Plethysmography variability index response to isovolemic hemodilution in children prior to surgery for congenital heart disease.

The aim of this study was to evaluate the response of pleth variability index (PVI) to phlebotomy in anesthetized children prior to surgery for congenital heart disease. After induction of general anesthesia and prior to surgical incision, approximately 10 mL/kg of blood was removed from 40 mechanically ventilated children over a 5-10 min period. The PVI was continuously monitored. Additionally, the volume of crystalloid required to ensure hemodynamic and near infrared spectroscopy stability was recorded. There was no difference between the pre-phlebotomy PVI (13% ± 6.2) and the post-phlebotomy PVI (16.4% ± 9.6) (P = 0.55). Patients who had a starting PVI ≤14% had a significant increase in PVI after phlebotomy from 9.1% ± 3 to 14.3% ± 7.2 (P = 0.0014). Although, patients with a pre-phlebotomy PVI of >14% required more crystalloid replacement (11 ± 9.4 mL/kg) than those with a PVI ≤14% (5.3 ± 4.7 mL/kg), this was not significant (P = 0.06). In patients who received less crystalloid replacement during phlebotomy, PVI did show a significant increase. Additionally, the data suggests that patients with a pre-phlebotomy PVI >14% required greater fluid replacement than those with a PVI < 14%. Further research is needed to better delineate the utility of PVI in this unique group of patients.