The Effect of Intra-Operative Plethysmography Variability Index-guided Fluid Therapy on Serum Lactate Levels; A Randomized Double-blinded Clinical Trial

Background: Goal-directed fluid therapy may improve perioperative fluid management. This study aimed to evaluate the effects of Pleth variability index (PVI)-guided fluid therapy on changes in intraoperative serum lactate levels in comparison with liberal fluid therapy. Methods: This study was a randomized double-blinded clinical trial that was conducted in the operating room of a university hospital. Inclusion criteria comprised patients aged 18–60 years and classified as American Society of Anesthesiologists physical status class I and II, who were candidates for elective thyroidectomy. In total, 44 patients meeting the inclusion criteria were enrolled in the study and randomly assigned to two groups: the liberal and PVI groups. In both groups, 5 mL/kg bolus of normal saline was infused prior to the anesthesia induction. In the PVI group, 100 mL bolus of normal saline was administered every 5 min if the PVI remained >13% during the operation. In the liberal group, continuous crystalloid infusion (5–6 mL/kg/h) was administered throughout the surgery. Arterial blood samples were taken, and serum lactate levels were measured following anesthesia induction and just before tracheal extubation. Results: In the PVI group, mean serum lactate decreased at the end of the surgery, with a difference of −0.6 ± 0.13 mmol/L, whereas it increased in the liberal group (0.070 ± 0.3, P<0.05). Conclusion: In conclusion, we found that using intraoperative PVI-guided fluid therapy could decrease serum lactate levels and total fluid administration compared to the liberal method.