Can Right Toe Perfusion Index or Pleth Variability Index Predict Spinal Anesthesia Induced Hypotension?

Spinal anesthesia for caesarean section is associated with a decrease in systemic vascular resistance and cardiac output and may cause hypotension in a significant portion of the parturients. Hypotension during delivery may cause maternal and fetal complications. If parturients who are likely to develop hypotension after spinal anesthesia can be identified before surgery, anesthesiologists would have opportunity to take measures such as prophylactic vasopressor administration. Perfusion index (PI) measured by pulse oximetry reflects vasomotor tone which affects the degree of hypotension after spinal anesthesia. This is a non-invasive method of assessing the relative vascular tone with the use of pulse oximeter which calculates the ratio of pulsatile versus the non-pulsatile component of the blood flow. A lower PI indicates greater peripheral vasomotor tone. Pleth variability index (PVI) is calculated using maximum and minimum values of perfusion index during respiratory cycles. PVI is one of the dynamic indices that can predict fluid responsiveness. There are several studies investigating the predictive value of finger PI and PVI on hypotension after spinal anesthesia. However the aortocaval compression by the gravid uterus directly effects the lower extremity perfusion. So, in this study we aimed to investigate whether the right toe PI and PVI values at supine and left lateral positions can predict hypotension during caesarean section.