Medication dose calculation errors and other numeracy mishaps in hospitals: Analysis of the nature and enablers of incident reports.

Aims: To investigate medication dose calculation errors and other numeracy mishaps in hospitals and examine mechanisms and enablers which lead to such errors.

Design: A retrospective study using descriptive statistics and thematic analysis of the nature and enablers of reported incidents.

Methods: Medication dose calculation errors and other numeracy mishaps were identified from medication-related incidents reported to the Norwegian Incident Reporting System in 2016 and 2017. The main outcome measures were medications and medication classes involved, severity of harm, outcome, and error enablers.

Results: In total, we identified 100 numeracy errors, of which most involved intravenous administration route (n = 70). Analgesics were the most commonly reported drug class and morphine was the most common individual medication. Overall, 78 incidents described patient harm. Frequent mechanisms were 10- or 100-fold errors, mixing up units, and incorrect strength/rate entered into infusion pumps. The most frequent error enablers were: double check omitted or deviated (n = 40), lack of safety barriers to intercept prescribing errors (n = 25), and emergency/stress (n = 21).

Conclusion: Numeracy errors due to lack of or improper safeguards occurred during all medication management stages. Dose miscalculation after dilution of intravenous solutions, infusion pump programming, and double-checking were identified as unsafe practices. We discuss measures to prevent future calculation and numeracy errors.

Impact: Our analysis of medication dose calculation errors and other numeracy mishaps demonstrates the need for improving safety steps and increase standardization for medication management procedures. We discuss organizational, technological, and educational measures to prevent harm from numeracy errors.