Pleth Variability Index in Orthopedic Surgery: Reply

We thank Kehlet and Foss¹  and Gelman²  for their correspondence and interest in our randomized study on goal-directed fluid management published in Anesthesiology.³  Limitations in our choice of hospital length of stay as a clinically significant primary outcome were rightly raised. One such limitation, highlighted by Kehlet and Foss, is its variability among health care systems but also within time according to the evolution of care. The primary outcome of the OPVI (Optimization using the Pleth Variability Index) study (real length of hospital stay after knee or hip arthroplasty) was chosen by the OPVI group as a clinically relevant surrogate measure of postoperative morbidity. The length of hospital stay used to calculate the sample size was based on the 2014 national French database, the year the study was approved by the ethics committee....