Intra-articular and Periarticular Infiltration of Local Anesthetics
Infiltration or instillation of local anesthetics around and into the joint as an analgesic adjunct for postoperative joint surgery pain has been used for decades. However, there has been a renewed interest in local infiltration analgesia (LIA), partly due to the work in 2008 of Kerr and Kohan,1 who demonstrated superior analgesia after total knee or hip arthroplasty with extended, diluted infiltration of local anesthesia with epinephrine and ketorolac added and repeated injections through intra-articular catheters. The interest in using LIA in knee and hip surgery may be also due to the lack of the simpler regional anesthesia alternatives that exist for other joints. For instance, analgesia after shoulder and upper extremity surgery can be accomplished with a simple, single injection block of the brachial plexus, whereas analgesia for hip and knee joints requires multiple and more technically challenging nerve blocks. Also, while motor weakness is common with nerve blocks, infiltration analgesia typically spares the motor function.
THE CONCEPT OF LOCAL INFILTRATION ANALGESIA
There are three basic components of the LIA concept: high volume of diluted, long-acting local anesthetic; nonlocal anesthetic adjuvants; and catheter bolus injections (top-ups) for 1–3 days.
High Volume of Diluted Long-Acting Anesthetic Drug
A problem with local anesthetic infiltration for major surgery is that many different structures and layers must be infiltrated. In doing so, a certain minimum volume of local anesthetic is required for an effective local infiltration to cover all relevant structures. With conventional concentrations of local anesthetic solutions, such high volumes carry an unacceptable risk of systemic toxicity (see Chapter 65, Local Anesthetic Systemic Toxicity). However, anesthesia of the small nerve endings in and around joints does not require high-concentration local anesthetic. Thus, the concentration of local anesthetic may be lowered and the volume increased, keeping the total dose within safe limits. Further, as the major joints are devoid of major blood vessels, the risk of inadvertent injection of a large bolus directly into circulation is small.
Nonlocal Anesthetic Adjuvants
As careful injections of local anesthetic are made close to the site of surgical injury, there is a potential for targeting the source of pain caused by local inflammation and pain to supply effective treatment close to the origin of pain. This is an alternative to the systemic approach to analgesia by which a potentially higher total dose of drug is needed and carries a higher potential of general side effects. Nonlocal anesthetic adjuvants such as anti-inflammatory agents, nonsteroidal anti-inflammatory drugs (NSAIDs—traditional or cyclooxygenase [COX] 2 inhibitors) and steroids, as well as opioids and ketamine have all been used.
The role of epinephrine or clonidine in the LIA mixture, however, has not been well studied. While both drugs have an analgesic effect on the spinal α2 receptors ...