A Prospective, Non-inferiority Randomized Double-blinded Trial Comparing Fentanyl and Midazolam vs Diazepam and Pethidine for Pain Relief During Oocyte Retrieval

In-vitro fertilization / embryo transfer (IVF / ET) is a well-established method to treat various causes of infertility. It involves multiple follicular development, retrieval of oocytes and embryo transfer after fertilization. Egg retrieval at the majority of IVF units is performed through the transvaginal route under ultrasound guidance (TUGOR) [1]. During TUGOR, the needle has to pass through the mucosa in the vaginal vault in order to puncture the follicles in the ovary. The procedures are generally short, lasting about 20-30 minutes but are still painful without anaesthesia or analgesia.

Intravenous sedation with or without local anaesthesia is the most widely used method. Conscious sedation is a safe and cost-effective method of providing analgesia and anesthesia for TUGOR. [2] It is easy to administer in cooperative and motivated patients. It has a relatively low risk for adverse effects on oocyte and embryo quality and pregnancy rates. [3] Paracervical block (PCB) in conjunction with conscious sedation during TUGOR was shown to significantly reduce the pain during TUGOR when compared to PCB alone [4].

A Cochrane review on various methods of sedation and analgesia for pain relief during TUGOR has shown no single method or delivery system appeared superior for pregnancy rates and pain relief. [5] Most of the methods seemed to work well and the effect was usually enhanced by addition of another method such as pain relief with paracervical block. [6]

The investigators' reproductive centre has recently aligned with the Assisted Reproduction Centre of the University of Hong Kong (HKU). The investigators are using 0.1mg fentanyl and 5mg midazolam intravenously for pain relief in TUGOR at Kwong Wah Hospital (KWH) whereas 5mg diazepam and 25mg pethidine intravenously are being used in HKU. The investigators would like to compare fentanyl and midazolam vs diazepam and pethidine in terms of pain levels and post-operative side effects of TUGOR in this prospective non-inferiority randomized double-blinded trial. The investigators postulate there are no differences in the pain levels between two groups but the postoperative side effects may be different.