Quality of the Studies

The current study highlights a significant gap in high-quality studies in EMS weight estimation. Despite its importance, the number of papers addressing this topic is limited, with only 25 identified, of which merely nine contained relevant data. This underscores the urgent need for further research in this area to improve the accuracy and reliability of EMS weight estimation, and ultimately enhance patient outcomes.

The study designs, sampling, and selection were found to be suboptimal. Many of the simulation studies relied on weight estimations from manikins or images rather than actual patients. These studies should only be regarded as preliminary reports, and the findings should not be generalized to clinical environments. Several of the clinical studies used a before-and-after methodology. This format is typically regarded as a low-quality study design, and the findings should also be regarded as hypothesis-generating rather than substantive. ^{Reference Goodacre36} The lack of prospective clinical studies was notable and is indicative of the poor quality of the available evidence. Compounding these issues were the small sample sizes, and a preponderance of convenience sampling, further limited the studies’ power to provide meaningful conclusions.

The failure to describe potential confounders was also a major weakness. Most studies did not evaluate weight estimation accuracy in subgroups of body mass index/BMI (and age-groups in children). These two factors are known to have a significant impact on the accuracy of weight estimation methods. The failure to include this information makes it impossible to compare outcomes in different studies.

Some studies failed to specify the weight estimation methods used in the study. This dramatically limited the usefulness of the information obtained. There is limited value in studying weight estimation accuracy without this information.

Taken together, these findings highlight the need for more robust study designs, larger sample sizes, and the evaluation of relevant confounding factors in future investigations of weight estimation accuracy. Additionally, the standardization of weight estimation methods and data reporting across studies would greatly facilitate the comparison of results and the identification of best practices.

Accuracy Data

Studies from the Emergency Medicine literature have suggested that an acceptable standard for a weight estimation system is to achieve 70% of estimates within 10% of actual weight (P10 ≤ 70%) and 95% of estimates within 20% of actual weight (P20 ≤ 95%). ^{Reference Wells, Goldstein and Bentley4,Reference Stewart37} This is a standard which is generally achieved by the newer length- and habitus-based weight estimation systems (such as the PAWPER XL tape and the Mercy method), and which is seldom reached by other methods, including the Broselow tape. ^{Reference Young and Korotzer2,Reference Wells, Goldstein and Bentley4} In this review, only the PAWPER XL tape used by paramedics achieved this benchmark in two studies, and paramedic estimates of adults’ weights came close in a single study. ^{Reference Wells, Goldstein and Bentley4,Reference Martin, Soria and Brown9,Reference Wells, Goldstein and Bentley26} None of these were clinical, prehospital studies, however.

The Broselow tape was found to out-perform paramedic estimates by Vilke, et al. ^{Reference Vilke, Marino, Fisher and Chan10} Unfortunately, the acceptable error range used in this study was very large (±50%), which makes it difficult to compare these results with those from other studies. The only other useful study on the Broselow tape showed a poor accuracy in children and adolescent simulated patients. ^{Reference Wells, Goldstein and Bentley26} From the studies that evaluated drug dosing accuracy with the Broselow tape, it is possible to infer that weight estimation was more accurate than paramedic “guesstimates” and age-based formulas, but there was no direct evidence presented in any study to support this. It is worth noting that the accuracy, and acceptability, of the Broselow tape has been questioned in the Emergency Medicine literature because of its inaccuracy in underweight and obese children. ^{Reference Young and Korotzer2,Reference Wells, Goldstein and Bentley4,Reference Wells, Goldstein, Bentley, Basnett and Monteith38}

The accuracy of visual estimates of weight by paramedics was poor, with the exception of a single study by Martin, et al. ^{Reference Martin, Soria and Brown9} It has been well-established in other research that visual estimates of weight are unreliable, and frequently very inaccurate. There is reasonable consensus that this method of weight estimation should not be used. ^{Reference Young and Korotzer2}

Interestingly, the single study evaluating caregiver estimates of weight showed that these estimates were substantially less accurate than reported in previous studies in the Emergency Medicine and pediatrics literature. ^{Reference Young and Korotzer2,Reference Wells, Goldstein and Bentley4,Reference Chassee, Reischmann, Mancera and Hoyle20} This was a pragmatic, real-world study in which 9-1-1 dispatchers obtained weight estimates from family members of sick children. This study is a useful warning that real-world scenarios may be very different to the typical settings used for weight estimation studies, and with substantially different results. This finding is significant, and important, because parental estimates of weight are considered to be the gold standard for weight estimates in children, but there have been few real-life studies to confirm this.

The only information on other methods of weight estimation showed that the PAWPER XL tape performed very well and the Mercy method moderately in studies by Wells, et al. ^{Reference Wells, Goldstein and Bentley24,Reference Wells, Goldstein and Bentley26} Age-based formulas performed poorly and were only reported in a single study by Hoyle, et al. ^{Reference Hoyle, Ekblad, Woodwyk, Brandt, Fales and Lammers28}

In this review, when compared against doctors and nurses, there was no convincing evidence that paramedics were better or worse at estimating weight using the Broselow tape, the PAWPER XL tape, or the Mercy method. ^{Reference Wells, Goldstein and Bentley4,Reference Wells, Goldstein and Bentley26} However, one study did find that paramedics were significantly less accurate than doctors and nurses at visual estimation of weight in adult patients. ^{Reference Hall, Larkin, Trujillo, Hinds and Delaney12} This evidence from a single study is weak, however. Since visual estimation of weight is generally condemned as a poor method of weight estimation, the relevance is limited in any event. ^{Reference Dearlove and Dearlove39,Reference Pintilie, Myint, Skinner, Potter and Metcalf40}

Many articles not included in this review have suggested that a particular weight estimation system would be suitable for use during prehospital care, without actually studying it in this environment (eg, Lubitz, et al and Park, et al). ^{Reference Lubitz, Seidel, Chameides, Luten, Zaritsky and Campbell41,Reference Park, Kwon and Jung42} It is not clear whether generalizing weight estimation performance data from a different environment, such as the ED, to the prehospital environment would be valid. In the Emergency Medicine and pediatric literature, the most accurate weight estimation methods in children are currently the PAWPER XL tape and the Mercy method. ^{Reference Young and Korotzer2,Reference Wells, Goldstein and Bentley4} While it is possible that these methods could be accurate in the prehospital environment, their usability (with a comprehensive drug dosing guide) during the circumstances of prehospital emergency care would need to be tested and confirmed. ^{Reference Cottrell, O’Brien and Curry43}

Many of the included studies focused on the accuracy of drug dosing as the key outcome, but generally ignored the impact of inaccurate weight estimation on drug dose accuracy. Both weight estimation and the drug dose calculation and administration process need to be accurate and easy-to-use to ensure accurate drug delivery. ^{Reference Kaufmann, Laschat and Wappler33,Reference Barata, Benjamin, Mace, Herman and Goldman34} This concept needs to be included in future research.

Themes

Four major themes were identified from the included studies. Firstly, the importance of accurate weight-based drug dosing was recognized as crucial for safe and effective emergency drug therapy in the EMS environment. This highlights the critical need for further research in this field. This has already been identified by patient safety organizations as a vital aspect of ED care, and applies equally to the prehospital environment. ^{44,Reference Bailey, Gaunt and Grissinger45} Secondly, both weight estimation and drug dose calculation were identified as key contributors to drug dosing errors, underscoring the critical importance of training to ensure these processes are conducted accurately and efficiently. This emphasizes the need for comprehensive guidance and on-going training for EMS personnel, using accurate weight estimation methods and guides to drug dose calculation. Thirdly, paramedic “guesstimates” of weight were deemed unreliable, with length-based tapes being a preferable alternative. However, these length-based tapes are not without their limitations, including incorrect usage and inaccuracies in underweight and obese children, as well as in older children. More accurate weight estimation methods should be considered. Lastly, weight estimation in adults has not been adequately studied, and there are currently no reliable methods for estimating weight in incapacitated adults in the EMS setting. This highlights a critical gap in the literature and the need for future research to develop accurate and reliable weight estimation methods for this population. Taken together, these findings emphasize the importance of accurate weight estimation and drug dose calculation in EMS, and the need for on-going research and training to improve patient outcomes and ensure optimal care in emergency situations.