Use reduces pain but may have toxic consequences

In many surgical specialties, the successful outcomes of ambulatory surgery have been attributed to various factors, not the least of which is successful postoperative pain control. The nature of many orthopaedic surgical procedures results in levels of postoperative pain that previously required hospital admission, overnight stays, or extended outpatient recovery. The development of less invasive surgical procedures and techniques, coupled with an increased awareness of the complexity of postoperative pain, has led to successful ambulatory surgery outcomes. The use of local anesthetics delivered by continuous infusion into or around surgical wounds has further enhanced the outpatient surgical experience for patients.

Recent reports of the toxicity of bupivacaine on articular cartilage have, however, resulted in a reevaluation of the merits of continuous infusion pumps using local anesthetics, particularly bupivacaine. The development of postarthroscopic glenohumeral chondrolysis (PAGCL) and subsequent litigation related to this debilitating condition have been reported.

Surgeons who have previously used intra-articular continuous infusion pumps and those who may be considering their use should be aware of the risks and complications related to these devices/medications when used in the management of postoperative pain in selected arthroscopic procedures. In addition, surgeons should be aware of the Food and Drug Administration (FDA) labeling of these devices.

Background
Toxicity of local anesthetics has received much attention in the medical literature for many years, mostly from a systemic perspective. More recent studies have demonstrated very clearly the toxic effects of local anesthetics, in particular bupivacaine, on chondrocytes.

As reported in the June 2008 issue of AAOS Now, research conducted by Constance R. Chu, MD, and colleagues, has demonstrated these effects in vitro. They reported a 99 percent bovine chondrocyte death rate after a 15-minute exposure to 0.5 percent bupivacaine solution. Lidocaine may also have similar dose/time effects on chondrocytes. Less concentrated solutions of bupivacaine (0.125 percent) did not result in significant chondrocyte toxicity, and, in fact, showed similar effects on chondrocyte viability as did normal saline. Similar results were reported for cultured human chondrocytes.

In other studies, epinephrine in combination with local anesthetics has also been found to cause chondrocyte death at statistically significant levels. This finding is not surprising; the vasoconstrictive effects of epinephrine would delay vascular uptake of the local anesthetic and effectively prolong its half life.

Knee surgeons have used continuous infusion pumps to deliver intra-articular anesthetics following surgeries such as anterior cruciate ligament reconstruction and arthroscopically assisted treatment of tibial plateau fractures. Although chondrolysis in the knee has been causally related to lateral meniscectomy, liver transplantation, psoriatic arthritis, stress injuries, trauma, chlorhexidine exposure, and other etiologies, it has not been reported in association with local anesthetics.

One study reported no cases of chondrolysis in the knee joint when continuous infusion pumps were used following arthroscopic procedures. Although the lack of any reports of “postarthroscopic femorotibial chondrolysis” seems reassuring, the evidence from in vitro studies and the reports of chondrolysis in the shoulder should cause knee arthroscopists to review their protocols for postoperative analgesia if continuous infusion of local anesthetics into the knee joint is contemplated.

Between 2004 and 2007, several reports of PAGCL appeared in the literature. Subsequently, continuous infusion of bupivacaine delivered via an intra-articular catheter was identified as the source of this debilitating complication, and PAGCL very quickly found its way into the public arena of litigation.

Litigation Status
As of this writing, more than 30 different shoulder pain pump lawsuits, naming 28 different corporations and medical providers, had been filed. Several manufacturers of both the devices and various anesthetic agents were named in different federal courts, and plaintiffs moved to consolidate all federal pain pump litigation on behalf of individuals in whom chondrolysis developed following shoulder arthroscopy and postoperative use of continuous infusion pumps. The U.S. Judicial Panel on Multidistrict Litigation denied this petition, allowing individual suits to proceed.

Various complaints have alleged that the pump manufacturers encouraged doctors to use the devices to directly infuse local anesthetics into the shoulder joint, a clinical decision that the plaintiffs allege is off label. Furthermore, plaintiffs have alleged that the FDA turned down requests by the device makers to include language in the labeling and promotional materials that direct delivery of local anesthetics into the shoulder joint was, in fact, an approved use of the device. The status of these legal proceedings, irrespective of how the federal courts choose to handle the various actions and litigants, has had and will continue to have significant effects on the use of these devices for continuous infusion of local anesthetics directly into a joint space.

Although catastrophic effects such as PAGCL have not been observed following the delivery of intra-articular local anesthetics by single injections or the use of continuous infusion of local anesthetic in an extra-articular location, the use of continuous infusion devices directly into the joint space should be approached with a thorough knowledge of the labeling of these devices.

Physician judgment
Clinical decision making allows physicians a range of choices in addressing a problem. At times, the use of a device in a given clinical scenario may not fit the FDA labeling, and the ability to use a device off label is sometimes necessary. Physicians can use devices off label, provided that they put the best interest of the patient first and use sound judgment and knowledge in the clinical decision-making process.

At the heart of the PAGCL litigation is the premise that continuous infusion pumps were not approved by the FDA for intra­articular use. If physicians use a device for an indication that is not in the approved labeling, the physician is responsible for understanding and having a thorough knowledge of the device. This includes, but is not limited to, technical aspects of using the device, proper implantation of the device (in the case of implantable catheters), and use of the device with appropriate solutions of local anesthetics. In any case, the device or drug should be used based on accepted scientific rationale and sound medical evidence. The physician must also maintain records of the off-label use and its effects.

Patient informed consent
The process of informed consent also enters into the discussion. Although existing litigation appears to be aimed primarily at manufacturers of continuous infusion pumps, undoubtedly the arguments will also raise the issue of informed consent.

Plaintiff’s attorneys have long noted that many medical liability suits arise due to the lack of thorough informed consent. The burden of obtaining informed consent from a patient rests on the surgeon, who should cover all aspects of a given procedure in adequate detail. If off-label use of any device (or pharmacologic agent) is contemplated, the physician must undertake and document appropriate patient education.

Alternatives
Several alternatives are available to address postoperative pain. The concept of “multimodal analgesia” has recently been discussed in orthopaedic literature (Table 1). Historically, these options have provided satisfactory levels of pain control without the added risk of devastating joint destruction due to continuous infusion of local anesthetics into a joint.

In addition, the role of proper surgical technique with anatomic exposure and closure and careful handling of soft tissues cannot be overemphasized. Before surgery, surgeons must counsel patients on the risks and potential complications of various pain management strategies.

Summary
The ideal postoperative analgesic protocol is one that results in the optimal control of pain with the least exposure to side effects and risk of complications. Although continuous infusion systems offer a certain degree of convenience, the ideal delivery system and agent for intra-articular infusions have yet to be defined.

Surgeons should develop an understanding of the basic science of chondrocyte toxicity as it relates to local anesthetic choices and delivery. Users of continuous infusion systems should be familiar with the FDA labeling and be prepared to provide adequate patient education as part of the informed consent process before surgery. Finally, surgeons should not discount the value of pain, because pain is often the first sign of an impending complication, and continuous infusion of local anesthetics into a surgical site may mask that warning.

Single stick peripheral nerve blocks are also capable of masking important “warning” pain and should be used only when appropriate, such as when postoperative compartment syndrome is unlikely to develop. Conversely, continuous infusion of local anesthetic into a peripheral nerve sheath should be used with caution.

The number of surgical procedures appropriate for the ambulatory surgery environment will undoubtedly continue to grow as surgical and analgesic techniques evolve. The surgeon should approach these evolving technologies with the critical eye of the scientist and avoid the pitfalls that may subject patients to unwanted complications.

Scott M. Morrell, MD, an orthopaedic surgeon specializing in total joint replacement at Resurgens Orthopaedics in Atlanta, prepared this article at the request of the ORM subcommittee of the AAOS Medical Liability Committee. He can be reached at morrellsm@resurgens.com

References:

1. AAOS Now, Aug 2008, V2 No 8 “ASRA Recommendations for Systemic Toxicity of Local Anesthetics”
2. Chu CR, Izzo NJ, Coyle CH, Papas NE, Logar A: “The in vitro Effects of Bupivacaine on Articular Chondrocytes,” JBJS (Br) 2008 Jun; 90(6): 814-20
3. Piper SL, Kim HT: “Comparison of Ropivacaine and Bupivacaine Toxicity in Human Articular Chondrocytes,” JBJS(Am) 2008 90:986-91
4. Dragoo JL, Korotkova T, Kanwar R, Wood B: “The Effect of Local Anesthetics Administered via Pain Pump on Chondrocyte Viability,” AmJSM Aug 2008; 36:1484-88
5. Hansen BP, Beck CL, Beck EP, Townsley, FW: “Post Arthroscopic Glenohumeral Chondrolysis,” AmJSM 2007 Oct; 35(10): 1628-34
6. Petty DH, Jazrawi LM, Estrada LS, Andresw JR: “Glenohumeral Chondrolysis after Shoulder Arthroscopy: Case Reports and Review of the Literature,” AmJSM 2004 Mar; 32(2): 509-15
7. Levine WN, Clark AM, D’Lesssandro DF, Yamaguchi K: Chondrolysis Following Arthroscopic Thermal Capsulorrhaphy to Treat Shoulder Instability,” JBJS (Am) 2005 87:616-621
8. Reuben SS, Buvanendran A: “Preventing the Development of Chronic Pain after Orthopaedic Surgery with Preventive Multimodal Analgesic Techniques,” JBJS(Am) 2007 89:1343