The Effects Of Lidocaine Infusion On The Recovery Of Cognitive Function Following General Anesthesia In Elderly Patients Undergoing Orthopedic Surgeries Requiring A Minimum Two Day Hospitalization

Advances in surgical techniques and anesthetic care have resulted in a substantial reduction in peri-operative morbidity and mortality in the elderly. However, post-operative cognitive dysfunction (POCD), as well as episodic post-operative delirium, are still recognized as significant complications following surgery in the elderly. Post-operative cognitive dysfunction is characterized by impairment of memory, concentration, language, comprehension, and social integration. Conversely, post-operative delirium is characterized by intermittent, short-term impaired cognition, disorientation, and abnormalities in memory and perception, which has been shown to lead to increased morbidity and mortality, delayed functional recovery, and prolonged hospital stays. Elderly patients are particularly sensitive to the central nervous system effects of many peri-anesthetic drugs, including benzodiazepines, barbiturates, opioids, and volatile anesthetics, which may play a role in POCD and consequent patient outcomes. Randomized clinical trials have demonstrated no difference in the recovery of cognitive function between commonly used volatile anesthetic agents.

Several simple, bedside tests are available to assess cognitive function and differentiate between cognitive dysfunction and an episode of delirium. The Confusion Assessment Method (CAM) is a standardized rating of delirium that has been validated and has high inter-observer reliability. The CAM criteria are the most commonly used method for diagnosing delirium in hospitalized patients. The Mini-Mental Status Examination (MMSE) and the Abbreviated Mental Test are tools used to assess cognitive function at the bedside.

Lidocaine is one of the most commonly used sodium-channel blockers in the medical armamentarium. It has long been used for its local anesthetic and anti-arrhythmic properties, and has been studied as an adjunct to general anesthesia. While lidocaine is cardio-toxic in excessive doses, the therapeutic and toxic levels are well-documented and wide, making lidocaine a drug with a favorable safety profile. Randomized clinical trials have shown perioperative lidocaine infusions to decrease postoperative pain scores, reduce postoperative opioid requirements, shortens hospital stays, improves postoperative recovery and fatigue score when administered as an adjuvant during surgery. Lidocaine has analgesic, antihypertensive, and anti-inflammatory properties. To date, no clinical trials have been conducted to establish the relationship between lidocaine infusions and postoperative recovery, particularly cognitive function, in elderly orthopedic surgery patients. It is therefore the aim of this study to evaluate the effects of lidocaine infusion on postoperative cognitive function in elderly patients having general anesthesia for orthopedic surgery, and to assess whether intraoperative lidocaine infusion decreases postoperative opioid usage and improves recovery.