Postoperative Analgesia and Hospital Stay: A Call for Better Study Design

To the Editor: Salinas et al. (1) recently reported a randomized study comparing single-injection femoral nerve block versus a continuous technique for total knee arthroplasty. They concluded that the continuous technique improved analgesia with minimal impact on hospital stay and long-term functional recovery. Although they should be congratulated for their analgesic data, it is questionable whether their conclusions about hospital stay are supported by their data. The discharge criteria were vague. The time course for repeated assessment was not described. It has been emphasized (2) that a key question in outcome studies is a daily recording of factors precluding discharge. In the study by Salinas et al. (1), there is no information on the factors precluding earlier discharge, and therefore the possibility remains that discharge was dependent on factors other than pain management, such as tradition and organization. This is particularly relevant because other data suggest shorter hospitalization with a continuous peripheral block technique (3). Future studies evaluating the influence of perioperative management, including pain management, must incorporate a better design to permit proper analysis of the relationship between perioperative interventions and duration of hospitalization. Henrik Kehlet, MD, PhD Section for Surgical Pathophysiology 4074 The Juliane Marie Centre Rigshospitalet Blegdamsvej 9, Denmark [email protected]