Effect of Oral Melatonin Versus Intraoperative Lidocaine Infusion on Incidence of Postoperative Delirium in Elderly Patients Undergoing Total Hip Arthroplasty

Effect of Oral Melatonin Versus Intraoperative Lidocaine Infusion on Incidence of Postoperative Delirium in Elderly Patients Undergoing Total Hip Arthroplasty: Prospective Randomized Controlled Blinded Study

The aim of this study is to assess the effect of oral melatonin versus intraoperative lidocaine infusion on incidence of postoperative delirium in elderly patients undergoing total hip arthroplasty under spinal anesthesia.

Delirium is defined according to The American Psychiatric Association's fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), as disturbance in attention and awareness developed over a short period of time , its severity tends to fluctuate during the course of a day, these disturbances cannot be better explained by other pre-existing neurocognitive disorders and do not occur in severely reduced arousal level such as coma. Delirium can be further classified into hyperactive, hypoactive and mixed.Postoperative delirium (POD) usually occurs in the recovery room and appears up to 5 days after surgery.

The prevalence of POD in elderly patients undergoing surgery varies from 20% to 45%. Patients undergoing hip fracture surgery are at higher risk of POD than patients undergoing other types of surgery. This may be related to their older age, higher incidence of comorbidities, and greater physical weakness.

Melatonin (N-acetyl-5-methoxytryptamine) is a neurohormone that is discharged by the pineal gland produced from the amino acid tryptophan. Synthetic melatonin has been effectively utilized in the treatment of sleep disorders. It was likewise utilized as a premedication and it provided excellent anxiolysis, sedation, and sympatholytic impacts with the merit of not influencing the patients' cognition in addition to its analgesic effect.

Lidocaine, an amide local anesthetic and class-1 antiarrhythmic with sedative and anti-inflammatory properties, is increasingly used as a part of a multimodal intraoperative anesthetic adjunct in a variety of surgical procedures.

Inclusion Criteria:

• Elderly patients aged >65 years old undergoing unilateral total hip arthroplasty.
• Patients with body mass index (BMI) (18-30) kg/m2.
• American Society of Anesthesiologists (ASA) physical status I-III, scheduled to undergo unilateral total hip arthroplasty.

Exclusion Criteria:

• History of mental illness or scoring less than 8 using abbreviated mental test (AMT) before operation.
• Obvious sinus bradycardia (heart rate of <50 beats per minute) or other serious cardiovascular diseases.
• Symptomatic cerebrovascular disease (such as previous stroke).
• History of liver and kidney dysfunction.
• Allergy to lidocaine or melatonin.
• Metabolic disorders and fluid, electrolytes disturbances.
• Alcohol dependence or drug abuse.
• Redo surgery or infectious complications.
• CNS medications (antipsychotics, anticonvulsants, antiparkinsonian, antidepressants).
• History of deep vein thrombosis.