Perioperative Anxiolysis and Analgesic Effect after Premedication with Melatonin and Pregabalin in Total Hip Arthroplasty under Spinal Anaesthesia: A Prospective Comparative Trial.

Background: Preoperative anxiety plays a critical role in post-operative pain response and other outcomes. Melatonin is a naturally secreted hormone which has anxiolytic, sedative, and analgesic properties. Pregabalin, analogue of gabapentin which has property of anxiolytic and analgesic effects. Materials and Methods: Total 96 patients undergoing total hip arthroplasty, divided into 3 groups of 32 each and were given placebo (group I), melatonin 6 mg (group II), and pregabalin 150 mg (group III). Anxiety level, postoperative pain score, sedation level and duration as well as characteristics of spinal anaesthesia were assessed with other vital parameters. Results: Group I showed an increment in the anxiety score from baseline whereas in group II and group III, there was a decline in pre-operative anxiety score from baseline at all the periods of observation and more significantly in group III. Visual analogue scale (VAS) score and total dose of rescue analgesia were highest in group I, but group II and group III were comparable to each other. However, the durations of spinal anaesthesia and motor blockade showed a statistically significant difference with maximum duration in group III followed by II and then I. The level of sedation among the three groups were comparable at all the periods of observation. Conclusions: Pregabalin was found better for perioperative anxiolysis, post-operative analgesia and for prolongation of duration of spinal anaesthesia when compared to melatonin.