SGEM #417: Everybody’s Changing…the Reference Ranges for Pediatric Vital Signs

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 Comparison of the distribution of heart and respiratory rates from study to APLS ranges 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] 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: Did the study address a clearly focused issue? Yes Did the authors use an appropriate method to answer their question? Yes Was the cohort recruited in an acceptable way? Unsure Was the exposure accurately measured to minimize bias? Yes Was the outcome accurately measured to minimize bias? Yes Have the authors identified all-important confounding factors? No Was the follow up of subjects complete enough? Unsure How precise are the results? Unsure Do you believe the results? Yes Can the results be applied to the local population? Unsure Do the results of this study fit with other available evidence? Yes 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.