Overinfusion Caused by Gravity Free-Flow from a Damaged Prefilled Glass Syringe
Hazard [Health Devices Dec 1996;25(12):476-7]
A member hospital reported an overinfusion of Demerol when a cracked
prefilled glass syringe was used in a patient-controlled analgesia (PCA) infusion pump.
The crack, which may have developed either before or during installation of the syringe in
the pump, allowed gravity free-flow of the analgesic from the syringe. Gravity free-flow
of a potent medication, such as Demerol, can cause potentially fatal respiratory and/or
Certain types of infusion pumps, specifically syringe pumps and many PCA
pumps, use syringes as liquid medication reservoirs. Because syringes are easy to prepare,
their use is convenient when small volumes of liquid medications (i.e., 60 mL or less)
need to be infused. Many medications can even be purchased in prefilled syringes. However,
because most prefilled syringes, including those used for certain PCA pumps, include a
glass barrel that can break or crack (prefilled syringes are not typically made of
plastic), they are particularly susceptible to damage that would allow leakage or gravity
free-flow incidents, as discussed below. We have not received any reports of gravity
free-flow resulting from damage to plastic syringes.
Infusion pumps that use a syringe as a reservoir rely on the integrity of
both the syringe barrel and the seal between the syringe's plunger and barrel to ensure
accurate delivery and to prevent leakage or gravity free-flow of medication. A damaged
barrel can cause several problems. For example, if the barrel is punctured or cracked,
medication is likely to leak as the plunger is advanced. This can result in underdelivery
and, with some chemotherapy drugs, a potentially hazardous spill. Also, as occurred in the
incident described in this report, if the pump is positioned above the infusion site by
more than a few inches, a damaged syringe barrel can result in an overinfusion.
Overinfusion can occur when a break in either
the syringe barrel or the plunger seal creates a vent that permits air to enter the barrel, eliminating the relative vacuum that
exists in an intact barrel. Without the relative vacuum and with the pump positioned sufficiently
above the infusion site, medication can be delivered to the patient at an excessive (uncontrolled)
rate by the force of gravity.(For systems that use a collapsible reservior,
gravity free-flow could occur even without air entry into the system.) In laboratory
testing, ECRI has found that aqueous solutions can be delivered by this means at flow
rates in excess of 30 mL/hr.
It is possible for personnel to identify a free-flow condition by noting
the presence of air in the syringe barrel. However, it is more likely that free-flow will
go unnoticed until a significant overinfusion has occurred because 1) many of the drugs
delivered with this type of system are very potent, and 2) syringe barrels are often not
clearly visible when loaded in a pump, for example, because of the pump or syringe design
or because labels are present on the syringe barrel.
The risks of gravity free-flow are eliminated when the tubing set
connecting the syringe to the patient contains an "anti-siphon" (or
"positive-pressure") valve. This type of valve prevents fluid that is being
propelled solely by gravity from passing through. Extension tubing sets with this type of
valve integral to the set are available for this application. In fact, the product
labeling for most, if not all, prefilled glass syringes specifies that the syringes be
used only with sets featuring anti-siphon-type valves.
- Instruct nurses and other personnel responsible for
administering PCA therapy or other potent medications delivered from glass
syringes to inspect the syringes for cracks or chips before they are
installed in the pump and connected to the patient. If assembly of the
syringe is necessary, personnel should check the integrity of the barrel
both before and after assembly.
- Review institutional policies and guidelines for
monitoring patients during PCA and other potent infusion therapies.
- Use infusion sets with integral antisiphon or
positive-pressure valves for all infusions delivered from glass syringes.
- In the event of an overinfusion accident:
A. Record all settings and the content of any memory from the infusion
pump. Perform this step as soon as possible after an incident because (1) the memory logs
of some pumps become cleared immediately or shortly after the unit is turned off, and (2)
testing of the unit may displace data from the incident and increase the difficulty of
distinguishing valid from invalid data.
B. Impound and save the pump and all components of the infusion
system, including the syringe, extension set, and any accessories (e.g., in-line valves or
filters), even if the pump is not initially implicated.
C. Measure the volume of any remaining solution, and compare this volume
to the expected values based on the settings of the pump. If this analysis does not reveal
a discrepancy with the intended settings, have a sample of the solution sent to an
independent laboratory to be assayed for content and concentration.
- Syringes, Cartridge [16-585]
- Syringes, Anesthesia [13-931]
- Syringe Cartridges [16-775]
- Infusion Pumps, Patient-Controlled Analgesic
- Infusion Pumps, Syringe [13-217]
Cause of Device-Related Incident
User errors: Failure to perform pre-use inspection; Incorrect clinical use
Support system failures: Error in hospital
policy; Lack of competent accident investigation; Use of inappropriate devices
Mechanism of Injury or Death