Authors: Emily Macnish, RVN, FdSc, BSc (Hons).

Emily qualified as a registered veterinary nurse in 2020. She worked in a 24-hour hospital, while studying towards the BSc veterinary nursing top-up at Nottingham Trent University, before moving to work at Sarah Smith Cardiology. She joined the University of Nottingham in January 2023 as a teaching associate in small animal clinical practice.

Heather Imrie, BA, VetMB, PGCHE, PhD, MRCVS, FHEA

Heather qualified as a veterinary surgeon in 1989. Having spent time in mixed practice, she undertook a PhD at the University of Nottingham before working as a postdoctoral research assistant at the University of Oxford, with an interest in immunology. She joined Nottingham Trent University in 2013, working as a senior lecturer in the veterinary nursing team.


Emily qualified as a veterinary surgeon in 2007 before joining a small animal first opinion practice. She taught veterinary nursing at Nottingham Trent University, then joined the Royal Veterinary College in 2021 as a lecturer in veterinary education. Emily’s research interests include heat-related illness in companion animals and preparing veterinary professionals for primary care practice.

DOI: 10.56496/RGWF9084

ABSTRACT Veterinary nurses have legal and professional responsibilities to maintain accurate controlled dug records. Recording wastage from needle/syringe dead space contributes to accurate record keeping, but only if the volumes recorded are accurate. This study investigated the volume of dead space present in needle/syringe combinations to determine whether recommendations to use a standard wastage volume (0.05 ml) are appropriate. Combinations of 1–20 ml syringes and 21/23/25G needles were used to draw up sterile water for injection. Syringes were filled to 10% and 100% of the measured syringe volume, and the water in the injection bottle was weighed before and after withdrawing each volume, to calculate the total volume of water removed. The volume withdrawn into the syringe (e.g. 1 ml) was subtracted from the total volume of water withdrawn from the bottle (e.g. 1.11 ml) to determine the volume in the needle/syringe dead space. Ten replicates of each needle/syringe combination were measured, and the effect of needle size, syringe size and syringe fill on dead-space volume were explored. Needle size was found to have a significant effect on dead-space volume for the 1 ml syringe (p < 0.001) but not for other syringe sizes. Syringe size had a significant effect on dead-space volume (p < 0.001), but there was no significant difference between 5 ml, 10 ml or 20 ml syringe discard volumes (p > 0.05). Syringe fill had no effect on dead-space volume (p = 0.488). The median combined needle/syringe dead space for a 1 ml syringe with a 23/25G needle was 0.08 ml; for a 1 ml syringe with a 21G needle it was 0.11 ml; for a 3 ml syringe with a 21–25G needle it was 0.16 ml; and for 5–20 ml syringes with 21–25G needles it was 0.19 ml. In conclusion, continued use of 0.05 ml for recording dead-space wastage cannot be recommended; using syringe size-dependent volumes may improve controlled drug record accuracy.

Keywords syringe, dead space, controlled, drug, record keeping, pharmaceutical, waste

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