In neonates and young infants, heat production occurs through metabolism of brown fat (located in small amounts around the scapulae, the mediastinum, the kidneys and adrenal glands) - known as non-shivering thermogenesis
- Brown fat metabolism occurs at the expense of increased oxygen consumption
- Volatile agents inhibit brown fat metabolism further affecting temperature regulation during general anaesthesia
- Neonates and young infants have limited glycogen stores and rely heavily on gluconeogenesis for maintenance of glucose levels
- Hypoglycaemia is common in the stressed neonate and young infant
- Glucose levels should be monitored regularly in the neonatal period
- Infusions of 10% glucose may be required to prevent hypoglycaemia and resultant neurological damage
- Fat tissue as a proportion of body weight is higher in infants, peaking between 3–6 months of age
- Altered body composition may affect volume of distribution of certain drugs
F: Renal System & Fluid Handling
What are the features of the paediatric renal system and fluid handling that differ from adults and what implications do these have?
Features
Implications
- Renal blood flow and glomerular filtration rate are low in the neonate and young infant due to increased vascular resistance
- Reach adult levels between 1 and 2 years age
- Alters the pharmacokinetics of drugs, particularly those renally excreted, requiring age related dose adjustment
- Less able to handle and excrete exogenous fluid and sodium loads – low sodium fluids often used in neonates
- Loop of Henle is short in newborns and tubular function is immature during first year
- Less able to reabsorb fluid and sodium resulting in production of dilute urine
- Hydrogen ion excretion, acid secretion & bicarbonate levels are lower
- Neonates and infants prone to dehydration as unable to produce concentrated urine to withstand fluid deprivation
- Prone to develop severe metabolic acidosis due to difficulties handling acid –base balance
- Total amount of water is 75-80 % of body weight in childhood, 60 % in adults
- There is a larger proportion of extra cellular fluid in children (40% body weight as compared to 20% in the adult)
- Alters the pharmacokinetics of drugs due to differences in the volume of distribution
- In the infant the bladder lies entirely in the abdomen descending into the pelvis by puberty
- Kidneys have less protective perinephric fact in children
- Bladder and kidneys more vulnerable to injury, particularly in blunt trauma
G: Gastrointestinal & Hepatic System
What are the features of the paediatric gastrointestinal and hepatic system that differ from adults and what implications do these have?
Features
Implications
- Liver function is initially immature, with decreased hepatic enzyme function
- Drug metabolism may be slower leading to a longer duration of action (e.g. barbiturates and opioids)
- Liver and spleen ride comparatively low within the abdomen and have minimal protection from ribs
- Intestines, especially the sigmoid and right colon, are not fully attached in the peritoneal cavity
- Abdominal viscera more prone to injury, particularly in blunt trauma
H: Haematological System
What are the features of the pediatric haematologcial system that differ from adults and what implications do these have?
Features
Implications
- Foetal haemoglobin (HbF) forms, 70-90% of the haemoglobin molecules at birthDrops to around 5% HbF by 3 months with HbA predominating
- Foetal haemoglobin contains less 2,3-DPG and combines more readily with oxygen
- Allows the foetus is able to retrieve oxygen from maternal blood
- Haemoglobin levels change rapidly with age:
- Newborn born with levels 180-200 g/L
- Levels drop over 3-6 months to 90-120 g/L
- Stabilises thereafter to at approximately 130 g/L
- Haemoglobin levels should be interpreted in an age dependent manner
- Development of the coagulation system not complete until about 6 months of age
- Vitamin K dependent factors are 70% of adult values at birth
- Vitamin K is given at birth to prevent haemorrhagic disease of the newborn
- Coagulation screening tests are prolonged in normal infants up to the age of 6 months, which is reflected in values for the normal ranges
- Total blood volume smaller in children than infants
- Relative blood volume per unit mass larger in the newborn and decreases with age
- Lower total blood volume leads to reduced tolerance for blood loss during surgery or trauma
- Transfusion is generally recommended when 15% of the circulating blood volume has been lost
- Higher relative blood volume required to support higher basal metabolic rate
- Affects pharmacokinetics of certain drugs
How does the normal blood volume change with age?
Age
Blood Volume
Premature Infant
90-100 ml/kg
Term Infant
80–90 ml/kg
Infant <1 year
75-80 ml/kg
Children
70-75 ml/kg
Adult
65-70 ml/kg
I: Immune System
What are the features of the paediatric immune system that differ from adults and what implications do these have?
Features
Implications
- Innate immune system is muted at birth and matures with increasing age
- Newborns and young infants relatively susceptible to bacterial and viral infections
- Allows the foetus to tolerate non-shared maternal antigens
- The adaptive immune system is immature, providing increased protection over time with accumulation of immunological memory
- Neonates and young infants receive IgG antibody transfer from the mother transplacentally and in breast milk
- Passive IgG antibodies provide some protection against infection
- Young children become more vulnerable to infections when passive IgG transfer stops until immune memory matures
Drug Handling
What are the differences in the way children handle drugs in comparison to adults? What implications do these have?
Features
Implications
- Liver function is initially immature, with decreased hepatic enzyme function
- Drug metabolism may be slower leading to a longer duration of action (e.g. barbiturates and opioids)
- Renal blood flow and glomerular filtration rate are low in the neonate and young infant due to increased vascular resistance
- Reach adult levels between 1 and 2 years age
- Alters the pharmacokinetics of drugs, particularly renally excreted, requiring age related dose adjustment
- Less able to handle and excrete exogenous fluid and sodium loads – low sodium fluids often used in neonates
- Loop of Henle is short in newborns and tubular function is immature during first year
- Less able to reabsorb fluid and sodium resulting in production of dilute urine
- Hydrogen ion excretion, acid secretion & bicarbonate levels are lower
- Neonates and infants prone to dehydration as unable to produce concentrated urine to withstand fluid deprivation
- Prone to develop severe metabolic acidosis due to difficulties handling acid –base balance
- Total amount of water is 75-80 % of body weight in childhood, 60 % in adults
- There is a larger proportion of extra cellular fluid in children (40% body weight as compared to 20% in the adult)
- Alters the pharmacokinetics of drugs
- Blood brain barrier is poorly formed
- Drugs such as barbiturates, opioids, antibiotics and bilirubin cross the blood brain barrier easily causing a prolonged and variable duration of action
