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.
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.
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.
Parallel
Melatonin
DrugPatients will receive one capsule of melatonin (5mg) orally the night before surgery at 9 pm, the night of the operation, and two nights after the surgical operation at 9 pm, also the patients will receive 10 ml bolus of saline intravenous (IV) over 10 min before induction of anesthesia, then continuous infusion of saline (20 ml/hr) until the end of surgery.
Lidocaine
DrugPatients will receive a bolus (10 ml) of intravenous lidocaine (1mg/kg) diluted with saline over 10 min before induction of anesthesia. Continuous infusion of 1.5 mg/kg/hr of intravenous lidocaine diluted with saline (20 ml/hr) will be administered until the end of the surgery, also will receive placebo capsule the night before surgery at 9 pm, the night of operation and two nights after the surgical operation at 9 pm.
Placebo
DrugPatients will receive a bolus (10 ml) of saline over 10 min before induction of anesthesia, then continuous infusion of saline (20 ml/hr) and placebo capsule the night before surgery at 9 pm, the night of the operation and two nights after the surgical operation at 9 pm.
The incidence of postoperative delirium (POD)
Incidence of postoperative delirium in elderly patients undergoing total hip arthroplasty will be recorded
Severity of delirium
Severity of delirium will be assessed using (CAM-S) score. The sum of the CAM-S scores ranges from 0 to 7 (7 = most severe).
Onset of delirium
The onset of delirium will be recorded.
Duration of delirium
The duration of delirium will be recorded.
Degree of pain
Postoperative pain will be assessed using the visual analogue scale (VAS) score (0 point indicates no pain and 10 indicate maximum pain). Patients will receive epidural analgesia if VAS score is ≥4.
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