Residual volume in semi-rigid bags used to prepare anticancer drugs: myth or reality? Evaluation and impact in practice

Introduction
Injectable anticancer drugs are prepared by the Centralized Chemotherapy Preparation Unit (UCPC) at our Hospital Center (CH), mainly by dilution in semi-rigid solvent bags of 0.9% sodium chloride (NaCl) or 5% glucose (G5). Nurses administer these preparations using an infusion pump, which they program according to the final volume of the bag (labeled Chimio^®) and the infusion rate. However, a residual volume remains after administration. The objective is to measure this volume and calculate the dose not administered to the patient.

Materials and methods
We recovered all the preparations of May 22, 23 and 24, 2023 administered in the oncohaematology day hospital service of the CH. The residual volume in the 100mL and 250mL bags was collected into the isolator to avoid contamination, using a syringe and a perforator. As a comparison, we repeated this manipulation on 10 unreconstituted 100mL and 250mL NaCl bags and 10 unreconstituted 100 mL and 250 mL G5 bags.

Results
A total of 42 bags of anticancer drugs were recovered: 15 bags of 100 mL NaCl, 6 bags of 100 mL glucose, 6 bags of 250 mL NaCl and 15 bags of 250 mL glucose.
The average residual volume of the bags was 5.00 mL, regardless of the nominal volume of the bag or the type of solvent. This equates to 3% [min: 1.36%; max: 6.84%] of the dose not being administered to the patient.
For 100 ml bags, the average residual dose was 4.5%, while for 250 ml bags it was 1.9%.
9 bags were recovered with a residual dose equivalent to more than 5% of the initial dose. This concerns only 100 ml bags, representing 43% of this type of preparation.
For non-reconstituted solvent bags, we found an average residual volume of 5.67 mL, with no significant difference depending on the solvent or the initial volume.

Discussion and conclusion
There is a risk of under-dosing, particularly in the case of 100-mL bags, since approximately half of patients received a dose at least 5% lower than that prescribed. This number is probably underestimated, as it was not possible to withdraw the entire residual volume.
This problem seems to be specific to bags and not dependent on the product added to the solvent, so it should be extended to all reconstituted medicinal products, even outside oncology. This risk is all the greater for drugs with a narrow therapeutic range or in pediatrics.
This should lead us to change our practices, and switching to flexible solvent bags could be an alternative, depending on their residual volume.

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