Vital signs are fundamental to paediatric assessment, yet interpreting them can be challenging. Children and young people’s physiological norms differ substantially from those of adults and vary considerably between age groups.
This article provides an overview of age-specific normal ranges, explores the physiological reasons behind these differences, and highlights red flags that should prompt clinical concern.
Paediatric physiology
Children’s physiology undergoes significant changes as they grow. Understanding why paediatric vital signs differ from adults is key to interpreting them correctly.
Higher metabolic rate
Children have a higher metabolic demand (they require more oxygen and calories per kilogram). This leads to higher baseline heart and respiratory rates.1
Their increased metabolic rate also means that they can decompensate more quickly in response to illness, as their reserves are limited and demands escalate rapidly during stress.
Smaller circulating volume
A child’s blood volume is approximately 80-90 mL/kg, meaning they can decompensate quickly from fluid or blood loss.2
Even relatively small losses (e.g. from vomiting, diarrhoea) can have a significant clinical impact, so early recognition and correction of fluid deficits is crucial.
Immature thermoregulation
Especially in neonates, temperature control is less effective due to a high surface area-to-volume ratio and limited subcutaneous fat.3 This makes them vulnerable to hypothermia and hyperthermia, both of which can be signs of systemic infection or environmental instability.
Accurate temperature monitoring is essential in this age group.
Different cardiovascular compensation
Children primarily increase heart rate to maintain cardiac output, unlike adults, who can also increase stroke volume.2 As a result, tachycardia is often the first and most sensitive sign of cardiovascular compromise in children. Hypotension, on the other hand, typically indicates late and severe decompensation.
Comparison of vital signs
Table 1. Summary of the general trends and clinical significance when comparing adult and paediatric vital signs
| Vital sign | Adults | Children | Clinical significance |
| Heart rate (HR) | 60 – 100 bpm | Higher | Early sign of distress – tachycardia compensates for a fixed stroke volume |
| Respiratory rate (RR) | 12 – 20 breaths per minute | Higher | Increased RR often precedes desaturation in respiratory illness |
| Blood pressure (BP) | 90 – 120/60 – 80 mmHg | Lower in younger children | Hypotension is a late sign of shock – monitor perfusion markers closely |
| Temperature | 36.5 – 37.5°C | Similar | Extremes of temperature can signal infection – neonates are particularly vulnerable |
| Oxygen saturation (SpO2) | ≥95% | Similar | Persistent hypoxia requires prompt assessment and likely escalation |
Paediatric vital signs
These ranges vary slightly by source. The following are derived from Advanced Paediatric Life Support Guidelines (APLS, 6th Edition) and RCN Standards.1-2
Heart rate (HR)
| Age group | Normal range (bpm) |
| Newborn (0 – 1 month) | 110 – 160 |
| Infant (1 – 12 months) | 100 – 160 |
| Toddler (1 – 2 years) | 90 – 150 |
| Pre-school (3 – 5 years) | 80 – 140 |
| School-age (6 – 12 years) | 70 – 120 |
| Adolescent (13+ years) | 60 – 100 |
Key considerations
- Infants cannot increase stroke volume significantly, so tachycardia is their first sign of shock, not hypotension
- An increase in HR is often an early sign of distress (pain, fever, dehydration)
- Bradycardia is a late and pre-terminal sign, especially in infants 4
Respiratory rate (RR)
| Age group | Normal range (breaths per minute) |
| Newborn | 30 – 60 |
| Infant | 30 – 50 |
| Toddler | 25 – 35 |
| Pre-school | 20 – 30 |
| School age | 18 – 25 |
| Adolescent | 12 – 20 |
Key considerations
- Count RR for a full minute, particularly in infants, as breathing can be irregular
- Raised RR is an early marker of respiratory distress or metabolic compensation (e.g. in diabetic ketoacidosis)
- Respiratory distress often presents before hypoxia in children with nasal flaring, tracheal tug, and grunting 5
Blood pressure (BP)
Blood pressure is not routinely measured in young children unless they are acutely unwell, but it becomes crucial in the sick child.
| Age group | Normal systolic BP (mmHg) |
| Neonate (<1 month) | ≥60 |
| Infant (1 – 12 months) | ≥70 |
| 1 – 10 years | ≥70 – (2 x age in years) |
| >10 years | ≥90 |
Key considerations
- Hypotension is a late sign of shock in children, often preceded by tachycardia, prolonged capillary refill time (CRT), or altered mental status
- If hypotensive, they are likely decompensating, so quick action is needed
- Use a manual BP cuff sized appropriately for the child 2
Temperature
Normal: 36.5 – 37.5°C
Fever: ≥38.0°C
Hypothermia: <36.0°C, especially concerning in neonates
Key considerations
- Neonates and young infants may not mount a febrile response to infection. They may present with low temperature or poor feeding rather than pyrexia.
- Always investigate fever in infants <3 months thoroughly (e.g. sepsis, UTI, meningitis) 3-4
Oxygen saturation (SpO2)
Normal: ≥95% in room air
Abnormal: <92% is usually considered abnormal and may warrant oxygen therapy or escalation
Key considerations
- SpO2 can appear deceptively normal in children with early respiratory failure. Watch their work of breathing and listen for a silent chest.
- Cyanosis may not be clinically evident until SpO2 <85%
- Persistent low saturations warrant further evaluation (e.g. congenital heart disease, bronchiolitis) 5
Paediatric early warning score (PEWS)
The Paediatric Early Warning Score (PEWS) is used to identify early signs of clinical deterioration. This tool combines vital signs with clinical features like consciousness level and respiratory effort.6
PEWS parameters include:
- Respiratory rate
- Respiratory distress
- SpO2
- Heart rate
- Blood pressure
- Capillary refill time
Escalation thresholds are age-specific, and persistent abnormalities warrant escalation regardless of the score.
PEWS does not replace clinical judgement. Concerns should always be escalated, even if the score is low.
Work of breathing
While heart rate and respiratory rate provide important quantitative data, observing how a child breathes gives critical qualitative information.
Observe for:
- Nasal flaring
- Tracheal tug
- Sub-costal/inter-costal recessions
- Grunting
- Head bobbing (in infants)
Increased work of breathing is a red flag for respiratory distress and should prompt urgent review, even if other vital signs are borderline.
Conversely, a child who is tiring and no longer making effortful respiratory movements may be decompensating, and this is a medical emergency.
Practical considerations
Measuring vital signs in a child can be different to an adult, and so important considerations include to:
- Take your time: allow the child to settle before recording, and measure observations whilst sleeping if possible
- Use distraction techniques or parent comfort: to get more accurate readings
- Use age-appropriate equipment: appropriately sized BP cuffs and paediatric oxygen saturation probes
- Consider the clinical context: is the child alert, feeding, playing? What is their colour and tone?
- Look at trends over time: rather than using isolated readings
Reviewer
Dr Frederick Speyer
Consultant Paediatrician
Editor
Dr Jamie Scriven
References
- Advanced Life Support Group. Advanced Paediatric Life Support: A Practical Approach to Emergencies. 6th ed. Wiley-Blackwell. 2016
- Royal College of Nursing (RCN). Standards for assessing, measuring, and monitoring vital signs in infants, children, and young people. 2017. Available from: [LINK].
- NICE. Fever in under 5s: assessment and initial management. 2021. Available from: [LINK].
- Kleinman K, McDaniel L, Molloy M. The Harriet Lane Handbook. 22nd ed. Elsevier. 2020.
- University Hospital of Leicester NHS Trust. Paediatric Emergency Medicine Leicester Handbook.
- NHS England. Standardising the early warning score in paediatrics (PEWS). 2021.
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