RESUMEN
CONTEXT: A reduction in the use of opioids by older adult patients could reduce unpleasant side effects for them. During general anesthesia, binaural beat (BB) listening has been found to reduce intraoperative fentanyl consumption as well as postoperative pain scores and discharge time. Auditory BBs are a perceptual phenomenon occurring when tones of 2 slightly different frequencies are presented simultaneously and separately to each ear. OBJECTIVE: The study intended to evaluate the ability of BBs, as a nonpharmacological premedication, to reduce postoperative morphine consumption in older adults undergoing total knee replacement surgery and to modify the levels of anxiety and feelings of pain that patients experience. DESIGN: The research team designed a prospective, single-center, randomized controlled study. SETTING: The study was conducted in the Orthopedic Department of the Santa Maria Maddalena Hospital (Volterra [Pisa], Italy). PARTICIPANTS: Forty older adults at the hospital who were undergoing total knee joint replacement with spinal anesthesia participated in the study. INTERVENTION: The study included 2 groups (n = 20 each), one receiving BBs stimulation with frequencies of 256 Hz in one ear and 260 Hz in the opposite ear producing a BB of 4 Hz (intervention group), and the other receiving acoustical stimulation at 256 Hz in both ears (control group). BBs, or acoustical stimulation, were administered before the surgical procedure. Both acoustical stimuli, generated with the Gnaural program, were delivered through stereo headphones connected to a laptop in the preoperative holding area. OUTCOME MEASURES: The study measured postoperative, cumulative, self-administered morphine consumption, in mg, through a patient-controlled analgesia device. Feelings of anxiety were also assessed using the State-Trait Anxiety Inventory, and feelings of pain were measured every 8 h during the first postoperative day using a numerical rating scale. RESULTS: Patients who received the intervention, consumed almost half of the dosage of morphine during the first postoperative day when compared with the control group's consumption, 5.75 mg ± 5.25 vs 11.85 mg ± 7.71, respectively. The consumption did not correlate to anxiety measures. Regarding pain perception, no differences between the groups were captured. CONCLUSIONS: BB stimulation before surgery can be successfully used as a nonpharmacological treatment to reduce morphine consumption in older adults who undergo knee replacement. The use of a noninvasive, safe, and inexpensive BB intervention can result in a positive effect on patients' postoperative recovery.