The Effect of Drug Concentration Expression on Epinephrine Dosing Errors

A Randomized Trial

1 January 2008 | Volume 148 Issue 1 | Pages 11-14

Background: The expression of drug concentration as a ratio may cause dosing errors.

Objective: To examine the effect of ratio expressions on drug administration.

Design: Randomized, blinded, controlled study.

Setting: Simulation center in an urban hospital.

Participants: 28 physicians.

Intervention: Participants managed a simulated pediatric acute anaphylaxis scenario by using epinephrine ampules labeled with mass concentration (1 mg in 1 mL) or a ratio (1 mL of a 1:1000 solution).

Measurements: The amount of epinephrine given and the time taken to administer it.

Results: Compared with providers using ampules with mass concentration labels, those using ratio labels gave more epinephrine (adjusted mean dose, 213 µg above target [95% CI, 76.4 to 350.1 µg]; P = 0.003), and took longer to do so (adjusted mean delay, 91 seconds, [CI, 61.0 to 122.1 seconds]; P  0.0001).

Limitations: Performance in simulated scenarios may not reflect clinical practice. In reality, ampule labels provide both expressions of concentration.

Conclusion: The use of ratios to express drug concentration may be a source of drug administration error. Patient safety might be improved by expressing drug concentrations exclusively as mass concentration.

Editors' Notes Context The use of ratios to express drug concentrations makes dosing calculations confusing and may cause drug errors. Contribution The researchers labeled epinephrine ampules with ratios only (1 mL of 1:1000) or concentration only (1 mg in 1 mL) and randomly assigned providers to use one or the other in a simulated anaphylactic arrest. Providers using ratios made many more errors and took longer to give the drug than providers using concentrations. Caution The case was simulated, and in reality, ampules are labeled with both expressions. Implication The use of ratios to express epinephrine concentration is confusing, and the revision of labeling to express concentration in more clinically intuitive ways may reduce errors. —The Editors

 

Author and Article Information

From the University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom, and Benito Menni—Centre Assistencial en Salut Mental Sant Boi de Llobregat, Barcelona, Spain.

Potential Financial Conflicts of Interest: None disclosed.

Reproducible Research Statement: Study protocol, statistical code, and data set: Available to approved individuals through written agreements.

Requests for Single Reprints: Daniel W. Wheeler, PhD, Division of Anaesthesia, University of Cambridge, Box 93, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, United Kingdom; e-mail, dww21{at}cam.ac.uk.

Current Author Addresses: Drs. Wheeler, Carter, Degnan, Menon, and Gupta and Mr. Dunling: University Division of Anaesthesia and Department of Anaesthetics, University of Cambridge, Box 93, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, United Kingdom.

Miss Murray: Simulation Centre, Addenbrooke's Hospital Postgraduate Centre, Box 111, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, United Kingdom.

Dr. Salvador: Benito Menni–Centre Assistencial en Salut Mental, Dr Pujadas 38, Sant Boi de Llobregat, 08830 Barcelona, Spain.

Author Contributions: Conception and design: D.W. Wheeler, B.A. Degnan.

Analysis and interpretation of data: D.W. Wheeler, B.A. Degnan, R. Salvador.

Drafting of the article: D.W. Wheeler.

Critical revision of the article for important intellectual content: D.W. Wheeler, J.J. Carter, L.J. Murray, B.A. Degnan, C.P. Dunling, R. Salvador, D.K. Menon, A.K. Gupta.

Final approval of the article: D.W. Wheeler, J.J. Carter, L.J. Murray, B.A. Degnan, C.P. Dunling, R. Salvador, D.K. Menon, A.K. Gupta.

Statistical expertise: R. Salvador, D.K. Menon

Obtaining of funding: D.W. Wheeler

Administrative, technical, or logistic support: J.J. Carter, L.J. Murray, B.A. Degnan, C.P. Dunling.

Collection and assembly of data: D.W. Wheeler, J.J. Carter, L.J. Murray, B.A. Degnan, C.P. Dunling.

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