It is common practice, including at the Children’s Hospital of Eastern Ontario, to maintain patency of IV tubing by NS flushing.10,11
Using a numeric rating scale and a visual hedonic scale, we found that modest disturbances in taste and/or odour occurred in the pediatric population following NS flushing of IV tubing from prefilled syringes. The minimum age for inclusion in the current study was set at 5 years, because previous studies have demonstrated the ability of children as young as 5 years to reliably evaluate palatability.4–9
The visual hedonic scale used here was previously used in taste studies of antibiotics in children.4–9
There were no obvious correlations between the subgroups studied (based on age, sex, and volume or rate of flushing), so these taste and/or odour sensations could occur in any patient. Identifying and preventing additional sources of alteration in taste and/or odour is especially important for patients receiving chemotherapy or radiotherapy, since these treatments may directly alter taste and odour perceptions, including the experience of metallic or bitter sensations.2
These disturbances in taste and/or odour perceptions may decrease patients’ quality of life and may lead to malnutrition and significant morbidity.12,13
In agreement with findings reported by Kongsgaard and others,1
who also used BD prefilled NS syringes, a high incidence of taste and/or odour disturbances was observed in this study among patients who underwent NS flushing of IV tubing. As reported by the authors of the earlier study,1
the manufacturer noted that volatile substances leaching into the saline from the plastic syringes are linked to patients’ experience of bad tastes or smells, but are not harmful to health. In addition, a smaller volume or slower flush rate did not appear to affect the incidence of taste and/or odour disturbance in the current study, in contrast to the manufacturer’s claims (as reported by Kongsgaard and others1
Just over a decade ago, unidentified compounds leached into prefilled syringes and ultimately led to adverse patient outcomes. Patients treated with epoetin alfa administered from prefilled syringes were found to have leached aromatic compounds in their bodies. These compounds led to the occurrence of adverse events, including antibody-positive pure red cell aplasia.14
Since then, modifications to the syringe-manufacturing process have been made to allow prospective identification of substances that may leach into prefilled syringes and cause deleterious effects on patients’ health.15
In recent years, the use of prefilled syringes has increased,16
and such syringes have become widely adopted in the self-administration of medications, such as insulin for treating diabetes mellitus.17
There are several potential or proven advantages to using prefilled syringes, including improved accuracy of dosing,18
reduced risk of dosing and medication errors, reduced risk of microbial contamination, less need for overfilling and hence less wastage, and increased safety and convenience for emergency use.19
However, the lack of data about compounds that leach into the contents of prefilled syringes suggests that reporting of adverse events associated with prefilled syringes needs to be improved.
One limitation of this study was the use of 2 different scales for the reporting of taste and/or odour disturbance. The validated visual hedonic scale has been used in several palatability studies,4–9
including studies in children aged 5 to 10 years,4
but the numeric scale used for children aged 11 to 18 years has not yet been validated. However, it appears that the modest alterations in intensity of taste and/or odour sensations observed in this study were similar to those reported by Kongsgaard and others,1
which suggests that it may be worthwhile to validate this numeric scale in future taste and/or odour studies involving children aged 11 to 18 years and adults.
The lack of a control group for comparison with patients receiving NS flush via prefilled syringes indicates the potential for taste and/or odour disturbances among hospital inpatients more generally. Potential sources that may contribute to abnormal taste and/or odour sensations include IV Viaflex bags (Baxter), tubing, or the parenteral medications themselves. These potential sources remain to be investigated. Another limitation of this study was the involvement of several different nurses, which may have prevented a standardized method of interviewing patients or introduced bias. Furthermore, the nurses were required to ask patients directly about possible taste or odour disturbances experienced, as a part of the interview process, rather than obtaining the information in some more objective manner.
There exists a risk of over-reporting taste and/or odour disturbances caused by NS flush with prefilled syringes. However, this study was initiated in response to spontaneous reports from pediatric patients who were able to independently link the abnormal sensations to flushing with a prefilled syringe (anecdotal evidence). The options to address this patient concern include replacing the syringes with syringes that do not leak unidentified compounds, asking the manufacturer to address the problem, or using syringes that have not been prefilled. Manufacturers should perform more vigilant quality control, using chromatographic and/or spectroscopic methods, to identify alterations in the long-term composition of prefilled syringe products.20,21
Use of control prefilled syringes manufactured by another company could also have improved the strength of the analysis. However, there are no reports that prefilled NS syringes sold by other manufacturers have been linked to taste and/or odour disturbances. Patients with abdominal pain, rhinorrhea, and/or cough were excluded from the study, because upper respiratory and gastrointestinal tract symptoms have been shown to alter taste perception.4
Bias was reduced by obtaining formal consent after routine administration of the NS flush, since patients may be more likely to report taste and/or smell anomalies when specifically told that such anomalies are the subject of the investigation.
Future studies could investigate potential taste and/or odour disturbances related to IV medications compounded in NS using BD syringes, since pediatric hospitals using this brand of syringe may store such medications for up to 30 days. Clinical outcomes were not assessed in the current study, but further investigation could be directed at assessing patients’ willingness to undergo subsequent NS flush after reporting altered taste and/or odour sensations and the effect of such altered sensations on inpatient quality of care. To improve inpatient quality of life, future studies should include blinding of the research team and should aim to compare different brands of prefilled syringes with syringes prepared fresh in the pharmacy.