Background and Importance 2.5% of operations are cancelled because of preoperative medication errors. Pharmaceutical preoperative consultations are an effective tool in detection and prevention of these errors, but cost-effectiveness of their implementation has not been evaluated.

Aim and Objectives To determine the cost-effectiveness of the implementation of a pharmaceutical preoperative consultation to review the correct medication management of patients undergoing surgery.

Material and Methods A retrospective, single-center study was conducted to analyze all medication errors prevented by a pharmacist during a preoperative care consultation since their implementation in 2016 until 12/2020. The pharmacist reconciled medication and reviewed their appropriate preoperative management. Recommendations were made based on an institutional protocol.

To assess the economic impact of prevented medication errors, a team of pharmacists and anesthesiologists assigned each error a probability of resulting in a patient-impacting adverse event (p). Following Nebit et al methodology, values of 0, 0.01, 0.1, 0.4, or 0.6 were assigned to each error, with 0.6 being the maximum probability as a conservative measure.

A cost of €6,924 per adverse event was established based on data from the Spanish Ministry of Health in 2005 and adjusted for the consumer price index in 2020. The cost of each prevented error was calculated as €6,924 x p. The annual cost of a hospital pharmacy specialist in Spain was €45,494 in 2020.

A sensitivity analysis was conducted, recalculating the results if the average cost of an adverse event was 20% higher (€8,309) or lower (€5,539).

Results The consultation was attended by 3,105 patients (mean age 67.0 years) and 1,179 medication errors were prevented. Six were classified as p=0, 224 as p=0.01, 346 as p=0.1, 497 as p=0.4, and 106 as p=0.6, corresponding to 299.2 prevented adverse events.

In monetary terms, the savings associated with these prevented adverse events were €2,076,785 over 5 years, while the cost of employing a pharmacist was €227,470. The net savings were €1,849,315, and the euro saved/invested ratio was 9.1/1. Applying the sensitivity analysis, this ratio would range from 7.3/1 to 10.9/1.

Conclusion and Relevance The implementation of a Pharmaceutical Preoperative Care consultation was cost-effective for the healthcare system, with a cost savings ranging from 7.3 and 10.9 euros per euro invested.

Conflict of Interest No conflict of interest.