Microbial growth in a mixture of hyperbaric bupivacaine and fentanyl prepared in a multi-dose syringe in the operating theatre environment
Date
2013-01-24
Authors
Morgan, Gwen
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Abstract
Introduction
A protocol has been devised in which a 20ml mixture of hyperbaric bupivacaine and fentanyl is prepared in a multi-dose syringe, from which aliquots are withdrawn into individual sterile syringes for use in spinal anaesthesia. The risk of microbial contamination of these multi-dose syringes is unknown and this study was designed to assess such risk.
Methodology
In this pilot study, each syringe was prepared using non-aseptic technique to contain a mixture comprising Fentanyl 10 μg.ml-1, Bupivacaine 4mg.ml-1and Dextrose 64mg.ml-1, with a total volume of 20ml. Syringes were then allocated to pairs. Aliquots were withdrawn hourly from one syringe of each pair for a twelve-hour study period, whilst the other syringe was sampled only at the beginning and end of the same period. All aliquots were withdrawn using standard aseptic technique in an operating theatre environment. For each syringe pair, both samples from the control syringe and four of the samples from the multi-dose syringe were submitted for microbiological culture.
Results
Of the 120 samples taken, one sample was excluded. Of the remaining 119 samples submitted for microbiological investigation, only one yielded growth. This sample had been taken from a multi-dose syringe at the beginning of the study period. Subsequent samples withdrawn from the same syringe were found to be sterile. The organism which had been cultured from this sample was Staphylococcus aureus (S. aureus).
Conclusion
It is possible that the culture medium which yielded the microbial growth was contaminated, which would explain why subsequent samples from the same syringe were sterile. Alternatively, bupivacaine is known to be strongly antimicrobial against some pathogens and it is conceivable that there may have been initial contamination of the syringe by S. aureus, which was inhibited by the bupivacaine to produce subsequent sterile samples. Whilst this may suggest that the use of multi-dose syringes for spinal anaesthesia could be safe, in light of the inconclusive result, further investigation is warranted.