A specific group of neurons in the brain produces hypocretin, a peptide which has been established as an important regulator of sleep and wakefulness. Activation of these neurons (increased hypocretin) stabilizes wakefulness; impairing or blocking these neurons (decreased hypocretin) promotes sleep. Evidence suggests that these neurons may be involved in the hypnotic properties of several anesthetics, and play a role in the induction and emergence from anesthesia. In humans there is a considerable inter-individual variability in hypocretin levels. This study aims to investigate how hypocretin levels affect the anesthetic care and recovery of patients undergoing elective hip surgery.

Inclusion Criteria:- Adult (18 years of age or older)

• Male or female
• Scheduled for elective total hip arthroplasty at the Stanford Orthopedic Clinic.
• Comprehend spoken and written English Exclusion Criteria:- ASA physical status > III (patients with severe systemic disease)
• Diagnosed psychiatric disease (except mild depression)
• Any diagnoses CNS disease or dementia
• History of stroke
• History of untreated thyroid disease
• Difficulty in airway management (ventilation and/or intubation)
• Body Mass Index (BMI) > 35 kg/m2

Patients scheduled for elective total hip arthroplasty through the Stanford Orthopedic Clinic.