Heart rate (HR) and respiratory rate (RR) are THE major vital signs used in Advanced Paediatric Life Support (APLS) guidance, sepsis guidelines, and Paediatric Early Warning Scores (e.g., PEWS). Vital signs outside the normal range are used as a proxy for the severity of illness and are also used in evaluating the risk for serious bacterial infection or risk for sepsis in children and young people (CYP). However, there has been continued debate on what ‘normal’ is in relation to HR and RR.
What did previous studies show?
The controversy around what is ‘normal’ in infants’ and children’s vitals was demonstrated in a 2011 systematic review by Fleming et al. and two cohort studies, one performed in Australia by O’Leary et al. and one in the US by Bonafide et al.
What is the problem?
Clinicians may under or over-estimate paediatric patients presenting to the ED as being at high-risk for sepsis if there do not have evidence-based heart and respiratory rate ranges,
Brennan et al set out to add to our understanding of what is ‘normal’ in paediatric vital signs.
Who were the patients?
This prospective cohort study included patients between 0-16 years old, who presented to one of four NHS hospital sites in Greater Manchester (a large metropolitan area in the North of England), consisting of an Urgent Care Centre and three Emergency Departments. Looking at the patient’s heart and respiratory rates at initial assessment, they investigated whether these patients were at risk of sepsis according to APLS, UK Sepsis Trust, or NICE guidelines.
What were the aims of the study?
The study focused on three main aims.
- Compare heart and respiratory rates of the children from the sample to selected published guidelines.
- Identify the percentage of children whose heart or respiratory rate would exceed the “severe” cut-off from the UK Sepsis Trust and NICE guidelines.
- Compare the heart and respiratory rates of children from this study to three previously published datasets by O’Leary, Bonafide and Fleming et al.
What were the results?
A total number of 191,292 heart rate records and 192,147 respiratory rate records were included. The median age was 5 years (IQR 1-10 years).
Aim 1: Comparing HR and RR to published guidelines
The children in this study had both higher heart and respiratory rates than APLS ranges; this difference was greater for heart rates than respiratory rates.
These results varied with age; the 95th centile for heart rate was higher than APLS guidelines for all ages except for infants under one. The 5th centile was also higher for almost every age range. The 95th centile for respiratory rates was also higher than APLS ranges for all ages, except at birth, although the 5th centile was similar to APLS.
Aim 2: What percentage of children’s HR and RR is higher than the “severe” cut-off?
23.3% of children under a year and 28.7% of children between 1 to 2 years old had a heart rate that would be classified as high-risk according to NICE guidelines.
The proportion of children who exceeded the severe cut-off decreased with age, falling to 2.2% for children 12 years and older.
The difference was smaller for respiratory rate: only 7.4% of children across all age groups would have been classified as high-risk according to NICE.
Aim 3: Comparing HR and RR to other published datasets
Both respiratory and heart rate centile values were marginally higher than the datasets used by O’Leary, Bonafide, and Fleming et al.
What were the limitations of the study?
Although this study had the advantage of using a multicentre dataset, there are a few limitations to think about.
Vital signs were recorded at the initial assessment only, and temperature, pain, and fear were not accounted for. These factors are known to influence vital signs. However, controlling for these across such a huge dataset is challenging. Additionally, the size of the dataset itself and the potential of these confounders to be present across all patient groups reduces the impact of this limiting factor.
The study also did not assess outcomes for each patient, and as such, the impact on deviation from the normal range was not explored.
CASP checklist for Cohort studies
Does this address a clearly focused issue?
Was the cohort recruited in an acceptable way?
Was the exposure accurately measured to minimize bias?
Was the outcome accurately measured to minimize bias?
Have the authors identified all-important confounding factors?
Yes, they acknowledge the limitations of the study design which made controlling for temperature, pain, and fear unfeasible.
Was the follow-up of subjects complete and accurate?
No. Patients were not followed-up, and although this has been acknowledged by the authors as a limitation, it does not affect the aims of the study.
What are the results?
Heart rate and respiratory rate values in over 190,000 children were higher than the previously published dataset.
A significant number of younger children were placed in the ‘high risk’ range as defined by NICE.
Do you believe the results?
Yes. The study was methodologically robust and demonstrated similar (but more pronounced) differences in observation centile values than comparator studies.
Can the results be applied to a local population?
Do the results fit with other evidence available?
What did the authors conclude and what does it mean for current practice?
This study showed that current APLS guidelines’ respiratory and heart rate ranges may not be wide enough.
This means there is an overclassification of children as being at ‘severe’ risk of sepsis, and that this overclassification is more significant in younger children. This study demonstrates the need for reviewing the current reference ranges of ‘normal’ heart rate and respiratory rate used in different guidelines.
A note from the author, Damian Roland
It is important that healthcare professionals have guidance on common vital signs in order to be able to recognize CYP who need observation or intervention. However, that guidance needs to take into account the influence of emotion, environment, body temperature, as well as the underlying disease process, on vital signs, especially in younger infants.
It has been well recognized that sepsis recognition tools are often poorly specific, that is many children trigger despite having minor viral aetiologies for their high heart or respiratory rate. This is compounded by management strategies being predicated on vital signs and clinicians are left having to ignore guidance. This then leads to open the possibility of sepsis being missed when it is indeed present.
Our study used non-tertiary institutions which are representative of the majority of departments that CYP would present to. We, therefore, believe our results have external validity and demonstrate that ‘normal’ ranges for heart rate and respiratory rate require review. There is a challenge in that deriving normal from well children at school is a different baseline than deriving normal from children already in a healthcare environment. We would argue that it is the latter dataset that reference ranges should be drawn from; a large proportion of children will have a raised heart rate just because they are scared, or have a fever, and this deviation needs to be accounted for.
Our study supports previous work by Nijman et al. and Gomes et al. We argue that it is now time to stop using APLS criteria as a cut-off point for sepsis evaluation and consider how more sensitive estimates can be developed.
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