5, 4, 3, 2, 1, 0: An evidence‐based mnemonic to aid recall and interpretation of heart rate values for pediatric patients presenting for acute care

“Is this heart rate normal?” This is a question frequently faced by providers who care for pediatric patients presenting for acute care. Providers who care for infants and children must be familiar with the normal ranges for vital signs, especially heart rates. Just like in adult patients, heart rate values outside of the expected range may greatly influence diagnostic considerations and can be an early indicator of significant, even life‐threatening, illness. However, unlike those of adults, children's heart rates vary significantly by age and thus it is important for providers to recognize when values are outside the expected range.

THE PROBLEM

When confronted with pediatric vital signs, providers often refer to the reference ranges published by various groups and organizations. One of the most widely used resources is from the Pediatric Advanced Life Support (PALS) provider manual published by the American Heart Association and American Academy of Pediatrics. ¹ In a systematic review of normal pediatric heart rate ranges, the authors note that PALS values often do not fall within the centile curves represented by their data and that most published heart rate guidelines lack any references, and those that did cited references based on weak evidence. ² It is important to note that the PALS values are intended as reference values for critically ill children and are not meant to be generalized across the spectrum of clinical settings in which pediatric patients present for acute or routine care. Other commonly accessed resources report the upper limit of a normal heart rate for a 1‐year‐old child as 110, 125, 140, 160, or 170 providing published ranges between 110 and 170. ³ , ⁴ , ⁵ , ⁶ , ⁷ This large range is neither helpful nor practical when attempting to interpret the heart rate of a potentially ill child. Additionally, recent evidence‐based measures of pediatric heart rates encountered in emergency departments (EDs) also differ significantly from these commonly used published reference ranges. ⁸

THE SOLUTION

We sought to create a recall method grounded in adult learning theory for evidence‐based pediatric heart rate values.

DEVELOPMENT PROCESS

We conducted a narrative review of the literature to identify evidence‐based values for pediatric heart rates. We identified three seminal manuscripts each with over 100,000 heart rate values collected from pediatric patients across the spectrum of outpatient, emergency, and inpatient settings. ² , ⁸ , ⁹ We identified the range of 75th percentile of heart rate values and then defined this as the “upper limit” of normal values as most values will be below this value and thus values that exceed these values can be considered “mild tachycardia.” Similarly, we identified the range of 90th percentile heart rate values and defined values that exceed these as “extreme tachycardia” (Table 1).

TABLE 1.

Pediatric heart rate values.

	Age	Upper limit of heart rate (~75th percentile a )	Extreme tachycardia (≥90th percentile a )	Bradycardia (≤10th percentile a )
	Infancy (0–6 months)	150 (145–154)	170 (155–165)	110 (114–123)
	Infancy (6–12 months)	140 (137–143)	160 (145–156)	100 (107–115)
	Toddler 1–2 years	130 (126–136)	150 (135–149)	90 (98–107)
	Preschool 2–5 years	120 (108–126)	140 (117–142)	80 (81–99)
	School aged 5–12 years	110 (93–111)	130 (103–128)	70 (67–88)
	Adolescence 12+ years	100 (83–97)	120 (92–112)	60 (58–66)

^a Percentiles are presented as the ranges reported from Fleming et al., ² O'Leary et al., ⁸ and Bonafide et al. ⁹ Ranges are pooled across studies and age groupings and then collapsed within the appropriate mnemonic‐based developmental age groupings.

We reviewed recall devices from the extant educational literature and chose to use a mnemonic device to aid in the recall of heart rate values. Mnemonic devices are excellent tools to recall information. ¹⁰ , ¹¹ Perhaps the best‐known mnemonic in medicine is the ABCDE approach to critical illness. ¹² We also chose the technique of “chunking” in which larger pieces of information are packaged into fewer parts and can be categorized into meaningful groupings which are easier to remember. ¹³ Children's ages are commonly grouped into ages based on developmental stage theories that are commonly referred to as infancy, toddlerhood, preschool, school age, and adolescence. ³

Based on these age categories, heart rates can then be recalled with a 5, 4, 3, 2, 1, 0 mnemonic to create the following list of values: 150, 140, 130, 120, 110, and 100, which are then assigned to early infancy, late infancy, toddlerhood, preschool, school age, and adolescence. To accommodate for the normal changes in heart rate during the first year of life, a substratification of infancy into early and late allows for better accuracy. These heart rates yield values that approximate the 75th percentile of values encountered in the medical literature and values that exceed these can be considered “mild” tachycardia. Then, by simply adding an additional value of 20 to this number, a value generally exceeding the 90th percentile can be approximated. By applying this “rule of 20” a value can be regarded as “extreme” offering a more nuanced approach to the interpretation of heart rates. This conceptualization may also help dissuade providers from simply dichotomizing heart rate values into normal or abnormal and bring more appreciation to the spectrum of tachycardic heart rate values. Values identified as extreme should demand greater scrutiny and should prompt a more thorough consideration of an underlying pathologic cause.

Providers may wonder how to utilize this method when faced with a pediatric patient whose age falls on one of the cut points such as a child of 5 years. Should a value of 120 be used based on the preschool age? Or 110 for school‐aged? Practically speaking either value will offer a valid approximation that can inform the provider. However, a more nuanced approach we suggest is to use the value midway between the two values. So, for a 5‐year‐old, a heart rate of 115 will approximate the 75 percentile and 135 (115 + 20) will exceed the 90th percentile.

It is important to point out that most often the cause of identified tachycardia is benign and frequently multifactorial due to activity (crying), fever, anemia, medications, anxiety, and pain and is also influenced by whether the patient is awake or asleep. A single value is thus insufficient to draw conclusions and serial measurements should be encouraged after interventions seeking to address the factors above. Heart rate values that remain elevated after interventions and observation should again prompt further consideration of a more serious illness.

Pediatric bradycardia, while less common, can also be indicative of underlying pathology, particularly in infancy. Fortunately, bradycardia can also be identified with this system as a value approximately 40 beats/min below the upper heart rate limit for age approximates the firest percentile. This “rule of 40” can then be used to quickly identify bradycardia.

REFLECTIVE DISCUSSION

The authors have been teaching this technique to medical students, residents, and practicing emergency providers. Our collective experience suggests that the ability to rapidly recall pediatric heart rate values can be aided with cognitive devices such as mnemonics. Furthermore, it emphasizes the notion that pediatric heart rates are not simply dichotomous as normal or abnormal. Rather, heart rate values are best interpreted along a spectrum. And persistent extreme values can be a harbinger of underlying pathology that requires urgent intervention.

Importantly, our values for extreme tachycardia are associated with significant patient‐oriented outcomes. For example, pediatric patients discharged from the ED with heart rates that closely approximate our “extreme” values were more likely to return to the ED within 72 h ¹⁴ and those with an additional vital sign abnormality at discharge (blood pressure, temperature, respiratory rate, or oxygen saturation) also were at increased risk for a revisit. ¹⁵ Others had found that these heart rate values are highly specific for serious infections compared to minor infections but have a lower sensitivity to detect serious infections. ¹⁶ Lastly, our “extreme” values are nearly identical to the recently updated National Institute for Health and Clinical Excellence (NICE) guidelines for “high‐risk” values for suspected sepsis. ¹⁷

CONFLICT OF INTEREST STATEMENT

The authors declare no conflicts of interest.

Dudas RA, Berezow JK. 5, 4, 3, 2, 1, 0: An evidence‐based mnemonic to aid recall and interpretation of heart rate values for pediatric patients presenting for acute care. AEM Educ Train. 2024;8:e11034. doi: 10.1002/aet2.11034