Pleth Variability Index in Orthopedic Surgery: Comment

At first glance, the recent 447-patient randomized controlled trial in major orthopedic surgery with new goal-directed fluid management methodology¹  may revitalize the debate, although no effect was demonstrated. Importantly, the concept of goal-directed fluid management has been discussed for more than a decade and, although initially promising, still remains debatable.^2,3 

However, a closer look on the methodology of the study¹  again shows that the gold standard of an randomized controlled trial in perioperative medicine may not always be the “gold standard” when it is performed in a clinical setup that limits the potential interaction between the intervention and the outcome.⁴  Thus, the trial had a primary outcome on length of stay which was similar between the groups (about 6 days), which is very far from common practice in many international centers with length of stay around 1 to 3 days in optimized pathways.^5,6  Interpretation is therefore difficult, because there was no information about perioperative care principles or why the patients were hospitalized, and as such the actual impact of the optimized fluid management on length of stay will be probably be negligible, as other factors clearly will determine length of stay. The power analysis assumes a reduction in length of stay from 6 to 5 days, but it is difficult to understand from the assumed focus on fluid management per se versus the known impact of care traditions (pain management, mobilization, physiotherapy). Finally, it is surprising that patients with high comorbidities or recommended to a cardiac output monitor were excluded, which essentially may represent those patients who may benefit from goal-directed fluid management.³ 

In summary, this is another perioperative outcome randomized controlled trial interventional study which unfortunately prevents sufficient interpretation by not considering available evidence-based care principles shown for many years to reduce length of stay in the specific surgeries investigated.⁷ 

Dr. Foss has received teaching fees from Edwards Lifesciences (Irvine, California). Dr Kehler declares no competing interests.