Variables Associated With Medication Errors in Pediatric Emergency Medicine

METHODS

We conducted a retrospective chart review of patients who were treated at the ED of the Hospital for Sick Children in Toronto, Canada. All charts of patients who were treated in the ED during 12 randomly selected days in the summer of 2000 were reviewed for potential medication errors. The Research Ethics Board of the Hospital approved the study.

Two medical students served as research assistants. They attended 2 training sessions that included extraction of data from charts under the supervision of 1 of the investigators, before data extraction. They subsequently extracted the data into a database that included information about patients’ demographics, clinical condition, diagnosis, acuity of condition (based on triage category), the prescribing physician, and all of the medications prescribed and given to the patient. Physicians were categorized according to their level of training as staff or trainees (interns, residents, and fellows). When the drug regimen was different (dose differed from the recommended dose by 20% or more, deviation by 2 hours or more from the recommended interval between doses, wrong units or route of administration) from the recommended regimen, it was flagged as a potential error. Medications ordered and not given and medications given without a written order were also flagged as an error. Delays of 1 hour or less in drug administration, the absence of date, or unclear signature were not considered errors. To establish the accuracy of data collection, a senior investigator reviewed a random sample of 3% of the charts. The entire database was further reviewed by both senior investigators for potential drug interactions and drugs incorrectly prescribed for any specific condition.

RESULTS

Study Population

There were 1549 visits to the ED during the study days. A total of 1532 charts (98.9%) were available for review. Twenty-five patients had more than 1 visit to the ED during the study period. The characteristics of the study population are presented in Table 1. The total number of medications ordered was 1678 with a median of 1 and a range of 0 to 12 medications ordered per patient.

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TABLE 1.

Characteristics of the study population

Potential errors in medications prescribed and given in the ED or for home use were identified in 403 charts. A senior investigator reviewed a random sample of 50 charts and identified 1 additional error (not found by the research assistants). In 330 cases (81.8%), there was initial agreement between the reviewers regarding whether an error occurred and on the ranking of the error. In 49 of the remaining 73 cases, agreement was achieved between reviewers after the case was discussed. Twenty-four cases were reviewed by a third researcher.

The κ for initial agreement between reviewers on whether an error occurred was 0.79, and the κ for ranking of the errors was 0.70, indicating a high level of agreement. Figure 1 presents the cohort flowchart and the methodology applied to identify the errors.

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Fig 1.

Study population flow chart. n indicates number of patient charts.

Characteristics of Medications Involved

The drugs most commonly involved in errors (Fig 2) were acetaminophen followed by antibiotics, asthma medications, and antihistamines. These drugs were also those most commonly prescribed in the ED (data not shown).

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Fig 2.

Medications most commonly involved in errors. Percentage of insignificant/minimal risk and significant errors for each drug type not statistically different from that of all errors.

DISCUSSION

In this retrospective chart review, we found that approximately 10% of patients who are seen in a pediatric ED are subjected to medication errors. We also found that compared with staff physicians, trainees were more likely to commit errors and that medication errors were more common among seriously ill patients. Approximately 50 000 children are treated each year at the Hospital for Sick Children ED. Extrapolating the data from this study to a 1-year period suggests that an estimated 5000 children each year may be subjected to a medication error and that 2500 may be subjected to significant errors. A previous study,¹⁵ reporting a much lower error rate, was based on incident reporting, which has been shown to identify only a small percentage of adverse drug events.¹⁶ Indeed, none of the events that we identified was reported through the hospital’s incident report system. Another study¹⁷ found errors in 95% of prescriptions issued in the ED. However, because of concerns related to the study methodology (eg, the definition of error included omission of instructions to shake the container or to keep the drug refrigerated), the high incidence reported should be interpreted with caution.

Previous studies have found that medication errors occur frequently in the intensive care setting,¹⁸ perhaps as a result of the complexity and intensity of treatment and the use of unfamiliar medications.^19,20 Although many patients who are seen at the ED do not have life-threatening conditions, some of the circumstances found in intensive care units also exist in the pediatric ED, which treats patients with a high acuity of illness and has a rapid turnover of patients. The incidence of medication errors that we found is comparable with the 6.6% to 11.7% incidence reported from pediatric intensive care units.^15,21 Our results suggest that seriously ill patients are susceptible to higher rates of medication errors. This may be related in part to increased use of medication in such patients.

Even in a favorable setting, a substantial proportion of pediatric residents make mistakes while calculating drug doses.^22,23 It is therefore not surprising that dosing errors were the most common errors made by physicians. These findings are consistent with previous studies identifying dosage calculations as the most frequent reason for medication errors in pediatric patients.^14,24

We found a significantly higher rate of errors in the ED between 4 am and 8 am compared with 8 am to 12 pm. Although one may surmise that this is the result of physicians’ tiredness, after adjusting for other variables, this association was no longer significant, suggesting that the association cannot simply be attributed to physicians’ tiredness. The higher rate of errors at night might be the result of a lower proportion of staff physicians during night shifts or of less supervision of trainees’ work at night or because patients who are seen late at night were more seriously ill. Our sample size was not sufficient to test all of these hypotheses; however, they should be considered in future research.

We used the waiting time before being seen by a physician as an indirect measure of the workload in the ED, with waiting time of >2 hours (which occurred in 20% of the patients) as an indicator for increased workload. This factor was not associated with an increased risk of errors. However, an association may not be ruled out on the basis of these data for 2 reasons. First, the study was conducted in the summer, when the workload in pediatric EDs is traditionally lighter. Second, in our study, the most seriously ill patients were seen promptly; thus, the effect of workload, as estimated by waiting time, could not be assessed in these patients.

Our findings suggest that the most important risk factor for errors in the pediatric ED is the physician’s level of training. Two previous studies demonstrated that the rate of medication errors in a pediatric service doubled when new physicians started their rotation¹⁸ and that first-year residents have higher rates of prescription errors.²⁵ The finding that trainees made more errors at the beginning of the academic year strengthens the plausibility of the association between level of training and the rate of errors. Contrary to these studies and to our findings, another study did not find differences in rates of errors made by attending physicians and residents.²⁶ One explanation for the effect of level of training on the proportion of errors in our study may be related to the setting in which this study was conducted. The Hospital for Sick Children is a tertiary care pediatric hospital, and its ED is the primary training site in pediatrics for University of Toronto medical residents. Approximately 360 trainees at different levels rotate through the ED each year. Only a small proportion of these trainees are pediatric residents. Most of them are in their first year of residency with very limited experience in pediatrics. In contrast, staff physicians are academic pediatricians with specialized training in emergency medicine.

The possibility of system errors as an underlying cause for medication mishaps has to be investigated. Although individuals make mistakes, characteristics of the system in which they are working can make errors more likely to happen and more difficult to detect.²⁷ It has been postulated that the best strategy to reduce drug errors is to improve the system by which drugs are given, thereby making it safer.²⁸ Examples of such approaches are the use of a unit-dose system, which has been shown to reduce significantly medication errors in committed hospital wards,^29,30 and the use of a computerized system for prescribing medications.^31,32 Including a pharmacist as part of the clinical team and having a satellite pharmacy in the ward were also suggested as measures to reduce medication errors.^15,33 These strategies could be adapted to the environment of the ED and then evaluated in clinical trials.

This study has several limitations. The retrospective design limited available data to those documented on the ED chart. This design could not detect many errors in drug administration. Other factors that could influence the medication error rate, such as the interaction among parents, patients, nurses, aides, noise, and concurrent events in the ED, were not analyzed because they were not documented on the chart and could not be measured accurately. Therefore, our analysis focused on prescribing errors. In many cases, we could not determine whether an adverse drug event occurred as a result of the error. ED patients are either admitted to inpatient units or discharged from the hospital from the ED. It was not possible to assess dosing intervals in admitted patients because ward physicians rewrote the orders. For discharged patients, we could not determine whether medications were given as ordered. Therefore, we included all documented errors in our analysis. Similar to other groups,² we believe that identifying these errors, even ones that were intercepted before harm was done, is important in developing strategies to reduce adverse drug events. An additional limitation of the study is that the only information collected on the prescribing physician was level of training. We therefore could not examine the effect by each physician. However, >80 different physicians worked in the ED on the study days and only a few of them were sampled >3 times. Therefore, it is unlikely that clustering of errors by 1 physician significantly affected the results. The relatively small sample size limited our ability to conduct stratified analyses. For example, we compared staff physicians with trainees but were unable to compare among trainees with different levels of training. It is also important to note that because the study was conducted in a tertiary care pediatric hospital, the results (especially the findings regarding trainees) may not be generalizable to other hospitals.

CONCLUSION

Approximately 10% of patients who are seen in a pediatric EDs may be exposed to medication errors. Our findings suggest that errors are more common among seriously ill patients and that trainees are more likely to make medical errors, particularly at the beginning of the academic year. Future research should focus on the development and evaluation of strategies to reduce medication errors in the pediatric ED.