How Lidocaine Affects Outcomes In Orthopedic Surgery Patients

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.

Inclusion Criteria:

- Scheduled to undergo orthopedic surgery under general anesthesia requiring a minimum
two-day hospitalization (e.g. THA, TKA, hardware removal)

- 65 years of age or older

- ASA Physical Classification I - IV

- Willingness and ability to sign an informed consent document

- English-speaking

Exclusion Criteria:

- Inability to consent or complete cognitive assessments

- Inability to use a PCA system

- Allergy to lidocaine or any other medication administered as part of this protocol

- Emergency surgery