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ASK THE EXPERTS
AUGUST 98 - VOLUME 18 - NUMBER 4
FILTER NEEDLES AND GLASS AMPULES
Q. Are special filter needles required when drawing up medication from a glass ampule? Are there hidden risks to patients, ie, sharp glass particles, if a filter needle is not used?
A. Fred L Meister, PharmD, replies:
Bacterial contamination has always been the major concern associated with the intravenous administration of medications and is a well-known cause of morbidity and mortality. Additional risk factors, however, have been identified and must also be considered.
The potential risks associated with administration of medications supplied in glass ampules is much greater than realized by most practitioners. Opening a glass ampule produces a shower of glass particles, many of which enter the ampule and contaminate the contents. Some of the particles have been shown to carry bacteria, though the significance of this has not been determined.
The number of glass particles found in opened ampules varies, but most reports indicate approximately 100 particles, ranging in size from 10 to 1,000 µm, per 10-mL ampule. The particle count increases as the size of the ampule increases (ie, a 20-mL ampule will contain more glass particles than a 10-mL ampule). When the content of a 10-mL ampule is aspirated through an 18-gauge, 1.5-inch needle, the particle count is reduced by approximately one third (ie, approximately 65 particles remain in the aspirate), and the maximum particle size is reduced to less than 400 µm.
The potential risks associated with intravenous administration of glass particles are based on animal studies, though similar risks would apply equally to humans. It has been shown that glass particles cause inflammatory reactions (eg, phlebitis) and granuloma formation in pulmonary, hepatic, splenic, renal, and intestinal tissue. This represents a significant risk of an adverse patient outcome.
The effective removal of glass particles from an opened ampule can be accomplished by aspirating through a 19-gauge, 5-µm filter needle. Using this method decreases the average total number of particles in the aspirate to approximately ±1, and the particle size to less than 200 µm. Using a 0.22-µm in-line filter offers little or no additional benefit, and is more costly and labor intensive—once the ampule content is aspirated into a syringe, the filter needle must be replaced with a standard needle prior to transferring or administering the medication.
Based on the available information, a filter needle is recommended when aspirating a medication from a glass ampule.