Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Measure paediatric observations accurately, compare them with current age-specific reference limits and interpret state, baseline and trend without missing compensated deterioration.
Paediatric reference ranges are age dependent and continuous. RCUK 2025 provides approximate lower and upper limits at 1 month, 1, 2, 5, 10 and 18 years and advises intermediate values between those ages. These are emergency reference values, not population centiles for every purpose. National PEWS charts use defined age bands and escalation rules. Use the chart adopted by the organisation while retaining clinical judgement when a child sits close to a boundary or has a known abnormal baseline.
Respiratory rate is often the earliest abnormal observation. Count before touching the chest or causing crying, ideally for a full 60 seconds in infants because breathing is irregular. Watch abdominal and chest movement and record apnoea, grunting, recession, nasal flare and pattern. At 1 month the approximate RCUK range is 25–60/min; it narrows progressively to 12–20/min by 18 years. A high rate may reflect fever, pain, acidosis or lung disease; a low or falling rate with drowsiness suggests central depression or exhaustion.
Heart rate also falls with age. Approximate RCUK limits are 110–180/min at 1 month, 100–170 at 1 year, 90–160 at 2 years, 70–140 at 5 years, 60–120 at 10 years and 60–100 at 18 years. Count an irregular infant pulse for a full minute and correlate monitor rate with a palpable pulse. Fever, distress, dehydration and beta-agonists cause tachycardia; pain treatment and settling should improve a physiological rise. Disproportionate, abrupt or fixed tachycardia raises arrhythmia.
A pulse must be compared with age, temperature, pain and trend before it is labelled physiological or pathological.
A previously rapid rate that falls alongside reduced effort, air entry or consciousness signals decompensation rather than normalisation.
Normal blood pressure with tachycardia, cool skin, weak peripheral pulses or delayed refill still represents possible shock.
Persistent low saturation with a good waveform, compatible respiratory findings and a warm probe site is more credible than one motion-affected number.
The same temperature carries different risk below 3 months, at 3–6 months and in an older child.
A value inside a population range may be abnormal for a child with chronic disease or a clear personal trend.
A child does not acquire a new normal range on a birthday; interpolate and use the chart's age band with judgement.
Vasoconstriction preserves pressure while tissue perfusion declines, making normal pressure a poor rule-out test for early shock.
Crying, sleep, oxygen and recent medicines can make identical observations mean very different things.
A small cuff, loose saturation probe or motion artefact can manufacture hypertension or hypoxaemia and trigger inappropriate treatment.
Severe hypoxaemia, bradycardia or reduced consciousness requires action even when other observations keep an aggregate score modest.
A chronically low saturation may be expected, but further fall, increased effort or altered perfusion still signals acute illness.
Do not use one adult normal range for all children.
Do not count infant respirations for only 15 seconds when breathing is irregular.
Do not accept a saturation without a credible waveform and compatible pulse.
Do not use a cuff that is too small and then diagnose hypertension.
Do not wait for hypotension before treating shock.
Do not interpret falling pulse or respiratory rate as recovery when appearance worsens.
Do not apply a healthy saturation target to cyanotic congenital heart disease without the individual plan.
Do not let fever or crying explain persistent marked tachycardia without reassessment.
Do not allow a low PEWS score to overrule family concern or clinical deterioration.
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A calm 10-year-old has repeated systolic blood pressure readings of 78 mmHg with a correctly sized cuff and cool peripheries. How should this be interpreted?
National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.
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Blood pressure rises with age and height. Use the correct cuff: bladder width about 40% of arm circumference and length covering 80–100% of the arm. A cuff that is too small overestimates and one too large may underestimate. RCUK median systolic values are about 75 mmHg at 1 month, 95 at 1 year, 98 at 2 years, 100 at 5 years, 110 at 10 years and 120 at 18 years. Fifth-centile values are about 50, 70, 73, 75, 80 and 90 mmHg respectively.
The blood-pressure table exposes why one adult cutoff is unsafe. A systolic pressure of 78 mmHg may be above the fifth centile at age 2 but below it at age 10. Even an age-normal pressure can coexist with shock because vasoconstriction preserves it until compensation fails. Assess central and peripheral pulses, skin temperature, capillary refill, consciousness, urine output and lactate. Repeat a surprising automated reading manually while resuscitation continues if the phenotype is concerning.
Oxygen saturation requires a pulsatile waveform, an appropriate probe and warm perfused site. Motion, cold limbs, nail products, venous pulsation and dyshemoglobinaemia can mislead. For most acutely ill previously healthy children, a persistent saturation below the locally defined normal range requires assessment; RCUK describes 90–93% in air as mild-to-moderate hypoxaemia and below 90% as severe. Do not force a normal target on a child with a documented cyanotic congenital-heart baseline; use the specialist target and assess change.
Temperature depends on site and device. Record the method because axillary, tympanic and core values are not interchangeable. NICE advises electronic axillary measurement below 4 weeks and electronic axillary or infrared tympanic measurement from 4 weeks to 5 years in healthcare settings. Fever of at least 38°C under 3 months is high risk; at 3–6 months, at least 39°C is at least intermediate risk. Hypothermia can also signal serious infection, environmental exposure or metabolic failure.
Capillary refill is measured by pressing a central site such as sternum for about five seconds and timing colour return, with adequate lighting and temperature. NICE includes refill of 3 seconds or longer as an abnormal feature in febrile under-5s. Cold environment, skin pigmentation, lighting and technique affect interpretation. Combine it with pulses, skin temperature and mental state. A normal value after compensation or early sepsis does not cancel other circulatory evidence.
Consciousness and behaviour are physiological observations. Record AVPU and interaction, tone, consolability, speech or cry. A toddler who stops playing or an infant who no longer fixes and follows may be deteriorating before a formal score changes. Pain, sleep and neurodevelopment affect assessment, so compare with baseline and caregiver observation. A new response only to voice or pain is an emergency airway and neurological concern.
Urine output integrates perfusion, intake and renal function but often lags. Weigh nappies when accurate measurement matters, using 1 g weight gain as approximately 1 mL urine. Common minimum targets are around 2 mL/kg/hour in infants, 1 in children and 0.5 in adolescents, although local critical-care definitions and renal conditions vary. Oliguria with tachycardia, poor perfusion or rising creatinine is more concerning than an isolated missed void after limited intake.
Always annotate context: asleep or awake, calm or crying, febrile, post-exercise, on oxygen, after salbutamol, analgesia or fluid and measurement site. Repeat after correcting artefact or treating distress. A trajectory across several observations is more powerful than a score at one time. Escalate if clinician or family concern persists, because PEWS complements rather than replaces recognition of abnormal appearance or rapid change.