Pain Pump Law Blog : Medical Device and Malpractice Lawyer & Attorney for Local Anesthetic Infusion Pump & Post-Operative Infection Cases

For most of the pain pumps on the market in 1999 (referred to in Part One of this post), scant information remains available online from the FDA.  However, the Summary of Safety Effectiveness for I-Flow's PainBuster under K980558 is still accessible.  In this document, I-Flow stated that the PainBuster was substantially equivalent in intended use to the Pain Control Infusion Pump (PCIP) (K896422) distributed by Sgarlato Laboratories and to the Homepump C-Series (K944692) and Homepump Eclipse (K932740) marketed by I-Flow. 

There are several interesting things about these statements of equivalence.  It was actually the Burron Ambulatory Drug Delivery System approved as K896422 and not the Sgarlato PCIP, which was K990101.  I-Flow's document did accurately state that the PCIP was produced by Burron/B. Braun.  And, K990101 does show that Sgarlato claimed equivalence to the Burron device and that Burron would manufacture the PCIP for Sgarlato.   The strange thing is that I-Flow's submission to the FDA was made in February 1998 and Sgarlato's was not made until January 1999.  On its face, therefore, I-Flow claimed substantial equivalence to a device that had not yet been submitted to the FDA for approval.  

Sgarlato's summary stated that its PCIP would be used for the same intended purpose as the Burron device.  Sgarlato's intended use was for continuous infusion of local anesthetics directly into the intraoperative site for management of postop surgical pain.  The Burron device was submitted to the FDA in 1989, however.  I am quite skeptical that it could have been approved for use as a pain pump at that time.  Unfortunately, all information about the 510(k) for the Burron device has been purged from FDA's 510(k) database. 

The other devices I-Flow claimed in 1998 as predicates were its own Homepumps.  However, both the C-Series and Eclipse pumps had much higher flow rates (up to several hundred ml/hr) and other routes of administration, including intravenous.  I-Flow claimed that the design of the PainBuster would be identical to that of the Homepump. 

In short, I-Flow claimed substantial equivalence to the Sgarlato PCIP for intended use and to its own Homepump for the components of the device.  The I-Flow PainBuster (which would be used by I-Flow as a predicate device for all of its later pain pumps and by numerous competitors for their devices in years to come) is premised upon what is known as a "split predicate."

A few weeks ago, the Center for Devices and Radiological Health at the FDA, issued extensive Preliminary Internal Evaluations of the 510(k) process.   This document contains a very useful history of the 510(k) program and a number of findings and recommendations by a working group charged with reviewing the existing process, including this finding:

"The term 'split predicate' refers to a situation in which a 510(k) submitter is attempting to 'split' the 510(k) decision-making process by demonstrating that the new device has the same 'intended use' as one predicate and the same 'technological characteristics' as another.  This practice is akin the combining different attributes of two or more devices into a single, nonexistent predicate device that may bear little resemblance to the device under review or to any marketed device.  Concerns have been raised that the use of a 'split predicate' may not allow for a valid comparison of safety and effectiveness because not such device exists, either in part or whole, and there is therefore no real world information about its risks and benefits." (p. 59)

In Part One of this post, I wrote that at some point there had to have been a step from an infusion pump intended to be used for other purposes to a pump intended to infuse local anesthetics.  It appears that I-Flow's PainBuster was one of the earliest (if not the first) of these steps.  Much of the current pain pump market has developed by making claims of substantial equivalence to I-Flow devices.  If there are serious questions about the basis of FDA approval for a threshold device like the PainBuster, those questions necessarily spread through the chains of substantial equivalence to numerous devices that have followed. 

 

 

 

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I am working on another post relating to FDA regulation of pain pumps, but expect it may be a week or two before I am able to complete it.  In the meantime, I thought I would share an article I recently came across----Disposable Infusion Pumps by Skryabina and Dunn.  It contains useful explanations of how some of the most common types of these pumps actually function.

These devices are used for many purposes beyond that of a "pain pump"--delivering local anesthetics post-operatively at or near a surgical site.  These include the delivery of other medications, including chemotherapy, antimicrobials, antibiotics, as well as the delivery of anesthetics or analgesics by other routes, eg., continuous epidural, peripheral nerve block, and i.v..  The authors provide concise descriptions of the mechanisms of several types of non-electric pumps including elastomeric, positive-pressure (spring-powered and gas-pressured powered), negative-pressure (vacuum), and patient-controlled analgesia (PCA) pumps. 

The flow rates of medications through disposable pumps are significantly inaccurate--typically within +/-15% or even +/-20%.  (Compared to +/-3% with electronic syringe pumps and +/-5% with electronic volumetric pumps).  I believe most pain pump manufacturers include the +/-15% figures in their written materials--see, eg. the flow rate table included in the product Insert for the On-Q Pump with Fixed Flow Rate. 

Nonetheless, I assume most surgeons who use a pain pump labeled with a 2 ml/hr flow rate are likely to believe that the device delivers only 48 ml of local anesthetic in the first 24 hours.  In fact, the same flow rate table in the Insert for the On-Q Pump (along with all other documents for the On-Q I've seen) shows that a 100 ml pump will actually deliver 65 ml in the first 24 hours.  For the first several hours, the flow rate is actually 2.5 ml or higher. 

If the anesthetic is 0.50% Marcaine, 65 ml means 325 mg.  The maximum 24 hour dose for Marcaine is 400 mg and, as I've stressed before, this is based on the risk of systemtic toxicity (neurological or cardiac) and not local (tissue) toxicity.  Surgeons commonly use additional injections of local anesthetics around surgical sites during procedures.  Thus, it would take only an additional 15 ml of 0.50% Marcaine, along with a 100 ml 2 ml/hr. pump, to reach a 400 mg dose in the first 24 hours after surgery. 

I believe many pain pump manufacturers have blithely assumed that any 24 hour dose of Marcaine as long as it remains less than 400 mg, in most any part of the body, regardless of the concentration, and regardless of the route of administration (continuous infusion vs. others), is inherently safe.  For all who have sustained injuries from pain pumps caused by local anesthetic toxicity, this has been a tragically flawed assumption. 

 

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I recently came across a post by Armand Rosetti which summarized some news articles relating to I-Flow Corporation and its Chief Executive, Donald Earhart. Especially interesting are some statements Mr. Earhart made in a November 5, 2008 conference call with investment analysts regarding the company’s third quarter earnings.  Earhart was answering questions regarding the status of the shoulder chondrolysis lawsuits, and said:

I’ve said this argument before on the conference calls, is that a pain pump or a delivery device, whether it be a syringe or one of our pumps delivering a drug, how do you blame the device, because there’s no way the device can cause the disappearance of cartilage. It would have to be whatever is delivered into the site or would have to be the technique by the doctor or would have to be the sutures or it would have to be the staples or it would have to be something else used during the surgery, but it can’t be our pump, because our pump can’t cause cartilage to disappear…. It’s like using a syringe to deliver a narcotic. We can’t be held responsible for the side effects, if I’m the syringe manufacturer, of the drug.

This raises an important point.  Clearly, it is the toxicity of the local anesthetic that causes the direct harm to the patient--whether the result be the destruction of shoulder or other joint cartilage, tissue necrosis around a surgical site, or other injury.  How then can a plaintiff reasonably seek to blame the maker of the device and not the drug?  Because a pain pump manufacturer retains a legal responsibility to patients to provide that their devices may be safely used with local anesthetics in a manner intended by the manufacturer of the local anesthetic.  Continuous infusion through a pain pump is not a listed intended use of a local anesthetic; it is an off-label use.   A statement such as I-Flow makes in its current Directions for Use for the On-Q pump, “medications or fluids must be administered per instructions provided by the drug manufacturer,” has little meaning when the use in question is not addressed by the manufacturer. 

Mr. Earhart and I-Flow appear to take for granted that continuous infusion is no different than the uses approved by the local anesthetics manufacturers. I contend pain pumps represent a categorically different use both because of the larger volume of local anesthetic infused and the significantly greater duration of exposure of the affected tissues to the medication. For example, a single bolus dose of 100 mg (20 ml) of Marcaine to produce a nerve block may well create less risk of local tissue toxicity than continuously infusing smaller volumes—2ml/hr—but with a larger total volume 240 mg (100 ml) over a much longer time—2-5 days.

On the other hand, the uses to which a syringe is put--—local infiltration around a surgery site and injections to produce various types of nerve blocks—are approved uses by the drug manufacturer.  Because there are a variety of known risks of patient injury with their devices, pain pump manufacturers have a duty  to timely and adequately convey warnings of such risks to the physicians who use them. 

 

 

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What steps did the manufacturers of pain pumps take to warn their physician customers of the risk of tissue necrosis and other wound-healing complications with the use of these devices? The leading manufacturer, I-Flow Corporation, which sells the On-Q PainBuster, included this caution in a June 2004 Product Insert:

Caution should be used when selecting appropriate volumes and flow rates keeping in mind potential fluid build-up in a restricted space that may lead to complications, particularly with hand and/or foot surgery.

This insert, however, contained no information regarding what complications might actually occur, even though I-Flow had received numerous adverse event reports of  tissue necrosis and other wound-healing problems.

It was not until late 2006 or early 2007 that I-Flow published a Technical Bulletin on its website: Hand and Foot Surgery Continuous Infusion—Volume and Flow Rate Selection. This bulletin cautions surgeons against inserting the pain pump catheter directly into the incision site in procedures involving fingers and toes. The bulletin indicates that complications including edema, blistering, wound dehiscence and tissue necrosis may occur when too much local anesthetic is delivered near the ends of the hands and feet. I-Flow recommends and publishes instructional guides describing nerve block approaches for bunionectomies by two podiatrists, Dr. Sprinkle and Dr. Watkins.

This Technical Bulletin raises more questions than it answers:

• Did I-Flow actively communicate the risk of these complications to its physician customers in the form of a “Dear Doctor” letter or did it rely on a passive post on its website?
• What is the actual source of these complications—the nature of local anesthetics? pressure created by the pumping mechanism?  the anatomy of the foot and hand?
• Did I-Flow intend for these warnings to apply to podiatric cases other than bunionectomies?
• What risk is there of these sorts of events in other podiatric cases and other surgeries, including knee surgeries?
• Did other manufacturers communicate similar warnings? 

I have a client who underwent foot surgery (not a bunionectomy) in which the pain pump catheter was inserted in the top portion of her foot, near the ankle, and not directly into the incision. She proceeded to develop edema, blistering, wound dehiscence, and tissue necrosis, which required her to undergo numerous additional surgeries and has left her with permanent nerve damage and scarring. Because it limits itself to bunionectomies, I-Flow's Technical Bulletin, even if it had been sent to my client's podiatrist (it was not), would not have applied to this procedure. The surgeon essentially used the pain pump to perform a continuous nerve block, as I-Flow suggests is safe, with disastrous results for my client. 

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