Since medication doses and equipment size vary with patient weight, accurately estimating the weight of pediatric emergency department patients is crucial for optimizing medical care. Often critically ill children cannot be safely weighed in the emergency department. While several different methods for estimating weight have been developed, one validated tool for rapidly estimating patient weight is the Broselow tape. However, some studies have found that this tape is less accurate in different settings, including those with a high prevalence of obesity or malnutrition. This review discusses the accuracy of the tape in several different populations, including children in various countries and those with obesity, compares it to other methods of weight estimation, and briefly addresses implementation of the Broselow tape in the emergency department.
Keywords: Broselow Tape,Leffler Formula, Pediatric Emergency Medicine, Theron Formula, Weight estimation.
In adult patients, medication doses and equipment size selection are relatively straightforward. In cardiac arrest, for example, medications such as adrenaline or sodium bicarbonate are often prepackaged to the standard dose based on Advanced Cardiac Life Support guidelines. Such standard adult doses can be administered with relative safety in a variety of adult patients. Similarly, an adult can be intubated with a limited range of endotracheal tube sizes. This is obviously not the case in pediatrics. Sizes of children vary dramatically from the premature infant to the adolescent, and so there exist many different sizes of medical equipment for children. Moreover, standard pediatric dosing is expressed in mg/kg. Therefore, a medical provider must know both the patient’s weight as well as the concentrations of medications available on the pharmacy formulary, and then perform a mathematical calculation in order to determine the safe and effective dose of medicine. Fluids volumes and ventilator settings are similarly variable. This complicates the medical care of children and creates frequent occasions for medical errors. For example, if the doctor miscalculates or a nurse fails to clarify an order, opiate medication may be underdosed leading to inadequate analgesia and unnecessary pain, or overdosed leading to respiratory depression. The daily practice of pediatrics involves constant interruptions to clarify correct dosing of medications. This article reviews various methods for estimating weight in the pediatric emergency department with particular emphasis on the use of the Broselow tape method.
Since medication doses and equipment sizes vary with patient weight, accurately estimating the weight of pediatric emergency department patients is crucial for optimizing medical care. Often children cannot be weighed in the emergency department if the child is too ill or unstable, and it is impractical to delay immediate resuscitation. Several different methods for estimating weight have been developed. These include formulas like APLS (weight in kg = [age+4] x 2), the Leffler formula (<1 yr: age in kg=[age in mo/2] +4; 1-10yr: weight in kg= [2xage in yr] + 10), or the Theron formula (weight in kg=exp[(0.175571xage in years) + 2.197099]).1,2,11 Physician estimation based on visual assessment is another simple but crude method.
One tool for rapidly estimating patient weight is the Broselow tape, which divides children into weight categories based on their height. John Broselow developed the tape in 1986, deriving his categories from US census data and the National Center for Health Statistics. Using NCHS data from 1979, Broselow determined the 50th percentile for several weights and heights. These were translated onto a measuring tape with spaces marked with weight in kilograms instead of length. The weight categories are color-coded on the tape. A study published in 1988 by Lubitz et al. validated for the first time the use of the Broselow tape in the USA. They found that the Broselow tape was very accurate for children between 3.5 and 25 kg. It was less accurate in children more the 25 kg. The authors concluded that the Broselow tape is a simple and accurate method for estimating weight, eliminating the need for memorization and calculation. 2
Since its initial development and validation, the Broselow tape has become a standard tool endorsed by the American Heart Association for pediatric resuscitation. The AHA Pediatric Advanced Life Support guideline for 2010 state: “If the child’s weight is unknown, it is reasonable to use a body length tape with precalculated doses (Class IIa, LOE C).” Moreover, the guidelines suggest that in very obese patients, when use of actual body weight for medication calculations may result in potentially toxic overdoses, it is reasonable to use either the actual body weight or a body length tape with precalculated doses based on ideal body weight such as the Broselow tape. 4
When compared to other modes of weight estimation, the Broselow tape seems to perform well. In a separate group of children than those used to validate the Broselow tape, Lubitz et al. found that the Broselow tape was more accurate than the opinion of pediatric residents and nurses.3 Rosenberg et al. also compared the Broselow tape with physician judgment in the emergency department. The tape differed from the actual weight by 11.3% and the physician judgment differed by 16.2%. However, in obese children the tape was less accurate.5 In a prospective study by Tsz-Tin So et al. published in 2010, the Broselow tape was compared to the Leffler and Theron formulas. They included 1011 subjects. The Broselow tape was the most accurate in patients under 25 kg. The Leffler formula and the Broselow tape had similar accuracy between 25.1 and 40 kg, and both were more accurate than the Theron formula. However, the Theron formula was the most accurate method when patients weighed more than 40 kg.1
Anthropometric factors such as foot-length and mid-arm circumference (MAC) have been proposed in place of age as the basis of weight-estimation formulas. While such anthropometric factors are widely accepted for use in assessing malnutrition, neither of these are currently accepted as standard of care in pediatric resuscitations, and few studies evaluate them specifically for use in emergency situations or directly compare them to the Broselow tape. Cattermole et al. performed a prospective population-based observational study in 1370 healthy Chinese children attending primary schools in Hong Kong. Using anthropometric data collected as part of the “Healthy Children’s Vital Signs and USCOM study”, the authors derived a weight-estimation formula based on MAC [Weight in kg= (2.94x MAC in cm)-29.14] and compared it to other methods of weight-estimation, including the Broselow tape. They found that as children grow older, age and foot-length correlate less closely with weight and only height and MAC remained important. In fact, they found that MAC was the strongest correlate with weight in all ages, and this relationship strengthened with increasing age, such that in older children, the MAC formula was more accurate than the Broselow tape. The MAC formula performed most poorly in the youngest children and was less suitable for children under 6 years old. In this group, the Broselow tape was more accurate. 6 However, further studies are needed to validate the MAC formula in other populations before it can be widely recommended. It should also be borne in mind that such an MAC formula currently does not offer the additional benefits of the Broselow tape, such as the lack of mental calculations and the inclusion of equipment sizes.
Overall, the Broselow tape seems to perform well when compared to various formulas or provider estimation, except at extremes of weight. Since weight can vary more dramatically as children grow older, the Broselow tape tends to perform better in younger children, while still outperforming many other methods in older children as well.
It should come as no surprise that the Broselow tape is less accurate in obese patients since it was developed to estimate weight based on the 50th percentile. Obviously, there are shifts in population statistics. Children may be taller or more obese than previously. Periodically, the Broselow tape is adjusted when new statistics are published in order to better reflect current population trends. Nevertheless, one may ask if the Broselow is always equally accurate across different times and places. In fact, a recent study by Nieman et al. suggests that the Broselow tape can frequently result in underestimation of weight. In their study, it underestimated weight in a third of 7500 American children.7 According to the authors, this may be due to the growing obesity epidemic in the USA.
Similarly, Knight et al., conducted a retrospective review of a trauma registry at a rural level 1 trauma center in West Virginia in the United States of America, and identified 657 patients who matched the height range of the Broselow tape. They found that 53.1% of the children had actual weights outside the predicted range and 77.1% of these patients had actual weights greater than those predicted by the Broselow tape. The authors concluded that the Broselow tape underestimated weight in over 50% of patients.8
Another Canadian study of First Nation children, who have higher rates of obesity as well as higher rates of injuries, also found that the Broselow tape was less accurate than expected. The authors examined the records of 243 children less than 10 years of age. The tape underestimated weights by more the 10% in almost half of the children.9 Obviously then, the tape does not have the same accuracy in all populations.
Many studies have also examined the accuracy of the Broselow tape in other countries with varying results. For example, Ramarajan et al. conducted a prospective study of 548 children in Chennai in a resource poor setting in India. They found that the Broselow tape overestimated the weight by more than 10% when children weighed more than 10kg. The color zones of the Broselow tape were determined by measuring with the tape and using a scale weight. There was agreement between the two measurements 70.8% of the time in children <10kg, 56.3% of the time in children between 10 and 18 kg, and 37.5% of the time in children >18 kg. 10 Thus, it may be that methods for estimated weight in settings with different resources will not be equally accurate. Differences of race, nutrition, and infectious disease burdens in the population may invalidate the use of the Broselow tape.
On the other hand, some studies suggest that the Broselow tape is accurate in populations outside the United States. A retrospective study by Jang et al. of 655 Korean children suggests that the Broselow tape accurately estimates the weight of children as well as equipment sizes and medication doses. Specifically, the Broselow tape estimated endotracheal tube size more accurately than standard age based formulas.11 In Hong Kong, Kun et al. found that the Broselow tape estimated the weight of 909 Chinese children within a 10% margin of error 69.5% of the time. It accurately estimated the weight 84.5% of the time if the acceptable margin of error was 15%. It was more accurate when the scale weight was between 10kg and 25 kg. They concluded that the Broselow tape accurately estimated the weight of Chinese children in Hong Kong.13 Geduld et al. evaluated the accuracy of the Broselow tape in 2832 South African children from a prospective database at Red Cross Hospital in Cape Town. They found that the Broselow tape estimated the weight to within 10% in 64% of the children and outperformed 3 age based formula.14 Finally, in Pacific Islander and Maori children many of the methods discussed above are known to underestimate weight. Theron et al. conducted a study of 909 children, of which 46% were Pacific Islander and 25% Maori. The difference between the actual weight and the Broselow tape estimate was significantly more for Pacific Islander and Maori children than European children. Thus, the Broselow tape tended to underestimate the weight of Pacific Islander and Maori children. 15
As noted above, Ramarajan et al. determined that the Broselow tape overestimated the weight of Indian Children at their pediatric hospital. They subsequently used their data to derive a correction factor for the Broselow predicted weight by serially testing corrections until the accuracy was within 10%. They cross-validated this correction factor and applied it to the Broselow tape to improve its accuracy in their local health care setting.10 Their methods could be applied in a similar manner to other populations where the standard distribution of the Broselow tape does not correlate with local weight trends. Once the Broselow tape is felt to accurately estimate weight in a physician’s local population, it can be incorporated into emergency care in a variety of ways, keeping in mind that the best methods for implementing the Broselow tape will of course depend on the specific conditions in a given hospital setting.
Prior to arrival at the emergency department, pre-hospital care may be improved with the use of the Broselow tape. Beginning in 2001, Los Angeles County Emergency Medical Services Agency in California, U.S.A mandated the use of the Broselow tape by paramedics treating pediatric patients in cardiopulmonary arrest outside of a healthcare setting. An observation study by Kaji et al. found that the odds ratio of children receiving the correct dose of epinephrine after implementing the Broselow tape was 3.0. 16 This suggests that training paramedics and base-station personnel in the use of the Broselow tape may reduce the rate of medication dosing errors in pediatric resuscitation even before they arrive at the emergency department.
Standard resuscitation carts in emergency departments often have drawers organized by the type of intervention or equipment, such as a drawer for intubation equipment, a drawer for obtaining IV access, etc. Agarwal et al. conducted a prospective, randomized, controlled trial in which health care providers where assigned to use either a standard resuscitation cart or a cart with drawers organized based on Broselow weight categories. Thus, is specific drawer would contain all the appropriate weight-based equipment needed to resuscitate a pediatric patient based on their weight. The authors assessed accuracy and time to selection of appropriate equipment as well as provider satisfaction following simulated resuscitation scenarios using the two carts. Of the 21 providers included in the study, 62% found the Broselow based cart easy or very easy to use versus 33% for the standard cart and 67% of providers preferred the Broselow cart. Correct equipment was provided 99% of the time from the Broselow cart versus 83% from standard carts, and was found significantly faster from the Broselow cart despite the fact the providers were overall less familiar with the Broselow cart.17
In addition to incorporating this type of Broselow-based resuscitation carts in emergency departments, the speed and accuracy of medication administration in pediatric resuscitations may be further improved by prepackaging medications into the correct doses based on Broselow weights. Additionally, medications could be reformulated by pharmacy into volume based ml/kg doses instead of mg/kg dosing to further simplify medication administration. This would remove the need to convert a dose in mg into a volume in milliliters and can potentially reduce drug preparation time without loss in accuracy.18
In conclusion, the Broselow tape, an instrument developed based on United States census data, has been tested in other populations and countries with varying results. Sometimes it overestimates the weight. Sometimes it underestimates the weight. Sometimes it accurately estimates weight, and in fact, performs better than other formulas and methods. Although an acceptable margin of error may vary depending on circumstances and medications, most studies have chosen 10% as the acceptable margin of error. Safe and effective doses of medication may still be calculated with significantly higher margins of error. Nonetheless, even in those cases where Broselow tape weight estimates lie outside a pre-determined acceptable margin of error, it may be feasible to derive and apply correction factors based on local population trends in order to improve the Broselow tape’s accuracy in specific settings, as Ramarajan et al demonstrated. Its greatest benefit may lie in its simplicity of use. It requires no calculations and so eliminates the potential for mathematical errors. This is especially valuable in stressful resuscitations when physicians may need to consider multiple aspects of patient care simultaneously. Designing resuscitation carts based on Broselow tape weight categories can further simply pediatric emergency care. Moreover, even if the Broselow tape overestimates or underestimates weight and medication dosing, such dosing errors are likely to be less severe than errors caused by miscalculation. For example, mathematical errors could easily result in a ten-fold overdose of a medication. This will not occur with the Brosleow tape. It serves as a useful adjunct for estimating weight in pediatric emergency departments, but should be used with caution in those populations in which it has not been studied or validated. To date no study has investigated the accuracy of the Broselow tape in a Latin-American population. Obviously, such information would be relevant to physicians caring for many Latin-American children, both in Latin-American and the United States of America. This remains an important area for further research on the utility of the Broselow tape in the emergency department.
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[1] Indiana University School of Medicine. Indianapolis, Indiana. United States.
[2] Área Académica de Medicina del Instituto de Ciencias de la Salud de la Universidad Autónoma del Estado de Hidalgo. Pachuca, Hidalgo. Mexico.
[3] Hospital del Niño DIF Hidalgo, Pachuca, Hidalgo. Mexico.
* Author for correspondence
Indiana University School of Medicine
Phone: 317-962-5975
Fax: 317-963-5394
mkhouli@iupui.edu