Minneapolis-based Medtronic Inc. is recalling some lots of its Quick-set infusion sets over concerns that they may cause insulin pumps to deliver too much or too little insulin.

The infusion sets in question have the reference numbers MMT-396, MMT-397, MMT-398, and MMT-399, and lot numbers starting with the number 8 printed on their packaging.

Customers are asked to return the affected infusion sets to the company. For more information, consumers can call 800-345-8139 or visit http://www.medtronicdiabetes.com/lot8.

Users experiencing adverse reactions can report them to the Food and Drug Administration at http://www.fda.gov/medwatch

The infusion sets, used with the company's MiniMed Paradigm insulin pumps, deliver insulin via a thin plastic tube from the pump to the patient. A malfunction could cause them to deliver too high or to low a dose of insulin, leading to hyperglycemia or hypoglycemia-both dangerous conditions for people with diabetes.

However, Medtronic says that there have been no reports of any malfunctions among users of the infusion sets. The recall is a precautionary measure intended to thwart a potential problem.

(Editor's Note: The message below, distributed by Medtronic, explains the company's recall decision. We are publishing it unaltered to assist Medtronic in getting the word out to Quick-set users.)

 A Message from Medtronic

To Customers Previously Using "Lot 8" Quick-set* Infusion Sets

Please know that we care about your safety - that's why Medtronic acted quickly to recall "Lot 8" Quick-set infusion sets. We would like to share some background information about this recall, and also describe how clogged vents on an infusion set could affect blood sugar levels.

Background Information

Please know that Medtronic voluntarily initiated this recall - it was not triggered by a patient injury report.  Medtronic received a report that an infusion set did not prime properly and our internal testing revealed that this was a result of clogged vents due to a change in the manufacturing process. Venting is necessary to equalize air pressure in the reservoir compartment with the surrounding atmosphere. Clogged vents could potentially cause too much or too little insulin to be delivered.

The manufacturing process was corrected and Medtronic is instructing patients to stop using "Lot 8" Quick-set infusion sets.  Last week, Medtronic sent more than one million infusion sets to customers to ensure therapy continuation. The company is also working closely with distributor partners to provide infusion sets to everyone who needs them.

Blood Glucose Variability and Clogged Vents

Although patients may wonder if their past blood sugar variability is a result of clogged vents, our internal testing shows that the possibility for insulin over or under delivery is limited to the following two scenarios:

Scenario 1:

A significant over-delivery of insulin caused by a rapid increase in altitude, potentially leading to a severe hypoglycemic event.

Scenario 2:

The  non-delivery of insulin closely following an infusion set change, potentially leading to a hyperglycemic event.

Scenario 1-Over-Delivery of Insulin

For a significant hypoglycemic event to occur as a result of clogged vents, a rapid change in air pressure would be necessary.  For example, when taking off in an airplane or quickly driving up a mountain, air pressure could build up inside the reservoir compartment and potentially cause over-delivery of insulin. This could result in a severe hypoglycemic event, which may require immediate action or assistance.

Since our testing shows that this occurs only with a rapid increase in altitude, this severe low blood sugar event is different than the typical low blood sugars that many people experience as part of their routine diabetes management.

Scenario 2-Non-Delivery of Insulin

During priming, clogged vents may prevent the reservoir compartment from equalizing air pressure. As a result, the insulin pump may appear to be properly primed when it is not.  Once the infusion set is inserted, this could lead to a period of non-delivery of insulin, which can potentially result in a hyperglycemic event following an infusion set change.

Since this occurs closely following an infusion set change, it may be different than the typical high blood sugars that many people experience as part of their routine diabetes management

So that we can serve all of our customers during this recall, we will be sending infusion sets at a rate of approximately one box every three weeks - we are doing this to ensure therapy continuation for everyone.  We deeply apologize for the inconvenience of this process.  Please know that patient safety is our highest priority.

-Medtronic Diabetes