Remifentanil and Fenantyl Concentrations in Follicular Fluid during Transvaginal Oocyte Retrieval

Transvaginal oocyte retrieval, under ultrasonic control, has become a method of choice for ovum retrieval worldwide. A major concern with administering anesthesia to these women is the amount of the anesthetic agents that diffuse into follicular fluid. It is felt by many reproductive surgeons performing these procedures that there may be a possibility that the anesthetic agents are deleterious to the oocyte. In addition, there is a continuous search for anesthetic agents that are short acting and give adequate anesthesia. The goal is to achieve an adequate level of anesthesia with the least amount of drug diffusion into the follicular fluid. The anesthetic agents currently used in transvaginal oocyte retrieval is a combination of a narcotic and a hypnotic given intravenously for pain control and sedation during the procedure. This is an acceptable anesthetic for this procedure, but these drugs remain to diffuse into follicular fluid at moderate levels. Remifentanil, an ultra short acting opioid, is a recently introduced agent that has been used successfully in procedures requiring the same level of anesthesia and analgesia that is required for transvaginal oocyte retrieval. The purpose of this study was to evaluate the level of diffusion of remifentanil, compared to fentanyl, in conjunction with propofol, into the follicular fluid during transvaginal oocyte retrieval. We hypothesized that there would be a significant difference between follicular fluid levels produced by the anesthetic agents remifentanil and fentanyl. The study consisted of two groups of subjects having in vitro fertilization. One group (n=20) received remifentanil and propofol, and the other group (n=20) received fentanyl and propofol. Blood and follicular fluid samples were taken thirty minutes after the start of the agents infusion. The fluid samples were analyzed for opioid levels using gas and liquid chromatographic-mass spectrometric procedures, and then compared using a Chi-Square Test. Remifentanil was not detected in a majority of the subjects follicular fluid samples. Five out of the twenty subjects had detectable levels of remifentanil in their follicular fluid. In the fentanyl group, thirteen out of the twenty subjects had detectable levels of fentanyl in their follicular fluid.Our data suggests that there is significantly less diffusion of remifentanil into follicular fluid as compared to fentanyl. Also, subjects receiving remifentanil had a shorter recovery time. Although the cost of remifentanil is greater than fentanyl, these advantages make it a favorable choice for transvaginal oocyte retrieval.