The Correlation Between Intraoperative End Tidal Carbon Dioxide, Perfusion Index and Pulse Variability Index on Postoperative Nausea Vomiting and Pain; Prospective Study

In recent years, laparoscopic gynecologic surgery has become a preferred technique over traditional open surgery due to its benefits such as better cosmetic results, lower risk of bleeding, minimally invasive surgery, lower postoperative pain and incidence of wound infection, and as a result, earlier discharge.

PI (Perfusion index), the ratio of alternating current component to direct current component, is a representation of the photoplethysmography waveform that quantitatively reflects real-time changes in peripheral blood flow in the monitored region. PVI (Pulse variability index) is another dynamic index and many studies have concluded that it is useful in assessing fluid responsiveness in patients. However, there are still uncertainties in the study regarding the effect of pneumoperitoneum on PVI. PVI, calculated from respiratory variations in perfusion index, has been shown to predict fluid responsiveness in mechanically ventilated patients; however, vasomotor tone changes induced by hypercapnia may affect PI and therefore reduce the accuracy of PVI.

Artificial pneumoperitoneum, which is commonly used in laparoscopic procedures and created with the Trendelenburg position and CO2 (carbon dioxide) insufflation, frequently leads to physiological changes such as PONV (postoperative nausea and vomiting) and pain. Although the mechanisms underlying its development are still unclear, PONV is caused by dopamine and serotonin released as a result of ischemia in the brain and intestinal tract, stimulating the medullary vomiting center. Therefore, ischemia has been shown to be one of the important factors for PONV. Hypocapnia is known to be associated with decreased cardiac output, and increased systematic vascular resistance can reduce blood flow in the brain and intestinal tract. Therefore, this study concluded that intraoperative hypocapnia may increase the risk of PONV. Another study reported that CO2 is a strong vasodilator and that intraoperative hypercarbia may be associated with increased perfusion to regions effective for PONV, including the brain and gastrointestinal tract. In a study examining the relationship between PI and postoperative pain, it was stated that there was a decrease in PI due to the activation of the sympathetic nervous system by pain, contraction in peripheral blood vessels and an increase in vasomotor tone, and an increase in PI values after the use of analgesics.