Correlation Between Pain Threshold and Analgesic Consumption in Transvaginal Oocyte Aspiration Patients

Plain-language summary

Nowadays, in vitro fertilization (IVF) is an important component of modern infertility treatment. One of the critical stages of the IVF process is oocyte (egg) retrieval, which requires both anesthesia and analgesia; this directly affects the comfort of the participants and the success of the procedure. Since its first implementation, various methods and techniques have been used for oocyte retrieval, and today it is most commonly performed under anesthesia with transvaginal ultrasonography guidance. Because this procedure is performed on an outpatient basis in IVF centers worldwide, the anesthetic agents used are expected to meet several essential criteria: they should have a short half-life, a rapid onset of action, and minimal, acceptable side effects. In addition, these agents should not adversely affect participants' recovery processes. While the agents used determine the quality of sedation and analgesia, concerns persist regarding their potential negative effects on reproductive outcomes. Considering that participants often experience high levels of anxiety, effective pain management must be ensured during the procedure. Moreover, participants must remain immobile throughout the procedure. To achieve this, general anesthesia, regional/local anesthesia, neuraxial anesthesia, patient-controlled analgesia, sedation, acupuncture, or combinations of these methods may be used. Conscious sedation is the most commonly applied anesthesia method for women undergoing transvaginal oocyte aspiration. This method is preferred by approximately 95% of IVF centers in the USA and 84% in the UK. Conscious sedation allows the participant to maintain airway control and adequate oxygenation independently, while also providing a reduction in consciousness. Currently, midazolam, propofol, and fentanyl are the most frequently preferred agents for this purpose. They are easy to administer and are safe for cooperative participants. Compared to other anesthetic agents, they have relatively lower negative effects on oocyte and embryo quality and fewer adverse impacts on pregnancy rates. However, studies have shown that midazolam, fentanyl, and alfentanil can be detected in follicular fluid even after a single dose. In vitro studies on mouse oocytes and some human studies have indicated that propofol may have dose-dependent harmful effects on fertilization. Therefore, some researchers recommend that propofol should be used with caution during oocyte retrieval, with attention to limiting the total dose administered. As prolonged exposure to anesthetic agents has been shown to negatively affect fertilization, it is recommended that oocytes be exposed to anesthetic agents at the lowest possible level. Thus, for successful outcomes, it is critical that the anesthetic agents used during transvaginal follicle aspiration be administered at appropriate doses and durations. The researchers aim in this study to examine the correlation between the amount of anesthetic agent required and the pain threshold in participants whose pain thresholds are measured and who receive patient-controlled analgesia combined with conscious sedation. As a secondary objective, the researchers aim to compare participants' demographic characteristics, sociocultural status, stress and anxiety levels, the amount of anesthetic agent used, and its hemodynamic effects. This study is designed as a prospective, open-label, single-arm, non-randomized study. Forty female participants aged 18-50 years who will undergo oocyte retrieval for IVF treatment at the Erciyes University Department of Obstetrics and Gynecology will be included. To assess participants' pre-procedural stress and anxiety levels, the Spielberger State-Trait Anxiety Inventory (STAI) will be administered. Each participant's pain threshold will be measured at three sites-one muscle area (deltoid) and two bony areas (thumb and mid-tibia)-using an algometer (Commander Echo Algometer, JTECH Medical, Midvale, UT, USA), with bilateral measurements taken once at each site. The average of these three measurements will be calculated to determine the overall body pressure pain threshold for each participant. Prior to the procedure, all participants will receive 1.5 mg midazolam IV. During conscious sedation, a pre-prepared solution of 15 cc 1% propofol (150 mg) and 5 cc fentanyl (250 mcg) in a total volume of 20 cc will be administered using a PCA device with no lockout interval. Participants will be instructed to press the PCA button whenever they begin to feel pain. Hemodynamic parameters (systolic, diastolic, and mean arterial pressure, heart rate, SpO₂), Ramsay Sedation Scale (RSS) and Facial Score (FS) values will be recorded throughout the procedure. After the procedure, participants will be closely monitored for nausea, vomiting, and respiratory depression. In addition, total follicle count, embryo count, and pregnancy status will be recorded

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