The Correlation between Corrected Flow Time (FTc) Based on Esophageal Doppler Monitoring and Pleth Variability Index (PVI) in the Fluid Therapy in Patients Undergoing Total Abdominal Hysterectomy

The occurrence of bleeding during major surgeries is common and requires timely and accurate management in the prevention and treatment of hypovolemia and hemodynamic instability during and after surgery. This study evaluated the correlation and agreement between the two protocols determining the status of the hypovolemia during hysterectomy.

This study was a randomized single-blinded clinical trial. The study population included 30 patients undergoing Total Abdominal Hysterectomy in Shariati Hospital in Tehran between 2015 and 2016. The patients were randomly assigned to two groups using a randomized table of numbers, so that in the FTc group, fluid therapy was performed based on the FTc index and in the PVI group based on the PVI index. The changes in FTc and PVI values were recorded every 5 minutes and the changes in the two indicators from the beginning to the end of the treatment were evaluated. At the beginning and end of the surgery, an arterial blood gas analysis (ABG) was also performed. The amount of bleeding during operation and urinary output were recorded in two groups.

There was no significant difference across the two groups in total fluid intake during surgery, mean volume of blood loss, mean urine output, and duration of surgery. The arterial blood gas status was also similar in both groups at the beginning and the end of the operation. We found a strong adverse correlation between FTC and PVI indices at the different time points evaluated within the surgery. In total, there was a strong correlation between the mean FTC and the mean PVI during the first hour (r=-0.765, P < 0.001) and the second hour (r=-0.941, -P < 0.001) of operation. Considering the cut-off point of 350msec for the FTC and 13% for the PVI in predicting hypovolemia, the agreement between the two protocols in fluid therapy during the first hour after surgery was 79.8% and 76.6%.

There is a strong and significant correlation between the two FTC (with a cut off of 350) and PVI (with a cut point of 13%) to predict need for fluid therapy.