Intravenous Lidocaine in Total Knee Replacement

Osteoarthritis of knees and hips is a common medical problem present in elderly, which poses significant impairment to their mobility, independence, and quality of life. Despite the availability of conservative treatment, such as simple analgesics and physiotherapy, total joint replacement is the only curative option for this disease entity.

The latter, however, is not without risk. A study by Poulakka has demonstrated that patients with poor pain control in the postoperative period were three to ten times more likely to develop chronic pain, which may significantly impair the patients' functional status and quality of life.

Optimal pain control is therefore essential in facilitating rehabilitation and in preventing long-term morbidities.

Lidocaine [2-(diethylamino)-N-(2,6-dimethylphenyl)acetamide] is an amide local anaesthetic that is characteristically fast in onset and short in duration of action. As such, it has long been used for providing regional anaesthesia for operation, but with limited role in terms of post operative analgesia.

Recently, intravenous infusion of lidocaine has been shown to be safe and effective in reducing post operative pain (resting and dynamic), opioid consumption, and chronic post-surgical pain. The mechanism of action involves both peripheral and central actions. In addition to blockade of the Voltage-gated Sodium Channel of the peripheral nerves, lidocaine also inhibits priming of the PolyMorphoNuclear granulocyte (PMN) by inducing a time-dependent inhibition of intracellular G-protein signalling molecule (Gq); thus reducing release of cytokines and Reactive Oxygen Species Centrally, lidocaine also causes blockade of NMDA receptors and Neurokinin Receptors of the Wide-Dynamic Range Neurons in the dorsal horn of spinal cord; thus reduces glutamate activity.

We therefore hypothesize that the use of intravenous lidocaine may reduce acute pain and improve the range of knee flexion after total knee replacement. Currently, there is strong evidence supporting its use in laparoscopic and open abdominal surgeries. There is, however, a paucity of studies in orthopedic surgeries. To date, there is no randomized controlled trial that studied its effect in total knee replacement.