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Reference: Brennan L et al. Time to change the reference ranges of children’s physiological observations in emergency care? A prospective study. J Paediatr Child Health. March 2023

Date: July 12th, 2023

Guest Skeptic: Dr. Vicki Currie is a paediatric emergency medicine registrar in the West Midlands in the United Kingdom. She is also a member of the Don’t’ Forget the Bubbles team where she serves as the editor for the monthly research round up, Bubble WRAP.

Dr, Vicki Currie

Case: A 5-year-old boy presents to the emergency department (ED) with his parents for fever and fatigue. He has had three days of high fevers at home. His parents report that he has also had a decreased appetite and does not seem interested in drinking liquids. He is usually a happy, active boy but has been very tired over the past day and the parents are having increasing difficulty getting him to wake up. When his vital signs are taken, he is noted to have a temperature of 40°C, a heart rate (HR) of 142 beats per minute (bpm), respiratory rate (RR) of 32 breaths per minute, and blood pressure of 98/60 mmHg. His capillary refill time is three seconds. His parents look at the monitor and ask you, “Is that heart rate normal for him? It seems awfully high. We have been reading online about something called sepsis that can be deadly. Does he have sepsis?”

Background: We have looked at pediatric vital signs on the SGEM back in 2014 with PedEM superhero Dr. Anthony Crocco (SGEM#98). That episode reviewed the 2011 Fleming et al systematic review for the normal ranges of HR and RR in children from birth to 18 years of age. The publication provided useful graphs for clinicians on what is normal.

Vital signs can be an important objective measurement while assessing a patient. They are often incorporated into many early warning systems, risk-stratification systems, and treatment protocols. Abnormal vital signs may be indicators of potential decompensation. Specifically, heart rate and respiratory rates are used in early attempts to detect sepsis.

Children’s vital signs can differ based on age. However, there remains variation regarding what the “normal” ranges of vital signs can be for pediatric patients. Vital sign ranges from common guidelines such as Pediatric Advanced Life Support (PALS) [1] or Advanced Pediatric Life Support (APLS) [2] can differ.

Clinical Question: How does a derived distribution of heart and respiratory rates for children compare to APLS and other national guidance?

Reference: Brennan L, Heal C, Brown S, Roland D, Rowland AG. Time to change the reference ranges of children’s physiological observations in emergency care? A prospective study. J Paediatr Child Health. March 2023

  • Population: Children 0-16 years recruited consecutively from October 2017 to September 2020 from three emergency departments and one urgent care centre in England- serving populations with significant inequalities in health and life expectancty.
    • Excluded: none (although impossible values were excluded- Impossible’ values were HR below 50, and RR below 9 or above 90. This did equate to a significant number of records (>11,000 HR and >10,000 RR)
  • Intervention: Anonymized data for patients’ heart rates and respiratory rates
  • Comparison: Reference standards in Advanced Paediatric Life Support (APLS)
  • Outcome: The authors had three aims with their study
  1. Comparison of the distribution of heart and respiratory rates from study to APLS ranges
  2. Proportion of patients from this study that would meet “severe” cut-off threshold compared to guidelines from the UK Sepsis Trust [3] and National Institute for Health and Care Excellence (NICE) [4]
  3. Comparison of distribution of heart and respiratory rates from study to previously published, large data sets [5-7].

Authors’ Conclusions: This study’s data set suggests normal heart rate ranges proposed by the APLS and others is too low and therefore “abnormal” measurement encompass too large a proportion. The respiratory rate of this data set was more consistent with the guidelines and other published data sets.

Quality Checklist for Observational Study:

  1. Did the study address a clearly focused issue? Yes
  2. Did the authors use an appropriate method to answer their question? Yes
  3. Was the cohort recruited in an acceptable way? Unsure
  4. Was the exposure accurately measured to minimize bias? Yes
  5. Was the outcome accurately measured to minimize bias? Yes
  6. Have the authors identified all-important confounding factors? No
  7. Was the follow up of subjects complete enough? Unsure
  8. How precise are the results? Unsure
  9. Do you believe the results? Yes
  10. Can the results be applied to the local population? Unsure
  11. Do the results of this study fit with other available evidence? Yes
  12. Funding of the Study. No conflicts of interest reported

Results: Their initial data set included 235,909 records. After excluding entries with missing or impossible values, there were 191,292 records of HR and 191,147 records of RR included in the final analysis. Median age was 5 [IQR 1-10] with 45% female.

Key Result: Distribution of heart rate in the study population was higher than the range in APLS potentially leading to over classification of children at “severe” risk of sepsis based on current guidelines.

Aim One: Comparison of vital signs distribution to APLS

For the under 1 year of age group, the 95th percentile heart rate was very similar compared to APLS. The HR was higher for all the other age groups ranging from 10 bpm (12 to 13-year-old group) to a maximum of 31 bpm higher (4 to 5-year-old group). The 5th percentile was higher at almost every age compared to the APLS range. This is most pronounced at birth and 1 year where the study data demonstrated HR that were 28.5 bpm and 26 bpm higher respectively.

The studies 95th percentile for respiratory rate was similar to APLS at birth but higher at other age ranges. The 5th percentile for RR was similar to APLS.

Aim Two: Proportion of those who would meet “severe” threshold per UK Sepsis TRUST and NICE guidelines.

Across all age groups, 17.5% would have met high-risk criteria based on NICE.

There was also a difference by age here. For children less than 1 year, 23.3% were considered high-risk based on HR by NICE guidelines. This percent decreased as age increased where only 2.2% cross that threshold in the older than 12 age groups.

 Based on the RR, only 7.4% would be considered high risk. There was an exception here in the age 6 to 11 group where up to 14.3% would have been considered high risk.

 Aim Three: Comparison of vital signs distribution to previous large data sets (O’Leary, Bonafide, Fleming).

As a reminder, O’Leary included patients in the emergency department. Bonafide included hospitalized children. Fleming was the meta-analysis of 69 studies.

The percentile for HR differed compared to O’Leary’s emergency department children and Bonafide’s hospitalized children by 7.9 with standard deviation of 7.9 and 6.5 respectively. The difference compared to Fleming’s data was larger at 15.2 with a standard deviation of 10.6.

The RR in comparison to the three previous studies differed by 3.5 to 3.7 with standard deviations ranging from 2.1 to 4.2.

Overall, the vital signs from this study tended to be higher.

Recorded Vital Signs:

The HR and RR were recorded only at the initial assessment. We know that children often will come to the ED with fever that then settles- as do the other numbers.  We are also not sure if these values being taken at the initial assessment impacts the study as the child and family can be particularly stressed/ anxious to find out what has been going on may have potentially skewed the data.

Additionally, it is not stated how the vital signs were recorded- was this done manually (counting HR and RR over 1 minute for example, or by monitor). Previous studies have shown that there is variability between clinical staff recording these numbers and would subsequently introduce another bias [8-9].

Derivation Population:

Previous studies looking at “normal” ranges for pediatric vital signs have been performed in different settings including patients in the ED and hospitalized patients. But is there really an ideal setting for obtaining this data? Is the ED the right place to draw this data from [10]?

We mentioned previously that children who are in the ED may have many reasons for why their HR are elevated compared to their own baseline. They can be anxious or scared. They could be experiencing pain or presenting with dehydration. They could also have fever (a group which the authors chose not to exclude) [11]. All these factors may contribute to an increased heart rate.

Treat the Patient, not the Numbers:

There are many reasons for why a child’s HR or RR may differ from the “normal” ranges. It is important to remember to always interpret those vital signs in the context of the patient in front of you.

A child with bradycardia may be a well-conditioned athlete or have an underlying eating disorder.

A child with acute asthma exacerbation may be tachycardic due to receiving albuterol or salmeterol. That same child with asthma who initially presented with tachypnea and a high respiratory rate which has slowly returned to the normal range may be because he is feeling more comfortable and breathing easier, or he is starting to tire out.

Examine the patient and don’t simply rely on monitors!

If the patient has been to the ED or been treated within the health system before, it  may be useful to compare their vital signs in the ED to previously recorded vital signs. Use the patient as their own baseline control.

What Happened to the Patients?

What we don’t know is if ANY of the patients that fell into the ‘severe’ category had sepsis. Or even what any of the diagnoses or discharge destination of any of these patients was. It would have perhaps been useful to see the percentage of children at the extremes of the distribution curve were admitted vs discharged. In view of this we cannot comment on the sensitivity or specificity for the values in this study for detection of sepsis (as we have no idea which patients actually were treated or diagnosed).

There was a previous study that looked at return visits, admission, and adverse outcomes for children discharged with abnormal vital signs and found that few returned and required admission [12].

Generalizability:

The data set was derived from three EDs and one urgent care centre. The authors acknowledge that most children are not seen at academic centers or children’s hospitals, so they purposely chose community sites for their study. They also chose sites that served populations with significant inequalities in health and life expectancy. These factors do help with the generalizability of this study.

However, this is still just four sites out of the entire UK. It is unclear how much we can rely on these derived vital signs ranges to be as accurate when applied broadly. But I do think that their method for extracting this data can be applied much more widely to generate a much larger data set.

Comment on Authors’ Conclusion Compared to SGEM Conclusion: We agree with the authors’ conclusion. But their findings may not be generalizable to all settings.

SGEM Bottom Line: The acceptable “normal” range of distribution for pediatric vital signs may vary based on practice location. Treat the child, not the number.

Clinical Application: The normal range of vital signs may differ based on patient and practice setting. Using standard guidelines from PALS and APLS may be appropriate, but they should always be interpreted within the context of the clinical presentation.

What Do I Tell My Patient/Family?

I am glad you took your child to the emergency department. I am also concerned for possible sepsis based on not only his elevated heart rate but also because he is acting very tired, and his capillary refill is delayed. This may be due to a variety of factors. Sometimes children look ill when they have a high fever and look better when the fever resolves. His heart rate could be elevated from the fever, from dehydration because he is not drinking well. Sometimes viral infections can present like this as well. However, we are trained to think about the worst possible scenario in the emergency department, so I think it is best that we obtain some blood work and give him some IV fluids and IV antibiotics and have him stay in the hospital for observation.

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.

References

  1. American Heart Association. Pediatric Advanced Life Support Provider Manual. American Heart Association; 2020
  2. Samuels M, Wieteska S, eds. Advanced Paediatric Life Support: A Practical Approach to Emergencies. Sixth edition. BMJI Books, Wiley/Blackwell; 2016.
  3. Nutbeam T, Daniels R, on behalf of the UK Sepsis Trust (n.d.) Clinical Tools. Tamworth, UK: UK Sepsis Trust. Available from sepsistrust.org/ [accessed 8 May 2023]
  4. National Institute for Health and Care Excellence (NICE) (2016). Sepsis: Recognition, ASsessmetn and Early Management (NICE Guideline 51) London, UK: NICE. Available from https://www.nice.org.uk/guidance/ng51 [accessed 8 May 2023]
  5. O’Leary F, Hayen A, Lockie F, Peat J. Defining normal ranges and centiles for heart and respiratory rates in infants and children: a cross-sectional study of patients attending an Australian tertiary hospital paediatric emergency department. Arch Dis Child. 2015;100(8):733-737.
  6. Fleming S, Thompson M, Stevens R, et al. Normal ranges of heart rate and respiratory rate in children from birth to 18 years of age: a systematic review of observational studies. Lancet. 2011;377(9770):1011-1018.
  7. Bonafide CP, Brady PW, Keren R, Conway PH, Marsolo K, Daymont C. Development of heart and respiratory rate percentile curves for hospitalized children. Pediatrics. 2013;131(4):e1150-1157.
  8. Heal C, Cotterill S, Rowland AG, et al. Inter-rater reliability of paediatric emergency assessment: physiological and clinical features. Arch Dis Child. 2021;106(2):149-153.
  9. Latten GHP, Spek M, Muris JWM, Cals JWL, Stassen PM. Accuracy and interobserver-agreement of respiratory rate measurements by healthcare professionals, and its effect on the outcomes of clinical prediction/diagnostic rules. PLoS One. 2019;14(10):e0223155.
  10. Ramgopal S, Sepanski RJ, Martin-Gill C. Empirically derived age-based vital signs for children in the out-of-hospital setting. Ann Emerg Med. 2023;81(4):402-412.
  11. Heal C, Harvey A, Brown S, Rowland AG, Roland D. The association between temperature, heart rate, and respiratory rate in children aged under 16 years attending urgent and emergency care settings. Eur J Emerg Med. 2022;29(6):413-416.
  12. Kazmierczak M, Thompson AD, DePiero AD, Selbst SM. Outcomes of patients discharged from the pediatric emergency department with abnormal vital signs. Am J Emerg Med. 2022;57:76-80.