Cause of Device-Related Incident
Support system failures; User errors

Clinical Specialty or Hospital Department
CCU / ICU / NICU; Clinical/Biomedical Engineering; Nursing; Pharmacy / IV therapy

Device Factors
*Not stated

Document Type
Hazard Reports

External Factors
*Not stated

Mechanism of Injury or Death
Overdose

Support System Failures
Error in hospital policy; Lack of competent accident investigation; Use of inappropriate devices

Tampering and/or Sabotage
*Not stated

User Errors
Failure to perform pre-use inspection; Incorrect clinical use

UMDNS
Syringes, Cartridge [16-585]; Syringes, Anesthesia [13-931]; Syringe Cartridges [16-775]; Infusion Pumps, Patient-Controlled Analgesic [16-924]; Infusion Pumps, Syringe [13-217]

Overinfusion Caused by Gravity Free-Flow from a Damaged Prefilled Glass Syringe



Hazard [Health Devices Dec 1996;25(12):476-7]

Problem

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 cardiac complications.

Background

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.

Discussion

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.

Recommendations

  1. 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.
  2. Review institutional policies and guidelines for monitoring patients during PCA and other potent infusion therapies.
  3. Use infusion sets with integral antisiphon or positive-pressure valves for all infusions delivered from glass syringes.
  4. 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.

UMDNS Terms

  • Syringes, Cartridge [16-585]
  • Syringes, Anesthesia [13-931]
  • Syringe Cartridges [16-775]
  • Infusion Pumps, Patient-Controlled Analgesic [16-924]
  • 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

Overdose


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